Merge remote-tracking branch 'origin/master' into llvm16

1 files changed, 1593 insertions, 1665 deletions

diff --git a/src/codegen/c.zig b/src/codegen/c.zig
index 0beb00b236..cf428d4bd6 100644
--- a/src/codegen/c.zig
+++ b/src/codegen/c.zig
@@ -23,12 +23,14 @@ const libcFloatSuffix = target_util.libcFloatSuffix;
 const compilerRtFloatAbbrev = target_util.compilerRtFloatAbbrev;
 const compilerRtIntAbbrev = target_util.compilerRtIntAbbrev;
 
-const Mutability = enum { Const, ConstArgument, Mut };
 const BigIntLimb = std.math.big.Limb;
 const BigInt = std.math.big.int;
 
+pub const CType = @import("c/type.zig").CType;
+
 pub const CValue = union(enum) {
     none: void,
+    new_local: LocalIndex,
     local: LocalIndex,
     /// Address of a local.
     local_ref: LocalIndex,
@@ -36,6 +38,8 @@ pub const CValue = union(enum) {
     constant: Air.Inst.Ref,
     /// Index into the parameters
     arg: usize,
+    /// The array field of a parameter
+    arg_array: usize,
     /// Index into a tuple's fields
     field: usize,
     /// By-value
@@ -45,6 +49,8 @@ pub const CValue = union(enum) {
     undef: Type,
     /// Render the slice as an identifier (using fmtIdent)
     identifier: []const u8,
+    /// Render the slice as an payload.identifier (using fmtIdent)
+    payload_identifier: []const u8,
     /// Render these bytes literally.
     /// TODO make this a [*:0]const u8 to save memory
     bytes: []const u8,
@@ -55,37 +61,43 @@ const BlockData = struct {
     result: CValue,
 };
 
-const TypedefKind = enum {
-    Forward,
-    Complete,
-};
-
 pub const CValueMap = std.AutoHashMap(Air.Inst.Ref, CValue);
-pub const TypedefMap = std.ArrayHashMap(
-    Type,
-    struct { name: []const u8, rendered: []u8 },
-    Type.HashContext32,
-    true,
-);
+
+pub const LazyFnKey = union(enum) {
+    tag_name: Decl.Index,
+    never_tail: Decl.Index,
+    never_inline: Decl.Index,
+};
+pub const LazyFnValue = struct {
+    fn_name: []const u8,
+    data: Data,
+
+    pub const Data = union {
+        tag_name: Type,
+        never_tail: void,
+        never_inline: void,
+    };
+};
+pub const LazyFnMap = std.AutoArrayHashMapUnmanaged(LazyFnKey, LazyFnValue);
 
 const LoopDepth = u16;
 const Local = struct {
-    ty: Type,
-    alignment: u32,
+    cty_idx: CType.Index,
     /// How many loops the last definition was nested in.
     loop_depth: LoopDepth,
+    alignas: CType.AlignAs,
+
+    pub fn getType(local: Local) LocalType {
+        return .{ .cty_idx = local.cty_idx, .alignas = local.alignas };
+    }
 };
 
 const LocalIndex = u16;
-const LocalsList = std.ArrayListUnmanaged(LocalIndex);
-const LocalsMap = std.ArrayHashMapUnmanaged(Type, LocalsList, Type.HashContext32, true);
+const LocalType = struct { cty_idx: CType.Index, alignas: CType.AlignAs };
+const LocalsList = std.AutoArrayHashMapUnmanaged(LocalIndex, void);
+const LocalsMap = std.AutoArrayHashMapUnmanaged(LocalType, LocalsList);
 const LocalsStack = std.ArrayListUnmanaged(LocalsMap);
 
-const FormatTypeAsCIdentContext = struct {
-    ty: Type,
-    mod: *Module,
-};
-
 const ValueRenderLocation = enum {
     FunctionArgument,
     Initializer,
@@ -106,26 +118,6 @@ const BuiltinInfo = enum {
     Bits,
 };
 
-fn formatTypeAsCIdentifier(
-    data: FormatTypeAsCIdentContext,
-    comptime fmt: []const u8,
-    options: std.fmt.FormatOptions,
-    writer: anytype,
-) !void {
-    var stack = std.heap.stackFallback(128, data.mod.gpa);
-    const allocator = stack.get();
-    const str = std.fmt.allocPrint(allocator, "{}", .{data.ty.fmt(data.mod)}) catch "";
-    defer allocator.free(str);
-    return formatIdent(str, fmt, options, writer);
-}
-
-pub fn typeToCIdentifier(ty: Type, mod: *Module) std.fmt.Formatter(formatTypeAsCIdentifier) {
-    return .{ .data = .{
-        .ty = ty,
-        .mod = mod,
-    } };
-}
-
 const reserved_idents = std.ComptimeStringMap(void, .{
     // C language
     .{ "alignas", {
@@ -224,6 +216,15 @@ const reserved_idents = std.ComptimeStringMap(void, .{
     .{ "volatile", {} },
     .{ "while ", {} },
 
+    // stdarg.h
+    .{ "va_start", {} },
+    .{ "va_arg", {} },
+    .{ "va_end", {} },
+    .{ "va_copy", {} },
+
+    // stddef.h
+    .{ "offsetof", {} },
+
     // windows.h
     .{ "max", {} },
     .{ "min", {} },
@@ -281,6 +282,7 @@ pub const Function = struct {
     next_arg_index: usize = 0,
     next_block_index: usize = 0,
     object: Object,
+    lazy_fns: LazyFnMap,
     func: *Module.Fn,
     /// All the locals, to be emitted at the top of the function.
     locals: std.ArrayListUnmanaged(Local) = .{},
@@ -299,10 +301,6 @@ pub const Function = struct {
     /// Needed for memory used by the keys of free_locals_stack entries.
     arena: std.heap.ArenaAllocator,
 
-    fn tyHashCtx(f: Function) Type.HashContext32 {
-        return .{ .mod = f.object.dg.module };
-    }
-
     fn resolveInst(f: *Function, inst: Air.Inst.Ref) !CValue {
         const gop = try f.value_map.getOrPut(inst);
         if (gop.found_existing) return gop.value_ptr.*;
@@ -310,19 +308,19 @@ pub const Function = struct {
         const val = f.air.value(inst).?;
         const ty = f.air.typeOf(inst);
 
-        const result = if (lowersToArray(ty, f.object.dg.module.getTarget())) result: {
+        const result: CValue = if (lowersToArray(ty, f.object.dg.module.getTarget())) result: {
             const writer = f.object.code_header.writer();
             const alignment = 0;
             const decl_c_value = try f.allocLocalValue(ty, alignment);
             const gpa = f.object.dg.gpa;
-            try f.allocs.put(gpa, decl_c_value.local, true);
+            try f.allocs.put(gpa, decl_c_value.new_local, true);
             try writer.writeAll("static ");
-            try f.object.dg.renderTypeAndName(writer, ty, decl_c_value, .Const, alignment, .Complete);
+            try f.object.dg.renderTypeAndName(writer, ty, decl_c_value, Const, alignment, .complete);
             try writer.writeAll(" = ");
             try f.object.dg.renderValue(writer, ty, val, .StaticInitializer);
             try writer.writeAll(";\n ");
             break :result decl_c_value;
-        } else CValue{ .constant = inst };
+        } else .{ .constant = inst };
 
         gop.value_ptr.* = result;
         return result;
@@ -342,32 +340,32 @@ pub const Function = struct {
     /// Skips the reuse logic.
     fn allocLocalValue(f: *Function, ty: Type, alignment: u32) !CValue {
         const gpa = f.object.dg.gpa;
+        const target = f.object.dg.module.getTarget();
         try f.locals.append(gpa, .{
-            .ty = ty,
-            .alignment = alignment,
+            .cty_idx = try f.typeToIndex(ty, .complete),
             .loop_depth = @intCast(LoopDepth, f.free_locals_stack.items.len - 1),
+            .alignas = CType.AlignAs.init(alignment, ty.abiAlignment(target)),
         });
-        return CValue{ .local = @intCast(LocalIndex, f.locals.items.len - 1) };
+        return .{ .new_local = @intCast(LocalIndex, f.locals.items.len - 1) };
     }
 
     fn allocLocal(f: *Function, inst: Air.Inst.Index, ty: Type) !CValue {
-        const result = try f.allocAlignedLocal(ty, .Mut, 0);
-        log.debug("%{d}: allocating t{d}", .{ inst, result.local });
+        const result = try f.allocAlignedLocal(ty, .{}, 0);
+        log.debug("%{d}: allocating t{d}", .{ inst, result.new_local });
         return result;
     }
 
     /// Only allocates the local; does not print anything.
-    fn allocAlignedLocal(f: *Function, ty: Type, mutability: Mutability, alignment: u32) !CValue {
-        _ = mutability;
-
-        if (f.getFreeLocals().getPtrContext(ty, f.tyHashCtx())) |locals_list| {
-            for (locals_list.items, 0..) |local_index, i| {
-                const local = &f.locals.items[local_index];
-                if (local.alignment >= alignment) {
-                    local.loop_depth = @intCast(LoopDepth, f.free_locals_stack.items.len - 1);
-                    _ = locals_list.swapRemove(i);
-                    return CValue{ .local = local_index };
-                }
+    fn allocAlignedLocal(f: *Function, ty: Type, _: CQualifiers, alignment: u32) !CValue {
+        const target = f.object.dg.module.getTarget();
+        if (f.getFreeLocals().getPtr(.{
+            .cty_idx = try f.typeToIndex(ty, .complete),
+            .alignas = CType.AlignAs.init(alignment, ty.abiAlignment(target)),
+        })) |locals_list| {
+            if (locals_list.popOrNull()) |local_entry| {
+                const local = &f.locals.items[local_entry.key];
+                local.loop_depth = @intCast(LoopDepth, f.free_locals_stack.items.len - 1);
+                return .{ .new_local = local_entry.key };
             }
         }
 
@@ -430,12 +428,20 @@ pub const Function = struct {
         return f.object.dg.fail(format, args);
     }
 
-    fn renderType(f: *Function, w: anytype, t: Type) !void {
-        return f.object.dg.renderType(w, t, .Complete);
+    fn indexToCType(f: *Function, idx: CType.Index) CType {
+        return f.object.dg.indexToCType(idx);
+    }
+
+    fn typeToIndex(f: *Function, ty: Type, kind: CType.Kind) !CType.Index {
+        return f.object.dg.typeToIndex(ty, kind);
     }
 
-    fn renderTypecast(f: *Function, w: anytype, t: Type) !void {
-        return f.object.dg.renderTypecast(w, t);
+    fn typeToCType(f: *Function, ty: Type, kind: CType.Kind) !CType {
+        return f.object.dg.typeToCType(ty, kind);
+    }
+
+    fn renderType(f: *Function, w: anytype, t: Type) !void {
+        return f.object.dg.renderType(w, t);
     }
 
     fn renderIntCast(f: *Function, w: anytype, dest_ty: Type, src: CValue, src_ty: Type, location: ValueRenderLocation) !void {
@@ -446,7 +452,39 @@ pub const Function = struct {
         return f.object.dg.fmtIntLiteral(ty, val);
     }
 
-    pub fn deinit(f: *Function, gpa: mem.Allocator) void {
+    fn getLazyFnName(f: *Function, key: LazyFnKey, data: LazyFnValue.Data) ![]const u8 {
+        const gpa = f.object.dg.gpa;
+        const gop = try f.lazy_fns.getOrPut(gpa, key);
+        if (!gop.found_existing) {
+            errdefer _ = f.lazy_fns.pop();
+
+            var promoted = f.object.dg.ctypes.promote(gpa);
+            defer f.object.dg.ctypes.demote(promoted);
+            const arena = promoted.arena.allocator();
+
+            gop.value_ptr.* = .{
+                .fn_name = switch (key) {
+                    .tag_name,
+                    .never_tail,
+                    .never_inline,
+                    => |owner_decl| try std.fmt.allocPrint(arena, "zig_{s}_{}__{d}", .{
+                        @tagName(key),
+                        fmtIdent(mem.span(f.object.dg.module.declPtr(owner_decl).name)),
+                        @enumToInt(owner_decl),
+                    }),
+                },
+                .data = switch (key) {
+                    .tag_name => .{ .tag_name = try data.tag_name.copy(arena) },
+                    .never_tail => .{ .never_tail = data.never_tail },
+                    .never_inline => .{ .never_inline = data.never_inline },
+                },
+            };
+        }
+        return gop.value_ptr.fn_name;
+    }
+
+    pub fn deinit(f: *Function) void {
+        const gpa = f.object.dg.gpa;
         f.allocs.deinit(gpa);
         f.locals.deinit(gpa);
         for (f.free_locals_stack.items) |*free_locals| {
@@ -455,11 +493,9 @@ pub const Function = struct {
         f.free_locals_stack.deinit(gpa);
         f.blocks.deinit(gpa);
         f.value_map.deinit();
+        f.lazy_fns.deinit(gpa);
         f.object.code.deinit();
-        for (f.object.dg.typedefs.values()) |typedef| {
-            gpa.free(typedef.rendered);
-        }
-        f.object.dg.typedefs.deinit();
+        f.object.dg.ctypes.deinit(gpa);
         f.object.dg.fwd_decl.deinit();
         f.arena.deinit();
     }
@@ -483,30 +519,20 @@ pub const Object = struct {
 pub const DeclGen = struct {
     gpa: std.mem.Allocator,
     module: *Module,
-    decl: *Decl,
-    decl_index: Decl.Index,
+    decl: ?*Decl,
+    decl_index: Decl.OptionalIndex,
     fwd_decl: std.ArrayList(u8),
     error_msg: ?*Module.ErrorMsg,
-    /// The key of this map is Type which has references to typedefs_arena.
-    typedefs: TypedefMap,
-    typedefs_arena: std.mem.Allocator,
+    ctypes: CType.Store,
 
     fn fail(dg: *DeclGen, comptime format: []const u8, args: anytype) error{ AnalysisFail, OutOfMemory } {
         @setCold(true);
         const src = LazySrcLoc.nodeOffset(0);
-        const src_loc = src.toSrcLoc(dg.decl);
+        const src_loc = src.toSrcLoc(dg.decl.?);
         dg.error_msg = try Module.ErrorMsg.create(dg.gpa, src_loc, format, args);
         return error.AnalysisFail;
     }
 
-    fn getTypedefName(dg: *DeclGen, t: Type) ?[]const u8 {
-        if (dg.typedefs.get(t)) |typedef| {
-            return typedef.name;
-        } else {
-            return null;
-        }
-    }
-
     fn renderDeclValue(
         dg: *DeclGen,
         writer: anytype,
@@ -520,7 +546,7 @@ pub const DeclGen = struct {
 
         // Render an undefined pointer if we have a pointer to a zero-bit or comptime type.
         if (ty.isPtrAtRuntime() and !decl.ty.isFnOrHasRuntimeBits()) {
-            return dg.writeCValue(writer, CValue{ .undef = ty });
+            return dg.writeCValue(writer, .{ .undef = ty });
         }
 
         // Chase function values in order to be able to reference the original function.
@@ -534,7 +560,7 @@ pub const DeclGen = struct {
                 try writer.writeByte('{');
             } else {
                 try writer.writeByte('(');
-                try dg.renderTypecast(writer, ty);
+                try dg.renderType(writer, ty);
                 try writer.writeAll("){ .ptr = ");
             }
 
@@ -561,7 +587,7 @@ pub const DeclGen = struct {
         const need_typecast = if (ty.castPtrToFn()) |_| false else !ty.eql(decl.ty, dg.module);
         if (need_typecast) {
             try writer.writeAll("((");
-            try dg.renderTypecast(writer, ty);
+            try dg.renderType(writer, ty);
             try writer.writeByte(')');
         }
         try writer.writeByte('&');
@@ -576,7 +602,7 @@ pub const DeclGen = struct {
     fn renderParentPtr(dg: *DeclGen, writer: anytype, ptr_val: Value, ptr_ty: Type, location: ValueRenderLocation) error{ OutOfMemory, AnalysisFail }!void {
         if (!ptr_ty.isSlice()) {
             try writer.writeByte('(');
-            try dg.renderTypecast(writer, ptr_ty);
+            try dg.renderType(writer, ptr_ty);
             try writer.writeByte(')');
         }
         switch (ptr_val.tag()) {
@@ -591,90 +617,71 @@ pub const DeclGen = struct {
                 try dg.renderDeclValue(writer, ptr_ty, ptr_val, decl_index, location);
             },
             .field_ptr => {
-                const ptr_info = ptr_ty.ptrInfo();
+                const target = dg.module.getTarget();
                 const field_ptr = ptr_val.castTag(.field_ptr).?.data;
-                const container_ty = field_ptr.container_ty;
-                const index = field_ptr.field_index;
-
-                var container_ptr_ty_pl: Type.Payload.ElemType = .{
-                    .base = .{ .tag = .c_mut_pointer },
-                    .data = field_ptr.container_ty,
-                };
-                const container_ptr_ty = Type.initPayload(&container_ptr_ty_pl.base);
 
-                const FieldInfo = struct { name: []const u8, ty: Type };
-                const field_info: FieldInfo = switch (container_ty.zigTypeTag()) {
-                    .Struct => switch (container_ty.containerLayout()) {
-                        .Auto, .Extern => FieldInfo{
-                            .name = container_ty.structFields().keys()[index],
-                            .ty = container_ty.structFields().values()[index].ty,
-                        },
-                        .Packed => if (ptr_info.data.host_size == 0) {
-                            const target = dg.module.getTarget();
-
-                            const byte_offset = container_ty.packedStructFieldByteOffset(index, target);
-                            var byte_offset_pl = Value.Payload.U64{
-                                .base = .{ .tag = .int_u64 },
-                                .data = byte_offset,
-                            };
-                            const byte_offset_val = Value.initPayload(&byte_offset_pl.base);
-
-                            var u8_ptr_pl = ptr_info;
-                            u8_ptr_pl.data.pointee_type = Type.u8;
-                            const u8_ptr_ty = Type.initPayload(&u8_ptr_pl.base);
-
-                            try writer.writeAll("&((");
-                            try dg.renderTypecast(writer, u8_ptr_ty);
-                            try writer.writeByte(')');
-                            try dg.renderParentPtr(writer, field_ptr.container_ptr, container_ptr_ty, location);
-                            return writer.print(")[{}]", .{try dg.fmtIntLiteral(Type.usize, byte_offset_val)});
-                        } else {
-                            var host_pl = Type.Payload.Bits{
-                                .base = .{ .tag = .int_unsigned },
-                                .data = ptr_info.data.host_size * 8,
-                            };
-                            const host_ty = Type.initPayload(&host_pl.base);
-
-                            try writer.writeByte('(');
-                            try dg.renderTypecast(writer, ptr_ty);
-                            try writer.writeByte(')');
-                            return dg.renderParentPtr(writer, field_ptr.container_ptr, host_ty, location);
-                        },
-                    },
-                    .Union => switch (container_ty.containerLayout()) {
-                        .Auto, .Extern => FieldInfo{
-                            .name = container_ty.unionFields().keys()[index],
-                            .ty = container_ty.unionFields().values()[index].ty,
-                        },
-                        .Packed => {
-                            return dg.renderParentPtr(writer, field_ptr.container_ptr, ptr_ty, location);
-                        },
+                // Ensure complete type definition is visible before accessing fields.
+                _ = try dg.typeToIndex(field_ptr.container_ty, .complete);
+
+                var container_ptr_pl = ptr_ty.ptrInfo();
+                container_ptr_pl.data.pointee_type = field_ptr.container_ty;
+                const container_ptr_ty = Type.initPayload(&container_ptr_pl.base);
+
+                switch (fieldLocation(
+                    field_ptr.container_ty,
+                    ptr_ty,
+                    @intCast(u32, field_ptr.field_index),
+                    target,
+                )) {
+                    .begin => try dg.renderParentPtr(
+                        writer,
+                        field_ptr.container_ptr,
+                        container_ptr_ty,
+                        location,
+                    ),
+                    .field => |field| {
+                        try writer.writeAll("&(");
+                        try dg.renderParentPtr(
+                            writer,
+                            field_ptr.container_ptr,
+                            container_ptr_ty,
+                            location,
+                        );
+                        try writer.writeAll(")->");
+                        try dg.writeCValue(writer, field);
                     },
-                    .Pointer => field_info: {
-                        assert(container_ty.isSlice());
-                        break :field_info switch (index) {
-                            0 => FieldInfo{ .name = "ptr", .ty = container_ty.childType() },
-                            1 => FieldInfo{ .name = "len", .ty = Type.usize },
-                            else => unreachable,
+                    .byte_offset => |byte_offset| {
+                        var u8_ptr_pl = ptr_ty.ptrInfo();
+                        u8_ptr_pl.data.pointee_type = Type.u8;
+                        const u8_ptr_ty = Type.initPayload(&u8_ptr_pl.base);
+
+                        var byte_offset_pl = Value.Payload.U64{
+                            .base = .{ .tag = .int_u64 },
+                            .data = byte_offset,
                         };
-                    },
-                    else => unreachable,
-                };
-
-                if (field_info.ty.hasRuntimeBitsIgnoreComptime()) {
-                    // Ensure complete type definition is visible before accessing fields.
-                    try dg.renderType(std.io.null_writer, field_ptr.container_ty, .Complete);
+                        const byte_offset_val = Value.initPayload(&byte_offset_pl.base);
 
-                    try writer.writeAll("&(");
-                    try dg.renderParentPtr(writer, field_ptr.container_ptr, container_ptr_ty, location);
-                    try writer.writeAll(")->");
-                    switch (field_ptr.container_ty.tag()) {
-                        .union_tagged, .union_safety_tagged => try writer.writeAll("payload."),
-                        else => {},
-                    }
-                    try writer.print("{ }", .{fmtIdent(field_info.name)});
-                } else {
-                    try dg.renderParentPtr(writer, field_ptr.container_ptr, container_ptr_ty, location);
+                        try writer.writeAll("((");
+                        try dg.renderType(writer, u8_ptr_ty);
+                        try writer.writeByte(')');
+                        try dg.renderParentPtr(
+                            writer,
+                            field_ptr.container_ptr,
+                            container_ptr_ty,
+                            location,
+                        );
+                        try writer.print(" + {})", .{try dg.fmtIntLiteral(Type.usize, byte_offset_val)});
+                    },
+                    .end => {
+                        try writer.writeAll("((");
+                        try dg.renderParentPtr(
+                            writer,
+                            field_ptr.container_ptr,
+                            container_ptr_ty,
+                            location,
+                        );
+                        try writer.print(") + {})", .{try dg.fmtIntLiteral(Type.usize, Value.one)});
+                    },
                 }
             },
             .elem_ptr => {
@@ -698,7 +705,7 @@ pub const DeclGen = struct {
                 const container_ptr_ty = Type.initPayload(&container_ptr_ty_pl.base);
 
                 // Ensure complete type definition is visible before accessing fields.
-                try dg.renderType(std.io.null_writer, payload_ptr.container_ty, .Complete);
+                _ = try dg.typeToIndex(payload_ptr.container_ty, .complete);
 
                 try writer.writeAll("&(");
                 try dg.renderParentPtr(writer, payload_ptr.container_ptr, container_ptr_ty, location);
@@ -747,7 +754,7 @@ pub const DeclGen = struct {
 
                     try writer.writeAll("zig_cast_");
                     try dg.renderTypeForBuiltinFnName(writer, ty);
-                    try writer.writeAll(" zig_as_");
+                    try writer.writeAll(" zig_make_");
                     try dg.renderTypeForBuiltinFnName(writer, ty);
                     try writer.writeByte('(');
                     switch (bits) {
@@ -765,18 +772,18 @@ pub const DeclGen = struct {
                 .Pointer => if (ty.isSlice()) {
                     if (!location.isInitializer()) {
                         try writer.writeByte('(');
-                        try dg.renderTypecast(writer, ty);
+                        try dg.renderType(writer, ty);
                         try writer.writeByte(')');
                     }
 
                     try writer.writeAll("{(");
                     var buf: Type.SlicePtrFieldTypeBuffer = undefined;
                     const ptr_ty = ty.slicePtrFieldType(&buf);
-                    try dg.renderTypecast(writer, ptr_ty);
+                    try dg.renderType(writer, ptr_ty);
                     return writer.print("){x}, {0x}}}", .{try dg.fmtIntLiteral(Type.usize, val)});
                 } else {
                     try writer.writeAll("((");
-                    try dg.renderTypecast(writer, ty);
+                    try dg.renderType(writer, ty);
                     return writer.print("){x})", .{try dg.fmtIntLiteral(Type.usize, val)});
                 },
                 .Optional => {
@@ -793,7 +800,7 @@ pub const DeclGen = struct {
 
                     if (!location.isInitializer()) {
                         try writer.writeByte('(');
-                        try dg.renderTypecast(writer, ty);
+                        try dg.renderType(writer, ty);
                         try writer.writeByte(')');
                     }
 
@@ -807,7 +814,7 @@ pub const DeclGen = struct {
                     .Auto, .Extern => {
                         if (!location.isInitializer()) {
                             try writer.writeByte('(');
-                            try dg.renderTypecast(writer, ty);
+                            try dg.renderType(writer, ty);
                             try writer.writeByte(')');
                         }
 
@@ -821,7 +828,7 @@ pub const DeclGen = struct {
 
                             empty = false;
                         }
-                        if (empty) try writer.print("{x}", .{try dg.fmtIntLiteral(Type.u8, Value.undef)});
+
                         return writer.writeByte('}');
                     },
                     .Packed => return writer.print("{x}", .{try dg.fmtIntLiteral(ty, Value.undef)}),
@@ -829,7 +836,7 @@ pub const DeclGen = struct {
                 .Union => {
                     if (!location.isInitializer()) {
                         try writer.writeByte('(');
-                        try dg.renderTypecast(writer, ty);
+                        try dg.renderType(writer, ty);
                         try writer.writeByte(')');
                     }
 
@@ -854,7 +861,7 @@ pub const DeclGen = struct {
                 .ErrorUnion => {
                     if (!location.isInitializer()) {
                         try writer.writeByte('(');
-                        try dg.renderTypecast(writer, ty);
+                        try dg.renderType(writer, ty);
                         try writer.writeByte(')');
                     }
 
@@ -867,7 +874,7 @@ pub const DeclGen = struct {
                 .Array, .Vector => {
                     if (!location.isInitializer()) {
                         try writer.writeByte('(');
-                        try dg.renderTypecast(writer, ty);
+                        try dg.renderType(writer, ty);
                         try writer.writeByte(')');
                     }
 
@@ -876,14 +883,14 @@ pub const DeclGen = struct {
                         var literal = stringLiteral(writer);
                         try literal.start();
                         const c_len = ty.arrayLenIncludingSentinel();
-                        var index: usize = 0;
+                        var index: u64 = 0;
                         while (index < c_len) : (index += 1)
                             try literal.writeChar(0xaa);
                         return literal.end();
                     } else {
                         try writer.writeByte('{');
                         const c_len = ty.arrayLenIncludingSentinel();
-                        var index: usize = 0;
+                        var index: u64 = 0;
                         while (index < c_len) : (index += 1) {
                             if (index > 0) try writer.writeAll(", ");
                             try dg.renderValue(writer, ty.childType(), val, initializer_type);
@@ -957,7 +964,7 @@ pub const DeclGen = struct {
                 try writer.writeByte(' ');
                 var empty = true;
                 if (std.math.isFinite(f128_val)) {
-                    try writer.writeAll("zig_as_");
+                    try writer.writeAll("zig_make_");
                     try dg.renderTypeForBuiltinFnName(writer, ty);
                     try writer.writeByte('(');
                     switch (bits) {
@@ -992,7 +999,7 @@ pub const DeclGen = struct {
                         //     return dg.fail("Only quiet nans are supported in global variable initializers", .{});
                     }
 
-                    try writer.writeAll("zig_as_special_");
+                    try writer.writeAll("zig_make_special_");
                     if (location == .StaticInitializer) try writer.writeAll("constant_");
                     try dg.renderTypeForBuiltinFnName(writer, ty);
                     try writer.writeByte('(');
@@ -1028,7 +1035,7 @@ pub const DeclGen = struct {
                     return dg.renderValue(writer, ty, slice_val, location);
                 } else {
                     try writer.writeAll("((");
-                    try dg.renderTypecast(writer, ty);
+                    try dg.renderType(writer, ty);
                     try writer.writeAll(")NULL)");
                 },
                 .variable => {
@@ -1038,7 +1045,7 @@ pub const DeclGen = struct {
                 .slice => {
                     if (!location.isInitializer()) {
                         try writer.writeByte('(');
-                        try dg.renderTypecast(writer, ty);
+                        try dg.renderType(writer, ty);
                         try writer.writeByte(')');
                     }
 
@@ -1061,7 +1068,7 @@ pub const DeclGen = struct {
                 },
                 .int_u64, .one => {
                     try writer.writeAll("((");
-                    try dg.renderTypecast(writer, ty);
+                    try dg.renderType(writer, ty);
                     return writer.print("){x})", .{try dg.fmtIntLiteral(Type.usize, val)});
                 },
                 .field_ptr,
@@ -1076,15 +1083,15 @@ pub const DeclGen = struct {
             .Array, .Vector => {
                 if (location == .FunctionArgument) {
                     try writer.writeByte('(');
-                    try dg.renderTypecast(writer, ty);
+                    try dg.renderType(writer, ty);
                     try writer.writeByte(')');
                 }
 
                 // First try specific tag representations for more efficiency.
                 switch (val.tag()) {
                     .undef, .empty_struct_value, .empty_array => {
-                        try writer.writeByte('{');
                         const ai = ty.arrayInfo();
+                        try writer.writeByte('{');
                         if (ai.sentinel) |s| {
                             try dg.renderValue(writer, ai.elem_type, s, initializer_type);
                         } else {
@@ -1092,13 +1099,19 @@ pub const DeclGen = struct {
                         }
                         try writer.writeByte('}');
                     },
-                    .bytes => {
-                        try writer.print("{s}", .{fmtStringLiteral(val.castTag(.bytes).?.data)});
-                    },
-                    .str_lit => {
-                        const str_lit = val.castTag(.str_lit).?.data;
-                        const bytes = dg.module.string_literal_bytes.items[str_lit.index..][0..str_lit.len];
-                        try writer.print("{s}", .{fmtStringLiteral(bytes)});
+                    .bytes, .str_lit => |t| {
+                        const bytes = switch (t) {
+                            .bytes => val.castTag(.bytes).?.data,
+                            .str_lit => bytes: {
+                                const str_lit = val.castTag(.str_lit).?.data;
+                                break :bytes dg.module.string_literal_bytes.items[str_lit.index..][0..str_lit.len];
+                            },
+                            else => unreachable,
+                        };
+                        const sentinel = if (ty.sentinel()) |sentinel| @intCast(u8, sentinel.toUnsignedInt(target)) else null;
+                        try writer.print("{s}", .{
+                            fmtStringLiteral(bytes[0..@intCast(usize, ty.arrayLen())], sentinel),
+                        });
                     },
                     else => {
                         // Fall back to generic implementation.
@@ -1122,7 +1135,7 @@ pub const DeclGen = struct {
                                 }
                                 if (ai.sentinel) |s| {
                                     const s_u8 = @intCast(u8, s.toUnsignedInt(target));
-                                    try literal.writeChar(s_u8);
+                                    if (s_u8 != 0) try literal.writeChar(s_u8);
                                 }
                                 try literal.end();
                             } else {
@@ -1179,7 +1192,7 @@ pub const DeclGen = struct {
 
                 if (!location.isInitializer()) {
                     try writer.writeByte('(');
-                    try dg.renderTypecast(writer, ty);
+                    try dg.renderType(writer, ty);
                     try writer.writeByte(')');
                 }
 
@@ -1213,7 +1226,7 @@ pub const DeclGen = struct {
 
                 if (!location.isInitializer()) {
                     try writer.writeByte('(');
-                    try dg.renderTypecast(writer, ty);
+                    try dg.renderType(writer, ty);
                     try writer.writeByte(')');
                 }
 
@@ -1277,7 +1290,7 @@ pub const DeclGen = struct {
 
                     if (!location.isInitializer()) {
                         try writer.writeByte('(');
-                        try dg.renderTypecast(writer, ty);
+                        try dg.renderType(writer, ty);
                         try writer.writeByte(')');
                     }
 
@@ -1292,7 +1305,6 @@ pub const DeclGen = struct {
 
                         empty = false;
                     }
-                    if (empty) try writer.print("{}", .{try dg.fmtIntLiteral(Type.u8, Value.zero)});
                     try writer.writeByte('}');
                 },
                 .Packed => {
@@ -1309,7 +1321,7 @@ pub const DeclGen = struct {
                     const bit_offset_val = Value.initPayload(&bit_offset_val_pl.base);
 
                     var eff_num_fields: usize = 0;
-                    for (field_vals, 0..) |_, index| {
+                    for (0..field_vals.len) |index| {
                         const field_ty = ty.structFieldType(index);
                         if (!field_ty.hasRuntimeBitsIgnoreComptime()) continue;
 
@@ -1365,7 +1377,7 @@ pub const DeclGen = struct {
 
                             if (!empty) try writer.writeAll(" | ");
                             try writer.writeByte('(');
-                            try dg.renderTypecast(writer, ty);
+                            try dg.renderType(writer, ty);
                             try writer.writeByte(')');
 
                             if (bit_offset_val_pl.data != 0) {
@@ -1388,7 +1400,7 @@ pub const DeclGen = struct {
 
                 if (!location.isInitializer()) {
                     try writer.writeByte('(');
-                    try dg.renderTypecast(writer, ty);
+                    try dg.renderType(writer, ty);
                     try writer.writeByte(')');
                 }
 
@@ -1399,11 +1411,11 @@ pub const DeclGen = struct {
                     if (field_ty.hasRuntimeBits()) {
                         if (field_ty.isPtrAtRuntime()) {
                             try writer.writeByte('(');
-                            try dg.renderTypecast(writer, ty);
+                            try dg.renderType(writer, ty);
                             try writer.writeByte(')');
                         } else if (field_ty.zigTypeTag() == .Float) {
                             try writer.writeByte('(');
-                            try dg.renderTypecast(writer, ty);
+                            try dg.renderType(writer, ty);
                             try writer.writeByte(')');
                         }
                         try dg.renderValue(writer, field_ty, union_obj.val, initializer_type);
@@ -1413,6 +1425,7 @@ pub const DeclGen = struct {
                     return;
                 }
 
+                var has_payload_init = false;
                 try writer.writeByte('{');
                 if (ty.unionTagTypeSafety()) |tag_ty| {
                     const layout = ty.unionGetLayout(target);
@@ -1421,7 +1434,10 @@ pub const DeclGen = struct {
                         try dg.renderValue(writer, tag_ty, union_obj.tag, initializer_type);
                         try writer.writeAll(", ");
                     }
-                    try writer.writeAll(".payload = {");
+                    if (!ty.unionHasAllZeroBitFieldTypes()) {
+                        try writer.writeAll(".payload = {");
+                        has_payload_init = true;
+                    }
                 }
 
                 var it = ty.unionFields().iterator();
@@ -1433,8 +1449,8 @@ pub const DeclGen = struct {
                     try writer.print(".{ } = ", .{fmtIdent(field.key_ptr.*)});
                     try dg.renderValue(writer, field.value_ptr.ty, Value.undef, initializer_type);
                     break;
-                } else try writer.writeAll(".empty_union = 0");
-                if (ty.unionTagTypeSafety()) |_| try writer.writeByte('}');
+                }
+                if (has_payload_init) try writer.writeByte('}');
                 try writer.writeByte('}');
             },
 
@@ -1456,497 +1472,93 @@ pub const DeclGen = struct {
         }
     }
 
-    fn renderFunctionSignature(dg: *DeclGen, w: anytype, kind: TypedefKind, export_index: u32) !void {
-        const fn_info = dg.decl.ty.fnInfo();
+    fn renderFunctionSignature(
+        dg: *DeclGen,
+        w: anytype,
+        fn_decl_index: Decl.Index,
+        kind: CType.Kind,
+        name: union(enum) {
+            export_index: u32,
+            string: []const u8,
+        },
+    ) !void {
+        const store = &dg.ctypes.set;
+        const module = dg.module;
+
+        const fn_decl = module.declPtr(fn_decl_index);
+        const fn_cty_idx = try dg.typeToIndex(fn_decl.ty, kind);
+
+        const fn_info = fn_decl.ty.fnInfo();
         if (fn_info.cc == .Naked) {
             switch (kind) {
-                .Forward => try w.writeAll("zig_naked_decl "),
-                .Complete => try w.writeAll("zig_naked "),
+                .forward => try w.writeAll("zig_naked_decl "),
+                .complete => try w.writeAll("zig_naked "),
+                else => unreachable,
             }
         }
-        if (dg.decl.val.castTag(.function)) |func_payload|
+        if (fn_decl.val.castTag(.function)) |func_payload|
             if (func_payload.data.is_cold) try w.writeAll("zig_cold ");
-
-        const target = dg.module.getTarget();
-        var ret_buf: LowerFnRetTyBuffer = undefined;
-        const ret_ty = lowerFnRetTy(fn_info.return_type, &ret_buf, target);
-
-        try dg.renderType(w, ret_ty, kind);
-        try w.writeByte(' ');
+        if (fn_info.return_type.tag() == .noreturn) try w.writeAll("zig_noreturn ");
+
+        const trailing = try renderTypePrefix(
+            dg.decl_index,
+            store.*,
+            module,
+            w,
+            fn_cty_idx,
+            .suffix,
+            .{},
+        );
+        try w.print("{}", .{trailing});
 
         if (toCallingConvention(fn_info.cc)) |call_conv| {
             try w.print("zig_callconv({s}) ", .{call_conv});
         }
 
-        if (fn_info.alignment > 0 and kind == .Complete) try w.print(" zig_align_fn({})", .{fn_info.alignment});
-
-        try dg.renderDeclName(w, dg.decl_index, export_index);
-        try w.writeByte('(');
-
-        var index: usize = 0;
-        for (fn_info.param_types) |param_type| {
-            if (!param_type.hasRuntimeBitsIgnoreComptime()) continue;
-            if (index > 0) try w.writeAll(", ");
-            const name = CValue{ .arg = index };
-            try dg.renderTypeAndName(w, param_type, name, .ConstArgument, 0, kind);
-            index += 1;
-        }
-
-        if (fn_info.is_var_args) {
-            if (index > 0) try w.writeAll(", ");
-            try w.writeAll("...");
-        } else if (index == 0) {
-            try dg.renderType(w, Type.void, kind);
-        }
-        try w.writeByte(')');
-        if (fn_info.alignment > 0 and kind == .Forward) try w.print(" zig_align_fn({})", .{fn_info.alignment});
-    }
-
-    fn renderPtrToFnTypedef(dg: *DeclGen, t: Type) error{ OutOfMemory, AnalysisFail }![]const u8 {
-        var buffer = std.ArrayList(u8).init(dg.typedefs.allocator);
-        defer buffer.deinit();
-        const bw = buffer.writer();
-
-        const fn_info = t.fnInfo();
-
-        const target = dg.module.getTarget();
-        var ret_buf: LowerFnRetTyBuffer = undefined;
-        const ret_ty = lowerFnRetTy(fn_info.return_type, &ret_buf, target);
-
-        try bw.writeAll("typedef ");
-        try dg.renderType(bw, ret_ty, .Forward);
-        try bw.writeAll(" (*");
-        const name_begin = buffer.items.len;
-        try bw.print("zig_F_{}", .{typeToCIdentifier(t, dg.module)});
-        const name_end = buffer.items.len;
-        try bw.writeAll(")(");
-
-        const param_len = fn_info.param_types.len;
-
-        var params_written: usize = 0;
-        var index: usize = 0;
-        while (index < param_len) : (index += 1) {
-            const param_ty = fn_info.param_types[index];
-            if (!param_ty.hasRuntimeBitsIgnoreComptime()) continue;
-            if (params_written > 0) {
-                try bw.writeAll(", ");
-            }
-            try dg.renderTypeAndName(bw, param_ty, .{ .bytes = "" }, .Mut, 0, .Forward);
-            params_written += 1;
-        }
-
-        if (fn_info.is_var_args) {
-            if (params_written != 0) try bw.writeAll(", ");
-            try bw.writeAll("...");
-        } else if (params_written == 0) {
-            try dg.renderType(bw, Type.void, .Forward);
-        }
-        try bw.writeAll(");\n");
-
-        const rendered = try buffer.toOwnedSlice();
-        errdefer dg.typedefs.allocator.free(rendered);
-        const name = rendered[name_begin..name_end];
-
-        try dg.typedefs.ensureUnusedCapacity(1);
-        dg.typedefs.putAssumeCapacityNoClobber(
-            try t.copy(dg.typedefs_arena),
-            .{ .name = name, .rendered = rendered },
-        );
-
-        return name;
-    }
-
-    fn renderSliceTypedef(dg: *DeclGen, t: Type) error{ OutOfMemory, AnalysisFail }![]const u8 {
-        std.debug.assert(t.sentinel() == null); // expected canonical type
-
-        var buffer = std.ArrayList(u8).init(dg.typedefs.allocator);
-        defer buffer.deinit();
-        const bw = buffer.writer();
-
-        var ptr_ty_buf: Type.SlicePtrFieldTypeBuffer = undefined;
-        const ptr_ty = t.slicePtrFieldType(&ptr_ty_buf);
-        const ptr_name = CValue{ .identifier = "ptr" };
-        const len_ty = Type.usize;
-        const len_name = CValue{ .identifier = "len" };
-
-        try bw.writeAll("typedef struct {\n ");
-        try dg.renderTypeAndName(bw, ptr_ty, ptr_name, .Mut, 0, .Complete);
-        try bw.writeAll(";\n ");
-        try dg.renderTypeAndName(bw, len_ty, len_name, .Mut, 0, .Complete);
-
-        try bw.writeAll(";\n} ");
-        const name_begin = buffer.items.len;
-        try bw.print("zig_{c}_{}", .{
-            @as(u8, if (t.isConstPtr()) 'L' else 'M'),
-            typeToCIdentifier(t.childType(), dg.module),
-        });
-        const name_end = buffer.items.len;
-        try bw.writeAll(";\n");
-
-        const rendered = try buffer.toOwnedSlice();
-        errdefer dg.typedefs.allocator.free(rendered);
-        const name = rendered[name_begin..name_end];
-
-        try dg.typedefs.ensureUnusedCapacity(1);
-        dg.typedefs.putAssumeCapacityNoClobber(
-            try t.copy(dg.typedefs_arena),
-            .{ .name = name, .rendered = rendered },
-        );
-
-        return name;
-    }
-
-    fn renderFwdTypedef(dg: *DeclGen, t: Type) error{ OutOfMemory, AnalysisFail }![]const u8 {
-        // The forward declaration for T is stored with a key of *const T.
-        const child_ty = t.childType();
-
-        var buffer = std.ArrayList(u8).init(dg.typedefs.allocator);
-        defer buffer.deinit();
-        const bw = buffer.writer();
-
-        const tag = switch (child_ty.zigTypeTag()) {
-            .Struct, .ErrorUnion, .Optional => "struct",
-            .Union => if (child_ty.unionTagTypeSafety()) |_| "struct" else "union",
-            else => unreachable,
-        };
-        try bw.writeAll("typedef ");
-        try bw.writeAll(tag);
-        const name_begin = buffer.items.len + " ".len;
-        try bw.writeAll(" zig_");
-        switch (child_ty.zigTypeTag()) {
-            .Struct, .Union => {
-                var fqn_buf = std.ArrayList(u8).init(dg.typedefs.allocator);
-                defer fqn_buf.deinit();
-
-                const owner_decl_index = child_ty.getOwnerDecl();
-                const owner_decl = dg.module.declPtr(owner_decl_index);
-                try owner_decl.renderFullyQualifiedName(dg.module, fqn_buf.writer());
-
-                try bw.print("S_{}__{d}", .{ fmtIdent(fqn_buf.items), @enumToInt(owner_decl_index) });
-            },
-            .ErrorUnion => {
-                try bw.print("E_{}", .{typeToCIdentifier(child_ty.errorUnionPayload(), dg.module)});
-            },
-            .Optional => {
-                var opt_buf: Type.Payload.ElemType = undefined;
-                try bw.print("Q_{}", .{typeToCIdentifier(child_ty.optionalChild(&opt_buf), dg.module)});
-            },
+        switch (kind) {
+            .forward => {},
+            .complete => if (fn_info.alignment > 0)
+                try w.print(" zig_align_fn({})", .{fn_info.alignment}),
             else => unreachable,
         }
-        const name_end = buffer.items.len;
-        try buffer.ensureUnusedCapacity(" ".len + (name_end - name_begin) + ";\n".len);
-        buffer.appendAssumeCapacity(' ');
-        buffer.appendSliceAssumeCapacity(buffer.items[name_begin..name_end]);
-        buffer.appendSliceAssumeCapacity(";\n");
-
-        const rendered = try buffer.toOwnedSlice();
-        errdefer dg.typedefs.allocator.free(rendered);
-        const name = rendered[name_begin..name_end];
-
-        try dg.typedefs.ensureUnusedCapacity(1);
-        dg.typedefs.putAssumeCapacityNoClobber(
-            try t.copy(dg.typedefs_arena),
-            .{ .name = name, .rendered = rendered },
-        );
-
-        return name;
-    }
-
-    fn renderStructTypedef(dg: *DeclGen, t: Type) error{ OutOfMemory, AnalysisFail }![]const u8 {
-        var ptr_pl = Type.Payload.ElemType{ .base = .{ .tag = .single_const_pointer }, .data = t };
-        const ptr_ty = Type.initPayload(&ptr_pl.base);
-        const name = dg.getTypedefName(ptr_ty) orelse
-            try dg.renderFwdTypedef(ptr_ty);
-
-        var buffer = std.ArrayList(u8).init(dg.typedefs.allocator);
-        defer buffer.deinit();
-
-        try buffer.appendSlice("struct ");
-
-        var needs_pack_attr = false;
-        {
-            var it = t.structFields().iterator();
-            while (it.next()) |field| {
-                const field_ty = field.value_ptr.ty;
-                if (!field_ty.hasRuntimeBits()) continue;
-                const alignment = field.value_ptr.abi_align;
-                if (alignment != 0 and alignment < field_ty.abiAlignment(dg.module.getTarget())) {
-                    needs_pack_attr = true;
-                    try buffer.appendSlice("zig_packed(");
-                    break;
-                }
-            }
-        }
-
-        try buffer.appendSlice(name);
-        try buffer.appendSlice(" {\n");
-        {
-            var it = t.structFields().iterator();
-            var empty = true;
-            while (it.next()) |field| {
-                const field_ty = field.value_ptr.ty;
-                if (!field_ty.hasRuntimeBits()) continue;
-
-                const alignment = field.value_ptr.alignment(dg.module.getTarget(), t.containerLayout());
-                const field_name = CValue{ .identifier = field.key_ptr.* };
-                try buffer.append(' ');
-                try dg.renderTypeAndName(buffer.writer(), field_ty, field_name, .Mut, alignment, .Complete);
-                try buffer.appendSlice(";\n");
-
-                empty = false;
-            }
-            if (empty) try buffer.appendSlice(" char empty_struct;\n");
-        }
-        if (needs_pack_attr) try buffer.appendSlice("});\n") else try buffer.appendSlice("};\n");
-
-        const rendered = try buffer.toOwnedSlice();
-        errdefer dg.typedefs.allocator.free(rendered);
-
-        try dg.typedefs.ensureUnusedCapacity(1);
-        dg.typedefs.putAssumeCapacityNoClobber(
-            try t.copy(dg.typedefs_arena),
-            .{ .name = name, .rendered = rendered },
-        );
-
-        return name;
-    }
-
-    fn renderTupleTypedef(dg: *DeclGen, t: Type) error{ OutOfMemory, AnalysisFail }![]const u8 {
-        var buffer = std.ArrayList(u8).init(dg.typedefs.allocator);
-        defer buffer.deinit();
-
-        try buffer.appendSlice("typedef struct {\n");
-        {
-            const fields = t.tupleFields();
-            var field_id: usize = 0;
-            for (fields.types, 0..) |field_ty, i| {
-                if (!field_ty.hasRuntimeBits() or fields.values[i].tag() != .unreachable_value) continue;
-
-                try buffer.append(' ');
-                try dg.renderTypeAndName(buffer.writer(), field_ty, .{ .field = field_id }, .Mut, 0, .Complete);
-                try buffer.appendSlice(";\n");
-
-                field_id += 1;
-            }
-            if (field_id == 0) try buffer.appendSlice(" char empty_tuple;\n");
-        }
-        const name_begin = buffer.items.len + "} ".len;
-        try buffer.writer().print("}} zig_T_{}_{d};\n", .{ typeToCIdentifier(t, dg.module), @truncate(u16, t.hash(dg.module)) });
-        const name_end = buffer.items.len - ";\n".len;
-
-        const rendered = try buffer.toOwnedSlice();
-        errdefer dg.typedefs.allocator.free(rendered);
-        const name = rendered[name_begin..name_end];
-
-        try dg.typedefs.ensureUnusedCapacity(1);
-        dg.typedefs.putAssumeCapacityNoClobber(
-            try t.copy(dg.typedefs_arena),
-            .{ .name = name, .rendered = rendered },
-        );
-
-        return name;
-    }
-
-    fn renderUnionTypedef(dg: *DeclGen, t: Type) error{ OutOfMemory, AnalysisFail }![]const u8 {
-        var ptr_pl = Type.Payload.ElemType{ .base = .{ .tag = .single_const_pointer }, .data = t };
-        const ptr_ty = Type.initPayload(&ptr_pl.base);
-        const name = dg.getTypedefName(ptr_ty) orelse
-            try dg.renderFwdTypedef(ptr_ty);
-
-        var buffer = std.ArrayList(u8).init(dg.typedefs.allocator);
-        defer buffer.deinit();
-
-        try buffer.appendSlice(if (t.unionTagTypeSafety()) |_| "struct " else "union ");
-        try buffer.appendSlice(name);
-        try buffer.appendSlice(" {\n");
-
-        const indent = if (t.unionTagTypeSafety()) |tag_ty| indent: {
-            const target = dg.module.getTarget();
-            const layout = t.unionGetLayout(target);
-            if (layout.tag_size != 0) {
-                try buffer.append(' ');
-                try dg.renderTypeAndName(buffer.writer(), tag_ty, .{ .identifier = "tag" }, .Mut, 0, .Complete);
-                try buffer.appendSlice(";\n");
-            }
-            try buffer.appendSlice(" union {\n");
-            break :indent "  ";
-        } else " ";
 
-        {
-            var it = t.unionFields().iterator();
-            var empty = true;
-            while (it.next()) |field| {
-                const field_ty = field.value_ptr.ty;
-                if (!field_ty.hasRuntimeBits()) continue;
-
-                const alignment = field.value_ptr.abi_align;
-                const field_name = CValue{ .identifier = field.key_ptr.* };
-                try buffer.appendSlice(indent);
-                try dg.renderTypeAndName(buffer.writer(), field_ty, field_name, .Mut, alignment, .Complete);
-                try buffer.appendSlice(";\n");
-
-                empty = false;
-            }
-            if (empty) {
-                try buffer.appendSlice(indent);
-                try buffer.appendSlice("char empty_union;\n");
-            }
+        switch (name) {
+            .export_index => |export_index| try dg.renderDeclName(w, fn_decl_index, export_index),
+            .string => |string| try w.writeAll(string),
         }
 
-        if (t.unionTagTypeSafety()) |_| try buffer.appendSlice(" } payload;\n");
-        try buffer.appendSlice("};\n");
-
-        const rendered = try buffer.toOwnedSlice();
-        errdefer dg.typedefs.allocator.free(rendered);
-
-        try dg.typedefs.ensureUnusedCapacity(1);
-        dg.typedefs.putAssumeCapacityNoClobber(
-            try t.copy(dg.typedefs_arena),
-            .{ .name = name, .rendered = rendered },
+        try renderTypeSuffix(
+            dg.decl_index,
+            store.*,
+            module,
+            w,
+            fn_cty_idx,
+            .suffix,
+            CQualifiers.init(.{ .@"const" = switch (kind) {
+                .forward => false,
+                .complete => true,
+                else => unreachable,
+            } }),
         );
 
-        return name;
-    }
-
-    fn renderErrorUnionTypedef(dg: *DeclGen, t: Type) error{ OutOfMemory, AnalysisFail }![]const u8 {
-        assert(t.errorUnionSet().tag() == .anyerror);
-
-        var ptr_pl = Type.Payload.ElemType{ .base = .{ .tag = .single_const_pointer }, .data = t };
-        const ptr_ty = Type.initPayload(&ptr_pl.base);
-        const name = dg.getTypedefName(ptr_ty) orelse
-            try dg.renderFwdTypedef(ptr_ty);
-
-        var buffer = std.ArrayList(u8).init(dg.typedefs.allocator);
-        defer buffer.deinit();
-        const bw = buffer.writer();
-
-        const payload_ty = t.errorUnionPayload();
-        const payload_name = CValue{ .identifier = "payload" };
-        const error_ty = t.errorUnionSet();
-        const error_name = CValue{ .identifier = "error" };
-
-        const target = dg.module.getTarget();
-        const payload_align = payload_ty.abiAlignment(target);
-        const error_align = error_ty.abiAlignment(target);
-        try bw.writeAll("struct ");
-        try bw.writeAll(name);
-        try bw.writeAll(" {\n ");
-        if (error_align > payload_align) {
-            try dg.renderTypeAndName(bw, payload_ty, payload_name, .Mut, 0, .Complete);
-            try bw.writeAll(";\n ");
-            try dg.renderTypeAndName(bw, error_ty, error_name, .Mut, 0, .Complete);
-        } else {
-            try dg.renderTypeAndName(bw, error_ty, error_name, .Mut, 0, .Complete);
-            try bw.writeAll(";\n ");
-            try dg.renderTypeAndName(bw, payload_ty, payload_name, .Mut, 0, .Complete);
+        switch (kind) {
+            .forward => if (fn_info.alignment > 0)
+                try w.print(" zig_align_fn({})", .{fn_info.alignment}),
+            .complete => {},
+            else => unreachable,
         }
-        try bw.writeAll(";\n};\n");
-
-        const rendered = try buffer.toOwnedSlice();
-        errdefer dg.typedefs.allocator.free(rendered);
-
-        try dg.typedefs.ensureUnusedCapacity(1);
-        dg.typedefs.putAssumeCapacityNoClobber(
-            try t.copy(dg.typedefs_arena),
-            .{ .name = name, .rendered = rendered },
-        );
-
-        return name;
     }
 
-    fn renderArrayTypedef(dg: *DeclGen, t: Type) error{ OutOfMemory, AnalysisFail }![]const u8 {
-        const info = t.arrayInfo();
-        std.debug.assert(info.sentinel == null); // expected canonical type
-
-        var buffer = std.ArrayList(u8).init(dg.typedefs.allocator);
-        defer buffer.deinit();
-        const bw = buffer.writer();
-
-        try bw.writeAll("typedef ");
-        try dg.renderType(bw, info.elem_type, .Complete);
-
-        const name_begin = buffer.items.len + " ".len;
-        try bw.print(" zig_A_{}_{d}", .{ typeToCIdentifier(info.elem_type, dg.module), info.len });
-        const name_end = buffer.items.len;
-
-        const c_len = if (info.len > 0) info.len else 1;
-        var c_len_pl: Value.Payload.U64 = .{ .base = .{ .tag = .int_u64 }, .data = c_len };
-        const c_len_val = Value.initPayload(&c_len_pl.base);
-        try bw.print("[{}];\n", .{try dg.fmtIntLiteral(Type.usize, c_len_val)});
-
-        const rendered = try buffer.toOwnedSlice();
-        errdefer dg.typedefs.allocator.free(rendered);
-        const name = rendered[name_begin..name_end];
-
-        try dg.typedefs.ensureUnusedCapacity(1);
-        dg.typedefs.putAssumeCapacityNoClobber(
-            try t.copy(dg.typedefs_arena),
-            .{ .name = name, .rendered = rendered },
-        );
-
-        return name;
+    fn indexToCType(dg: *DeclGen, idx: CType.Index) CType {
+        return dg.ctypes.indexToCType(idx);
     }
 
-    fn renderOptionalTypedef(dg: *DeclGen, t: Type) error{ OutOfMemory, AnalysisFail }![]const u8 {
-        var ptr_pl = Type.Payload.ElemType{ .base = .{ .tag = .single_const_pointer }, .data = t };
-        const ptr_ty = Type.initPayload(&ptr_pl.base);
-        const name = dg.getTypedefName(ptr_ty) orelse
-            try dg.renderFwdTypedef(ptr_ty);
-
-        var buffer = std.ArrayList(u8).init(dg.typedefs.allocator);
-        defer buffer.deinit();
-        const bw = buffer.writer();
-
-        var opt_buf: Type.Payload.ElemType = undefined;
-        const child_ty = t.optionalChild(&opt_buf);
-
-        try bw.writeAll("struct ");
-        try bw.writeAll(name);
-        try bw.writeAll(" {\n");
-        try dg.renderTypeAndName(bw, child_ty, .{ .identifier = "payload" }, .Mut, 0, .Complete);
-        try bw.writeAll(";\n ");
-        try dg.renderTypeAndName(bw, Type.bool, .{ .identifier = "is_null" }, .Mut, 0, .Complete);
-        try bw.writeAll(";\n};\n");
-
-        const rendered = try buffer.toOwnedSlice();
-        errdefer dg.typedefs.allocator.free(rendered);
-
-        try dg.typedefs.ensureUnusedCapacity(1);
-        dg.typedefs.putAssumeCapacityNoClobber(
-            try t.copy(dg.typedefs_arena),
-            .{ .name = name, .rendered = rendered },
-        );
-
-        return name;
+    fn typeToIndex(dg: *DeclGen, ty: Type, kind: CType.Kind) !CType.Index {
+        return dg.ctypes.typeToIndex(dg.gpa, ty, dg.module, kind);
     }
 
-    fn renderOpaqueTypedef(dg: *DeclGen, t: Type) error{ OutOfMemory, AnalysisFail }![]const u8 {
-        const opaque_ty = t.cast(Type.Payload.Opaque).?.data;
-        const unqualified_name = dg.module.declPtr(opaque_ty.owner_decl).name;
-        const fqn = try opaque_ty.getFullyQualifiedName(dg.module);
-        defer dg.typedefs.allocator.free(fqn);
-
-        var buffer = std.ArrayList(u8).init(dg.typedefs.allocator);
-        defer buffer.deinit();
-
-        try buffer.writer().print("typedef struct { } ", .{fmtIdent(std.mem.span(unqualified_name))});
-
-        const name_begin = buffer.items.len;
-        try buffer.writer().print("zig_O_{}", .{fmtIdent(fqn)});
-        const name_end = buffer.items.len;
-        try buffer.appendSlice(";\n");
-
-        const rendered = try buffer.toOwnedSlice();
-        errdefer dg.typedefs.allocator.free(rendered);
-        const name = rendered[name_begin..name_end];
-
-        try dg.typedefs.ensureUnusedCapacity(1);
-        dg.typedefs.putAssumeCapacityNoClobber(
-            try t.copy(dg.typedefs_arena),
-            .{ .name = name, .rendered = rendered },
-        );
-
-        return name;
+    fn typeToCType(dg: *DeclGen, ty: Type, kind: CType.Kind) !CType {
+        return dg.ctypes.typeToCType(dg.gpa, ty, dg.module, kind);
     }
 
     /// Renders a type as a single identifier, generating intermediate typedefs
@@ -1957,277 +1569,15 @@ pub const DeclGen = struct {
     /// There are three type formats in total that we support rendering:
     ///   | Function            | Example 1 (*u8) | Example 2 ([10]*u8) |
     ///   |---------------------|-----------------|---------------------|
-    ///   | `renderTypecast`    | "uint8_t *"     | "uint8_t *[10]"     |
     ///   | `renderTypeAndName` | "uint8_t *name" | "uint8_t *name[10]" |
-    ///   | `renderType`        | "uint8_t *"     | "zig_A_uint8_t_10"  |
+    ///   | `renderType`        | "uint8_t *"     | "uint8_t *[10]"     |
     ///
-    fn renderType(
-        dg: *DeclGen,
-        w: anytype,
-        t: Type,
-        kind: TypedefKind,
-    ) error{ OutOfMemory, AnalysisFail }!void {
-        const target = dg.module.getTarget();
-
-        switch (t.zigTypeTag()) {
-            .Void => try w.writeAll("void"),
-            .Bool => try w.writeAll("bool"),
-            .NoReturn, .Float => {
-                try w.writeAll("zig_");
-                try t.print(w, dg.module);
-            },
-            .Int => {
-                if (t.isNamedInt()) {
-                    try w.writeAll("zig_");
-                    try t.print(w, dg.module);
-                } else {
-                    return renderTypeUnnamed(dg, w, t, kind);
-                }
-            },
-            .ErrorSet => {
-                return renderTypeUnnamed(dg, w, t, kind);
-            },
-            .Pointer => {
-                const ptr_info = t.ptrInfo().data;
-                if (ptr_info.size == .Slice) {
-                    var slice_pl = Type.Payload.ElemType{
-                        .base = .{ .tag = if (t.ptrIsMutable()) .mut_slice else .const_slice },
-                        .data = ptr_info.pointee_type,
-                    };
-                    const slice_ty = Type.initPayload(&slice_pl.base);
-
-                    const name = dg.getTypedefName(slice_ty) orelse
-                        try dg.renderSliceTypedef(slice_ty);
-
-                    return w.writeAll(name);
-                }
-
-                if (ptr_info.pointee_type.zigTypeTag() == .Fn) {
-                    const name = dg.getTypedefName(ptr_info.pointee_type) orelse
-                        try dg.renderPtrToFnTypedef(ptr_info.pointee_type);
-
-                    return w.writeAll(name);
-                }
-
-                if (ptr_info.host_size != 0) {
-                    var host_pl = Type.Payload.Bits{
-                        .base = .{ .tag = .int_unsigned },
-                        .data = ptr_info.host_size * 8,
-                    };
-                    const host_ty = Type.initPayload(&host_pl.base);
-
-                    try dg.renderType(w, host_ty, .Forward);
-                } else if (t.isCPtr() and ptr_info.pointee_type.eql(Type.u8, dg.module) and
-                    (dg.decl.val.tag() == .extern_fn or
-                    std.mem.eql(u8, std.mem.span(dg.decl.name), "main")))
-                {
-                    // This is a hack, since the c compiler expects a lot of external
-                    // library functions to have char pointers in their signatures, but
-                    // u8 and i8 produce unsigned char and signed char respectively,
-                    // which in C are (not very usefully) different than char.
-                    try w.writeAll("char");
-                } else try dg.renderType(w, switch (ptr_info.pointee_type.tag()) {
-                    .anyopaque => Type.void,
-                    else => ptr_info.pointee_type,
-                }, .Forward);
-                if (t.isConstPtr()) try w.writeAll(" const");
-                if (t.isVolatilePtr()) try w.writeAll(" volatile");
-                return w.writeAll(" *");
-            },
-            .Array, .Vector => {
-                var array_pl = Type.Payload.Array{ .base = .{ .tag = .array }, .data = .{
-                    .len = t.arrayLenIncludingSentinel(),
-                    .elem_type = t.childType(),
-                } };
-                const array_ty = Type.initPayload(&array_pl.base);
-
-                const name = dg.getTypedefName(array_ty) orelse
-                    try dg.renderArrayTypedef(array_ty);
-
-                return w.writeAll(name);
-            },
-            .Optional => {
-                var opt_buf: Type.Payload.ElemType = undefined;
-                const child_ty = t.optionalChild(&opt_buf);
-
-                if (!child_ty.hasRuntimeBitsIgnoreComptime())
-                    return dg.renderType(w, Type.bool, kind);
-
-                if (t.optionalReprIsPayload())
-                    return dg.renderType(w, child_ty, kind);
-
-                switch (kind) {
-                    .Complete => {
-                        const name = dg.getTypedefName(t) orelse
-                            try dg.renderOptionalTypedef(t);
-
-                        try w.writeAll(name);
-                    },
-                    .Forward => {
-                        var ptr_pl = Type.Payload.ElemType{
-                            .base = .{ .tag = .single_const_pointer },
-                            .data = t,
-                        };
-                        const ptr_ty = Type.initPayload(&ptr_pl.base);
-
-                        const name = dg.getTypedefName(ptr_ty) orelse
-                            try dg.renderFwdTypedef(ptr_ty);
-
-                        try w.writeAll(name);
-                    },
-                }
-            },
-            .ErrorUnion => {
-                const payload_ty = t.errorUnionPayload();
-
-                if (!payload_ty.hasRuntimeBitsIgnoreComptime())
-                    return dg.renderType(w, Type.anyerror, kind);
-
-                var error_union_pl = Type.Payload.ErrorUnion{
-                    .data = .{ .error_set = Type.anyerror, .payload = payload_ty },
-                };
-                const error_union_ty = Type.initPayload(&error_union_pl.base);
-
-                switch (kind) {
-                    .Complete => {
-                        const name = dg.getTypedefName(error_union_ty) orelse
-                            try dg.renderErrorUnionTypedef(error_union_ty);
-
-                        try w.writeAll(name);
-                    },
-                    .Forward => {
-                        var ptr_pl = Type.Payload.ElemType{
-                            .base = .{ .tag = .single_const_pointer },
-                            .data = error_union_ty,
-                        };
-                        const ptr_ty = Type.initPayload(&ptr_pl.base);
-
-                        const name = dg.getTypedefName(ptr_ty) orelse
-                            try dg.renderFwdTypedef(ptr_ty);
-
-                        try w.writeAll(name);
-                    },
-                }
-            },
-            .Struct, .Union => |tag| if (t.containerLayout() == .Packed) {
-                if (t.castTag(.@"struct")) |struct_obj| {
-                    try dg.renderType(w, struct_obj.data.backing_int_ty, kind);
-                } else {
-                    var buf: Type.Payload.Bits = .{
-                        .base = .{ .tag = .int_unsigned },
-                        .data = @intCast(u16, t.bitSize(target)),
-                    };
-                    try dg.renderType(w, Type.initPayload(&buf.base), kind);
-                }
-            } else if (t.isSimpleTupleOrAnonStruct()) {
-                const ExpectedContents = struct { types: [8]Type, values: [8]Value };
-                var stack align(@alignOf(ExpectedContents)) =
-                    std.heap.stackFallback(@sizeOf(ExpectedContents), dg.gpa);
-                const allocator = stack.get();
-
-                var tuple_storage = std.MultiArrayList(struct { type: Type, value: Value }){};
-                defer tuple_storage.deinit(allocator);
-                try tuple_storage.ensureTotalCapacity(allocator, t.structFieldCount());
-
-                const fields = t.tupleFields();
-                for (fields.values, 0..) |value, index|
-                    if (value.tag() == .unreachable_value)
-                        tuple_storage.appendAssumeCapacity(.{
-                            .type = fields.types[index],
-                            .value = value,
-                        });
-
-                const tuple_slice = tuple_storage.slice();
-                var tuple_pl = Type.Payload.Tuple{ .data = .{
-                    .types = tuple_slice.items(.type),
-                    .values = tuple_slice.items(.value),
-                } };
-                const tuple_ty = Type.initPayload(&tuple_pl.base);
-
-                const name = dg.getTypedefName(tuple_ty) orelse
-                    try dg.renderTupleTypedef(tuple_ty);
-
-                try w.writeAll(name);
-            } else switch (kind) {
-                .Complete => {
-                    const name = dg.getTypedefName(t) orelse switch (tag) {
-                        .Struct => try dg.renderStructTypedef(t),
-                        .Union => try dg.renderUnionTypedef(t),
-                        else => unreachable,
-                    };
-
-                    try w.writeAll(name);
-                },
-                .Forward => {
-                    var ptr_pl = Type.Payload.ElemType{
-                        .base = .{ .tag = .single_const_pointer },
-                        .data = t,
-                    };
-                    const ptr_ty = Type.initPayload(&ptr_pl.base);
-
-                    const name = dg.getTypedefName(ptr_ty) orelse
-                        try dg.renderFwdTypedef(ptr_ty);
-
-                    try w.writeAll(name);
-                },
-            },
-            .Enum => {
-                // For enums, we simply use the integer tag type.
-                var int_tag_buf: Type.Payload.Bits = undefined;
-                const int_tag_ty = t.intTagType(&int_tag_buf);
-
-                try dg.renderType(w, int_tag_ty, kind);
-            },
-            .Opaque => switch (t.tag()) {
-                .@"opaque" => {
-                    const name = dg.getTypedefName(t) orelse
-                        try dg.renderOpaqueTypedef(t);
-
-                    try w.writeAll(name);
-                },
-                else => unreachable,
-            },
-
-            .Frame,
-            .AnyFrame,
-            => |tag| return dg.fail("TODO: C backend: implement value of type {s}", .{
-                @tagName(tag),
-            }),
-
-            .Fn => unreachable, // This is a function body, not a function pointer.
-
-            .Null,
-            .Undefined,
-            .EnumLiteral,
-            .ComptimeFloat,
-            .ComptimeInt,
-            .Type,
-            => unreachable, // must be const or comptime
-        }
-    }
-
-    fn renderTypeUnnamed(
-        dg: *DeclGen,
-        w: anytype,
-        t: Type,
-        kind: TypedefKind,
-    ) error{ OutOfMemory, AnalysisFail }!void {
-        const target = dg.module.getTarget();
-        const int_info = t.intInfo(target);
-        if (toCIntBits(int_info.bits)) |c_bits|
-            return w.print("zig_{c}{d}", .{ signAbbrev(int_info.signedness), c_bits })
-        else if (loweredArrayInfo(t, target)) |array_info| {
-            assert(array_info.sentinel == null);
-            var array_pl = Type.Payload.Array{
-                .base = .{ .tag = .array },
-                .data = .{ .len = array_info.len, .elem_type = array_info.elem_type },
-            };
-            const array_ty = Type.initPayload(&array_pl.base);
-
-            return dg.renderType(w, array_ty, kind);
-        } else return dg.fail("C backend: Unable to lower unnamed integer type {}", .{
-            t.fmt(dg.module),
-        });
+    fn renderType(dg: *DeclGen, w: anytype, t: Type) error{ OutOfMemory, AnalysisFail }!void {
+        const store = &dg.ctypes.set;
+        const module = dg.module;
+        const idx = try dg.typeToIndex(t, .complete);
+        _ = try renderTypePrefix(dg.decl_index, store.*, module, w, idx, .suffix, .{});
+        try renderTypeSuffix(dg.decl_index, store.*, module, w, idx, .suffix, .{});
     }
 
     const IntCastContext = union(enum) {
@@ -2254,16 +1604,16 @@ pub const DeclGen = struct {
     /// Renders a cast to an int type, from either an int or a pointer.
     ///
     /// Some platforms don't have 128 bit integers, so we need to use
-    /// the zig_as_ and zig_lo_ macros in those cases.
+    /// the zig_make_ and zig_lo_ macros in those cases.
     ///
     ///   | Dest type bits   | Src type         | Result
     ///   |------------------|------------------|---------------------------|
     ///   | < 64 bit integer | pointer          | (zig_<dest_ty>)(zig_<u|i>size)src
     ///   | < 64 bit integer | < 64 bit integer | (zig_<dest_ty>)src
     ///   | < 64 bit integer | > 64 bit integer | zig_lo(src)
-    ///   | > 64 bit integer | pointer          | zig_as_<dest_ty>(0, (zig_<u|i>size)src)
-    ///   | > 64 bit integer | < 64 bit integer | zig_as_<dest_ty>(0, src)
-    ///   | > 64 bit integer | > 64 bit integer | zig_as_<dest_ty>(zig_hi_<src_ty>(src), zig_lo_<src_ty>(src))
+    ///   | > 64 bit integer | pointer          | zig_make_<dest_ty>(0, (zig_<u|i>size)src)
+    ///   | > 64 bit integer | < 64 bit integer | zig_make_<dest_ty>(0, src)
+    ///   | > 64 bit integer | > 64 bit integer | zig_make_<dest_ty>(zig_hi_<src_ty>(src), zig_lo_<src_ty>(src))
     fn renderIntCast(dg: *DeclGen, w: anytype, dest_ty: Type, context: IntCastContext, src_ty: Type, location: ValueRenderLocation) !void {
         const target = dg.module.getTarget();
         const dest_bits = dest_ty.bitSize(target);
@@ -2284,36 +1634,41 @@ pub const DeclGen = struct {
 
             if (needs_cast) {
                 try w.writeByte('(');
-                try dg.renderTypecast(w, dest_ty);
+                try dg.renderType(w, dest_ty);
                 try w.writeByte(')');
             }
             if (src_is_ptr) {
                 try w.writeByte('(');
-                try dg.renderTypecast(w, src_eff_ty);
+                try dg.renderType(w, src_eff_ty);
                 try w.writeByte(')');
             }
             try context.writeValue(dg, w, src_ty, location);
         } else if (dest_bits <= 64 and src_bits > 64) {
             assert(!src_is_ptr);
+            if (dest_bits < 64) {
+                try w.writeByte('(');
+                try dg.renderType(w, dest_ty);
+                try w.writeByte(')');
+            }
             try w.writeAll("zig_lo_");
             try dg.renderTypeForBuiltinFnName(w, src_eff_ty);
             try w.writeByte('(');
             try context.writeValue(dg, w, src_ty, .FunctionArgument);
             try w.writeByte(')');
         } else if (dest_bits > 64 and src_bits <= 64) {
-            try w.writeAll("zig_as_");
+            try w.writeAll("zig_make_");
             try dg.renderTypeForBuiltinFnName(w, dest_ty);
             try w.writeAll("(0, "); // TODO: Should the 0 go through fmtIntLiteral?
             if (src_is_ptr) {
                 try w.writeByte('(');
-                try dg.renderTypecast(w, src_eff_ty);
+                try dg.renderType(w, src_eff_ty);
                 try w.writeByte(')');
             }
             try context.writeValue(dg, w, src_ty, .FunctionArgument);
             try w.writeByte(')');
         } else {
             assert(!src_is_ptr);
-            try w.writeAll("zig_as_");
+            try w.writeAll("zig_make_");
             try dg.renderTypeForBuiltinFnName(w, dest_ty);
             try w.writeAll("(zig_hi_");
             try dg.renderTypeForBuiltinFnName(w, src_eff_ty);
@@ -2327,151 +1682,50 @@ pub const DeclGen = struct {
         }
     }
 
-    /// Renders a type in C typecast format.
-    ///
-    /// This is guaranteed to be valid in a typecast expression, but not
-    /// necessarily in a variable/field declaration.
-    ///
-    /// There are three type formats in total that we support rendering:
-    ///   | Function            | Example 1 (*u8) | Example 2 ([10]*u8) |
-    ///   |---------------------|-----------------|---------------------|
-    ///   | `renderTypecast`    | "uint8_t *"     | "uint8_t *[10]"     |
-    ///   | `renderTypeAndName` | "uint8_t *name" | "uint8_t *name[10]" |
-    ///   | `renderType`        | "uint8_t *"     | "zig_A_uint8_t_10"  |
-    ///
-    fn renderTypecast(dg: *DeclGen, w: anytype, ty: Type) error{ OutOfMemory, AnalysisFail }!void {
-        return renderTypeAndName(dg, w, ty, .{ .bytes = "" }, .Mut, 0, .Complete);
-    }
-
     /// Renders a type and name in field declaration/definition format.
     ///
     /// There are three type formats in total that we support rendering:
     ///   | Function            | Example 1 (*u8) | Example 2 ([10]*u8) |
     ///   |---------------------|-----------------|---------------------|
-    ///   | `renderTypecast`    | "uint8_t *"     | "uint8_t *[10]"     |
     ///   | `renderTypeAndName` | "uint8_t *name" | "uint8_t *name[10]" |
-    ///   | `renderType`        | "uint8_t *"     | "zig_A_uint8_t_10"  |
+    ///   | `renderType`        | "uint8_t *"     | "uint8_t *[10]"     |
     ///
     fn renderTypeAndName(
         dg: *DeclGen,
         w: anytype,
         ty: Type,
         name: CValue,
-        mutability: Mutability,
+        qualifiers: CQualifiers,
         alignment: u32,
-        kind: TypedefKind,
+        kind: CType.Kind,
     ) error{ OutOfMemory, AnalysisFail }!void {
-        var suffix = std.ArrayList(u8).init(dg.gpa);
-        defer suffix.deinit();
-        const suffix_writer = suffix.writer();
-
-        // Any top-level array types are rendered here as a suffix, which
-        // avoids creating typedefs for every array type
         const target = dg.module.getTarget();
-        var render_ty = ty;
-        var depth: u32 = 0;
-        while (loweredArrayInfo(render_ty, target)) |array_info| {
-            const c_len = array_info.len + @boolToInt(array_info.sentinel != null);
-            var c_len_pl: Value.Payload.U64 = .{ .base = .{ .tag = .int_u64 }, .data = c_len };
-            const c_len_val = Value.initPayload(&c_len_pl.base);
-
-            try suffix_writer.writeByte('[');
-            if (mutability == .ConstArgument and depth == 0) try suffix_writer.writeAll("zig_const_arr ");
-            try suffix.writer().print("{}]", .{try dg.fmtIntLiteral(Type.usize, c_len_val)});
-            render_ty = array_info.elem_type;
-            depth += 1;
-        }
-
-        if (alignment != 0) {
-            const abi_alignment = ty.abiAlignment(target);
-            if (alignment < abi_alignment) {
-                try w.print("zig_under_align({}) ", .{alignment});
-            } else if (alignment > abi_alignment) {
-                try w.print("zig_align({}) ", .{alignment});
-            }
-        }
-        try dg.renderType(w, render_ty, kind);
-
-        const const_prefix = switch (mutability) {
-            .Const, .ConstArgument => "const ",
-            .Mut => "",
-        };
-        try w.print(" {s}", .{const_prefix});
-        try dg.writeCValue(w, name);
-        try w.writeAll(suffix.items);
+        const alignas = CType.AlignAs.init(alignment, ty.abiAlignment(target));
+        try dg.renderCTypeAndName(w, try dg.typeToIndex(ty, kind), name, qualifiers, alignas);
     }
 
-    fn renderTagNameFn(dg: *DeclGen, enum_ty: Type) error{ OutOfMemory, AnalysisFail }![]const u8 {
-        var buffer = std.ArrayList(u8).init(dg.typedefs.allocator);
-        defer buffer.deinit();
-        const bw = buffer.writer();
-
-        const name_slice_ty = Type.initTag(.const_slice_u8_sentinel_0);
-
-        try buffer.appendSlice("static ");
-        try dg.renderType(bw, name_slice_ty, .Complete);
-        const name_begin = buffer.items.len + " ".len;
-        try bw.print(" zig_tagName_{}_{d}(", .{ typeToCIdentifier(enum_ty, dg.module), @enumToInt(enum_ty.getOwnerDecl()) });
-        const name_end = buffer.items.len - "(".len;
-        try dg.renderTypeAndName(bw, enum_ty, .{ .identifier = "tag" }, .Const, 0, .Complete);
-        try buffer.appendSlice(") {\n switch (tag) {\n");
-        for (enum_ty.enumFields().keys(), 0..) |name, index| {
-            const name_z = try dg.typedefs.allocator.dupeZ(u8, name);
-            defer dg.typedefs.allocator.free(name_z);
-            const name_bytes = name_z[0 .. name_z.len + 1];
-
-            var tag_pl: Value.Payload.U32 = .{
-                .base = .{ .tag = .enum_field_index },
-                .data = @intCast(u32, index),
-            };
-            const tag_val = Value.initPayload(&tag_pl.base);
-
-            var int_pl: Value.Payload.U64 = undefined;
-            const int_val = tag_val.enumToInt(enum_ty, &int_pl);
-
-            var name_ty_pl = Type.Payload.Len{ .base = .{ .tag = .array_u8_sentinel_0 }, .data = name.len };
-            const name_ty = Type.initPayload(&name_ty_pl.base);
-
-            var name_pl = Value.Payload.Bytes{ .base = .{ .tag = .bytes }, .data = name_bytes };
-            const name_val = Value.initPayload(&name_pl.base);
-
-            var len_pl = Value.Payload.U64{ .base = .{ .tag = .int_u64 }, .data = name.len };
-            const len_val = Value.initPayload(&len_pl.base);
-
-            try bw.print("  case {}: {{\n   static ", .{try dg.fmtIntLiteral(enum_ty, int_val)});
-            try dg.renderTypeAndName(bw, name_ty, .{ .identifier = "name" }, .Const, 0, .Complete);
-            try buffer.appendSlice(" = ");
-            try dg.renderValue(bw, name_ty, name_val, .Initializer);
-            try buffer.appendSlice(";\n   return (");
-            try dg.renderTypecast(bw, name_slice_ty);
-            try bw.print("){{{}, {}}};\n", .{
-                fmtIdent("name"), try dg.fmtIntLiteral(Type.usize, len_val),
-            });
+    fn renderCTypeAndName(
+        dg: *DeclGen,
+        w: anytype,
+        cty_idx: CType.Index,
+        name: CValue,
+        qualifiers: CQualifiers,
+        alignas: CType.AlignAs,
+    ) error{ OutOfMemory, AnalysisFail }!void {
+        const store = &dg.ctypes.set;
+        const module = dg.module;
 
-            try buffer.appendSlice("  }\n");
+        switch (std.math.order(alignas.@"align", alignas.abi)) {
+            .lt => try w.print("zig_under_align({}) ", .{alignas.getAlign()}),
+            .eq => {},
+            .gt => try w.print("zig_align({}) ", .{alignas.getAlign()}),
         }
-        try buffer.appendSlice(" }\n while (");
-        try dg.renderValue(bw, Type.bool, Value.true, .Other);
-        try buffer.appendSlice(") ");
-        _ = try airBreakpoint(bw);
-        try buffer.appendSlice("}\n");
-
-        const rendered = try buffer.toOwnedSlice();
-        errdefer dg.typedefs.allocator.free(rendered);
-        const name = rendered[name_begin..name_end];
-
-        try dg.typedefs.ensureUnusedCapacity(1);
-        dg.typedefs.putAssumeCapacityNoClobber(
-            try enum_ty.copy(dg.typedefs_arena),
-            .{ .name = name, .rendered = rendered },
-        );
-
-        return name;
-    }
 
-    fn getTagNameFn(dg: *DeclGen, enum_ty: Type) ![]const u8 {
-        return dg.getTypedefName(enum_ty) orelse
-            try dg.renderTagNameFn(enum_ty);
+        const trailing =
+            try renderTypePrefix(dg.decl_index, store.*, module, w, cty_idx, .suffix, qualifiers);
+        try w.print("{}", .{trailing});
+        try dg.writeCValue(w, name);
+        try renderTypeSuffix(dg.decl_index, store.*, module, w, cty_idx, .suffix, .{});
     }
 
     fn declIsGlobal(dg: *DeclGen, tv: TypedValue) bool {
@@ -2492,10 +1746,11 @@ pub const DeclGen = struct {
     fn writeCValue(dg: *DeclGen, w: anytype, c_value: CValue) !void {
         switch (c_value) {
             .none => unreachable,
-            .local => |i| return w.print("t{d}", .{i}),
+            .local, .new_local => |i| return w.print("t{d}", .{i}),
             .local_ref => |i| return w.print("&t{d}", .{i}),
             .constant => unreachable,
             .arg => |i| return w.print("a{d}", .{i}),
+            .arg_array => |i| return dg.writeCValueMember(w, .{ .arg = i }, .{ .identifier = "array" }),
             .field => |i| return w.print("f{d}", .{i}),
             .decl => |decl| return dg.renderDeclName(w, decl, 0),
             .decl_ref => |decl| {
@@ -2504,6 +1759,10 @@ pub const DeclGen = struct {
             },
             .undef => |ty| return dg.renderValue(w, ty, Value.undef, .Other),
             .identifier => |ident| return w.print("{ }", .{fmtIdent(ident)}),
+            .payload_identifier => |ident| return w.print("{ }.{ }", .{
+                fmtIdent("payload"),
+                fmtIdent(ident),
+            }),
             .bytes => |bytes| return w.writeAll(bytes),
         }
     }
@@ -2511,10 +1770,15 @@ pub const DeclGen = struct {
     fn writeCValueDeref(dg: *DeclGen, w: anytype, c_value: CValue) !void {
         switch (c_value) {
             .none => unreachable,
-            .local => |i| return w.print("(*t{d})", .{i}),
+            .local, .new_local => |i| return w.print("(*t{d})", .{i}),
             .local_ref => |i| return w.print("t{d}", .{i}),
             .constant => unreachable,
             .arg => |i| return w.print("(*a{d})", .{i}),
+            .arg_array => |i| {
+                try w.writeAll("(*");
+                try dg.writeCValueMember(w, .{ .arg = i }, .{ .identifier = "array" });
+                return w.writeByte(')');
+            },
             .field => |i| return w.print("f{d}", .{i}),
             .decl => |decl| {
                 try w.writeAll("(*");
@@ -2524,6 +1788,10 @@ pub const DeclGen = struct {
             .decl_ref => |decl| return dg.renderDeclName(w, decl, 0),
             .undef => unreachable,
             .identifier => |ident| return w.print("(*{ })", .{fmtIdent(ident)}),
+            .payload_identifier => |ident| return w.print("(*{ }.{ })", .{
+                fmtIdent("payload"),
+                fmtIdent(ident),
+            }),
             .bytes => |bytes| {
                 try w.writeAll("(*");
                 try w.writeAll(bytes);
@@ -2541,7 +1809,7 @@ pub const DeclGen = struct {
     fn writeCValueDerefMember(dg: *DeclGen, writer: anytype, c_value: CValue, member: CValue) !void {
         switch (c_value) {
             .none, .constant, .field, .undef => unreachable,
-            .local, .arg, .decl, .identifier, .bytes => {
+            .new_local, .local, .arg, .arg_array, .decl, .identifier, .payload_identifier, .bytes => {
                 try dg.writeCValue(writer, c_value);
                 try writer.writeAll("->");
             },
@@ -2668,12 +1936,465 @@ pub const DeclGen = struct {
     }
 };
 
-pub fn genGlobalAsm(mod: *Module, code: *std.ArrayList(u8)) !void {
-    var it = mod.global_assembly.valueIterator();
-    while (it.next()) |asm_source| {
-        try code.writer().print("__asm({s});\n", .{fmtStringLiteral(asm_source.*)});
+const CTypeFix = enum { prefix, suffix };
+const CQualifiers = std.enums.EnumSet(enum { @"const", @"volatile", restrict });
+const Const = CQualifiers.init(.{ .@"const" = true });
+const RenderCTypeTrailing = enum {
+    no_space,
+    maybe_space,
+
+    pub fn format(
+        self: @This(),
+        comptime fmt: []const u8,
+        _: std.fmt.FormatOptions,
+        w: anytype,
+    ) @TypeOf(w).Error!void {
+        if (fmt.len != 0)
+            @compileError("invalid format string '" ++ fmt ++ "' for type '" ++
+                @typeName(@This()) ++ "'");
+        comptime assert(fmt.len == 0);
+        switch (self) {
+            .no_space => {},
+            .maybe_space => try w.writeByte(' '),
+        }
+    }
+};
+fn renderTypeName(
+    mod: *Module,
+    w: anytype,
+    idx: CType.Index,
+    cty: CType,
+    attributes: []const u8,
+) !void {
+    switch (cty.tag()) {
+        else => unreachable,
+
+        .fwd_anon_struct,
+        .fwd_anon_union,
+        => |tag| try w.print("{s} {s}anon__lazy_{d}", .{
+            @tagName(tag)["fwd_anon_".len..],
+            attributes,
+            idx,
+        }),
+
+        .fwd_struct,
+        .fwd_union,
+        => |tag| {
+            const owner_decl = cty.cast(CType.Payload.FwdDecl).?.data;
+            try w.print("{s} {s}{}__{d}", .{
+                @tagName(tag)["fwd_".len..],
+                attributes,
+                fmtIdent(mem.span(mod.declPtr(owner_decl).name)),
+                @enumToInt(owner_decl),
+            });
+        },
     }
 }
+fn renderTypePrefix(
+    decl: Decl.OptionalIndex,
+    store: CType.Store.Set,
+    mod: *Module,
+    w: anytype,
+    idx: CType.Index,
+    parent_fix: CTypeFix,
+    qualifiers: CQualifiers,
+) @TypeOf(w).Error!RenderCTypeTrailing {
+    var trailing = RenderCTypeTrailing.maybe_space;
+
+    const cty = store.indexToCType(idx);
+    switch (cty.tag()) {
+        .void,
+        .char,
+        .@"signed char",
+        .short,
+        .int,
+        .long,
+        .@"long long",
+        ._Bool,
+        .@"unsigned char",
+        .@"unsigned short",
+        .@"unsigned int",
+        .@"unsigned long",
+        .@"unsigned long long",
+        .float,
+        .double,
+        .@"long double",
+        .bool,
+        .size_t,
+        .ptrdiff_t,
+        .uint8_t,
+        .int8_t,
+        .uint16_t,
+        .int16_t,
+        .uint32_t,
+        .int32_t,
+        .uint64_t,
+        .int64_t,
+        .uintptr_t,
+        .intptr_t,
+        .zig_u128,
+        .zig_i128,
+        .zig_f16,
+        .zig_f32,
+        .zig_f64,
+        .zig_f80,
+        .zig_f128,
+        .zig_c_longdouble,
+        => |tag| try w.writeAll(@tagName(tag)),
+
+        .pointer,
+        .pointer_const,
+        .pointer_volatile,
+        .pointer_const_volatile,
+        => |tag| {
+            const child_idx = cty.cast(CType.Payload.Child).?.data;
+            const child_trailing = try renderTypePrefix(
+                decl,
+                store,
+                mod,
+                w,
+                child_idx,
+                .prefix,
+                CQualifiers.init(.{ .@"const" = switch (tag) {
+                    .pointer, .pointer_volatile => false,
+                    .pointer_const, .pointer_const_volatile => true,
+                    else => unreachable,
+                }, .@"volatile" = switch (tag) {
+                    .pointer, .pointer_const => false,
+                    .pointer_volatile, .pointer_const_volatile => true,
+                    else => unreachable,
+                } }),
+            );
+            try w.print("{}*", .{child_trailing});
+            trailing = .no_space;
+        },
+
+        .array,
+        .vector,
+        => {
+            const child_idx = cty.cast(CType.Payload.Sequence).?.data.elem_type;
+            const child_trailing = try renderTypePrefix(
+                decl,
+                store,
+                mod,
+                w,
+                child_idx,
+                .suffix,
+                qualifiers,
+            );
+            switch (parent_fix) {
+                .prefix => {
+                    try w.print("{}(", .{child_trailing});
+                    return .no_space;
+                },
+                .suffix => return child_trailing,
+            }
+        },
+
+        .fwd_anon_struct,
+        .fwd_anon_union,
+        => if (decl.unwrap()) |decl_index|
+            try w.print("anon__{d}_{d}", .{ @enumToInt(decl_index), idx })
+        else
+            try renderTypeName(mod, w, idx, cty, ""),
+
+        .fwd_struct,
+        .fwd_union,
+        => try renderTypeName(mod, w, idx, cty, ""),
+
+        .unnamed_struct,
+        .unnamed_union,
+        .packed_unnamed_struct,
+        .packed_unnamed_union,
+        => |tag| {
+            try w.print("{s} {s}", .{
+                @tagName(tag)["unnamed_".len..],
+                if (cty.isPacked()) "zig_packed(" else "",
+            });
+            try renderAggregateFields(mod, w, store, cty, 1);
+            if (cty.isPacked()) try w.writeByte(')');
+        },
+
+        .anon_struct,
+        .anon_union,
+        .@"struct",
+        .@"union",
+        .packed_struct,
+        .packed_union,
+        => return renderTypePrefix(
+            decl,
+            store,
+            mod,
+            w,
+            cty.cast(CType.Payload.Aggregate).?.data.fwd_decl,
+            parent_fix,
+            qualifiers,
+        ),
+
+        .function,
+        .varargs_function,
+        => {
+            const child_trailing = try renderTypePrefix(
+                decl,
+                store,
+                mod,
+                w,
+                cty.cast(CType.Payload.Function).?.data.return_type,
+                .suffix,
+                .{},
+            );
+            switch (parent_fix) {
+                .prefix => {
+                    try w.print("{}(", .{child_trailing});
+                    return .no_space;
+                },
+                .suffix => return child_trailing,
+            }
+        },
+    }
+
+    var qualifier_it = qualifiers.iterator();
+    while (qualifier_it.next()) |qualifier| {
+        try w.print("{}{s}", .{ trailing, @tagName(qualifier) });
+        trailing = .maybe_space;
+    }
+
+    return trailing;
+}
+fn renderTypeSuffix(
+    decl: Decl.OptionalIndex,
+    store: CType.Store.Set,
+    mod: *Module,
+    w: anytype,
+    idx: CType.Index,
+    parent_fix: CTypeFix,
+    qualifiers: CQualifiers,
+) @TypeOf(w).Error!void {
+    const cty = store.indexToCType(idx);
+    switch (cty.tag()) {
+        .void,
+        .char,
+        .@"signed char",
+        .short,
+        .int,
+        .long,
+        .@"long long",
+        ._Bool,
+        .@"unsigned char",
+        .@"unsigned short",
+        .@"unsigned int",
+        .@"unsigned long",
+        .@"unsigned long long",
+        .float,
+        .double,
+        .@"long double",
+        .bool,
+        .size_t,
+        .ptrdiff_t,
+        .uint8_t,
+        .int8_t,
+        .uint16_t,
+        .int16_t,
+        .uint32_t,
+        .int32_t,
+        .uint64_t,
+        .int64_t,
+        .uintptr_t,
+        .intptr_t,
+        .zig_u128,
+        .zig_i128,
+        .zig_f16,
+        .zig_f32,
+        .zig_f64,
+        .zig_f80,
+        .zig_f128,
+        .zig_c_longdouble,
+        => {},
+
+        .pointer,
+        .pointer_const,
+        .pointer_volatile,
+        .pointer_const_volatile,
+        => try renderTypeSuffix(
+            decl,
+            store,
+            mod,
+            w,
+            cty.cast(CType.Payload.Child).?.data,
+            .prefix,
+            .{},
+        ),
+
+        .array,
+        .vector,
+        => {
+            switch (parent_fix) {
+                .prefix => try w.writeByte(')'),
+                .suffix => {},
+            }
+
+            try w.print("[{}]", .{cty.cast(CType.Payload.Sequence).?.data.len});
+            try renderTypeSuffix(
+                decl,
+                store,
+                mod,
+                w,
+                cty.cast(CType.Payload.Sequence).?.data.elem_type,
+                .suffix,
+                .{},
+            );
+        },
+
+        .fwd_anon_struct,
+        .fwd_anon_union,
+        .fwd_struct,
+        .fwd_union,
+        .unnamed_struct,
+        .unnamed_union,
+        .packed_unnamed_struct,
+        .packed_unnamed_union,
+        .anon_struct,
+        .anon_union,
+        .@"struct",
+        .@"union",
+        .packed_struct,
+        .packed_union,
+        => {},
+
+        .function,
+        .varargs_function,
+        => |tag| {
+            switch (parent_fix) {
+                .prefix => try w.writeByte(')'),
+                .suffix => {},
+            }
+
+            const data = cty.cast(CType.Payload.Function).?.data;
+
+            try w.writeByte('(');
+            var need_comma = false;
+            for (data.param_types, 0..) |param_type, param_i| {
+                if (need_comma) try w.writeAll(", ");
+                need_comma = true;
+                const trailing =
+                    try renderTypePrefix(decl, store, mod, w, param_type, .suffix, qualifiers);
+                if (qualifiers.contains(.@"const")) try w.print("{}a{d}", .{ trailing, param_i });
+                try renderTypeSuffix(decl, store, mod, w, param_type, .suffix, .{});
+            }
+            switch (tag) {
+                .function => {},
+                .varargs_function => {
+                    if (need_comma) try w.writeAll(", ");
+                    need_comma = true;
+                    try w.writeAll("...");
+                },
+                else => unreachable,
+            }
+            if (!need_comma) try w.writeAll("void");
+            try w.writeByte(')');
+
+            try renderTypeSuffix(decl, store, mod, w, data.return_type, .suffix, .{});
+        },
+    }
+}
+fn renderAggregateFields(
+    mod: *Module,
+    writer: anytype,
+    store: CType.Store.Set,
+    cty: CType,
+    indent: usize,
+) !void {
+    try writer.writeAll("{\n");
+    const fields = cty.fields();
+    for (fields) |field| {
+        try writer.writeByteNTimes(' ', indent + 1);
+        switch (std.math.order(field.alignas.@"align", field.alignas.abi)) {
+            .lt => try writer.print("zig_under_align({}) ", .{field.alignas.getAlign()}),
+            .eq => {},
+            .gt => try writer.print("zig_align({}) ", .{field.alignas.getAlign()}),
+        }
+        const trailing = try renderTypePrefix(.none, store, mod, writer, field.type, .suffix, .{});
+        try writer.print("{}{ }", .{ trailing, fmtIdent(mem.span(field.name)) });
+        try renderTypeSuffix(.none, store, mod, writer, field.type, .suffix, .{});
+        try writer.writeAll(";\n");
+    }
+    try writer.writeByteNTimes(' ', indent);
+    try writer.writeByte('}');
+}
+
+pub fn genTypeDecl(
+    mod: *Module,
+    writer: anytype,
+    global_store: CType.Store.Set,
+    global_idx: CType.Index,
+    decl: Decl.OptionalIndex,
+    decl_store: CType.Store.Set,
+    decl_idx: CType.Index,
+    found_existing: bool,
+) !void {
+    const global_cty = global_store.indexToCType(global_idx);
+    switch (global_cty.tag()) {
+        .fwd_anon_struct => if (decl != .none) {
+            try writer.writeAll("typedef ");
+            _ = try renderTypePrefix(.none, global_store, mod, writer, global_idx, .suffix, .{});
+            try writer.writeByte(' ');
+            _ = try renderTypePrefix(decl, decl_store, mod, writer, decl_idx, .suffix, .{});
+            try writer.writeAll(";\n");
+        },
+
+        .fwd_struct,
+        .fwd_union,
+        .anon_struct,
+        .anon_union,
+        .@"struct",
+        .@"union",
+        .packed_struct,
+        .packed_union,
+        => |tag| if (!found_existing) {
+            switch (tag) {
+                .fwd_struct,
+                .fwd_union,
+                => {
+                    const owner_decl = global_cty.cast(CType.Payload.FwdDecl).?.data;
+                    _ = try renderTypePrefix(.none, global_store, mod, writer, global_idx, .suffix, .{});
+                    try writer.writeAll("; // ");
+                    try mod.declPtr(owner_decl).renderFullyQualifiedName(mod, writer);
+                    try writer.writeByte('\n');
+                },
+
+                .anon_struct,
+                .anon_union,
+                .@"struct",
+                .@"union",
+                .packed_struct,
+                .packed_union,
+                => {
+                    const fwd_idx = global_cty.cast(CType.Payload.Aggregate).?.data.fwd_decl;
+                    try renderTypeName(
+                        mod,
+                        writer,
+                        fwd_idx,
+                        global_store.indexToCType(fwd_idx),
+                        if (global_cty.isPacked()) "zig_packed(" else "",
+                    );
+                    try writer.writeByte(' ');
+                    try renderAggregateFields(mod, writer, global_store, global_cty, 0);
+                    if (global_cty.isPacked()) try writer.writeByte(')');
+                    try writer.writeAll(";\n");
+                },
+
+                else => unreachable,
+            }
+        },
+
+        else => {},
+    }
+}
+
+pub fn genGlobalAsm(mod: *Module, writer: anytype) !void {
+    var it = mod.global_assembly.valueIterator();
+    while (it.next()) |asm_source| try writer.print("__asm({s});\n", .{fmtStringLiteral(asm_source.*, null)});
+}
 
 pub fn genErrDecls(o: *Object) !void {
     const writer = o.writer();
@@ -2690,26 +2411,24 @@ pub fn genErrDecls(o: *Object) !void {
     o.indent_writer.popIndent();
     try writer.writeAll("};\n");
 
-    const name_prefix = "zig_errorName";
-    const name_buf = try o.dg.gpa.alloc(u8, name_prefix.len + "_".len + max_name_len + 1);
+    const array_identifier = "zig_errorName";
+    const name_prefix = array_identifier ++ "_";
+    const name_buf = try o.dg.gpa.alloc(u8, name_prefix.len + max_name_len);
     defer o.dg.gpa.free(name_buf);
 
-    std.mem.copy(u8, name_buf, name_prefix ++ "_");
+    std.mem.copy(u8, name_buf, name_prefix);
     for (o.dg.module.error_name_list.items) |name| {
-        std.mem.copy(u8, name_buf[name_prefix.len + "_".len ..], name);
-        name_buf[name_prefix.len + "_".len + name.len] = 0;
-
-        const identifier = name_buf[0 .. name_prefix.len + "_".len + name.len :0];
-        const name_z = identifier[name_prefix.len + "_".len ..];
+        std.mem.copy(u8, name_buf[name_prefix.len..], name);
+        const identifier = name_buf[0 .. name_prefix.len + name.len];
 
         var name_ty_pl = Type.Payload.Len{ .base = .{ .tag = .array_u8_sentinel_0 }, .data = name.len };
         const name_ty = Type.initPayload(&name_ty_pl.base);
 
-        var name_pl = Value.Payload.Bytes{ .base = .{ .tag = .bytes }, .data = name_z };
+        var name_pl = Value.Payload.Bytes{ .base = .{ .tag = .bytes }, .data = name };
         const name_val = Value.initPayload(&name_pl.base);
 
         try writer.writeAll("static ");
-        try o.dg.renderTypeAndName(writer, name_ty, .{ .identifier = identifier }, .Const, 0, .Complete);
+        try o.dg.renderTypeAndName(writer, name_ty, .{ .identifier = identifier }, Const, 0, .complete);
         try writer.writeAll(" = ");
         try o.dg.renderValue(writer, name_ty, name_val, .StaticInitializer);
         try writer.writeAll(";\n");
@@ -2722,7 +2441,7 @@ pub fn genErrDecls(o: *Object) !void {
     const name_array_ty = Type.initPayload(&name_array_ty_pl.base);
 
     try writer.writeAll("static ");
-    try o.dg.renderTypeAndName(writer, name_array_ty, .{ .identifier = name_prefix }, .Const, 0, .Complete);
+    try o.dg.renderTypeAndName(writer, name_array_ty, .{ .identifier = array_identifier }, Const, 0, .complete);
     try writer.writeAll(" = {");
     for (o.dg.module.error_name_list.items, 0..) |name, value| {
         if (value != 0) try writer.writeByte(',');
@@ -2730,7 +2449,7 @@ pub fn genErrDecls(o: *Object) !void {
         var len_pl = Value.Payload.U64{ .base = .{ .tag = .int_u64 }, .data = name.len };
         const len_val = Value.initPayload(&len_pl.base);
 
-        try writer.print("{{" ++ name_prefix ++ "_{}, {}}}", .{
+        try writer.print("{{" ++ name_prefix ++ "{}, {}}}", .{
             fmtIdent(name), try o.dg.fmtIntLiteral(Type.usize, len_val),
         });
     }
@@ -2742,14 +2461,95 @@ fn genExports(o: *Object) !void {
     defer tracy.end();
 
     const fwd_decl_writer = o.dg.fwd_decl.writer();
-    if (o.dg.module.decl_exports.get(o.dg.decl_index)) |exports| for (exports.items[1..], 0..) |@"export", i| {
-        try fwd_decl_writer.writeAll("zig_export(");
-        try o.dg.renderFunctionSignature(fwd_decl_writer, .Forward, @intCast(u32, 1 + i));
-        try fwd_decl_writer.print(", {s}, {s});\n", .{
-            fmtStringLiteral(exports.items[0].options.name),
-            fmtStringLiteral(@"export".options.name),
-        });
-    };
+    if (o.dg.module.decl_exports.get(o.dg.decl_index.unwrap().?)) |exports| {
+        for (exports.items[1..], 1..) |@"export", i| {
+            try fwd_decl_writer.writeAll("zig_export(");
+            try o.dg.renderFunctionSignature(fwd_decl_writer, o.dg.decl_index.unwrap().?, .forward, .{ .export_index = @intCast(u32, i) });
+            try fwd_decl_writer.print(", {s}, {s});\n", .{
+                fmtStringLiteral(exports.items[0].options.name, null),
+                fmtStringLiteral(@"export".options.name, null),
+            });
+        }
+    }
+}
+
+pub fn genLazyFn(o: *Object, lazy_fn: LazyFnMap.Entry) !void {
+    const w = o.writer();
+    const key = lazy_fn.key_ptr.*;
+    const val = lazy_fn.value_ptr;
+    const fn_name = val.fn_name;
+    switch (key) {
+        .tag_name => {
+            const enum_ty = val.data.tag_name;
+
+            const name_slice_ty = Type.initTag(.const_slice_u8_sentinel_0);
+
+            try w.writeAll("static ");
+            try o.dg.renderType(w, name_slice_ty);
+            try w.writeByte(' ');
+            try w.writeAll(fn_name);
+            try w.writeByte('(');
+            try o.dg.renderTypeAndName(w, enum_ty, .{ .identifier = "tag" }, Const, 0, .complete);
+            try w.writeAll(") {\n switch (tag) {\n");
+            for (enum_ty.enumFields().keys(), 0..) |name, index| {
+                var tag_pl: Value.Payload.U32 = .{
+                    .base = .{ .tag = .enum_field_index },
+                    .data = @intCast(u32, index),
+                };
+                const tag_val = Value.initPayload(&tag_pl.base);
+
+                var int_pl: Value.Payload.U64 = undefined;
+                const int_val = tag_val.enumToInt(enum_ty, &int_pl);
+
+                var name_ty_pl = Type.Payload.Len{ .base = .{ .tag = .array_u8_sentinel_0 }, .data = name.len };
+                const name_ty = Type.initPayload(&name_ty_pl.base);
+
+                var name_pl = Value.Payload.Bytes{ .base = .{ .tag = .bytes }, .data = name };
+                const name_val = Value.initPayload(&name_pl.base);
+
+                var len_pl = Value.Payload.U64{ .base = .{ .tag = .int_u64 }, .data = name.len };
+                const len_val = Value.initPayload(&len_pl.base);
+
+                try w.print("  case {}: {{\n   static ", .{try o.dg.fmtIntLiteral(enum_ty, int_val)});
+                try o.dg.renderTypeAndName(w, name_ty, .{ .identifier = "name" }, Const, 0, .complete);
+                try w.writeAll(" = ");
+                try o.dg.renderValue(w, name_ty, name_val, .Initializer);
+                try w.writeAll(";\n   return (");
+                try o.dg.renderType(w, name_slice_ty);
+                try w.print("){{{}, {}}};\n", .{
+                    fmtIdent("name"), try o.dg.fmtIntLiteral(Type.usize, len_val),
+                });
+
+                try w.writeAll("  }\n");
+            }
+            try w.writeAll(" }\n while (");
+            try o.dg.renderValue(w, Type.bool, Value.true, .Other);
+            try w.writeAll(") ");
+            _ = try airBreakpoint(w);
+            try w.writeAll("}\n");
+        },
+        .never_tail, .never_inline => |fn_decl_index| {
+            const fn_decl = o.dg.module.declPtr(fn_decl_index);
+            const fn_cty = try o.dg.typeToCType(fn_decl.ty, .complete);
+            const fn_info = fn_cty.cast(CType.Payload.Function).?.data;
+
+            const fwd_decl_writer = o.dg.fwd_decl.writer();
+            try fwd_decl_writer.print("static zig_{s} ", .{@tagName(key)});
+            try o.dg.renderFunctionSignature(fwd_decl_writer, fn_decl_index, .forward, .{ .string = fn_name });
+            try fwd_decl_writer.writeAll(";\n");
+
+            try w.print("static zig_{s} ", .{@tagName(key)});
+            try o.dg.renderFunctionSignature(w, fn_decl_index, .complete, .{ .string = fn_name });
+            try w.writeAll(" {\n return ");
+            try o.dg.renderDeclName(w, fn_decl_index, 0);
+            try w.writeByte('(');
+            for (0..fn_info.param_types.len) |arg| {
+                if (arg > 0) try w.writeAll(", ");
+                try o.dg.writeCValue(w, .{ .arg = arg });
+            }
+            try w.writeAll(");\n}\n");
+        },
+    }
 }
 
 pub fn genFunc(f: *Function) !void {
@@ -2758,9 +2558,10 @@ pub fn genFunc(f: *Function) !void {
 
     const o = &f.object;
     const gpa = o.dg.gpa;
+    const decl_index = o.dg.decl_index.unwrap().?;
     const tv: TypedValue = .{
-        .ty = o.dg.decl.ty,
-        .val = o.dg.decl.val,
+        .ty = o.dg.decl.?.ty,
+        .val = o.dg.decl.?.val,
     };
 
     o.code_header = std.ArrayList(u8).init(gpa);
@@ -2769,13 +2570,13 @@ pub fn genFunc(f: *Function) !void {
     const is_global = o.dg.declIsGlobal(tv);
     const fwd_decl_writer = o.dg.fwd_decl.writer();
     try fwd_decl_writer.writeAll(if (is_global) "zig_extern " else "static ");
-    try o.dg.renderFunctionSignature(fwd_decl_writer, .Forward, 0);
+    try o.dg.renderFunctionSignature(fwd_decl_writer, decl_index, .forward, .{ .export_index = 0 });
     try fwd_decl_writer.writeAll(";\n");
     try genExports(o);
 
     try o.indent_writer.insertNewline();
     if (!is_global) try o.writer().writeAll("static ");
-    try o.dg.renderFunctionSignature(o.writer(), .Complete, 0);
+    try o.dg.renderFunctionSignature(o.writer(), decl_index, .complete, .{ .export_index = 0 });
     try o.writer().writeByte(' ');
 
     // In case we need to use the header, populate it with a copy of the function
@@ -2799,41 +2600,31 @@ pub fn genFunc(f: *Function) !void {
     // missing. These are added now to complete the map. Then we can sort by
     // alignment, descending.
     const free_locals = f.getFreeLocals();
-    const values = f.allocs.values();
-    for (f.allocs.keys(), 0..) |local_index, i| {
-        if (values[i]) continue; // static
+    for (f.allocs.keys(), f.allocs.values()) |local_index, value| {
+        if (value) continue; // static
         const local = f.locals.items[local_index];
         log.debug("inserting local {d} into free_locals", .{local_index});
-        const gop = try free_locals.getOrPutContext(gpa, local.ty, f.tyHashCtx());
+        const gop = try free_locals.getOrPut(gpa, local.getType());
         if (!gop.found_existing) gop.value_ptr.* = .{};
-        try gop.value_ptr.append(gpa, local_index);
+        try gop.value_ptr.putNoClobber(gpa, local_index, {});
     }
 
     const SortContext = struct {
-        target: std.Target,
-        keys: []const Type,
+        keys: []const LocalType,
 
-        pub fn lessThan(ctx: @This(), a_index: usize, b_index: usize) bool {
-            const a_ty = ctx.keys[a_index];
-            const b_ty = ctx.keys[b_index];
-            return b_ty.abiAlignment(ctx.target) < a_ty.abiAlignment(ctx.target);
+        pub fn lessThan(ctx: @This(), lhs_index: usize, rhs_index: usize) bool {
+            const lhs_ty = ctx.keys[lhs_index];
+            const rhs_ty = ctx.keys[rhs_index];
+            return lhs_ty.alignas.getAlign() > rhs_ty.alignas.getAlign();
         }
     };
-    const target = o.dg.module.getTarget();
-    free_locals.sort(SortContext{ .target = target, .keys = free_locals.keys() });
+    free_locals.sort(SortContext{ .keys = free_locals.keys() });
 
     const w = o.code_header.writer();
     for (free_locals.values()) |list| {
-        for (list.items) |local_index| {
+        for (list.keys()) |local_index| {
             const local = f.locals.items[local_index];
-            try o.dg.renderTypeAndName(
-                w,
-                local.ty,
-                .{ .local = local_index },
-                .Mut,
-                local.alignment,
-                .Complete,
-            );
+            try o.dg.renderCTypeAndName(w, local.cty_idx, .{ .local = local_index }, .{}, local.alignas);
             try w.writeAll(";\n ");
         }
     }
@@ -2850,15 +2641,15 @@ pub fn genDecl(o: *Object) !void {
     const tracy = trace(@src());
     defer tracy.end();
 
-    const tv: TypedValue = .{
-        .ty = o.dg.decl.ty,
-        .val = o.dg.decl.val,
-    };
+    const decl = o.dg.decl.?;
+    const decl_c_value = .{ .decl = o.dg.decl_index.unwrap().? };
+    const tv: TypedValue = .{ .ty = decl.ty, .val = decl.val };
+
     if (!tv.ty.isFnOrHasRuntimeBitsIgnoreComptime()) return;
     if (tv.val.tag() == .extern_fn) {
         const fwd_decl_writer = o.dg.fwd_decl.writer();
         try fwd_decl_writer.writeAll("zig_extern ");
-        try o.dg.renderFunctionSignature(fwd_decl_writer, .Forward, 0);
+        try o.dg.renderFunctionSignature(fwd_decl_writer, decl_c_value.decl, .forward, .{ .export_index = 0 });
         try fwd_decl_writer.writeAll(";\n");
         try genExports(o);
     } else if (tv.val.castTag(.variable)) |var_payload| {
@@ -2867,11 +2658,9 @@ pub fn genDecl(o: *Object) !void {
         const is_global = o.dg.declIsGlobal(tv) or variable.is_extern;
         const fwd_decl_writer = o.dg.fwd_decl.writer();
 
-        const decl_c_value = CValue{ .decl = o.dg.decl_index };
-
         try fwd_decl_writer.writeAll(if (is_global) "zig_extern " else "static ");
         if (variable.is_threadlocal) try fwd_decl_writer.writeAll("zig_threadlocal ");
-        try o.dg.renderTypeAndName(fwd_decl_writer, o.dg.decl.ty, decl_c_value, .Mut, o.dg.decl.@"align", .Complete);
+        try o.dg.renderTypeAndName(fwd_decl_writer, decl.ty, decl_c_value, .{}, decl.@"align", .complete);
         try fwd_decl_writer.writeAll(";\n");
         try genExports(o);
 
@@ -2880,27 +2669,26 @@ pub fn genDecl(o: *Object) !void {
         const w = o.writer();
         if (!is_global) try w.writeAll("static ");
         if (variable.is_threadlocal) try w.writeAll("zig_threadlocal ");
-        if (o.dg.decl.@"linksection") |section| try w.print("zig_linksection(\"{s}\", ", .{section});
-        try o.dg.renderTypeAndName(w, o.dg.decl.ty, decl_c_value, .Mut, o.dg.decl.@"align", .Complete);
-        if (o.dg.decl.@"linksection" != null) try w.writeAll(", read, write)");
+        if (decl.@"linksection") |section| try w.print("zig_linksection(\"{s}\", ", .{section});
+        try o.dg.renderTypeAndName(w, tv.ty, decl_c_value, .{}, decl.@"align", .complete);
+        if (decl.@"linksection" != null) try w.writeAll(", read, write)");
         try w.writeAll(" = ");
         try o.dg.renderValue(w, tv.ty, variable.init, .StaticInitializer);
         try w.writeByte(';');
         try o.indent_writer.insertNewline();
     } else {
-        const is_global = o.dg.module.decl_exports.contains(o.dg.decl_index);
+        const is_global = o.dg.module.decl_exports.contains(decl_c_value.decl);
         const fwd_decl_writer = o.dg.fwd_decl.writer();
-        const decl_c_value: CValue = .{ .decl = o.dg.decl_index };
 
         try fwd_decl_writer.writeAll(if (is_global) "zig_extern " else "static ");
-        try o.dg.renderTypeAndName(fwd_decl_writer, tv.ty, decl_c_value, .Const, o.dg.decl.@"align", .Complete);
+        try o.dg.renderTypeAndName(fwd_decl_writer, tv.ty, decl_c_value, Const, decl.@"align", .complete);
         try fwd_decl_writer.writeAll(";\n");
 
         const w = o.writer();
         if (!is_global) try w.writeAll("static ");
-        if (o.dg.decl.@"linksection") |section| try w.print("zig_linksection(\"{s}\", ", .{section});
-        try o.dg.renderTypeAndName(w, tv.ty, decl_c_value, .Const, o.dg.decl.@"align", .Complete);
-        if (o.dg.decl.@"linksection" != null) try w.writeAll(", read)");
+        if (decl.@"linksection") |section| try w.print("zig_linksection(\"{s}\", ", .{section});
+        try o.dg.renderTypeAndName(w, tv.ty, decl_c_value, Const, decl.@"align", .complete);
+        if (decl.@"linksection" != null) try w.writeAll(", read)");
         try w.writeAll(" = ");
         try o.dg.renderValue(w, tv.ty, tv.val, .StaticInitializer);
         try w.writeAll(";\n");
@@ -2912,8 +2700,8 @@ pub fn genHeader(dg: *DeclGen) error{ AnalysisFail, OutOfMemory }!void {
     defer tracy.end();
 
     const tv: TypedValue = .{
-        .ty = dg.decl.ty,
-        .val = dg.decl.val,
+        .ty = dg.decl.?.ty,
+        .val = dg.decl.?.val,
     };
     const writer = dg.fwd_decl.writer();
 
@@ -2922,7 +2710,7 @@ pub fn genHeader(dg: *DeclGen) error{ AnalysisFail, OutOfMemory }!void {
             const is_global = dg.declIsGlobal(tv);
             if (is_global) {
                 try writer.writeAll("zig_extern ");
-                try dg.renderFunctionSignature(writer, .Complete, 0);
+                try dg.renderFunctionSignature(writer, dg.decl_index.unwrap().?, .complete, .{ .export_index = 0 });
                 try dg.fwd_decl.appendSlice(";\n");
             }
         },
@@ -2951,7 +2739,7 @@ fn genBodyInner(f: *Function, body: []const Air.Inst.Index) error{ AnalysisFail,
             // zig fmt: off
             .constant => unreachable, // excluded from function bodies
             .const_ty => unreachable, // excluded from function bodies
-            .arg      => airArg(f),
+            .arg      => try airArg(f, inst),
 
             .breakpoint => try airBreakpoint(f.object.writer()),
             .ret_addr   => try airRetAddr(f, inst),
@@ -3112,10 +2900,10 @@ fn genBodyInner(f: *Function, body: []const Air.Inst.Index) error{ AnalysisFail,
 
             .dbg_block_begin,
             .dbg_block_end,
-            => CValue{ .none = {} },
+            => .none,
 
             .call              => try airCall(f, inst, .auto),
-            .call_always_tail  => try airCall(f, inst, .always_tail),
+            .call_always_tail  => .none,
             .call_never_tail   => try airCall(f, inst, .never_tail),
             .call_never_inline => try airCall(f, inst, .never_inline),
 
@@ -3194,19 +2982,20 @@ fn genBodyInner(f: *Function, body: []const Air.Inst.Index) error{ AnalysisFail,
             .error_set_has_value => return f.fail("TODO: C backend: implement error_set_has_value", .{}),
             .vector_store_elem => return f.fail("TODO: C backend: implement vector_store_elem", .{}),
 
-            .c_va_arg => return f.fail("TODO implement c_va_arg", .{}),
-            .c_va_copy => return f.fail("TODO implement c_va_copy", .{}),
-            .c_va_end => return f.fail("TODO implement c_va_end", .{}),
-            .c_va_start => return f.fail("TODO implement c_va_start", .{}),
+            .c_va_start => try airCVaStart(f, inst),
+            .c_va_arg => try airCVaArg(f, inst),
+            .c_va_end => try airCVaEnd(f, inst),
+            .c_va_copy => try airCVaCopy(f, inst),
             // zig fmt: on
         };
-        if (result_value == .local) {
-            log.debug("map %{d} to t{d}", .{ inst, result_value.local });
-        }
-        switch (result_value) {
-            .none => {},
-            else => try f.value_map.putNoClobber(Air.indexToRef(inst), result_value),
+        if (result_value == .new_local) {
+            log.debug("map %{d} to t{d}", .{ inst, result_value.new_local });
         }
+        try f.value_map.putNoClobber(Air.indexToRef(inst), switch (result_value) {
+            .none => continue,
+            .new_local => |i| .{ .local = i },
+            else => result_value,
+        });
     }
 }
 
@@ -3215,7 +3004,7 @@ fn airSliceField(f: *Function, inst: Air.Inst.Index, is_ptr: bool, field_name: [
 
     if (f.liveness.isUnused(inst)) {
         try reap(f, inst, &.{ty_op.operand});
-        return CValue.none;
+        return .none;
     }
 
     const inst_ty = f.air.typeOfIndex(inst);
@@ -3241,7 +3030,7 @@ fn airPtrElemVal(f: *Function, inst: Air.Inst.Index) !CValue {
         !inst_ty.hasRuntimeBitsIgnoreComptime())
     {
         try reap(f, inst, &.{ bin_op.lhs, bin_op.rhs });
-        return CValue.none;
+        return .none;
     }
 
     const ptr = try f.resolveInst(bin_op.lhs);
@@ -3267,7 +3056,7 @@ fn airPtrElemVal(f: *Function, inst: Air.Inst.Index) !CValue {
     try writer.writeByte(']');
     if (is_array) {
         try writer.writeAll(", sizeof(");
-        try f.renderTypecast(writer, inst_ty);
+        try f.renderType(writer, inst_ty);
         try writer.writeAll("))");
     }
     try writer.writeAll(";\n");
@@ -3280,9 +3069,10 @@ fn airPtrElemPtr(f: *Function, inst: Air.Inst.Index) !CValue {
 
     if (f.liveness.isUnused(inst)) {
         try reap(f, inst, &.{ bin_op.lhs, bin_op.rhs });
-        return CValue.none;
+        return .none;
     }
 
+    const inst_ty = f.air.typeOfIndex(inst);
     const ptr_ty = f.air.typeOf(bin_op.lhs);
     const child_ty = ptr_ty.childType();
 
@@ -3297,7 +3087,9 @@ fn airPtrElemPtr(f: *Function, inst: Air.Inst.Index) !CValue {
     const writer = f.object.writer();
     const local = try f.allocLocal(inst, f.air.typeOfIndex(inst));
     try f.writeCValue(writer, local, .Other);
-    try writer.writeAll(" = &(");
+    try writer.writeAll(" = (");
+    try f.renderType(writer, inst_ty);
+    try writer.writeAll(")&(");
     if (ptr_ty.ptrSize() == .One) {
         // It's a pointer to an array, so we need to de-reference.
         try f.writeCValueDeref(writer, ptr);
@@ -3318,7 +3110,7 @@ fn airSliceElemVal(f: *Function, inst: Air.Inst.Index) !CValue {
         !inst_ty.hasRuntimeBitsIgnoreComptime())
     {
         try reap(f, inst, &.{ bin_op.lhs, bin_op.rhs });
-        return CValue.none;
+        return .none;
     }
 
     const slice = try f.resolveInst(bin_op.lhs);
@@ -3344,7 +3136,7 @@ fn airSliceElemVal(f: *Function, inst: Air.Inst.Index) !CValue {
     try writer.writeByte(']');
     if (is_array) {
         try writer.writeAll(", sizeof(");
-        try f.renderTypecast(writer, inst_ty);
+        try f.renderType(writer, inst_ty);
         try writer.writeAll("))");
     }
     try writer.writeAll(";\n");
@@ -3357,7 +3149,7 @@ fn airSliceElemPtr(f: *Function, inst: Air.Inst.Index) !CValue {
 
     if (f.liveness.isUnused(inst)) {
         try reap(f, inst, &.{ bin_op.lhs, bin_op.rhs });
-        return CValue.none;
+        return .none;
     }
 
     const slice_ty = f.air.typeOf(bin_op.lhs);
@@ -3387,7 +3179,7 @@ fn airArrayElemVal(f: *Function, inst: Air.Inst.Index) !CValue {
     const inst_ty = f.air.typeOfIndex(inst);
     if (f.liveness.isUnused(inst) or !inst_ty.hasRuntimeBitsIgnoreComptime()) {
         try reap(f, inst, &.{ bin_op.lhs, bin_op.rhs });
-        return CValue.none;
+        return .none;
     }
 
     const array = try f.resolveInst(bin_op.lhs);
@@ -3413,7 +3205,7 @@ fn airArrayElemVal(f: *Function, inst: Air.Inst.Index) !CValue {
     try writer.writeByte(']');
     if (is_array) {
         try writer.writeAll(", sizeof(");
-        try f.renderTypecast(writer, inst_ty);
+        try f.renderType(writer, inst_ty);
         try writer.writeAll("))");
     }
     try writer.writeAll(";\n");
@@ -3425,16 +3217,19 @@ fn airAlloc(f: *Function, inst: Air.Inst.Index) !CValue {
 
     const elem_type = inst_ty.elemType();
     if (!elem_type.isFnOrHasRuntimeBitsIgnoreComptime()) {
-        return CValue{ .undef = inst_ty };
+        return .{ .undef = inst_ty };
     }
 
-    const mutability: Mutability = if (inst_ty.isConstPtr()) .Const else .Mut;
     const target = f.object.dg.module.getTarget();
-    const local = try f.allocAlignedLocal(elem_type, mutability, inst_ty.ptrAlignment(target));
-    log.debug("%{d}: allocated unfreeable t{d}", .{ inst, local.local });
+    const local = try f.allocAlignedLocal(
+        elem_type,
+        CQualifiers.init(.{ .@"const" = inst_ty.isConstPtr() }),
+        inst_ty.ptrAlignment(target),
+    );
+    log.debug("%{d}: allocated unfreeable t{d}", .{ inst, local.new_local });
     const gpa = f.object.dg.module.gpa;
-    try f.allocs.put(gpa, local.local, false);
-    return CValue{ .local_ref = local.local };
+    try f.allocs.put(gpa, local.new_local, false);
+    return .{ .local_ref = local.new_local };
 }
 
 fn airRetPtr(f: *Function, inst: Air.Inst.Index) !CValue {
@@ -3442,22 +3237,31 @@ fn airRetPtr(f: *Function, inst: Air.Inst.Index) !CValue {
 
     const elem_ty = inst_ty.elemType();
     if (!elem_ty.isFnOrHasRuntimeBitsIgnoreComptime()) {
-        return CValue{ .undef = inst_ty };
+        return .{ .undef = inst_ty };
     }
 
-    const mutability: Mutability = if (inst_ty.isConstPtr()) .Const else .Mut;
     const target = f.object.dg.module.getTarget();
-    const local = try f.allocAlignedLocal(elem_ty, mutability, inst_ty.ptrAlignment(target));
-    log.debug("%{d}: allocated unfreeable t{d}", .{ inst, local.local });
+    const local = try f.allocAlignedLocal(
+        elem_ty,
+        CQualifiers.init(.{ .@"const" = inst_ty.isConstPtr() }),
+        inst_ty.ptrAlignment(target),
+    );
+    log.debug("%{d}: allocated unfreeable t{d}", .{ inst, local.new_local });
     const gpa = f.object.dg.module.gpa;
-    try f.allocs.put(gpa, local.local, false);
-    return CValue{ .local_ref = local.local };
+    try f.allocs.put(gpa, local.new_local, false);
+    return .{ .local_ref = local.new_local };
 }
 
-fn airArg(f: *Function) CValue {
+fn airArg(f: *Function, inst: Air.Inst.Index) !CValue {
+    const inst_ty = f.air.typeOfIndex(inst);
+    const inst_cty = try f.typeToIndex(inst_ty, .parameter);
+
     const i = f.next_arg_index;
     f.next_arg_index += 1;
-    return .{ .arg = i };
+    return if (inst_cty != try f.typeToIndex(inst_ty, .complete))
+        .{ .arg_array = i }
+    else
+        .{ .arg = i };
 }
 
 fn airLoad(f: *Function, inst: Air.Inst.Index) !CValue {
@@ -3469,7 +3273,7 @@ fn airLoad(f: *Function, inst: Air.Inst.Index) !CValue {
         (!ptr_info.@"volatile" and f.liveness.isUnused(inst)))
     {
         try reap(f, inst, &.{ty_op.operand});
-        return CValue.none;
+        return .none;
     }
 
     const operand = try f.resolveInst(ty_op.operand);
@@ -3491,7 +3295,7 @@ fn airLoad(f: *Function, inst: Air.Inst.Index) !CValue {
         try writer.writeAll(", (const char *)");
         try f.writeCValue(writer, operand, .Other);
         try writer.writeAll(", sizeof(");
-        try f.renderTypecast(writer, src_ty);
+        try f.renderType(writer, src_ty);
         try writer.writeAll("))");
     } else if (ptr_info.host_size != 0) {
         var host_pl = Type.Payload.Bits{
@@ -3520,11 +3324,11 @@ fn airLoad(f: *Function, inst: Air.Inst.Index) !CValue {
 
         try f.writeCValue(writer, local, .Other);
         try writer.writeAll(" = (");
-        try f.renderTypecast(writer, src_ty);
+        try f.renderType(writer, src_ty);
         try writer.writeAll(")zig_wrap_");
         try f.object.dg.renderTypeForBuiltinFnName(writer, field_ty);
         try writer.writeAll("((");
-        try f.renderTypecast(writer, field_ty);
+        try f.renderType(writer, field_ty);
         try writer.writeByte(')');
         const cant_cast = host_ty.isInt() and host_ty.bitSize(target) > 64;
         if (cant_cast) {
@@ -3554,20 +3358,24 @@ fn airRet(f: *Function, inst: Air.Inst.Index, is_ptr: bool) !CValue {
     const un_op = f.air.instructions.items(.data)[inst].un_op;
     const writer = f.object.writer();
     const target = f.object.dg.module.getTarget();
+    const op_inst = Air.refToIndex(un_op);
     const op_ty = f.air.typeOf(un_op);
     const ret_ty = if (is_ptr) op_ty.childType() else op_ty;
     var lowered_ret_buf: LowerFnRetTyBuffer = undefined;
     const lowered_ret_ty = lowerFnRetTy(ret_ty, &lowered_ret_buf, target);
 
-    if (lowered_ret_ty.hasRuntimeBitsIgnoreComptime()) {
-        var deref = is_ptr;
+    if (op_inst != null and f.air.instructions.items(.tag)[op_inst.?] == .call_always_tail) {
+        try reap(f, inst, &.{un_op});
+        _ = try airCall(f, op_inst.?, .always_tail);
+    } else if (lowered_ret_ty.hasRuntimeBitsIgnoreComptime()) {
         const operand = try f.resolveInst(un_op);
         try reap(f, inst, &.{un_op});
+        var deref = is_ptr;
         const is_array = lowersToArray(ret_ty, target);
         const ret_val = if (is_array) ret_val: {
             const array_local = try f.allocLocal(inst, try lowered_ret_ty.copy(f.arena.allocator()));
             try writer.writeAll("memcpy(");
-            try f.writeCValueMember(writer, array_local, .{ .field = 0 });
+            try f.writeCValueMember(writer, array_local, .{ .identifier = "array" });
             try writer.writeAll(", ");
             if (deref)
                 try f.writeCValueDeref(writer, operand)
@@ -3575,7 +3383,7 @@ fn airRet(f: *Function, inst: Air.Inst.Index, is_ptr: bool) !CValue {
                 try f.writeCValue(writer, operand, .FunctionArgument);
             deref = false;
             try writer.writeAll(", sizeof(");
-            try f.renderTypecast(writer, ret_ty);
+            try f.renderType(writer, ret_ty);
             try writer.writeAll("));\n");
             break :ret_val array_local;
         } else operand;
@@ -3587,16 +3395,15 @@ fn airRet(f: *Function, inst: Air.Inst.Index, is_ptr: bool) !CValue {
             try f.writeCValue(writer, ret_val, .Other);
         try writer.writeAll(";\n");
         if (is_array) {
-            try freeLocal(f, inst, ret_val.local, 0);
+            try freeLocal(f, inst, ret_val.new_local, 0);
         }
     } else {
         try reap(f, inst, &.{un_op});
-        if (f.object.dg.decl.ty.fnCallingConvention() != .Naked) {
-            // Not even allowed to return void in a naked function.
+        // Not even allowed to return void in a naked function.
+        if (if (f.object.dg.decl) |decl| decl.ty.fnCallingConvention() != .Naked else true)
             try writer.writeAll("return;\n");
-        }
     }
-    return CValue.none;
+    return .none;
 }
 
 fn airIntCast(f: *Function, inst: Air.Inst.Index) !CValue {
@@ -3604,7 +3411,7 @@ fn airIntCast(f: *Function, inst: Air.Inst.Index) !CValue {
 
     if (f.liveness.isUnused(inst)) {
         try reap(f, inst, &.{ty_op.operand});
-        return CValue.none;
+        return .none;
     }
 
     const operand = try f.resolveInst(ty_op.operand);
@@ -3625,7 +3432,7 @@ fn airTrunc(f: *Function, inst: Air.Inst.Index) !CValue {
     const ty_op = f.air.instructions.items(.data)[inst].ty_op;
     if (f.liveness.isUnused(inst)) {
         try reap(f, inst, &.{ty_op.operand});
-        return CValue.none;
+        return .none;
     }
 
     const operand = try f.resolveInst(ty_op.operand);
@@ -3644,15 +3451,17 @@ fn airTrunc(f: *Function, inst: Air.Inst.Index) !CValue {
     try f.writeCValue(writer, local, .Other);
     try writer.writeAll(" = ");
 
+    if (dest_c_bits < 64) {
+        try writer.writeByte('(');
+        try f.renderType(writer, inst_ty);
+        try writer.writeByte(')');
+    }
+
     const needs_lo = operand_int_info.bits > 64 and dest_bits <= 64;
     if (needs_lo) {
         try writer.writeAll("zig_lo_");
         try f.object.dg.renderTypeForBuiltinFnName(writer, operand_ty);
         try writer.writeByte('(');
-    } else if (dest_c_bits <= 64) {
-        try writer.writeByte('(');
-        try f.renderTypecast(writer, inst_ty);
-        try writer.writeByte(')');
     }
 
     if (dest_bits >= 8 and std.math.isPowerOfTwo(dest_bits)) {
@@ -3712,7 +3521,7 @@ fn airBoolToInt(f: *Function, inst: Air.Inst.Index) !CValue {
     const un_op = f.air.instructions.items(.data)[inst].un_op;
     if (f.liveness.isUnused(inst)) {
         try reap(f, inst, &.{un_op});
-        return CValue.none;
+        return .none;
     }
     const operand = try f.resolveInst(un_op);
     try reap(f, inst, &.{un_op});
@@ -3732,10 +3541,10 @@ fn storeUndefined(f: *Function, lhs_child_ty: Type, dest_ptr: CValue) !CValue {
         try writer.writeAll("memset(");
         try f.writeCValue(writer, dest_ptr, .FunctionArgument);
         try writer.print(", {x}, sizeof(", .{try f.fmtIntLiteral(Type.u8, Value.undef)});
-        try f.renderTypecast(writer, lhs_child_ty);
+        try f.renderType(writer, lhs_child_ty);
         try writer.writeAll("));\n");
     }
-    return CValue.none;
+    return .none;
 }
 
 fn airStore(f: *Function, inst: Air.Inst.Index) !CValue {
@@ -3744,7 +3553,7 @@ fn airStore(f: *Function, inst: Air.Inst.Index) !CValue {
     const ptr_info = f.air.typeOf(bin_op.lhs).ptrInfo().data;
     if (!ptr_info.pointee_type.hasRuntimeBitsIgnoreComptime()) {
         try reap(f, inst, &.{ bin_op.lhs, bin_op.rhs });
-        return CValue.none;
+        return .none;
     }
 
     const ptr_val = try f.resolveInst(bin_op.lhs);
@@ -3793,10 +3602,10 @@ fn airStore(f: *Function, inst: Air.Inst.Index) !CValue {
         if (!is_array) try writer.writeByte('&');
         try f.writeCValue(writer, array_src, .FunctionArgument);
         try writer.writeAll(", sizeof(");
-        try f.renderTypecast(writer, src_ty);
+        try f.renderType(writer, src_ty);
         try writer.writeAll("))");
         if (src_val == .constant) {
-            try freeLocal(f, inst, array_src.local, 0);
+            try freeLocal(f, inst, array_src.new_local, 0);
         }
     } else if (ptr_info.host_size != 0) {
         const host_bits = ptr_info.host_size * 8;
@@ -3847,18 +3656,18 @@ fn airStore(f: *Function, inst: Air.Inst.Index) !CValue {
         const cant_cast = host_ty.isInt() and host_ty.bitSize(target) > 64;
         if (cant_cast) {
             if (src_ty.bitSize(target) > 64) return f.fail("TODO: C backend: implement casting between types > 64 bits", .{});
-            try writer.writeAll("zig_as_");
+            try writer.writeAll("zig_make_");
             try f.object.dg.renderTypeForBuiltinFnName(writer, host_ty);
             try writer.writeAll("(0, ");
         } else {
             try writer.writeByte('(');
-            try f.renderTypecast(writer, host_ty);
+            try f.renderType(writer, host_ty);
             try writer.writeByte(')');
         }
 
         if (src_ty.isPtrAtRuntime()) {
             try writer.writeByte('(');
-            try f.renderTypecast(writer, Type.usize);
+            try f.renderType(writer, Type.usize);
             try writer.writeByte(')');
         }
         try f.writeCValue(writer, src_val, .Other);
@@ -3870,7 +3679,7 @@ fn airStore(f: *Function, inst: Air.Inst.Index) !CValue {
         try f.writeCValue(writer, src_val, .Other);
     }
     try writer.writeAll(";\n");
-    return CValue.none;
+    return .none;
 }
 
 fn airOverflow(f: *Function, inst: Air.Inst.Index, operation: []const u8, info: BuiltinInfo) !CValue {
@@ -3879,7 +3688,7 @@ fn airOverflow(f: *Function, inst: Air.Inst.Index, operation: []const u8, info:
 
     if (f.liveness.isUnused(inst)) {
         try reap(f, inst, &.{ bin_op.lhs, bin_op.rhs });
-        return CValue.none;
+        return .none;
     }
 
     const lhs = try f.resolveInst(bin_op.lhs);
@@ -3935,7 +3744,7 @@ fn airNot(f: *Function, inst: Air.Inst.Index) !CValue {
 
     if (f.liveness.isUnused(inst)) {
         try reap(f, inst, &.{ty_op.operand});
-        return CValue.none;
+        return .none;
     }
 
     const op = try f.resolveInst(ty_op.operand);
@@ -3970,7 +3779,7 @@ fn airBinOp(
 
     try reap(f, inst, &.{ bin_op.lhs, bin_op.rhs });
 
-    if (f.liveness.isUnused(inst)) return CValue.none;
+    if (f.liveness.isUnused(inst)) return .none;
 
     const inst_ty = f.air.typeOfIndex(inst);
 
@@ -3993,7 +3802,7 @@ fn airCmpOp(f: *Function, inst: Air.Inst.Index, operator: []const u8, operation:
 
     if (f.liveness.isUnused(inst)) {
         try reap(f, inst, &.{ bin_op.lhs, bin_op.rhs });
-        return CValue.none;
+        return .none;
     }
 
     const operand_ty = f.air.typeOf(bin_op.lhs);
@@ -4033,7 +3842,7 @@ fn airEquality(
 
     if (f.liveness.isUnused(inst)) {
         try reap(f, inst, &.{ bin_op.lhs, bin_op.rhs });
-        return CValue.none;
+        return .none;
     }
 
     const operand_ty = f.air.typeOf(bin_op.lhs);
@@ -4089,7 +3898,7 @@ fn airCmpLtErrorsLen(f: *Function, inst: Air.Inst.Index) !CValue {
 
     if (f.liveness.isUnused(inst)) {
         try reap(f, inst, &.{un_op});
-        return CValue.none;
+        return .none;
     }
 
     const inst_ty = f.air.typeOfIndex(inst);
@@ -4110,7 +3919,7 @@ fn airPtrAddSub(f: *Function, inst: Air.Inst.Index, operator: u8) !CValue {
     const bin_op = f.air.extraData(Air.Bin, ty_pl.payload).data;
     if (f.liveness.isUnused(inst)) {
         try reap(f, inst, &.{ bin_op.lhs, bin_op.rhs });
-        return CValue.none;
+        return .none;
     }
 
     const lhs = try f.resolveInst(bin_op.lhs);
@@ -4118,32 +3927,31 @@ fn airPtrAddSub(f: *Function, inst: Air.Inst.Index, operator: u8) !CValue {
     try reap(f, inst, &.{ bin_op.lhs, bin_op.rhs });
 
     const inst_ty = f.air.typeOfIndex(inst);
-    const elem_ty = switch (inst_ty.ptrSize()) {
-        .One => blk: {
-            const array_ty = inst_ty.childType();
-            break :blk array_ty.childType();
-        },
-        else => inst_ty.childType(),
-    };
+    const elem_ty = inst_ty.elemType2();
 
-    // We must convert to and from integer types to prevent UB if the operation
-    // results in a NULL pointer, or if LHS is NULL. The operation is only UB
-    // if the result is NULL and then dereferenced.
     const local = try f.allocLocal(inst, inst_ty);
     const writer = f.object.writer();
     try f.writeCValue(writer, local, .Other);
-    try writer.writeAll(" = (");
-    try f.renderTypecast(writer, inst_ty);
-    try writer.writeAll(")(((uintptr_t)");
-    try f.writeCValue(writer, lhs, .Other);
-    try writer.writeAll(") ");
-    try writer.writeByte(operator);
-    try writer.writeAll(" (");
-    try f.writeCValue(writer, rhs, .Other);
-    try writer.writeAll("*sizeof(");
-    try f.renderTypecast(writer, elem_ty);
-    try writer.writeAll(")));\n");
+    try writer.writeAll(" = ");
+
+    if (elem_ty.hasRuntimeBitsIgnoreComptime()) {
+        // We must convert to and from integer types to prevent UB if the operation
+        // results in a NULL pointer, or if LHS is NULL. The operation is only UB
+        // if the result is NULL and then dereferenced.
+        try writer.writeByte('(');
+        try f.renderType(writer, inst_ty);
+        try writer.writeAll(")(((uintptr_t)");
+        try f.writeCValue(writer, lhs, .Other);
+        try writer.writeAll(") ");
+        try writer.writeByte(operator);
+        try writer.writeAll(" (");
+        try f.writeCValue(writer, rhs, .Other);
+        try writer.writeAll("*sizeof(");
+        try f.renderType(writer, elem_ty);
+        try writer.writeAll(")))");
+    } else try f.writeCValue(writer, lhs, .Initializer);
 
+    try writer.writeAll(";\n");
     return local;
 }
 
@@ -4152,7 +3960,7 @@ fn airMinMax(f: *Function, inst: Air.Inst.Index, operator: u8, operation: []cons
 
     if (f.liveness.isUnused(inst)) {
         try reap(f, inst, &.{ bin_op.lhs, bin_op.rhs });
-        return CValue.none;
+        return .none;
     }
 
     const inst_ty = f.air.typeOfIndex(inst);
@@ -4191,7 +3999,7 @@ fn airSlice(f: *Function, inst: Air.Inst.Index) !CValue {
 
     if (f.liveness.isUnused(inst)) {
         try reap(f, inst, &.{ bin_op.lhs, bin_op.rhs });
-        return CValue.none;
+        return .none;
     }
 
     const ptr = try f.resolveInst(bin_op.lhs);
@@ -4204,7 +4012,7 @@ fn airSlice(f: *Function, inst: Air.Inst.Index) !CValue {
     try f.writeCValue(writer, local, .Other);
     try writer.writeAll(".ptr = (");
     var buf: Type.SlicePtrFieldTypeBuffer = undefined;
-    try f.renderTypecast(writer, inst_ty.slicePtrFieldType(&buf));
+    try f.renderType(writer, inst_ty.slicePtrFieldType(&buf));
     try writer.writeByte(')');
     try f.writeCValue(writer, ptr, .Other);
     try writer.writeAll("; ");
@@ -4222,24 +4030,41 @@ fn airCall(
     modifier: std.builtin.CallModifier,
 ) !CValue {
     // Not even allowed to call panic in a naked function.
-    if (f.object.dg.decl.ty.fnCallingConvention() == .Naked) return .none;
+    if (f.object.dg.decl) |decl| if (decl.ty.fnCallingConvention() == .Naked) return .none;
+
     const gpa = f.object.dg.gpa;
+    const module = f.object.dg.module;
+    const target = module.getTarget();
+    const writer = f.object.writer();
 
-    switch (modifier) {
-        .auto => {},
-        .always_tail => return f.fail("TODO: C backend: call with always_tail attribute", .{}),
-        .never_tail => return f.fail("TODO: C backend: call with never_tail attribute", .{}),
-        .never_inline => return f.fail("TODO: C backend: call with never_inline attribute", .{}),
-        else => unreachable,
-    }
     const pl_op = f.air.instructions.items(.data)[inst].pl_op;
     const extra = f.air.extraData(Air.Call, pl_op.payload);
     const args = @ptrCast([]const Air.Inst.Ref, f.air.extra[extra.end..][0..extra.data.args_len]);
 
     const resolved_args = try gpa.alloc(CValue, args.len);
     defer gpa.free(resolved_args);
-    for (args, 0..) |arg, i| {
-        resolved_args[i] = try f.resolveInst(arg);
+    for (resolved_args, args) |*resolved_arg, arg| {
+        const arg_ty = f.air.typeOf(arg);
+        const arg_cty = try f.typeToIndex(arg_ty, .parameter);
+        if (f.indexToCType(arg_cty).tag() == .void) {
+            resolved_arg.* = .none;
+            continue;
+        }
+        resolved_arg.* = try f.resolveInst(arg);
+        if (arg_cty != try f.typeToIndex(arg_ty, .complete)) {
+            var lowered_arg_buf: LowerFnRetTyBuffer = undefined;
+            const lowered_arg_ty = lowerFnRetTy(arg_ty, &lowered_arg_buf, target);
+
+            const array_local = try f.allocLocal(inst, try lowered_arg_ty.copy(f.arena.allocator()));
+            try writer.writeAll("memcpy(");
+            try f.writeCValueMember(writer, array_local, .{ .identifier = "array" });
+            try writer.writeAll(", ");
+            try f.writeCValue(writer, resolved_arg.*, .FunctionArgument);
+            try writer.writeAll(", sizeof(");
+            try f.renderType(writer, lowered_arg_ty);
+            try writer.writeAll("));\n");
+            resolved_arg.* = array_local;
+        }
     }
 
     const callee = try f.resolveInst(pl_op.operand);
@@ -4256,18 +4081,19 @@ fn airCall(
         .Pointer => callee_ty.childType(),
         else => unreachable,
     };
-    const writer = f.object.writer();
 
-    const target = f.object.dg.module.getTarget();
     const ret_ty = fn_ty.fnReturnType();
     var lowered_ret_buf: LowerFnRetTyBuffer = undefined;
     const lowered_ret_ty = lowerFnRetTy(ret_ty, &lowered_ret_buf, target);
 
-    const result_local: CValue = if (!lowered_ret_ty.hasRuntimeBitsIgnoreComptime())
+    const result_local = if (modifier == .always_tail) r: {
+        try writer.writeAll("zig_always_tail return ");
+        break :r .none;
+    } else if (!lowered_ret_ty.hasRuntimeBitsIgnoreComptime())
         .none
     else if (f.liveness.isUnused(inst)) r: {
         try writer.writeByte('(');
-        try f.renderTypecast(writer, Type.void);
+        try f.renderType(writer, Type.void);
         try writer.writeByte(')');
         break :r .none;
     } else r: {
@@ -4277,48 +4103,44 @@ fn airCall(
         break :r local;
     };
 
-    var is_extern = false;
-    var name: [*:0]const u8 = "";
     callee: {
         known: {
             const fn_decl = fn_decl: {
                 const callee_val = f.air.value(pl_op.operand) orelse break :known;
                 break :fn_decl switch (callee_val.tag()) {
-                    .extern_fn => blk: {
-                        is_extern = true;
-                        break :blk callee_val.castTag(.extern_fn).?.data.owner_decl;
-                    },
+                    .extern_fn => callee_val.castTag(.extern_fn).?.data.owner_decl,
                     .function => callee_val.castTag(.function).?.data.owner_decl,
                     .decl_ref => callee_val.castTag(.decl_ref).?.data,
                     else => break :known,
                 };
             };
-            name = f.object.dg.module.declPtr(fn_decl).name;
-            try f.object.dg.renderDeclName(writer, fn_decl, 0);
+            switch (modifier) {
+                .auto, .always_tail => try f.object.dg.renderDeclName(writer, fn_decl, 0),
+                inline .never_tail, .never_inline => |mod| try writer.writeAll(try f.getLazyFnName(
+                    @unionInit(LazyFnKey, @tagName(mod), fn_decl),
+                    @unionInit(LazyFnValue.Data, @tagName(mod), {}),
+                )),
+                else => unreachable,
+            }
             break :callee;
         }
+        switch (modifier) {
+            .auto, .always_tail => {},
+            .never_tail => return f.fail("CBE: runtime callee with never_tail attribute unsupported", .{}),
+            .never_inline => return f.fail("CBE: runtime callee with never_inline attribute unsupported", .{}),
+            else => unreachable,
+        }
         // Fall back to function pointer call.
         try f.writeCValue(writer, callee, .Other);
     }
 
     try writer.writeByte('(');
     var args_written: usize = 0;
-    for (args, 0..) |arg, arg_i| {
-        const ty = f.air.typeOf(arg);
-        if (!ty.hasRuntimeBitsIgnoreComptime()) continue;
-        if (args_written != 0) {
-            try writer.writeAll(", ");
-        }
-        if ((is_extern or std.mem.eql(u8, std.mem.span(name), "main")) and
-            ty.isCPtr() and ty.childType().tag() == .u8)
-        {
-            // Corresponds with hack in renderType .Pointer case.
-            try writer.writeAll("(char");
-            if (ty.isConstPtr()) try writer.writeAll(" const");
-            if (ty.isVolatilePtr()) try writer.writeAll(" volatile");
-            try writer.writeAll(" *)");
-        }
-        try f.writeCValue(writer, resolved_args[arg_i], .FunctionArgument);
+    for (resolved_args) |resolved_arg| {
+        if (resolved_arg == .none) continue;
+        if (args_written != 0) try writer.writeAll(", ");
+        try f.writeCValue(writer, resolved_arg, .FunctionArgument);
+        if (resolved_arg == .new_local) try freeLocal(f, inst, resolved_arg.new_local, 0);
         args_written += 1;
     }
     try writer.writeAll(");\n");
@@ -4331,11 +4153,11 @@ fn airCall(
         try writer.writeAll("memcpy(");
         try f.writeCValue(writer, array_local, .FunctionArgument);
         try writer.writeAll(", ");
-        try f.writeCValueMember(writer, result_local, .{ .field = 0 });
+        try f.writeCValueMember(writer, result_local, .{ .identifier = "array" });
         try writer.writeAll(", sizeof(");
-        try f.renderTypecast(writer, ret_ty);
+        try f.renderType(writer, ret_ty);
         try writer.writeAll("));\n");
-        try freeLocal(f, inst, result_local.local, 0);
+        try freeLocal(f, inst, result_local.new_local, 0);
         break :r array_local;
     };
 
@@ -4354,7 +4176,7 @@ fn airDbgStmt(f: *Function, inst: Air.Inst.Index) !CValue {
     // Perhaps an additional compilation option is in order?
     //try writer.print("#line {d}\n", .{dbg_stmt.line + 1});
     try writer.print("/* file:{d}:{d} */\n", .{ dbg_stmt.line + 1, dbg_stmt.column + 1 });
-    return CValue.none;
+    return .none;
 }
 
 fn airDbgInline(f: *Function, inst: Air.Inst.Index) !CValue {
@@ -4363,7 +4185,7 @@ fn airDbgInline(f: *Function, inst: Air.Inst.Index) !CValue {
     const function = f.air.values[ty_pl.payload].castTag(.function).?.data;
     const mod = f.object.dg.module;
     try writer.print("/* dbg func:{s} */\n", .{mod.declPtr(function.owner_decl).name});
-    return CValue.none;
+    return .none;
 }
 
 fn airDbgVar(f: *Function, inst: Air.Inst.Index) !CValue {
@@ -4375,7 +4197,7 @@ fn airDbgVar(f: *Function, inst: Air.Inst.Index) !CValue {
     try reap(f, inst, &.{pl_op.operand});
     const writer = f.object.writer();
     try writer.print("/* var:{s} */\n", .{name});
-    return CValue.none;
+    return .none;
 }
 
 fn airBlock(f: *Function, inst: Air.Inst.Index) !CValue {
@@ -4391,7 +4213,7 @@ fn airBlock(f: *Function, inst: Air.Inst.Index) !CValue {
     const result = if (inst_ty.tag() != .void and !f.liveness.isUnused(inst))
         try f.allocLocal(inst, inst_ty)
     else
-        CValue{ .none = {} };
+        .none;
 
     try f.blocks.putNoClobber(f.object.dg.gpa, inst, .{
         .block_id = block_id,
@@ -4400,8 +4222,9 @@ fn airBlock(f: *Function, inst: Air.Inst.Index) !CValue {
 
     try genBodyInner(f, body);
     try f.object.indent_writer.insertNewline();
+    // label might be unused, add a dummy goto
     // label must be followed by an expression, add an empty one.
-    try writer.print("zig_block_{d}:;\n", .{block_id});
+    try writer.print("goto zig_block_{d};\nzig_block_{d}: (void)0;\n", .{ block_id, block_id });
     return result;
 }
 
@@ -4460,7 +4283,7 @@ fn lowerTry(
 
     if (!payload_has_bits) {
         if (!operand_is_ptr) {
-            return CValue.none;
+            return .none;
         } else {
             return err_union;
         }
@@ -4469,7 +4292,7 @@ fn lowerTry(
     try reap(f, inst, &.{operand});
 
     if (f.liveness.isUnused(inst)) {
-        return CValue.none;
+        return .none;
     }
 
     const target = f.object.dg.module.getTarget();
@@ -4481,7 +4304,7 @@ fn lowerTry(
         try writer.writeAll(", ");
         try f.writeCValueMember(writer, err_union, .{ .identifier = "payload" });
         try writer.writeAll(", sizeof(");
-        try f.renderTypecast(writer, payload_ty);
+        try f.renderType(writer, payload_ty);
         try writer.writeAll("));\n");
     } else {
         try f.writeCValue(writer, local, .Other);
@@ -4514,7 +4337,7 @@ fn airBr(f: *Function, inst: Air.Inst.Index) !CValue {
             try writer.writeAll(", ");
             try f.writeCValue(writer, operand, .FunctionArgument);
             try writer.writeAll(", sizeof(");
-            try f.renderTypecast(writer, operand_ty);
+            try f.renderType(writer, operand_ty);
             try writer.writeAll("))");
         } else {
             try f.writeCValue(writer, result, .Other);
@@ -4525,7 +4348,7 @@ fn airBr(f: *Function, inst: Air.Inst.Index) !CValue {
     }
 
     try writer.print("goto zig_block_{d};\n", .{block.block_id});
-    return CValue.none;
+    return .none;
 }
 
 fn airBitcast(f: *Function, inst: Air.Inst.Index) !CValue {
@@ -4535,7 +4358,7 @@ fn airBitcast(f: *Function, inst: Air.Inst.Index) !CValue {
     // https://github.com/ziglang/zig/issues/13410
     if (f.liveness.isUnused(inst) or !dest_ty.hasRuntimeBits()) {
         try reap(f, inst, &.{ty_op.operand});
-        return CValue.none;
+        return .none;
     }
 
     const operand = try f.resolveInst(ty_op.operand);
@@ -4563,7 +4386,7 @@ fn airBitcast(f: *Function, inst: Air.Inst.Index) !CValue {
     if (dest_ty.isPtrAtRuntime() and operand_ty.isPtrAtRuntime()) {
         try f.writeCValue(writer, local, .Other);
         try writer.writeAll(" = (");
-        try f.renderTypecast(writer, dest_ty);
+        try f.renderType(writer, dest_ty);
         try writer.writeByte(')');
         try f.writeCValue(writer, operand, .Other);
         try writer.writeAll(";\n");
@@ -4584,7 +4407,7 @@ fn airBitcast(f: *Function, inst: Air.Inst.Index) !CValue {
     try writer.writeAll(", &");
     try f.writeCValue(writer, operand_lval, .Other);
     try writer.writeAll(", sizeof(");
-    try f.renderTypecast(writer, dest_ty);
+    try f.renderType(writer, dest_ty);
     try writer.writeAll("));\n");
 
     // Ensure padding bits have the expected value.
@@ -4599,7 +4422,7 @@ fn airBitcast(f: *Function, inst: Air.Inst.Index) !CValue {
     }
 
     if (operand == .constant) {
-        try freeLocal(f, inst, operand_lval.local, 0);
+        try freeLocal(f, inst, operand_lval.new_local, 0);
     }
 
     return local;
@@ -4607,27 +4430,27 @@ fn airBitcast(f: *Function, inst: Air.Inst.Index) !CValue {
 
 fn airBreakpoint(writer: anytype) !CValue {
     try writer.writeAll("zig_breakpoint();\n");
-    return CValue.none;
+    return .none;
 }
 
 fn airRetAddr(f: *Function, inst: Air.Inst.Index) !CValue {
-    if (f.liveness.isUnused(inst)) return CValue.none;
+    if (f.liveness.isUnused(inst)) return .none;
     const writer = f.object.writer();
     const local = try f.allocLocal(inst, Type.usize);
     try f.writeCValue(writer, local, .Other);
     try writer.writeAll(" = (");
-    try f.renderTypecast(writer, Type.usize);
+    try f.renderType(writer, Type.usize);
     try writer.writeAll(")zig_return_address();\n");
     return local;
 }
 
 fn airFrameAddress(f: *Function, inst: Air.Inst.Index) !CValue {
-    if (f.liveness.isUnused(inst)) return CValue.none;
+    if (f.liveness.isUnused(inst)) return .none;
     const writer = f.object.writer();
     const local = try f.allocLocal(inst, Type.usize);
     try f.writeCValue(writer, local, .Other);
     try writer.writeAll(" = (");
-    try f.renderTypecast(writer, Type.usize);
+    try f.renderType(writer, Type.usize);
     try writer.writeAll(")zig_frame_address();\n");
     return local;
 }
@@ -4640,15 +4463,15 @@ fn airFence(f: *Function, inst: Air.Inst.Index) !CValue {
     try writeMemoryOrder(writer, atomic_order);
     try writer.writeAll(");\n");
 
-    return CValue.none;
+    return .none;
 }
 
 fn airUnreach(f: *Function) !CValue {
     // Not even allowed to call unreachable in a naked function.
-    if (f.object.dg.decl.ty.fnCallingConvention() == .Naked) return .none;
+    if (f.object.dg.decl) |decl| if (decl.ty.fnCallingConvention() == .Naked) return .none;
 
     try f.object.writer().writeAll("zig_unreachable();\n");
-    return CValue.none;
+    return .none;
 }
 
 fn airLoop(f: *Function, inst: Air.Inst.Index) !CValue {
@@ -4669,18 +4492,18 @@ fn airLoop(f: *Function, inst: Air.Inst.Index) !CValue {
     const new_free_locals = f.getFreeLocals();
     var it = new_free_locals.iterator();
     while (it.next()) |entry| {
-        const gop = try old_free_locals.getOrPutContext(gpa, entry.key_ptr.*, f.tyHashCtx());
+        const gop = try old_free_locals.getOrPut(gpa, entry.key_ptr.*);
         if (gop.found_existing) {
-            try gop.value_ptr.appendSlice(gpa, entry.value_ptr.items);
-        } else {
-            gop.value_ptr.* = entry.value_ptr.*;
-            entry.value_ptr.* = .{};
-        }
+            try gop.value_ptr.ensureUnusedCapacity(gpa, entry.value_ptr.count());
+            for (entry.value_ptr.keys()) |local_index| {
+                gop.value_ptr.putAssumeCapacityNoClobber(local_index, {});
+            }
+        } else gop.value_ptr.* = entry.value_ptr.move();
     }
     deinitFreeLocalsMap(gpa, new_free_locals);
     new_free_locals.* = old_free_locals.move();
 
-    return CValue.none;
+    return .none;
 }
 
 fn airCondBr(f: *Function, inst: Air.Inst.Index) !CValue {
@@ -4705,6 +4528,10 @@ fn airCondBr(f: *Function, inst: Air.Inst.Index) !CValue {
     // that we can notice and use them in the else branch. Any new locals must
     // necessarily be free already after the then branch is complete.
     const pre_locals_len = @intCast(LocalIndex, f.locals.items.len);
+    // Remember how many allocs there were before entering the then branch so
+    // that we can notice and make sure not to use them in the else branch.
+    // Any new allocs must be removed from the free list.
+    const pre_allocs_len = @intCast(LocalIndex, f.allocs.count());
     const pre_clone_depth = f.free_locals_clone_depth;
     f.free_locals_clone_depth = @intCast(LoopDepth, f.free_locals_stack.items.len);
 
@@ -4735,7 +4562,7 @@ fn airCondBr(f: *Function, inst: Air.Inst.Index) !CValue {
         try die(f, inst, Air.indexToRef(operand));
     }
 
-    try noticeBranchFrees(f, pre_locals_len, inst);
+    try noticeBranchFrees(f, pre_locals_len, pre_allocs_len, inst);
 
     if (needs_else) {
         try genBody(f, else_body);
@@ -4745,7 +4572,7 @@ fn airCondBr(f: *Function, inst: Air.Inst.Index) !CValue {
 
     try f.object.indent_writer.insertNewline();
 
-    return CValue.none;
+    return .none;
 }
 
 fn airSwitchBr(f: *Function, inst: Air.Inst.Index) !CValue {
@@ -4759,11 +4586,11 @@ fn airSwitchBr(f: *Function, inst: Air.Inst.Index) !CValue {
     try writer.writeAll("switch (");
     if (condition_ty.zigTypeTag() == .Bool) {
         try writer.writeByte('(');
-        try f.renderTypecast(writer, Type.u1);
+        try f.renderType(writer, Type.u1);
         try writer.writeByte(')');
     } else if (condition_ty.isPtrAtRuntime()) {
         try writer.writeByte('(');
-        try f.renderTypecast(writer, Type.usize);
+        try f.renderType(writer, Type.usize);
         try writer.writeByte(')');
     }
     try f.writeCValue(writer, condition, .Other);
@@ -4780,8 +4607,7 @@ fn airSwitchBr(f: *Function, inst: Air.Inst.Index) !CValue {
     const last_case_i = switch_br.data.cases_len - @boolToInt(switch_br.data.else_body_len == 0);
 
     var extra_index: usize = switch_br.end;
-    var case_i: u32 = 0;
-    while (case_i < switch_br.data.cases_len) : (case_i += 1) {
+    for (0..switch_br.data.cases_len) |case_i| {
         const case = f.air.extraData(Air.SwitchBr.Case, extra_index);
         const items = @ptrCast([]const Air.Inst.Ref, f.air.extra[case.end..][0..case.data.items_len]);
         const case_body = f.air.extra[case.end + items.len ..][0..case.data.body_len];
@@ -4792,7 +4618,7 @@ fn airSwitchBr(f: *Function, inst: Air.Inst.Index) !CValue {
             try writer.writeAll("case ");
             if (condition_ty.isPtrAtRuntime()) {
                 try writer.writeByte('(');
-                try f.renderTypecast(writer, Type.usize);
+                try f.renderType(writer, Type.usize);
                 try writer.writeByte(')');
             }
             try f.object.dg.renderValue(writer, condition_ty, f.air.value(item).?, .Other);
@@ -4811,6 +4637,10 @@ fn airSwitchBr(f: *Function, inst: Air.Inst.Index) !CValue {
             // we can notice and use them in subsequent branches. Any new locals must
             // necessarily be free already after the previous branch is complete.
             const pre_locals_len = @intCast(LocalIndex, f.locals.items.len);
+            // Remember how many allocs there were before entering each branch so that
+            // we can notice and make sure not to use them in subsequent branches.
+            // Any new allocs must be removed from the free list.
+            const pre_allocs_len = @intCast(LocalIndex, f.allocs.count());
             const pre_clone_depth = f.free_locals_clone_depth;
             f.free_locals_clone_depth = @intCast(LoopDepth, f.free_locals_stack.items.len);
 
@@ -4831,7 +4661,7 @@ fn airSwitchBr(f: *Function, inst: Air.Inst.Index) !CValue {
                 try genBody(f, case_body);
             }
 
-            try noticeBranchFrees(f, pre_locals_len, inst);
+            try noticeBranchFrees(f, pre_locals_len, pre_allocs_len, inst);
         } else {
             for (liveness.deaths[case_i]) |operand| {
                 try die(f, inst, Air.indexToRef(operand));
@@ -4858,7 +4688,7 @@ fn airSwitchBr(f: *Function, inst: Air.Inst.Index) !CValue {
 
     f.object.indent_writer.popIndent();
     try writer.writeAll("}\n");
-    return CValue.none;
+    return .none;
 }
 
 fn asmInputNeedsLocal(constraint: []const u8, value: CValue) bool {
@@ -4880,8 +4710,8 @@ fn airAsm(f: *Function, inst: Air.Inst.Index) !CValue {
     const inputs = @ptrCast([]const Air.Inst.Ref, f.air.extra[extra_i..][0..extra.data.inputs_len]);
     extra_i += inputs.len;
 
-    const result: CValue = r: {
-        if (!is_volatile and f.liveness.isUnused(inst)) break :r CValue.none;
+    const result = r: {
+        if (!is_volatile and f.liveness.isUnused(inst)) break :r .none;
 
         const writer = f.object.writer();
         const inst_ty = f.air.typeOfIndex(inst);
@@ -4918,14 +4748,7 @@ fn airAsm(f: *Function, inst: Air.Inst.Index) !CValue {
                 try writer.writeAll("register ");
                 const alignment = 0;
                 const local_value = try f.allocLocalValue(output_ty, alignment);
-                try f.object.dg.renderTypeAndName(
-                    writer,
-                    output_ty,
-                    local_value,
-                    .Mut,
-                    alignment,
-                    .Complete,
-                );
+                try f.object.dg.renderTypeAndName(writer, output_ty, local_value, .{}, alignment, .complete);
                 try writer.writeAll(" __asm(\"");
                 try writer.writeAll(constraint["={".len .. constraint.len - "}".len]);
                 try writer.writeAll("\")");
@@ -4957,14 +4780,7 @@ fn airAsm(f: *Function, inst: Air.Inst.Index) !CValue {
                 if (is_reg) try writer.writeAll("register ");
                 const alignment = 0;
                 const local_value = try f.allocLocalValue(input_ty, alignment);
-                try f.object.dg.renderTypeAndName(
-                    writer,
-                    input_ty,
-                    local_value,
-                    .Const,
-                    alignment,
-                    .Complete,
-                );
+                try f.object.dg.renderTypeAndName(writer, input_ty, local_value, Const, alignment, .complete);
                 if (is_reg) {
                     try writer.writeAll(" __asm(\"");
                     try writer.writeAll(constraint["{".len .. constraint.len - "}".len]);
@@ -4975,14 +4791,11 @@ fn airAsm(f: *Function, inst: Air.Inst.Index) !CValue {
                 try writer.writeAll(";\n");
             }
         }
-        {
-            var clobber_i: u32 = 0;
-            while (clobber_i < clobbers_len) : (clobber_i += 1) {
-                const clobber = std.mem.sliceTo(std.mem.sliceAsBytes(f.air.extra[extra_i..]), 0);
-                // This equation accounts for the fact that even if we have exactly 4 bytes
-                // for the string, we still use the next u32 for the null terminator.
-                extra_i += clobber.len / 4 + 1;
-            }
+        for (0..clobbers_len) |_| {
+            const clobber = std.mem.sliceTo(std.mem.sliceAsBytes(f.air.extra[extra_i..]), 0);
+            // This equation accounts for the fact that even if we have exactly 4 bytes
+            // for the string, we still use the next u32 for the null terminator.
+            extra_i += clobber.len / 4 + 1;
         }
 
         {
@@ -5037,7 +4850,7 @@ fn airAsm(f: *Function, inst: Air.Inst.Index) !CValue {
 
             try writer.writeAll("__asm");
             if (is_volatile) try writer.writeAll(" volatile");
-            try writer.print("({s}", .{fmtStringLiteral(fixed_asm_source[0..dst_i])});
+            try writer.print("({s}", .{fmtStringLiteral(fixed_asm_source[0..dst_i], null)});
         }
 
         extra_i = constraints_extra_begin;
@@ -5055,7 +4868,7 @@ fn airAsm(f: *Function, inst: Air.Inst.Index) !CValue {
             try writer.writeByte(' ');
             if (!std.mem.eql(u8, name, "_")) try writer.print("[{s}]", .{name});
             const is_reg = constraint[1] == '{';
-            try writer.print("{s}(", .{fmtStringLiteral(if (is_reg) "=r" else constraint)});
+            try writer.print("{s}(", .{fmtStringLiteral(if (is_reg) "=r" else constraint, null)});
             if (is_reg) {
                 try f.writeCValue(writer, .{ .local = locals_index }, .Other);
                 locals_index += 1;
@@ -5081,28 +4894,25 @@ fn airAsm(f: *Function, inst: Air.Inst.Index) !CValue {
 
             const is_reg = constraint[0] == '{';
             const input_val = try f.resolveInst(input);
-            try writer.print("{s}(", .{fmtStringLiteral(if (is_reg) "r" else constraint)});
+            try writer.print("{s}(", .{fmtStringLiteral(if (is_reg) "r" else constraint, null)});
             try f.writeCValue(writer, if (asmInputNeedsLocal(constraint, input_val)) local: {
-                const input_local = CValue{ .local = locals_index };
+                const input_local = .{ .local = locals_index };
                 locals_index += 1;
                 break :local input_local;
             } else input_val, .Other);
             try writer.writeByte(')');
         }
         try writer.writeByte(':');
-        {
-            var clobber_i: u32 = 0;
-            while (clobber_i < clobbers_len) : (clobber_i += 1) {
-                const clobber = std.mem.sliceTo(std.mem.sliceAsBytes(f.air.extra[extra_i..]), 0);
-                // This equation accounts for the fact that even if we have exactly 4 bytes
-                // for the string, we still use the next u32 for the null terminator.
-                extra_i += clobber.len / 4 + 1;
+        for (0..clobbers_len) |clobber_i| {
+            const clobber = std.mem.sliceTo(std.mem.sliceAsBytes(f.air.extra[extra_i..]), 0);
+            // This equation accounts for the fact that even if we have exactly 4 bytes
+            // for the string, we still use the next u32 for the null terminator.
+            extra_i += clobber.len / 4 + 1;
 
-                if (clobber.len == 0) continue;
+            if (clobber.len == 0) continue;
 
-                if (clobber_i > 0) try writer.writeByte(',');
-                try writer.print(" {s}", .{fmtStringLiteral(clobber)});
-            }
+            if (clobber_i > 0) try writer.writeByte(',');
+            try writer.print(" {s}", .{fmtStringLiteral(clobber, null)});
         }
         try writer.writeAll(");\n");
 
@@ -5119,7 +4929,7 @@ fn airAsm(f: *Function, inst: Air.Inst.Index) !CValue {
             const is_reg = constraint[1] == '{';
             if (is_reg) {
                 try f.writeCValueDeref(writer, if (output == .none)
-                    CValue{ .local_ref = local.local }
+                    .{ .local_ref = local.new_local }
                 else
                     try f.resolveInst(output));
                 try writer.writeAll(" = ");
@@ -5154,7 +4964,7 @@ fn airIsNull(
 
     if (f.liveness.isUnused(inst)) {
         try reap(f, inst, &.{un_op});
-        return CValue.none;
+        return .none;
     }
 
     const writer = f.object.writer();
@@ -5204,7 +5014,7 @@ fn airOptionalPayload(f: *Function, inst: Air.Inst.Index) !CValue {
 
     if (f.liveness.isUnused(inst)) {
         try reap(f, inst, &.{ty_op.operand});
-        return CValue.none;
+        return .none;
     }
 
     const operand = try f.resolveInst(ty_op.operand);
@@ -5215,7 +5025,7 @@ fn airOptionalPayload(f: *Function, inst: Air.Inst.Index) !CValue {
     const payload_ty = opt_ty.optionalChild(&buf);
 
     if (!payload_ty.hasRuntimeBitsIgnoreComptime()) {
-        return CValue.none;
+        return .none;
     }
 
     const inst_ty = f.air.typeOfIndex(inst);
@@ -5244,7 +5054,7 @@ fn airOptionalPayload(f: *Function, inst: Air.Inst.Index) !CValue {
     try f.writeCValueMember(writer, operand, .{ .identifier = "payload" });
     if (is_array) {
         try writer.writeAll(", sizeof(");
-        try f.renderTypecast(writer, inst_ty);
+        try f.renderType(writer, inst_ty);
         try writer.writeAll("))");
     }
     try writer.writeAll(";\n");
@@ -5256,7 +5066,7 @@ fn airOptionalPayloadPtr(f: *Function, inst: Air.Inst.Index) !CValue {
 
     if (f.liveness.isUnused(inst)) {
         try reap(f, inst, &.{ty_op.operand});
-        return CValue.none;
+        return .none;
     }
 
     const writer = f.object.writer();
@@ -5267,7 +5077,7 @@ fn airOptionalPayloadPtr(f: *Function, inst: Air.Inst.Index) !CValue {
     const inst_ty = f.air.typeOfIndex(inst);
 
     if (!inst_ty.childType().hasRuntimeBitsIgnoreComptime()) {
-        return CValue{ .undef = inst_ty };
+        return .{ .undef = inst_ty };
     }
 
     const local = try f.allocLocal(inst, inst_ty);
@@ -5299,7 +5109,7 @@ fn airOptionalPayloadPtrSet(f: *Function, inst: Air.Inst.Index) !CValue {
 
     if (opt_ty.optionalReprIsPayload()) {
         if (f.liveness.isUnused(inst)) {
-            return CValue.none;
+            return .none;
         }
         const local = try f.allocLocal(inst, inst_ty);
         // The payload and the optional are the same value.
@@ -5316,7 +5126,7 @@ fn airOptionalPayloadPtrSet(f: *Function, inst: Air.Inst.Index) !CValue {
         try writer.writeAll(";\n");
 
         if (f.liveness.isUnused(inst)) {
-            return CValue.none;
+            return .none;
         }
 
         const local = try f.allocLocal(inst, inst_ty);
@@ -5328,6 +5138,62 @@ fn airOptionalPayloadPtrSet(f: *Function, inst: Air.Inst.Index) !CValue {
     }
 }
 
+fn fieldLocation(
+    container_ty: Type,
+    field_ptr_ty: Type,
+    field_index: u32,
+    target: std.Target,
+) union(enum) {
+    begin: void,
+    field: CValue,
+    byte_offset: u32,
+    end: void,
+} {
+    return switch (container_ty.zigTypeTag()) {
+        .Struct => switch (container_ty.containerLayout()) {
+            .Auto, .Extern => for (field_index..container_ty.structFieldCount()) |next_field_index| {
+                if (container_ty.structFieldIsComptime(next_field_index)) continue;
+                const field_ty = container_ty.structFieldType(next_field_index);
+                if (!field_ty.hasRuntimeBitsIgnoreComptime()) continue;
+                break .{ .field = if (container_ty.isSimpleTuple())
+                    .{ .field = next_field_index }
+                else
+                    .{ .identifier = container_ty.structFieldName(next_field_index) } };
+            } else if (container_ty.hasRuntimeBitsIgnoreComptime()) .end else .begin,
+            .Packed => if (field_ptr_ty.ptrInfo().data.host_size == 0)
+                .{ .byte_offset = container_ty.packedStructFieldByteOffset(field_index, target) }
+            else
+                .begin,
+        },
+        .Union => switch (container_ty.containerLayout()) {
+            .Auto, .Extern => {
+                const field_ty = container_ty.structFieldType(field_index);
+                if (!field_ty.hasRuntimeBitsIgnoreComptime())
+                    return if (container_ty.unionTagTypeSafety() != null and
+                        !container_ty.unionHasAllZeroBitFieldTypes())
+                        .{ .field = .{ .identifier = "payload" } }
+                    else
+                        .begin;
+                const field_name = container_ty.unionFields().keys()[field_index];
+                return .{ .field = if (container_ty.unionTagTypeSafety()) |_|
+                    .{ .payload_identifier = field_name }
+                else
+                    .{ .identifier = field_name } };
+            },
+            .Packed => .begin,
+        },
+        .Pointer => switch (container_ty.ptrSize()) {
+            .Slice => switch (field_index) {
+                0 => .{ .field = .{ .identifier = "ptr" } },
+                1 => .{ .field = .{ .identifier = "len" } },
+                else => unreachable,
+            },
+            .One, .Many, .C => unreachable,
+        },
+        else => unreachable,
+    };
+}
+
 fn airStructFieldPtr(f: *Function, inst: Air.Inst.Index) !CValue {
     const ty_pl = f.air.instructions.items(.data)[inst].ty_pl;
     const extra = f.air.extraData(Air.StructField, ty_pl.payload).data;
@@ -5337,10 +5203,10 @@ fn airStructFieldPtr(f: *Function, inst: Air.Inst.Index) !CValue {
         return .none;
     }
 
-    const struct_ptr = try f.resolveInst(extra.struct_operand);
+    const container_ptr_val = try f.resolveInst(extra.struct_operand);
     try reap(f, inst, &.{extra.struct_operand});
-    const struct_ptr_ty = f.air.typeOf(extra.struct_operand);
-    return structFieldPtr(f, inst, struct_ptr_ty, struct_ptr, extra.field_index);
+    const container_ptr_ty = f.air.typeOf(extra.struct_operand);
+    return fieldPtr(f, inst, container_ptr_ty, container_ptr_val, extra.field_index);
 }
 
 fn airStructFieldPtrIndex(f: *Function, inst: Air.Inst.Index, index: u8) !CValue {
@@ -5351,10 +5217,10 @@ fn airStructFieldPtrIndex(f: *Function, inst: Air.Inst.Index, index: u8) !CValue
         return .none;
     }
 
-    const struct_ptr = try f.resolveInst(ty_op.operand);
+    const container_ptr_val = try f.resolveInst(ty_op.operand);
     try reap(f, inst, &.{ty_op.operand});
-    const struct_ptr_ty = f.air.typeOf(ty_op.operand);
-    return structFieldPtr(f, inst, struct_ptr_ty, struct_ptr, index);
+    const container_ptr_ty = f.air.typeOf(ty_op.operand);
+    return fieldPtr(f, inst, container_ptr_ty, container_ptr_val, index);
 }
 
 fn airFieldParentPtr(f: *Function, inst: Air.Inst.Index) !CValue {
@@ -5363,137 +5229,119 @@ fn airFieldParentPtr(f: *Function, inst: Air.Inst.Index) !CValue {
 
     if (f.liveness.isUnused(inst)) {
         try reap(f, inst, &.{extra.field_ptr});
-        return CValue.none;
+        return .none;
     }
 
-    const struct_ptr_ty = f.air.typeOfIndex(inst);
+    const target = f.object.dg.module.getTarget();
+    const container_ptr_ty = f.air.typeOfIndex(inst);
+    const container_ty = container_ptr_ty.childType();
+
     const field_ptr_ty = f.air.typeOf(extra.field_ptr);
     const field_ptr_val = try f.resolveInst(extra.field_ptr);
     try reap(f, inst, &.{extra.field_ptr});
 
-    const target = f.object.dg.module.getTarget();
-    const struct_ty = struct_ptr_ty.childType();
-    const field_offset = struct_ty.structFieldOffset(extra.field_index, target);
-
-    var field_offset_pl = Value.Payload.I64{
-        .base = .{ .tag = .int_i64 },
-        .data = -@intCast(i64, field_offset),
-    };
-    const field_offset_val = Value.initPayload(&field_offset_pl.base);
-
-    var u8_ptr_pl = field_ptr_ty.ptrInfo();
-    u8_ptr_pl.data.pointee_type = Type.u8;
-    const u8_ptr_ty = Type.initPayload(&u8_ptr_pl.base);
-
     const writer = f.object.writer();
-    const local = try f.allocLocal(inst, struct_ptr_ty);
+    const local = try f.allocLocal(inst, container_ptr_ty);
     try f.writeCValue(writer, local, .Other);
     try writer.writeAll(" = (");
-    try f.renderTypecast(writer, struct_ptr_ty);
-    try writer.writeAll(")&((");
-    try f.renderTypecast(writer, u8_ptr_ty);
+    try f.renderType(writer, container_ptr_ty);
     try writer.writeByte(')');
-    try f.writeCValue(writer, field_ptr_val, .Other);
-    try writer.print(")[{}];\n", .{try f.fmtIntLiteral(Type.isize, field_offset_val)});
+
+    switch (fieldLocation(container_ty, field_ptr_ty, extra.field_index, target)) {
+        .begin => try f.writeCValue(writer, field_ptr_val, .Initializer),
+        .field => |field| {
+            var u8_ptr_pl = field_ptr_ty.ptrInfo();
+            u8_ptr_pl.data.pointee_type = Type.u8;
+            const u8_ptr_ty = Type.initPayload(&u8_ptr_pl.base);
+
+            try writer.writeAll("((");
+            try f.renderType(writer, u8_ptr_ty);
+            try writer.writeByte(')');
+            try f.writeCValue(writer, field_ptr_val, .Other);
+            try writer.writeAll(" - offsetof(");
+            try f.renderType(writer, container_ty);
+            try writer.writeAll(", ");
+            try f.writeCValue(writer, field, .Other);
+            try writer.writeAll("))");
+        },
+        .byte_offset => |byte_offset| {
+            var u8_ptr_pl = field_ptr_ty.ptrInfo();
+            u8_ptr_pl.data.pointee_type = Type.u8;
+            const u8_ptr_ty = Type.initPayload(&u8_ptr_pl.base);
+
+            var byte_offset_pl = Value.Payload.U64{
+                .base = .{ .tag = .int_u64 },
+                .data = byte_offset,
+            };
+            const byte_offset_val = Value.initPayload(&byte_offset_pl.base);
+
+            try writer.writeAll("((");
+            try f.renderType(writer, u8_ptr_ty);
+            try writer.writeByte(')');
+            try f.writeCValue(writer, field_ptr_val, .Other);
+            try writer.print(" - {})", .{try f.fmtIntLiteral(Type.usize, byte_offset_val)});
+        },
+        .end => {
+            try f.writeCValue(writer, field_ptr_val, .Other);
+            try writer.print(" - {}", .{try f.fmtIntLiteral(Type.usize, Value.one)});
+        },
+    }
+
+    try writer.writeAll(";\n");
     return local;
 }
 
-fn structFieldPtr(f: *Function, inst: Air.Inst.Index, struct_ptr_ty: Type, struct_ptr: CValue, index: u32) !CValue {
-    const writer = f.object.writer();
+fn fieldPtr(
+    f: *Function,
+    inst: Air.Inst.Index,
+    container_ptr_ty: Type,
+    container_ptr_val: CValue,
+    field_index: u32,
+) !CValue {
+    const target = f.object.dg.module.getTarget();
+    const container_ty = container_ptr_ty.elemType();
     const field_ptr_ty = f.air.typeOfIndex(inst);
-    const field_ptr_info = field_ptr_ty.ptrInfo();
-    const struct_ty = struct_ptr_ty.elemType();
-    const field_ty = struct_ty.structFieldType(index);
 
     // Ensure complete type definition is visible before accessing fields.
-    try f.renderType(std.io.null_writer, struct_ty);
+    _ = try f.typeToIndex(container_ty, .complete);
 
+    const writer = f.object.writer();
     const local = try f.allocLocal(inst, field_ptr_ty);
     try f.writeCValue(writer, local, .Other);
     try writer.writeAll(" = (");
-    try f.renderTypecast(writer, field_ptr_ty);
+    try f.renderType(writer, field_ptr_ty);
     try writer.writeByte(')');
 
-    const extra_name: CValue = switch (struct_ty.tag()) {
-        .union_tagged, .union_safety_tagged => .{ .identifier = "payload" },
-        else => .none,
-    };
-
-    const FieldLoc = union(enum) {
-        begin: void,
-        field: CValue,
-        end: void,
-    };
-    const field_loc = switch (struct_ty.tag()) {
-        .@"struct" => switch (struct_ty.containerLayout()) {
-            .Auto, .Extern => for (struct_ty.structFields().values()[index..], 0..) |field, offset| {
-                if (field.ty.hasRuntimeBitsIgnoreComptime()) break FieldLoc{ .field = .{
-                    .identifier = struct_ty.structFieldName(index + offset),
-                } };
-            } else @as(FieldLoc, .end),
-            .Packed => if (field_ptr_info.data.host_size == 0) {
-                const target = f.object.dg.module.getTarget();
-
-                const byte_offset = struct_ty.packedStructFieldByteOffset(index, target);
-                var byte_offset_pl = Value.Payload.U64{
-                    .base = .{ .tag = .int_u64 },
-                    .data = byte_offset,
-                };
-                const byte_offset_val = Value.initPayload(&byte_offset_pl.base);
-
-                var u8_ptr_pl = field_ptr_info;
-                u8_ptr_pl.data.pointee_type = Type.u8;
-                const u8_ptr_ty = Type.initPayload(&u8_ptr_pl.base);
+    switch (fieldLocation(container_ty, field_ptr_ty, field_index, target)) {
+        .begin => try f.writeCValue(writer, container_ptr_val, .Initializer),
+        .field => |field| {
+            try writer.writeByte('&');
+            try f.writeCValueDerefMember(writer, container_ptr_val, field);
+        },
+        .byte_offset => |byte_offset| {
+            var u8_ptr_pl = field_ptr_ty.ptrInfo();
+            u8_ptr_pl.data.pointee_type = Type.u8;
+            const u8_ptr_ty = Type.initPayload(&u8_ptr_pl.base);
 
-                if (!std.mem.isAligned(byte_offset, field_ptr_ty.ptrAlignment(target))) {
-                    return f.fail("TODO: CBE: unaligned packed struct field pointer", .{});
-                }
+            var byte_offset_pl = Value.Payload.U64{
+                .base = .{ .tag = .int_u64 },
+                .data = byte_offset,
+            };
+            const byte_offset_val = Value.initPayload(&byte_offset_pl.base);
 
-                try writer.writeAll("&((");
-                try f.renderTypecast(writer, u8_ptr_ty);
-                try writer.writeByte(')');
-                try f.writeCValue(writer, struct_ptr, .Other);
-                try writer.print(")[{}];\n", .{try f.fmtIntLiteral(Type.usize, byte_offset_val)});
-                return local;
-            } else @as(FieldLoc, .begin),
-        },
-        .@"union", .union_safety_tagged, .union_tagged => if (struct_ty.containerLayout() == .Packed) {
-            try f.writeCValue(writer, struct_ptr, .Other);
-            try writer.writeAll(";\n");
-            return local;
-        } else if (field_ty.hasRuntimeBitsIgnoreComptime()) FieldLoc{ .field = .{
-            .identifier = struct_ty.unionFields().keys()[index],
-        } } else @as(FieldLoc, .end),
-        .tuple, .anon_struct => field_name: {
-            const tuple = struct_ty.tupleFields();
-            if (tuple.values[index].tag() != .unreachable_value) return CValue.none;
-
-            var id: usize = 0;
-            break :field_name for (tuple.values, 0..) |value, i| {
-                if (value.tag() != .unreachable_value) continue;
-                if (!tuple.types[i].hasRuntimeBitsIgnoreComptime()) continue;
-                if (i >= index) break FieldLoc{ .field = .{ .field = id } };
-                id += 1;
-            } else @as(FieldLoc, .end);
+            try writer.writeAll("((");
+            try f.renderType(writer, u8_ptr_ty);
+            try writer.writeByte(')');
+            try f.writeCValue(writer, container_ptr_val, .Other);
+            try writer.print(" + {})", .{try f.fmtIntLiteral(Type.usize, byte_offset_val)});
         },
-        else => unreachable,
-    };
-
-    try writer.writeByte('&');
-    switch (field_loc) {
-        .begin, .end => {
+        .end => {
             try writer.writeByte('(');
-            try f.writeCValue(writer, struct_ptr, .Other);
-            try writer.print(")[{}]", .{
-                @boolToInt(field_loc == .end and struct_ty.hasRuntimeBitsIgnoreComptime()),
-            });
+            try f.writeCValue(writer, container_ptr_val, .Other);
+            try writer.print(" + {})", .{try f.fmtIntLiteral(Type.usize, Value.one)});
         },
-        .field => |field| if (extra_name != .none) {
-            try f.writeCValueDerefMember(writer, struct_ptr, extra_name);
-            try writer.writeByte('.');
-            try f.writeCValue(writer, field, .Other);
-        } else try f.writeCValueDerefMember(writer, struct_ptr, field),
     }
+
     try writer.writeAll(";\n");
     return local;
 }
@@ -5504,13 +5352,13 @@ fn airStructFieldVal(f: *Function, inst: Air.Inst.Index) !CValue {
 
     if (f.liveness.isUnused(inst)) {
         try reap(f, inst, &.{extra.struct_operand});
-        return CValue.none;
+        return .none;
     }
 
     const inst_ty = f.air.typeOfIndex(inst);
     if (!inst_ty.hasRuntimeBitsIgnoreComptime()) {
         try reap(f, inst, &.{extra.struct_operand});
-        return CValue.none;
+        return .none;
     }
 
     const target = f.object.dg.module.getTarget();
@@ -5520,16 +5368,14 @@ fn airStructFieldVal(f: *Function, inst: Air.Inst.Index) !CValue {
     const writer = f.object.writer();
 
     // Ensure complete type definition is visible before accessing fields.
-    try f.renderType(std.io.null_writer, struct_ty);
-
-    const extra_name: CValue = switch (struct_ty.tag()) {
-        .union_tagged, .union_safety_tagged => .{ .identifier = "payload" },
-        else => .none,
-    };
+    _ = try f.typeToIndex(struct_ty, .complete);
 
     const field_name: CValue = switch (struct_ty.tag()) {
-        .@"struct" => switch (struct_ty.containerLayout()) {
-            .Auto, .Extern => .{ .identifier = struct_ty.structFieldName(extra.field_index) },
+        .tuple, .anon_struct, .@"struct" => switch (struct_ty.containerLayout()) {
+            .Auto, .Extern => if (struct_ty.isSimpleTuple())
+                .{ .field = extra.field_index }
+            else
+                .{ .identifier = struct_ty.structFieldName(extra.field_index) },
             .Packed => {
                 const struct_obj = struct_ty.castTag(.@"struct").?.data;
                 const int_info = struct_ty.intInfo(target);
@@ -5564,7 +5410,7 @@ fn airStructFieldVal(f: *Function, inst: Air.Inst.Index) !CValue {
                 try writer.writeAll(" = zig_wrap_");
                 try f.object.dg.renderTypeForBuiltinFnName(writer, field_int_ty);
                 try writer.writeAll("((");
-                try f.renderTypecast(writer, field_int_ty);
+                try f.renderType(writer, field_int_ty);
                 try writer.writeByte(')');
                 const cant_cast = int_info.bits > 64;
                 if (cant_cast) {
@@ -5587,13 +5433,13 @@ fn airStructFieldVal(f: *Function, inst: Air.Inst.Index) !CValue {
 
                 const local = try f.allocLocal(inst, inst_ty);
                 try writer.writeAll("memcpy(");
-                try f.writeCValue(writer, .{ .local_ref = local.local }, .FunctionArgument);
+                try f.writeCValue(writer, .{ .local_ref = local.new_local }, .FunctionArgument);
                 try writer.writeAll(", ");
-                try f.writeCValue(writer, .{ .local_ref = temp_local.local }, .FunctionArgument);
+                try f.writeCValue(writer, .{ .local_ref = temp_local.new_local }, .FunctionArgument);
                 try writer.writeAll(", sizeof(");
-                try f.renderTypecast(writer, inst_ty);
+                try f.renderType(writer, inst_ty);
                 try writer.writeAll("));\n");
-                try freeLocal(f, inst, temp_local.local, 0);
+                try freeLocal(f, inst, temp_local.new_local, 0);
                 return local;
             },
         },
@@ -5613,48 +5459,37 @@ fn airStructFieldVal(f: *Function, inst: Air.Inst.Index) !CValue {
             try writer.writeAll(", &");
             try f.writeCValue(writer, operand_lval, .FunctionArgument);
             try writer.writeAll(", sizeof(");
-            try f.renderTypecast(writer, inst_ty);
+            try f.renderType(writer, inst_ty);
             try writer.writeAll("));\n");
 
             if (struct_byval == .constant) {
-                try freeLocal(f, inst, operand_lval.local, 0);
+                try freeLocal(f, inst, operand_lval.new_local, 0);
             }
 
             return local;
-        } else .{
-            .identifier = struct_ty.unionFields().keys()[extra.field_index],
-        },
-        .tuple, .anon_struct => blk: {
-            const tuple = struct_ty.tupleFields();
-            if (tuple.values[extra.field_index].tag() != .unreachable_value) return CValue.none;
-
-            var id: usize = 0;
-            for (tuple.values[0..extra.field_index]) |value|
-                id += @boolToInt(value.tag() == .unreachable_value);
-            break :blk .{ .field = id };
+        } else field_name: {
+            const name = struct_ty.unionFields().keys()[extra.field_index];
+            break :field_name if (struct_ty.unionTagTypeSafety()) |_|
+                .{ .payload_identifier = name }
+            else
+                .{ .identifier = name };
         },
         else => unreachable,
     };
 
-    const is_array = lowersToArray(inst_ty, target);
     const local = try f.allocLocal(inst, inst_ty);
-    if (is_array) {
+    if (lowersToArray(inst_ty, target)) {
         try writer.writeAll("memcpy(");
         try f.writeCValue(writer, local, .FunctionArgument);
         try writer.writeAll(", ");
+        try f.writeCValueMember(writer, struct_byval, field_name);
+        try writer.writeAll(", sizeof(");
+        try f.renderType(writer, inst_ty);
+        try writer.writeAll("))");
     } else {
         try f.writeCValue(writer, local, .Other);
         try writer.writeAll(" = ");
-    }
-    if (extra_name != .none) {
-        try f.writeCValueMember(writer, struct_byval, extra_name);
-        try writer.writeByte('.');
-        try f.writeCValue(writer, field_name, .Other);
-    } else try f.writeCValueMember(writer, struct_byval, field_name);
-    if (is_array) {
-        try writer.writeAll(", sizeof(");
-        try f.renderTypecast(writer, inst_ty);
-        try writer.writeAll("))");
+        try f.writeCValueMember(writer, struct_byval, field_name);
     }
     try writer.writeAll(";\n");
     return local;
@@ -5667,7 +5502,7 @@ fn airUnwrapErrUnionErr(f: *Function, inst: Air.Inst.Index) !CValue {
 
     if (f.liveness.isUnused(inst)) {
         try reap(f, inst, &.{ty_op.operand});
-        return CValue.none;
+        return .none;
     }
 
     const inst_ty = f.air.typeOfIndex(inst);
@@ -5704,7 +5539,7 @@ fn airUnwrapErrUnionPay(f: *Function, inst: Air.Inst.Index, is_ptr: bool) !CValu
 
     if (f.liveness.isUnused(inst)) {
         try reap(f, inst, &.{ty_op.operand});
-        return CValue.none;
+        return .none;
     }
 
     const inst_ty = f.air.typeOfIndex(inst);
@@ -5715,13 +5550,13 @@ fn airUnwrapErrUnionPay(f: *Function, inst: Air.Inst.Index, is_ptr: bool) !CValu
     const error_union_ty = if (operand_is_ptr) operand_ty.childType() else operand_ty;
 
     if (!error_union_ty.errorUnionPayload().hasRuntimeBits()) {
-        if (!is_ptr) return CValue.none;
+        if (!is_ptr) return .none;
 
         const w = f.object.writer();
         const local = try f.allocLocal(inst, inst_ty);
         try f.writeCValue(w, local, .Other);
         try w.writeAll(" = (");
-        try f.renderTypecast(w, inst_ty);
+        try f.renderType(w, inst_ty);
         try w.writeByte(')');
         try f.writeCValue(w, operand, .Initializer);
         try w.writeAll(";\n");
@@ -5746,7 +5581,7 @@ fn airWrapOptional(f: *Function, inst: Air.Inst.Index) !CValue {
 
     if (f.liveness.isUnused(inst)) {
         try reap(f, inst, &.{ty_op.operand});
-        return CValue.none;
+        return .none;
     }
 
     const inst_ty = f.air.typeOfIndex(inst);
@@ -5782,7 +5617,7 @@ fn airWrapOptional(f: *Function, inst: Air.Inst.Index) !CValue {
         try writer.writeAll(", ");
         try f.writeCValue(writer, payload, .FunctionArgument);
         try writer.writeAll(", sizeof(");
-        try f.renderTypecast(writer, payload_ty);
+        try f.renderType(writer, payload_ty);
         try writer.writeAll("));\n");
     }
     return local;
@@ -5792,7 +5627,7 @@ fn airWrapErrUnionErr(f: *Function, inst: Air.Inst.Index) !CValue {
     const ty_op = f.air.instructions.items(.data)[inst].ty_op;
     if (f.liveness.isUnused(inst)) {
         try reap(f, inst, &.{ty_op.operand});
-        return CValue.none;
+        return .none;
     }
 
     const writer = f.object.writer();
@@ -5846,7 +5681,7 @@ fn airErrUnionPayloadPtrSet(f: *Function, inst: Air.Inst.Index) !CValue {
     try writer.writeAll(";\n");
 
     // Then return the payload pointer (only if it is used)
-    if (f.liveness.isUnused(inst)) return CValue.none;
+    if (f.liveness.isUnused(inst)) return .none;
 
     const local = try f.allocLocal(inst, f.air.typeOfIndex(inst));
     try f.writeCValue(writer, local, .Other);
@@ -5857,7 +5692,7 @@ fn airErrUnionPayloadPtrSet(f: *Function, inst: Air.Inst.Index) !CValue {
 }
 
 fn airErrReturnTrace(f: *Function, inst: Air.Inst.Index) !CValue {
-    if (f.liveness.isUnused(inst)) return CValue.none;
+    if (f.liveness.isUnused(inst)) return .none;
     return f.fail("TODO: C backend: implement airErrReturnTrace", .{});
 }
 
@@ -5875,7 +5710,7 @@ fn airWrapErrUnionPay(f: *Function, inst: Air.Inst.Index) !CValue {
     const ty_op = f.air.instructions.items(.data)[inst].ty_op;
     if (f.liveness.isUnused(inst)) {
         try reap(f, inst, &.{ty_op.operand});
-        return CValue.none;
+        return .none;
     }
 
     const inst_ty = f.air.typeOfIndex(inst);
@@ -5902,7 +5737,7 @@ fn airWrapErrUnionPay(f: *Function, inst: Air.Inst.Index) !CValue {
         try writer.writeAll(", ");
         try f.writeCValue(writer, payload, .FunctionArgument);
         try writer.writeAll(", sizeof(");
-        try f.renderTypecast(writer, payload_ty);
+        try f.renderType(writer, payload_ty);
         try writer.writeAll("));\n");
     }
     return local;
@@ -5913,7 +5748,7 @@ fn airIsErr(f: *Function, inst: Air.Inst.Index, is_ptr: bool, operator: []const
 
     if (f.liveness.isUnused(inst)) {
         try reap(f, inst, &.{un_op});
-        return CValue.none;
+        return .none;
     }
 
     const writer = f.object.writer();
@@ -5951,7 +5786,7 @@ fn airArrayToSlice(f: *Function, inst: Air.Inst.Index) !CValue {
 
     if (f.liveness.isUnused(inst)) {
         try reap(f, inst, &.{ty_op.operand});
-        return CValue.none;
+        return .none;
     }
 
     const operand = try f.resolveInst(ty_op.operand);
@@ -5959,26 +5794,28 @@ fn airArrayToSlice(f: *Function, inst: Air.Inst.Index) !CValue {
     const inst_ty = f.air.typeOfIndex(inst);
     const writer = f.object.writer();
     const local = try f.allocLocal(inst, inst_ty);
-    try f.writeCValue(writer, local, .Other);
-    const array_len = f.air.typeOf(ty_op.operand).elemType().arrayLen();
+    const array_ty = f.air.typeOf(ty_op.operand).childType();
 
-    try writer.writeAll(".ptr = ");
+    try f.writeCValueMember(writer, local, .{ .identifier = "ptr" });
+    try writer.writeAll(" = ");
+    // Unfortunately, C does not support any equivalent to
+    // &(*(void *)p)[0], although LLVM does via GetElementPtr
     if (operand == .undef) {
-        // Unfortunately, C does not support any equivalent to
-        // &(*(void *)p)[0], although LLVM does via GetElementPtr
         var buf: Type.SlicePtrFieldTypeBuffer = undefined;
-        try f.writeCValue(writer, CValue{ .undef = inst_ty.slicePtrFieldType(&buf) }, .Initializer);
-    } else {
+        try f.writeCValue(writer, .{ .undef = inst_ty.slicePtrFieldType(&buf) }, .Initializer);
+    } else if (array_ty.hasRuntimeBitsIgnoreComptime()) {
         try writer.writeAll("&(");
         try f.writeCValueDeref(writer, operand);
         try writer.print(")[{}]", .{try f.fmtIntLiteral(Type.usize, Value.zero)});
-    }
+    } else try f.writeCValue(writer, operand, .Initializer);
+    try writer.writeAll("; ");
 
+    const array_len = array_ty.arrayLen();
     var len_pl: Value.Payload.U64 = .{ .base = .{ .tag = .int_u64 }, .data = array_len };
     const len_val = Value.initPayload(&len_pl.base);
-    try writer.writeAll("; ");
-    try f.writeCValue(writer, local, .Other);
-    try writer.print(".len = {};\n", .{try f.fmtIntLiteral(Type.usize, len_val)});
+    try f.writeCValueMember(writer, local, .{ .identifier = "len" });
+    try writer.print(" = {};\n", .{try f.fmtIntLiteral(Type.usize, len_val)});
+
     return local;
 }
 
@@ -5987,7 +5824,7 @@ fn airFloatCast(f: *Function, inst: Air.Inst.Index) !CValue {
 
     if (f.liveness.isUnused(inst)) {
         try reap(f, inst, &.{ty_op.operand});
-        return CValue.none;
+        return .none;
     }
 
     const inst_ty = f.air.typeOfIndex(inst);
@@ -6035,7 +5872,7 @@ fn airPtrToInt(f: *Function, inst: Air.Inst.Index) !CValue {
 
     if (f.liveness.isUnused(inst)) {
         try reap(f, inst, &.{un_op});
-        return CValue.none;
+        return .none;
     }
 
     const operand = try f.resolveInst(un_op);
@@ -6046,7 +5883,7 @@ fn airPtrToInt(f: *Function, inst: Air.Inst.Index) !CValue {
     try f.writeCValue(writer, local, .Other);
 
     try writer.writeAll(" = (");
-    try f.renderTypecast(writer, inst_ty);
+    try f.renderType(writer, inst_ty);
     try writer.writeByte(')');
     try f.writeCValue(writer, operand, .Other);
     try writer.writeAll(";\n");
@@ -6063,7 +5900,7 @@ fn airUnBuiltinCall(
 
     if (f.liveness.isUnused(inst)) {
         try reap(f, inst, &.{ty_op.operand});
-        return CValue.none;
+        return .none;
     }
 
     const operand = try f.resolveInst(ty_op.operand);
@@ -6095,7 +5932,7 @@ fn airBinBuiltinCall(
 
     if (f.liveness.isUnused(inst)) {
         try reap(f, inst, &.{ bin_op.lhs, bin_op.rhs });
-        return CValue.none;
+        return .none;
     }
 
     const lhs = try f.resolveInst(bin_op.lhs);
@@ -6168,7 +6005,7 @@ fn airCmpxchg(f: *Function, inst: Air.Inst.Index, flavor: [*:0]const u8) !CValue
         try writer.writeAll(";\n");
         try writer.writeAll("if (");
         try writer.print("zig_cmpxchg_{s}((zig_atomic(", .{flavor});
-        try f.renderTypecast(writer, ptr_ty.childType());
+        try f.renderType(writer, ptr_ty.childType());
         try writer.writeByte(')');
         if (ptr_ty.isVolatilePtr()) try writer.writeAll(" volatile");
         try writer.writeAll(" *)");
@@ -6197,7 +6034,7 @@ fn airCmpxchg(f: *Function, inst: Air.Inst.Index, flavor: [*:0]const u8) !CValue
         try writer.writeAll(";\n");
         try f.writeCValue(writer, local, .Other);
         try writer.print(".is_null = zig_cmpxchg_{s}((zig_atomic(", .{flavor});
-        try f.renderTypecast(writer, ptr_ty.childType());
+        try f.renderType(writer, ptr_ty.childType());
         try writer.writeByte(')');
         if (ptr_ty.isVolatilePtr()) try writer.writeAll(" volatile");
         try writer.writeAll(" *)");
@@ -6217,8 +6054,8 @@ fn airCmpxchg(f: *Function, inst: Air.Inst.Index, flavor: [*:0]const u8) !CValue
     }
 
     if (f.liveness.isUnused(inst)) {
-        try freeLocal(f, inst, local.local, 0);
-        return CValue.none;
+        try freeLocal(f, inst, local.new_local, 0);
+        return .none;
     }
 
     return local;
@@ -6240,12 +6077,12 @@ fn airAtomicRmw(f: *Function, inst: Air.Inst.Index) !CValue {
     switch (extra.op()) {
         else => {
             try writer.writeAll("zig_atomic(");
-            try f.renderTypecast(writer, ptr_ty.elemType());
+            try f.renderType(writer, ptr_ty.elemType());
             try writer.writeByte(')');
         },
         .Nand, .Min, .Max => {
             // These are missing from stdatomic.h, so no atomic types for now.
-            try f.renderTypecast(writer, ptr_ty.elemType());
+            try f.renderType(writer, ptr_ty.elemType());
         },
     }
     if (ptr_ty.isVolatilePtr()) try writer.writeAll(" volatile");
@@ -6260,8 +6097,8 @@ fn airAtomicRmw(f: *Function, inst: Air.Inst.Index) !CValue {
     try writer.writeAll(");\n");
 
     if (f.liveness.isUnused(inst)) {
-        try freeLocal(f, inst, local.local, 0);
-        return CValue.none;
+        try freeLocal(f, inst, local.new_local, 0);
+        return .none;
     }
 
     return local;
@@ -6273,7 +6110,7 @@ fn airAtomicLoad(f: *Function, inst: Air.Inst.Index) !CValue {
     try reap(f, inst, &.{atomic_load.ptr});
     const ptr_ty = f.air.typeOf(atomic_load.ptr);
     if (!ptr_ty.isVolatilePtr() and f.liveness.isUnused(inst)) {
-        return CValue.none;
+        return .none;
     }
 
     const inst_ty = f.air.typeOfIndex(inst);
@@ -6282,7 +6119,7 @@ fn airAtomicLoad(f: *Function, inst: Air.Inst.Index) !CValue {
     try f.writeCValue(writer, local, .Other);
 
     try writer.writeAll(" = zig_atomic_load((zig_atomic(");
-    try f.renderTypecast(writer, ptr_ty.elemType());
+    try f.renderType(writer, ptr_ty.elemType());
     try writer.writeByte(')');
     if (ptr_ty.isVolatilePtr()) try writer.writeAll(" volatile");
     try writer.writeAll(" *)");
@@ -6305,7 +6142,7 @@ fn airAtomicStore(f: *Function, inst: Air.Inst.Index, order: [*:0]const u8) !CVa
     const writer = f.object.writer();
 
     try writer.writeAll("zig_atomic_store((zig_atomic(");
-    try f.renderTypecast(writer, ptr_ty.elemType());
+    try f.renderType(writer, ptr_ty.elemType());
     try writer.writeByte(')');
     if (ptr_ty.isVolatilePtr()) try writer.writeAll(" volatile");
     try writer.writeAll(" *)");
@@ -6316,7 +6153,7 @@ fn airAtomicStore(f: *Function, inst: Air.Inst.Index, order: [*:0]const u8) !CVa
     try f.object.dg.renderTypeForBuiltinFnName(writer, ptr_ty.childType());
     try writer.writeAll(");\n");
 
-    return CValue.none;
+    return .none;
 }
 
 fn airMemset(f: *Function, inst: Air.Inst.Index) !CValue {
@@ -6347,7 +6184,7 @@ fn airMemset(f: *Function, inst: Air.Inst.Index) !CValue {
         try writer.writeAll(" += ");
         try f.object.dg.renderValue(writer, Type.usize, Value.one, .Other);
         try writer.writeAll(") ((");
-        try f.renderTypecast(writer, u8_ptr_ty);
+        try f.renderType(writer, u8_ptr_ty);
         try writer.writeByte(')');
         try f.writeCValue(writer, dest_ptr, .FunctionArgument);
         try writer.writeAll(")[");
@@ -6357,9 +6194,9 @@ fn airMemset(f: *Function, inst: Air.Inst.Index) !CValue {
         try writer.writeAll(";\n");
 
         try reap(f, inst, &.{ pl_op.operand, extra.lhs, extra.rhs });
-        try freeLocal(f, inst, index.local, 0);
+        try freeLocal(f, inst, index.new_local, 0);
 
-        return CValue.none;
+        return .none;
     }
 
     try reap(f, inst, &.{ pl_op.operand, extra.lhs, extra.rhs });
@@ -6371,7 +6208,7 @@ fn airMemset(f: *Function, inst: Air.Inst.Index) !CValue {
     try f.writeCValue(writer, len, .FunctionArgument);
     try writer.writeAll(");\n");
 
-    return CValue.none;
+    return .none;
 }
 
 fn airMemcpy(f: *Function, inst: Air.Inst.Index) !CValue {
@@ -6391,7 +6228,7 @@ fn airMemcpy(f: *Function, inst: Air.Inst.Index) !CValue {
     try f.writeCValue(writer, len, .FunctionArgument);
     try writer.writeAll(");\n");
 
-    return CValue.none;
+    return .none;
 }
 
 fn airSetUnionTag(f: *Function, inst: Air.Inst.Index) !CValue {
@@ -6404,7 +6241,7 @@ fn airSetUnionTag(f: *Function, inst: Air.Inst.Index) !CValue {
     const union_ty = f.air.typeOf(bin_op.lhs).childType();
     const target = f.object.dg.module.getTarget();
     const layout = union_ty.unionGetLayout(target);
-    if (layout.tag_size == 0) return CValue.none;
+    if (layout.tag_size == 0) return .none;
 
     try writer.writeByte('(');
     try f.writeCValue(writer, union_ptr, .Other);
@@ -6412,7 +6249,7 @@ fn airSetUnionTag(f: *Function, inst: Air.Inst.Index) !CValue {
     try f.writeCValue(writer, new_tag, .Other);
     try writer.writeAll(";\n");
 
-    return CValue.none;
+    return .none;
 }
 
 fn airGetUnionTag(f: *Function, inst: Air.Inst.Index) !CValue {
@@ -6420,7 +6257,7 @@ fn airGetUnionTag(f: *Function, inst: Air.Inst.Index) !CValue {
 
     if (f.liveness.isUnused(inst)) {
         try reap(f, inst, &.{ty_op.operand});
-        return CValue.none;
+        return .none;
     }
 
     const operand = try f.resolveInst(ty_op.operand);
@@ -6430,7 +6267,7 @@ fn airGetUnionTag(f: *Function, inst: Air.Inst.Index) !CValue {
 
     const target = f.object.dg.module.getTarget();
     const layout = un_ty.unionGetLayout(target);
-    if (layout.tag_size == 0) return CValue.none;
+    if (layout.tag_size == 0) return .none;
 
     const inst_ty = f.air.typeOfIndex(inst);
     const writer = f.object.writer();
@@ -6448,7 +6285,7 @@ fn airTagName(f: *Function, inst: Air.Inst.Index) !CValue {
 
     if (f.liveness.isUnused(inst)) {
         try reap(f, inst, &.{un_op});
-        return CValue.none;
+        return .none;
     }
 
     const inst_ty = f.air.typeOfIndex(inst);
@@ -6459,7 +6296,9 @@ fn airTagName(f: *Function, inst: Air.Inst.Index) !CValue {
     const writer = f.object.writer();
     const local = try f.allocLocal(inst, inst_ty);
     try f.writeCValue(writer, local, .Other);
-    try writer.print(" = {s}(", .{try f.object.dg.getTagNameFn(enum_ty)});
+    try writer.print(" = {s}(", .{
+        try f.getLazyFnName(.{ .tag_name = enum_ty.getOwnerDecl() }, .{ .tag_name = enum_ty }),
+    });
     try f.writeCValue(writer, operand, .Other);
     try writer.writeAll(");\n");
 
@@ -6471,7 +6310,7 @@ fn airErrorName(f: *Function, inst: Air.Inst.Index) !CValue {
 
     if (f.liveness.isUnused(inst)) {
         try reap(f, inst, &.{un_op});
-        return CValue.none;
+        return .none;
     }
 
     const writer = f.object.writer();
@@ -6491,7 +6330,7 @@ fn airSplat(f: *Function, inst: Air.Inst.Index) !CValue {
     const ty_op = f.air.instructions.items(.data)[inst].ty_op;
     if (f.liveness.isUnused(inst)) {
         try reap(f, inst, &.{ty_op.operand});
-        return CValue.none;
+        return .none;
     }
 
     const inst_ty = f.air.typeOfIndex(inst);
@@ -6507,13 +6346,13 @@ fn airSplat(f: *Function, inst: Air.Inst.Index) !CValue {
 }
 
 fn airSelect(f: *Function, inst: Air.Inst.Index) !CValue {
-    if (f.liveness.isUnused(inst)) return CValue.none;
+    if (f.liveness.isUnused(inst)) return .none;
 
     return f.fail("TODO: C backend: implement airSelect", .{});
 }
 
 fn airShuffle(f: *Function, inst: Air.Inst.Index) !CValue {
-    if (f.liveness.isUnused(inst)) return CValue.none;
+    if (f.liveness.isUnused(inst)) return .none;
 
     return f.fail("TODO: C backend: implement airShuffle", .{});
 }
@@ -6523,7 +6362,7 @@ fn airReduce(f: *Function, inst: Air.Inst.Index) !CValue {
 
     if (f.liveness.isUnused(inst)) {
         try reap(f, inst, &.{reduce.operand});
-        return CValue.none;
+        return .none;
     }
 
     const target = f.object.dg.module.getTarget();
@@ -6599,10 +6438,9 @@ fn airReduce(f: *Function, inst: Air.Inst.Index) !CValue {
     //
     // Equivalent to:
     //   reduce: {
-    //     var i: usize = 0;
     //     var accum: T = init;
-    //     while (i < vec.len) : (i += 1) {
-    //       accum = func(accum, vec[i]);
+    //     for (vec) : (elem) {
+    //       accum = func(accum, elem);
     //     }
     //     break :reduce accum;
     //   }
@@ -6674,7 +6512,7 @@ fn airReduce(f: *Function, inst: Air.Inst.Index) !CValue {
 
     try writer.writeAll(";\n");
 
-    try freeLocal(f, inst, it.local, 0);
+    try freeLocal(f, inst, it.new_local, 0);
 
     return accum;
 }
@@ -6687,8 +6525,8 @@ fn airAggregateInit(f: *Function, inst: Air.Inst.Index) !CValue {
     const gpa = f.object.dg.gpa;
     const resolved_elements = try gpa.alloc(CValue, elements.len);
     defer gpa.free(resolved_elements);
-    for (elements, 0..) |element, i| {
-        resolved_elements[i] = try f.resolveInst(element);
+    for (resolved_elements, elements) |*resolved_element, element| {
+        resolved_element.* = try f.resolveInst(element);
     }
     {
         var bt = iterateBigTomb(f, inst);
@@ -6697,7 +6535,7 @@ fn airAggregateInit(f: *Function, inst: Air.Inst.Index) !CValue {
         }
     }
 
-    if (f.liveness.isUnused(inst)) return CValue.none;
+    if (f.liveness.isUnused(inst)) return .none;
 
     const target = f.object.dg.module.getTarget();
 
@@ -6723,50 +6561,51 @@ fn airAggregateInit(f: *Function, inst: Air.Inst.Index) !CValue {
             .Auto, .Extern => {
                 try f.writeCValue(writer, local, .Other);
                 try writer.writeAll(" = (");
-                try f.renderTypecast(writer, inst_ty);
+                try f.renderType(writer, inst_ty);
                 try writer.writeAll(")");
                 try writer.writeByte('{');
                 var empty = true;
-                for (elements, 0..) |element, index| {
-                    if (inst_ty.structFieldValueComptime(index)) |_| continue;
+                for (elements, resolved_elements, 0..) |element, resolved_element, field_i| {
+                    if (inst_ty.structFieldValueComptime(field_i)) |_| continue;
 
                     if (!empty) try writer.writeAll(", ");
-                    if (!inst_ty.isTupleOrAnonStruct()) {
-                        try writer.print(".{ } = ", .{fmtIdent(inst_ty.structFieldName(index))});
-                    }
+
+                    const field_name: CValue = if (inst_ty.isSimpleTuple())
+                        .{ .field = field_i }
+                    else
+                        .{ .identifier = inst_ty.structFieldName(field_i) };
+                    try writer.writeByte('.');
+                    try f.object.dg.writeCValue(writer, field_name);
+                    try writer.writeAll(" = ");
 
                     const element_ty = f.air.typeOf(element);
                     try f.writeCValue(writer, switch (element_ty.zigTypeTag()) {
-                        .Array => CValue{ .undef = element_ty },
-                        else => resolved_elements[index],
+                        .Array => .{ .undef = element_ty },
+                        else => resolved_element,
                     }, .Initializer);
                     empty = false;
                 }
-                if (empty) try writer.print("{}", .{try f.fmtIntLiteral(Type.u8, Value.zero)});
                 try writer.writeAll("};\n");
 
-                var field_id: usize = 0;
-                for (elements, 0..) |element, index| {
-                    if (inst_ty.structFieldValueComptime(index)) |_| continue;
+                for (elements, resolved_elements, 0..) |element, resolved_element, field_i| {
+                    if (inst_ty.structFieldValueComptime(field_i)) |_| continue;
 
                     const element_ty = f.air.typeOf(element);
                     if (element_ty.zigTypeTag() != .Array) continue;
 
-                    const field_name = if (inst_ty.isTupleOrAnonStruct())
-                        CValue{ .field = field_id }
+                    const field_name: CValue = if (inst_ty.isSimpleTuple())
+                        .{ .field = field_i }
                     else
-                        CValue{ .identifier = inst_ty.structFieldName(index) };
+                        .{ .identifier = inst_ty.structFieldName(field_i) };
 
                     try writer.writeAll(";\n");
                     try writer.writeAll("memcpy(");
                     try f.writeCValueMember(writer, local, field_name);
                     try writer.writeAll(", ");
-                    try f.writeCValue(writer, resolved_elements[index], .FunctionArgument);
+                    try f.writeCValue(writer, resolved_element, .FunctionArgument);
                     try writer.writeAll(", sizeof(");
-                    try f.renderTypecast(writer, element_ty);
+                    try f.renderType(writer, element_ty);
                     try writer.writeAll("));\n");
-
-                    field_id += 1;
                 }
             },
             .Packed => {
@@ -6784,7 +6623,7 @@ fn airAggregateInit(f: *Function, inst: Air.Inst.Index) !CValue {
                 const bit_offset_val = Value.initPayload(&bit_offset_val_pl.base);
 
                 var empty = true;
-                for (elements, 0..) |_, index| {
+                for (0..elements.len) |index| {
                     const field_ty = inst_ty.structFieldType(index);
                     if (!field_ty.hasRuntimeBitsIgnoreComptime()) continue;
 
@@ -6810,11 +6649,11 @@ fn airAggregateInit(f: *Function, inst: Air.Inst.Index) !CValue {
                         try f.renderIntCast(writer, inst_ty, element, field_ty, .FunctionArgument);
                     } else {
                         try writer.writeByte('(');
-                        try f.renderTypecast(writer, inst_ty);
+                        try f.renderType(writer, inst_ty);
                         try writer.writeByte(')');
                         if (field_ty.isPtrAtRuntime()) {
                             try writer.writeByte('(');
-                            try f.renderTypecast(writer, switch (int_info.signedness) {
+                            try f.renderType(writer, switch (int_info.signedness) {
                                 .unsigned => Type.usize,
                                 .signed => Type.isize,
                             });
@@ -6833,13 +6672,6 @@ fn airAggregateInit(f: *Function, inst: Air.Inst.Index) !CValue {
                     empty = false;
                 }
 
-                if (empty) {
-                    try writer.writeByte('(');
-                    try f.renderTypecast(writer, inst_ty);
-                    try writer.writeByte(')');
-                    try f.writeCValue(writer, .{ .undef = inst_ty }, .Initializer);
-                }
-
                 try writer.writeAll(";\n");
             },
         },
@@ -6855,7 +6687,7 @@ fn airUnionInit(f: *Function, inst: Air.Inst.Index) !CValue {
 
     if (f.liveness.isUnused(inst)) {
         try reap(f, inst, &.{extra.init});
-        return CValue.none;
+        return .none;
     }
 
     const union_ty = f.air.typeOfIndex(inst);
@@ -6875,7 +6707,7 @@ fn airUnionInit(f: *Function, inst: Air.Inst.Index) !CValue {
         return local;
     }
 
-    if (union_ty.unionTagTypeSafety()) |tag_ty| {
+    const field: CValue = if (union_ty.unionTagTypeSafety()) |tag_ty| field: {
         const layout = union_ty.unionGetLayout(target);
         if (layout.tag_size != 0) {
             const field_index = tag_ty.enumFieldIndex(field_name).?;
@@ -6892,18 +6724,13 @@ fn airUnionInit(f: *Function, inst: Air.Inst.Index) !CValue {
             try f.writeCValue(writer, local, .Other);
             try writer.print(".tag = {}; ", .{try f.fmtIntLiteral(tag_ty, int_val)});
         }
-        try f.writeCValue(writer, local, .Other);
-        try writer.print(".payload.{ } = ", .{fmtIdent(field_name)});
-        try f.writeCValue(writer, payload, .Other);
-        try writer.writeAll(";\n");
-        return local;
-    }
+        break :field .{ .payload_identifier = field_name };
+    } else .{ .identifier = field_name };
 
-    try f.writeCValue(writer, local, .Other);
-    try writer.print(".{ } = ", .{fmtIdent(field_name)});
+    try f.writeCValueMember(writer, local, field);
+    try writer.writeAll(" = ");
     try f.writeCValue(writer, payload, .Other);
     try writer.writeAll(";\n");
-
     return local;
 }
 
@@ -6914,7 +6741,7 @@ fn airPrefetch(f: *Function, inst: Air.Inst.Index) !CValue {
         // The available prefetch intrinsics do not accept a cache argument; only
         // address, rw, and locality. So unless the cache is data, we do not lower
         // this instruction.
-        .instruction => return CValue.none,
+        .instruction => return .none,
     }
     const ptr = try f.resolveInst(prefetch.ptr);
     try reap(f, inst, &.{prefetch.ptr});
@@ -6924,11 +6751,11 @@ fn airPrefetch(f: *Function, inst: Air.Inst.Index) !CValue {
     try writer.print(", {d}, {d});\n", .{
         @enumToInt(prefetch.rw), prefetch.locality,
     });
-    return CValue.none;
+    return .none;
 }
 
 fn airWasmMemorySize(f: *Function, inst: Air.Inst.Index) !CValue {
-    if (f.liveness.isUnused(inst)) return CValue.none;
+    if (f.liveness.isUnused(inst)) return .none;
 
     const pl_op = f.air.instructions.items(.data)[inst].pl_op;
 
@@ -6965,7 +6792,7 @@ fn airFloatNeg(f: *Function, inst: Air.Inst.Index) !CValue {
     const un_op = f.air.instructions.items(.data)[inst].un_op;
     if (f.liveness.isUnused(inst)) {
         try reap(f, inst, &.{un_op});
-        return CValue.none;
+        return .none;
     }
 
     const operand = try f.resolveInst(un_op);
@@ -6987,7 +6814,7 @@ fn airUnFloatOp(f: *Function, inst: Air.Inst.Index, operation: []const u8) !CVal
     const un_op = f.air.instructions.items(.data)[inst].un_op;
     if (f.liveness.isUnused(inst)) {
         try reap(f, inst, &.{un_op});
-        return CValue.none;
+        return .none;
     }
     const operand = try f.resolveInst(un_op);
     try reap(f, inst, &.{un_op});
@@ -7009,7 +6836,7 @@ fn airBinFloatOp(f: *Function, inst: Air.Inst.Index, operation: []const u8) !CVa
     const bin_op = f.air.instructions.items(.data)[inst].bin_op;
     if (f.liveness.isUnused(inst)) {
         try reap(f, inst, &.{ bin_op.lhs, bin_op.rhs });
-        return CValue.none;
+        return .none;
     }
     const lhs = try f.resolveInst(bin_op.lhs);
     const rhs = try f.resolveInst(bin_op.rhs);
@@ -7036,7 +6863,7 @@ fn airMulAdd(f: *Function, inst: Air.Inst.Index) !CValue {
     const bin_op = f.air.extraData(Air.Bin, pl_op.payload).data;
     if (f.liveness.isUnused(inst)) {
         try reap(f, inst, &.{ bin_op.lhs, bin_op.rhs, pl_op.operand });
-        return CValue.none;
+        return .none;
     }
     const inst_ty = f.air.typeOfIndex(inst);
     const mulend1 = try f.resolveInst(bin_op.lhs);
@@ -7058,6 +6885,81 @@ fn airMulAdd(f: *Function, inst: Air.Inst.Index) !CValue {
     return local;
 }
 
+fn airCVaStart(f: *Function, inst: Air.Inst.Index) !CValue {
+    if (f.liveness.isUnused(inst)) return .none;
+
+    const inst_ty = f.air.typeOfIndex(inst);
+    const fn_cty = try f.typeToCType(f.object.dg.decl.?.ty, .complete);
+    const param_len = fn_cty.castTag(.varargs_function).?.data.param_types.len;
+
+    const writer = f.object.writer();
+    const local = try f.allocLocal(inst, inst_ty);
+    try writer.writeAll("va_start(*(va_list *)&");
+    try f.writeCValue(writer, local, .Other);
+    if (param_len > 0) {
+        try writer.writeAll(", ");
+        try f.writeCValue(writer, .{ .arg = param_len - 1 }, .FunctionArgument);
+    }
+    try writer.writeAll(");\n");
+    return local;
+}
+
+fn airCVaArg(f: *Function, inst: Air.Inst.Index) !CValue {
+    const ty_op = f.air.instructions.items(.data)[inst].ty_op;
+    if (f.liveness.isUnused(inst)) {
+        try reap(f, inst, &.{ty_op.operand});
+        return .none;
+    }
+
+    const inst_ty = f.air.typeOfIndex(inst);
+    const va_list = try f.resolveInst(ty_op.operand);
+    try reap(f, inst, &.{ty_op.operand});
+
+    const writer = f.object.writer();
+    const local = try f.allocLocal(inst, inst_ty);
+    try f.writeCValue(writer, local, .Other);
+    try writer.writeAll(" = va_arg(*(va_list *)");
+    try f.writeCValue(writer, va_list, .Other);
+    try writer.writeAll(", ");
+    try f.renderType(writer, f.air.getRefType(ty_op.ty));
+    try writer.writeAll(");\n");
+    return local;
+}
+
+fn airCVaEnd(f: *Function, inst: Air.Inst.Index) !CValue {
+    const un_op = f.air.instructions.items(.data)[inst].un_op;
+
+    const va_list = try f.resolveInst(un_op);
+    try reap(f, inst, &.{un_op});
+
+    const writer = f.object.writer();
+    try writer.writeAll("va_end(*(va_list *)");
+    try f.writeCValue(writer, va_list, .Other);
+    try writer.writeAll(");\n");
+    return .none;
+}
+
+fn airCVaCopy(f: *Function, inst: Air.Inst.Index) !CValue {
+    const ty_op = f.air.instructions.items(.data)[inst].ty_op;
+    if (f.liveness.isUnused(inst)) {
+        try reap(f, inst, &.{ty_op.operand});
+        return .none;
+    }
+
+    const inst_ty = f.air.typeOfIndex(inst);
+    const va_list = try f.resolveInst(ty_op.operand);
+    try reap(f, inst, &.{ty_op.operand});
+
+    const writer = f.object.writer();
+    const local = try f.allocLocal(inst, inst_ty);
+    try writer.writeAll("va_copy(*(va_list *)&");
+    try f.writeCValue(writer, local, .Other);
+    try writer.writeAll(", *(va_list *)");
+    try f.writeCValue(writer, va_list, .Other);
+    try writer.writeAll(");\n");
+    return local;
+}
+
 fn toMemoryOrder(order: std.builtin.AtomicOrder) [:0]const u8 {
     return switch (order) {
         // Note: unordered is actually even less atomic than relaxed
@@ -7243,8 +7145,9 @@ fn stringLiteral(child_stream: anytype) StringLiteral(@TypeOf(child_stream)) {
     return .{ .counting_writer = std.io.countingWriter(child_stream) };
 }
 
+const FormatStringContext = struct { str: []const u8, sentinel: ?u8 };
 fn formatStringLiteral(
-    str: []const u8,
+    data: FormatStringContext,
     comptime fmt: []const u8,
     _: std.fmt.FormatOptions,
     writer: anytype,
@@ -7253,13 +7156,13 @@ fn formatStringLiteral(
 
     var literal = stringLiteral(writer);
     try literal.start();
-    for (str) |c|
-        try literal.writeChar(c);
+    for (data.str) |c| try literal.writeChar(c);
+    if (data.sentinel) |sentinel| if (sentinel != 0) try literal.writeChar(sentinel);
     try literal.end();
 }
 
-fn fmtStringLiteral(str: []const u8) std.fmt.Formatter(formatStringLiteral) {
-    return .{ .data = str };
+fn fmtStringLiteral(str: []const u8, sentinel: ?u8) std.fmt.Formatter(formatStringLiteral) {
+    return .{ .data = .{ .str = str, .sentinel = sentinel } };
 }
 
 fn undefPattern(comptime IntType: type) IntType {
@@ -7344,7 +7247,7 @@ fn formatIntLiteral(
                 use_twos_comp = true;
             } else {
                 // TODO: Use fmtIntLiteral for 0?
-                try writer.print("zig_sub_{c}{d}(zig_as_{c}{d}(0, 0), ", .{ signAbbrev(int_info.signedness), c_bits, signAbbrev(int_info.signedness), c_bits });
+                try writer.print("zig_sub_{c}{d}(zig_make_{c}{d}(0, 0), ", .{ signAbbrev(int_info.signedness), c_bits, signAbbrev(int_info.signedness), c_bits });
             }
         } else {
             try writer.writeByte('-');
@@ -7354,11 +7257,16 @@ fn formatIntLiteral(
     switch (data.ty.tag()) {
         .c_short, .c_ushort, .c_int, .c_uint, .c_long, .c_ulong, .c_longlong, .c_ulonglong => {},
         else => {
-            if (int_info.bits > 64 and data.location != null and data.location.? == .StaticInitializer) {
+            if (int_info.bits <= 64) {
+                try writer.print("{s}INT{d}_C(", .{ switch (int_info.signedness) {
+                    .signed => "",
+                    .unsigned => "U",
+                }, c_bits });
+            } else if (data.location != null and data.location.? == .StaticInitializer) {
                 // MSVC treats casting the struct initializer as not constant (C2099), so an alternate form is used in global initializers
-                try writer.print("zig_as_constant_{c}{d}(", .{ signAbbrev(int_info.signedness), c_bits });
+                try writer.print("zig_make_constant_{c}{d}(", .{ signAbbrev(int_info.signedness), c_bits });
             } else {
-                try writer.print("zig_as_{c}{d}(", .{ signAbbrev(int_info.signedness), c_bits });
+                try writer.print("zig_make_{c}{d}(", .{ signAbbrev(int_info.signedness), c_bits });
             }
         },
     }
@@ -7467,17 +7375,20 @@ fn isByRef(ty: Type) bool {
 }
 
 const LowerFnRetTyBuffer = struct {
+    names: [1][]const u8,
     types: [1]Type,
     values: [1]Value,
-    payload: Type.Payload.Tuple,
+    payload: Type.Payload.AnonStruct,
 };
 fn lowerFnRetTy(ret_ty: Type, buffer: *LowerFnRetTyBuffer, target: std.Target) Type {
     if (ret_ty.zigTypeTag() == .NoReturn) return Type.initTag(.noreturn);
 
     if (lowersToArray(ret_ty, target)) {
+        buffer.names = [1][]const u8{"array"};
         buffer.types = [1]Type{ret_ty};
         buffer.values = [1]Value{Value.initTag(.unreachable_value)};
         buffer.payload = .{ .data = .{
+            .names = &buffer.names,
             .types = &buffer.types,
             .values = &buffer.values,
         } };
@@ -7533,7 +7444,7 @@ fn die(f: *Function, inst: Air.Inst.Index, ref: Air.Inst.Ref) !void {
     if (f.air.instructions.items(.tag)[ref_inst] == .constant) return;
     const c_value = (f.value_map.fetchRemove(ref) orelse return).value;
     const local_index = switch (c_value) {
-        .local => |l| l,
+        .local, .new_local => |l| l,
         else => return,
     };
     try freeLocal(f, inst, local_index, ref_inst);
@@ -7544,21 +7455,16 @@ fn freeLocal(f: *Function, inst: Air.Inst.Index, local_index: LocalIndex, ref_in
     const local = &f.locals.items[local_index];
     log.debug("%{d}: freeing t{d} (operand %{d})", .{ inst, local_index, ref_inst });
     if (local.loop_depth < f.free_locals_clone_depth) return;
-    const gop = try f.free_locals_stack.items[local.loop_depth].getOrPutContext(
-        gpa,
-        local.ty,
-        f.tyHashCtx(),
-    );
+    const gop = try f.free_locals_stack.items[local.loop_depth].getOrPut(gpa, local.getType());
     if (!gop.found_existing) gop.value_ptr.* = .{};
     if (std.debug.runtime_safety) {
-        // If this trips, it means a local is being inserted into the
-        // free_locals map while it already exists in the map, which is not
-        // allowed.
-        assert(mem.indexOfScalar(LocalIndex, gop.value_ptr.items, local_index) == null);
         // If this trips, an unfreeable allocation was attempted to be freed.
         assert(!f.allocs.contains(local_index));
     }
-    try gop.value_ptr.append(gpa, local_index);
+    // If this trips, it means a local is being inserted into the
+    // free_locals map while it already exists in the map, which is not
+    // allowed.
+    try gop.value_ptr.putNoClobber(gpa, local_index, {});
 }
 
 const BigTomb = struct {
@@ -7607,14 +7513,36 @@ fn deinitFreeLocalsMap(gpa: mem.Allocator, map: *LocalsMap) void {
     map.deinit(gpa);
 }
 
-fn noticeBranchFrees(f: *Function, pre_locals_len: LocalIndex, inst: Air.Inst.Index) !void {
-    for (f.locals.items[pre_locals_len..], 0..) |*local, local_offset| {
-        const local_index = pre_locals_len + @intCast(LocalIndex, local_offset);
-        if (f.allocs.contains(local_index)) continue; // allocs are not freeable
+fn noticeBranchFrees(
+    f: *Function,
+    pre_locals_len: LocalIndex,
+    pre_allocs_len: LocalIndex,
+    inst: Air.Inst.Index,
+) !void {
+    const free_locals = f.getFreeLocals();
+
+    for (f.locals.items[pre_locals_len..], pre_locals_len..) |*local, local_i| {
+        const local_index = @intCast(LocalIndex, local_i);
+        if (f.allocs.contains(local_index)) {
+            if (std.debug.runtime_safety) {
+                // new allocs are no longer freeable, so make sure they aren't in the free list
+                if (free_locals.getPtr(local.getType())) |locals_list| {
+                    assert(!locals_list.contains(local_index));
+                }
+            }
+            continue;
+        }
 
         // free more deeply nested locals from other branches at current depth
         assert(local.loop_depth >= f.free_locals_stack.items.len - 1);
         local.loop_depth = @intCast(LoopDepth, f.free_locals_stack.items.len - 1);
         try freeLocal(f, inst, local_index, 0);
     }
+
+    for (f.allocs.keys()[pre_allocs_len..]) |local_i| {
+        const local_index = @intCast(LocalIndex, local_i);
+        const local = &f.locals.items[local_index];
+        // new allocs are no longer freeable, so remove them from the free list
+        if (free_locals.getPtr(local.getType())) |locals_list| _ = locals_list.swapRemove(local_index);
+    }
 }