stage2: extract ZIR printing code into print_zir.zig

also implement textual printing of the ZIR instruction `atomic_rmw`.

3 files changed, 1869 insertions, 1845 deletions

diff --git a/src/Zir.zig b/src/Zir.zig
index f8dbef2534..f4c3e58eb0 100644
--- a/src/Zir.zig
+++ b/src/Zir.zig
@@ -112,51 +112,6 @@ pub fn deinit(code: *Zir, gpa: *Allocator) void {
     code.* = undefined;
 }
 
-/// Write human-readable, debug formatted ZIR code to a file.
-pub fn renderAsTextToFile(
-    gpa: *Allocator,
-    scope_file: *Module.Scope.File,
-    fs_file: std.fs.File,
-) !void {
-    var arena = std.heap.ArenaAllocator.init(gpa);
-    defer arena.deinit();
-
-    var writer: Writer = .{
-        .gpa = gpa,
-        .arena = &arena.allocator,
-        .file = scope_file,
-        .code = scope_file.zir,
-        .indent = 0,
-        .parent_decl_node = 0,
-    };
-
-    const main_struct_inst = scope_file.zir.getMainStruct();
-    try fs_file.writer().print("%{d} ", .{main_struct_inst});
-    try writer.writeInstToStream(fs_file.writer(), main_struct_inst);
-    try fs_file.writeAll("\n");
-    const imports_index = scope_file.zir.extra[@enumToInt(ExtraIndex.imports)];
-    if (imports_index != 0) {
-        try fs_file.writeAll("Imports:\n");
-
-        const extra = scope_file.zir.extraData(Inst.Imports, imports_index);
-        var import_i: u32 = 0;
-        var extra_index = extra.end;
-
-        while (import_i < extra.data.imports_len) : (import_i += 1) {
-            const item = scope_file.zir.extraData(Inst.Imports.Item, extra_index);
-            extra_index = item.end;
-
-            const src: LazySrcLoc = .{ .token_abs = item.data.token };
-            const import_path = scope_file.zir.nullTerminatedString(item.data.name);
-            try fs_file.writer().print("  @import(\"{}\") ", .{
-                std.zig.fmtEscapes(import_path),
-            });
-            try writer.writeSrc(fs_file.writer(), src);
-            try fs_file.writer().writeAll("\n");
-        }
-    }
-}
-
 /// These are untyped instructions generated from an Abstract Syntax Tree.
 /// The data here is immutable because it is possible to have multiple
 /// analyses on the same ZIR happening at the same time.
@@ -2904,1805 +2859,6 @@ pub const Inst = struct {
 
 pub const SpecialProng = enum { none, @"else", under };
 
-const Writer = struct {
-    gpa: *Allocator,
-    arena: *Allocator,
-    file: *Module.Scope.File,
-    code: Zir,
-    indent: u32,
-    parent_decl_node: u32,
-
-    fn relativeToNodeIndex(self: *Writer, offset: i32) Ast.Node.Index {
-        return @bitCast(Ast.Node.Index, offset + @bitCast(i32, self.parent_decl_node));
-    }
-
-    fn writeInstToStream(
-        self: *Writer,
-        stream: anytype,
-        inst: Inst.Index,
-    ) (@TypeOf(stream).Error || error{OutOfMemory})!void {
-        const tags = self.code.instructions.items(.tag);
-        const tag = tags[inst];
-        try stream.print("= {s}(", .{@tagName(tags[inst])});
-        switch (tag) {
-            .array_type,
-            .as,
-            .coerce_result_ptr,
-            .elem_ptr,
-            .elem_val,
-            .store,
-            .store_to_block_ptr,
-            .store_to_inferred_ptr,
-            .field_ptr_type,
-            => try self.writeBin(stream, inst),
-
-            .alloc,
-            .alloc_mut,
-            .alloc_comptime,
-            .indexable_ptr_len,
-            .anyframe_type,
-            .bit_not,
-            .bool_not,
-            .negate,
-            .negate_wrap,
-            .load,
-            .ensure_result_used,
-            .ensure_result_non_error,
-            .ret_node,
-            .ret_load,
-            .resolve_inferred_alloc,
-            .optional_type,
-            .optional_payload_safe,
-            .optional_payload_unsafe,
-            .optional_payload_safe_ptr,
-            .optional_payload_unsafe_ptr,
-            .err_union_payload_safe,
-            .err_union_payload_unsafe,
-            .err_union_payload_safe_ptr,
-            .err_union_payload_unsafe_ptr,
-            .err_union_code,
-            .err_union_code_ptr,
-            .is_non_null,
-            .is_non_null_ptr,
-            .is_non_err,
-            .is_non_err_ptr,
-            .typeof,
-            .typeof_elem,
-            .struct_init_empty,
-            .type_info,
-            .size_of,
-            .bit_size_of,
-            .typeof_log2_int_type,
-            .log2_int_type,
-            .ptr_to_int,
-            .error_to_int,
-            .int_to_error,
-            .compile_error,
-            .set_eval_branch_quota,
-            .enum_to_int,
-            .align_of,
-            .bool_to_int,
-            .embed_file,
-            .error_name,
-            .panic,
-            .set_align_stack,
-            .set_cold,
-            .set_float_mode,
-            .set_runtime_safety,
-            .sqrt,
-            .sin,
-            .cos,
-            .exp,
-            .exp2,
-            .log,
-            .log2,
-            .log10,
-            .fabs,
-            .floor,
-            .ceil,
-            .trunc,
-            .round,
-            .tag_name,
-            .reify,
-            .type_name,
-            .frame_type,
-            .frame_size,
-            .clz,
-            .ctz,
-            .pop_count,
-            .byte_swap,
-            .bit_reverse,
-            .elem_type,
-            .@"resume",
-            .@"await",
-            .await_nosuspend,
-            .fence,
-            => try self.writeUnNode(stream, inst),
-
-            .ref,
-            .ret_coerce,
-            .ensure_err_payload_void,
-            => try self.writeUnTok(stream, inst),
-
-            .bool_br_and,
-            .bool_br_or,
-            => try self.writeBoolBr(stream, inst),
-
-            .array_type_sentinel => try self.writeArrayTypeSentinel(stream, inst),
-            .param_type => try self.writeParamType(stream, inst),
-            .ptr_type_simple => try self.writePtrTypeSimple(stream, inst),
-            .ptr_type => try self.writePtrType(stream, inst),
-            .int => try self.writeInt(stream, inst),
-            .int_big => try self.writeIntBig(stream, inst),
-            .float => try self.writeFloat(stream, inst),
-            .float128 => try self.writeFloat128(stream, inst),
-            .str => try self.writeStr(stream, inst),
-            .int_type => try self.writeIntType(stream, inst),
-
-            .@"break",
-            .break_inline,
-            => try self.writeBreak(stream, inst),
-
-            .elem_ptr_node,
-            .elem_val_node,
-            .field_ptr_named,
-            .field_val_named,
-            .slice_start,
-            .slice_end,
-            .slice_sentinel,
-            .array_init,
-            .array_init_anon,
-            .array_init_ref,
-            .array_init_anon_ref,
-            .union_init_ptr,
-            .shuffle,
-            .select,
-            .atomic_rmw,
-            .mul_add,
-            .builtin_call,
-            .field_parent_ptr,
-            .memcpy,
-            .memset,
-            .builtin_async_call,
-            => try self.writePlNode(stream, inst),
-
-            .struct_init,
-            .struct_init_ref,
-            => try self.writeStructInit(stream, inst),
-
-            .cmpxchg_strong, .cmpxchg_weak => try self.writeCmpxchg(stream, inst),
-            .atomic_store => try self.writeAtomicStore(stream, inst),
-
-            .struct_init_anon,
-            .struct_init_anon_ref,
-            => try self.writeStructInitAnon(stream, inst),
-
-            .field_type => try self.writeFieldType(stream, inst),
-            .field_type_ref => try self.writeFieldTypeRef(stream, inst),
-
-            .add,
-            .addwrap,
-            .array_cat,
-            .array_mul,
-            .mul,
-            .mulwrap,
-            .sub,
-            .subwrap,
-            .cmp_lt,
-            .cmp_lte,
-            .cmp_eq,
-            .cmp_gte,
-            .cmp_gt,
-            .cmp_neq,
-            .div,
-            .has_decl,
-            .has_field,
-            .mod_rem,
-            .shl,
-            .shl_exact,
-            .shr,
-            .shr_exact,
-            .xor,
-            .store_node,
-            .error_union_type,
-            .merge_error_sets,
-            .bit_and,
-            .bit_or,
-            .float_to_int,
-            .int_to_float,
-            .int_to_ptr,
-            .int_to_enum,
-            .float_cast,
-            .int_cast,
-            .err_set_cast,
-            .ptr_cast,
-            .truncate,
-            .align_cast,
-            .div_exact,
-            .div_floor,
-            .div_trunc,
-            .mod,
-            .rem,
-            .bit_offset_of,
-            .offset_of,
-            .splat,
-            .reduce,
-            .atomic_load,
-            .bitcast,
-            .bitcast_result_ptr,
-            .vector_type,
-            .maximum,
-            .minimum,
-            => try self.writePlNodeBin(stream, inst),
-
-            .@"export" => try self.writePlNodeExport(stream, inst),
-
-            .call,
-            .call_chkused,
-            .call_compile_time,
-            .call_nosuspend,
-            .call_async,
-            => try self.writePlNodeCall(stream, inst),
-
-            .block,
-            .block_inline,
-            .suspend_block,
-            .loop,
-            .validate_struct_init_ptr,
-            .validate_array_init_ptr,
-            .c_import,
-            => try self.writePlNodeBlock(stream, inst),
-
-            .condbr,
-            .condbr_inline,
-            => try self.writePlNodeCondBr(stream, inst),
-
-            .opaque_decl => try self.writeOpaqueDecl(stream, inst, .parent),
-            .opaque_decl_anon => try self.writeOpaqueDecl(stream, inst, .anon),
-            .opaque_decl_func => try self.writeOpaqueDecl(stream, inst, .func),
-
-            .error_set_decl => try self.writeErrorSetDecl(stream, inst, .parent),
-            .error_set_decl_anon => try self.writeErrorSetDecl(stream, inst, .anon),
-            .error_set_decl_func => try self.writeErrorSetDecl(stream, inst, .func),
-
-            .switch_block => try self.writePlNodeSwitchBr(stream, inst, .none),
-            .switch_block_else => try self.writePlNodeSwitchBr(stream, inst, .@"else"),
-            .switch_block_under => try self.writePlNodeSwitchBr(stream, inst, .under),
-            .switch_block_ref => try self.writePlNodeSwitchBr(stream, inst, .none),
-            .switch_block_ref_else => try self.writePlNodeSwitchBr(stream, inst, .@"else"),
-            .switch_block_ref_under => try self.writePlNodeSwitchBr(stream, inst, .under),
-
-            .switch_block_multi => try self.writePlNodeSwitchBlockMulti(stream, inst, .none),
-            .switch_block_else_multi => try self.writePlNodeSwitchBlockMulti(stream, inst, .@"else"),
-            .switch_block_under_multi => try self.writePlNodeSwitchBlockMulti(stream, inst, .under),
-            .switch_block_ref_multi => try self.writePlNodeSwitchBlockMulti(stream, inst, .none),
-            .switch_block_ref_else_multi => try self.writePlNodeSwitchBlockMulti(stream, inst, .@"else"),
-            .switch_block_ref_under_multi => try self.writePlNodeSwitchBlockMulti(stream, inst, .under),
-
-            .field_ptr,
-            .field_val,
-            => try self.writePlNodeField(stream, inst),
-
-            .as_node => try self.writeAs(stream, inst),
-
-            .breakpoint,
-            .repeat,
-            .repeat_inline,
-            .alloc_inferred,
-            .alloc_inferred_mut,
-            .alloc_inferred_comptime,
-            => try self.writeNode(stream, inst),
-
-            .error_value,
-            .enum_literal,
-            .decl_ref,
-            .decl_val,
-            .import,
-            .ret_err_value,
-            .ret_err_value_code,
-            .param_anytype,
-            .param_anytype_comptime,
-            => try self.writeStrTok(stream, inst),
-
-            .param, .param_comptime => try self.writeParam(stream, inst),
-
-            .func => try self.writeFunc(stream, inst, false),
-            .func_inferred => try self.writeFunc(stream, inst, true),
-
-            .@"unreachable" => try self.writeUnreachable(stream, inst),
-
-            .switch_capture,
-            .switch_capture_ref,
-            .switch_capture_multi,
-            .switch_capture_multi_ref,
-            .switch_capture_else,
-            .switch_capture_else_ref,
-            => try self.writeSwitchCapture(stream, inst),
-
-            .dbg_stmt => try self.writeDbgStmt(stream, inst),
-
-            .extended => try self.writeExtended(stream, inst),
-        }
-    }
-
-    fn writeExtended(self: *Writer, stream: anytype, inst: Inst.Index) !void {
-        const extended = self.code.instructions.items(.data)[inst].extended;
-        try stream.print("{s}(", .{@tagName(extended.opcode)});
-        switch (extended.opcode) {
-            .ret_ptr,
-            .ret_type,
-            .this,
-            .ret_addr,
-            .error_return_trace,
-            .frame,
-            .frame_address,
-            .builtin_src,
-            => try self.writeExtNode(stream, extended),
-
-            .@"asm" => try self.writeAsm(stream, extended),
-            .func => try self.writeFuncExtended(stream, extended),
-            .variable => try self.writeVarExtended(stream, extended),
-
-            .compile_log,
-            .typeof_peer,
-            => try self.writeNodeMultiOp(stream, extended),
-
-            .add_with_overflow,
-            .sub_with_overflow,
-            .mul_with_overflow,
-            .shl_with_overflow,
-            => try self.writeOverflowArithmetic(stream, extended),
-
-            .add_with_saturation,
-            .sub_with_saturation,
-            .mul_with_saturation,
-            .shl_with_saturation,
-            => try self.writeSaturatingArithmetic(stream, extended),
-            .struct_decl => try self.writeStructDecl(stream, extended),
-            .union_decl => try self.writeUnionDecl(stream, extended),
-            .enum_decl => try self.writeEnumDecl(stream, extended),
-
-            .alloc,
-            .builtin_extern,
-            .c_undef,
-            .c_include,
-            .c_define,
-            .wasm_memory_size,
-            .wasm_memory_grow,
-            => try stream.writeAll("TODO))"),
-        }
-    }
-
-    fn writeExtNode(self: *Writer, stream: anytype, extended: Inst.Extended.InstData) !void {
-        const src: LazySrcLoc = .{ .node_offset = @bitCast(i32, extended.operand) };
-        try stream.writeAll(")) ");
-        try self.writeSrc(stream, src);
-    }
-
-    fn writeBin(self: *Writer, stream: anytype, inst: Inst.Index) !void {
-        const inst_data = self.code.instructions.items(.data)[inst].bin;
-        try self.writeInstRef(stream, inst_data.lhs);
-        try stream.writeAll(", ");
-        try self.writeInstRef(stream, inst_data.rhs);
-        try stream.writeByte(')');
-    }
-
-    fn writeUnNode(
-        self: *Writer,
-        stream: anytype,
-        inst: Inst.Index,
-    ) (@TypeOf(stream).Error || error{OutOfMemory})!void {
-        const inst_data = self.code.instructions.items(.data)[inst].un_node;
-        try self.writeInstRef(stream, inst_data.operand);
-        try stream.writeAll(") ");
-        try self.writeSrc(stream, inst_data.src());
-    }
-
-    fn writeUnTok(
-        self: *Writer,
-        stream: anytype,
-        inst: Inst.Index,
-    ) (@TypeOf(stream).Error || error{OutOfMemory})!void {
-        const inst_data = self.code.instructions.items(.data)[inst].un_tok;
-        try self.writeInstRef(stream, inst_data.operand);
-        try stream.writeAll(") ");
-        try self.writeSrc(stream, inst_data.src());
-    }
-
-    fn writeArrayTypeSentinel(
-        self: *Writer,
-        stream: anytype,
-        inst: Inst.Index,
-    ) (@TypeOf(stream).Error || error{OutOfMemory})!void {
-        const inst_data = self.code.instructions.items(.data)[inst].array_type_sentinel;
-        _ = inst_data;
-        try stream.writeAll("TODO)");
-    }
-
-    fn writeParamType(
-        self: *Writer,
-        stream: anytype,
-        inst: Inst.Index,
-    ) (@TypeOf(stream).Error || error{OutOfMemory})!void {
-        const inst_data = self.code.instructions.items(.data)[inst].param_type;
-        try self.writeInstRef(stream, inst_data.callee);
-        try stream.print(", {d})", .{inst_data.param_index});
-    }
-
-    fn writePtrTypeSimple(
-        self: *Writer,
-        stream: anytype,
-        inst: Inst.Index,
-    ) (@TypeOf(stream).Error || error{OutOfMemory})!void {
-        const inst_data = self.code.instructions.items(.data)[inst].ptr_type_simple;
-        const str_allowzero = if (inst_data.is_allowzero) "allowzero, " else "";
-        const str_const = if (!inst_data.is_mutable) "const, " else "";
-        const str_volatile = if (inst_data.is_volatile) "volatile, " else "";
-        try self.writeInstRef(stream, inst_data.elem_type);
-        try stream.print(", {s}{s}{s}{s})", .{
-            str_allowzero,
-            str_const,
-            str_volatile,
-            @tagName(inst_data.size),
-        });
-    }
-
-    fn writePtrType(
-        self: *Writer,
-        stream: anytype,
-        inst: Inst.Index,
-    ) (@TypeOf(stream).Error || error{OutOfMemory})!void {
-        const inst_data = self.code.instructions.items(.data)[inst].ptr_type;
-        _ = inst_data;
-        try stream.writeAll("TODO)");
-    }
-
-    fn writeInt(self: *Writer, stream: anytype, inst: Inst.Index) !void {
-        const inst_data = self.code.instructions.items(.data)[inst].int;
-        try stream.print("{d})", .{inst_data});
-    }
-
-    fn writeIntBig(self: *Writer, stream: anytype, inst: Inst.Index) !void {
-        const inst_data = self.code.instructions.items(.data)[inst].str;
-        const byte_count = inst_data.len * @sizeOf(std.math.big.Limb);
-        const limb_bytes = self.code.string_bytes[inst_data.start..][0..byte_count];
-        // limb_bytes is not aligned properly; we must allocate and copy the bytes
-        // in order to accomplish this.
-        const limbs = try self.gpa.alloc(std.math.big.Limb, inst_data.len);
-        defer self.gpa.free(limbs);
-
-        mem.copy(u8, mem.sliceAsBytes(limbs), limb_bytes);
-        const big_int: std.math.big.int.Const = .{
-            .limbs = limbs,
-            .positive = true,
-        };
-        const as_string = try big_int.toStringAlloc(self.gpa, 10, .lower);
-        defer self.gpa.free(as_string);
-        try stream.print("{s})", .{as_string});
-    }
-
-    fn writeFloat(self: *Writer, stream: anytype, inst: Inst.Index) !void {
-        const number = self.code.instructions.items(.data)[inst].float;
-        try stream.print("{d})", .{number});
-    }
-
-    fn writeFloat128(self: *Writer, stream: anytype, inst: Inst.Index) !void {
-        const inst_data = self.code.instructions.items(.data)[inst].pl_node;
-        const extra = self.code.extraData(Inst.Float128, inst_data.payload_index).data;
-        const src = inst_data.src();
-        const number = extra.get();
-        // TODO improve std.format to be able to print f128 values
-        try stream.print("{d}) ", .{@floatCast(f64, number)});
-        try self.writeSrc(stream, src);
-    }
-
-    fn writeStr(
-        self: *Writer,
-        stream: anytype,
-        inst: Inst.Index,
-    ) (@TypeOf(stream).Error || error{OutOfMemory})!void {
-        const inst_data = self.code.instructions.items(.data)[inst].str;
-        const str = inst_data.get(self.code);
-        try stream.print("\"{}\")", .{std.zig.fmtEscapes(str)});
-    }
-
-    fn writePlNode(self: *Writer, stream: anytype, inst: Inst.Index) !void {
-        const inst_data = self.code.instructions.items(.data)[inst].pl_node;
-        try stream.writeAll("TODO) ");
-        try self.writeSrc(stream, inst_data.src());
-    }
-
-    fn writeParam(self: *Writer, stream: anytype, inst: Inst.Index) !void {
-        const inst_data = self.code.instructions.items(.data)[inst].pl_tok;
-        const extra = self.code.extraData(Inst.Param, inst_data.payload_index);
-        const body = self.code.extra[extra.end..][0..extra.data.body_len];
-        try stream.print("\"{}\", ", .{
-            std.zig.fmtEscapes(self.code.nullTerminatedString(extra.data.name)),
-        });
-        try stream.writeAll("{\n");
-        self.indent += 2;
-        try self.writeBody(stream, body);
-        self.indent -= 2;
-        try stream.writeByteNTimes(' ', self.indent);
-        try stream.writeAll("}) ");
-        try self.writeSrc(stream, inst_data.src());
-    }
-
-    fn writePlNodeBin(self: *Writer, stream: anytype, inst: Inst.Index) !void {
-        const inst_data = self.code.instructions.items(.data)[inst].pl_node;
-        const extra = self.code.extraData(Inst.Bin, inst_data.payload_index).data;
-        try self.writeInstRef(stream, extra.lhs);
-        try stream.writeAll(", ");
-        try self.writeInstRef(stream, extra.rhs);
-        try stream.writeAll(") ");
-        try self.writeSrc(stream, inst_data.src());
-    }
-
-    fn writePlNodeExport(self: *Writer, stream: anytype, inst: Inst.Index) !void {
-        const inst_data = self.code.instructions.items(.data)[inst].pl_node;
-        const extra = self.code.extraData(Inst.Export, inst_data.payload_index).data;
-        const decl_name = self.code.nullTerminatedString(extra.decl_name);
-
-        try self.writeInstRef(stream, extra.namespace);
-        try stream.print(", {}, ", .{std.zig.fmtId(decl_name)});
-        try self.writeInstRef(stream, extra.options);
-        try stream.writeAll(") ");
-        try self.writeSrc(stream, inst_data.src());
-    }
-
-    fn writeStructInit(self: *Writer, stream: anytype, inst: Inst.Index) !void {
-        const inst_data = self.code.instructions.items(.data)[inst].pl_node;
-        const extra = self.code.extraData(Inst.StructInit, inst_data.payload_index);
-        var field_i: u32 = 0;
-        var extra_index = extra.end;
-
-        while (field_i < extra.data.fields_len) : (field_i += 1) {
-            const item = self.code.extraData(Inst.StructInit.Item, extra_index);
-            extra_index = item.end;
-
-            if (field_i != 0) {
-                try stream.writeAll(", [");
-            } else {
-                try stream.writeAll("[");
-            }
-            try self.writeInstIndex(stream, item.data.field_type);
-            try stream.writeAll(", ");
-            try self.writeInstRef(stream, item.data.init);
-            try stream.writeAll("]");
-        }
-        try stream.writeAll(") ");
-        try self.writeSrc(stream, inst_data.src());
-    }
-
-    fn writeCmpxchg(self: *Writer, stream: anytype, inst: Inst.Index) !void {
-        const inst_data = self.code.instructions.items(.data)[inst].pl_node;
-        const extra = self.code.extraData(Inst.Cmpxchg, inst_data.payload_index).data;
-
-        try self.writeInstRef(stream, extra.ptr);
-        try stream.writeAll(", ");
-        try self.writeInstRef(stream, extra.expected_value);
-        try stream.writeAll(", ");
-        try self.writeInstRef(stream, extra.new_value);
-        try stream.writeAll(", ");
-        try self.writeInstRef(stream, extra.success_order);
-        try stream.writeAll(", ");
-        try self.writeInstRef(stream, extra.failure_order);
-        try stream.writeAll(") ");
-        try self.writeSrc(stream, inst_data.src());
-    }
-
-    fn writeAtomicStore(self: *Writer, stream: anytype, inst: Inst.Index) !void {
-        const inst_data = self.code.instructions.items(.data)[inst].pl_node;
-        const extra = self.code.extraData(Inst.AtomicStore, inst_data.payload_index).data;
-
-        try self.writeInstRef(stream, extra.ptr);
-        try stream.writeAll(", ");
-        try self.writeInstRef(stream, extra.operand);
-        try stream.writeAll(", ");
-        try self.writeInstRef(stream, extra.ordering);
-        try stream.writeAll(") ");
-        try self.writeSrc(stream, inst_data.src());
-    }
-
-    fn writeStructInitAnon(self: *Writer, stream: anytype, inst: Inst.Index) !void {
-        const inst_data = self.code.instructions.items(.data)[inst].pl_node;
-        const extra = self.code.extraData(Inst.StructInitAnon, inst_data.payload_index);
-        var field_i: u32 = 0;
-        var extra_index = extra.end;
-
-        while (field_i < extra.data.fields_len) : (field_i += 1) {
-            const item = self.code.extraData(Inst.StructInitAnon.Item, extra_index);
-            extra_index = item.end;
-
-            const field_name = self.code.nullTerminatedString(item.data.field_name);
-
-            const prefix = if (field_i != 0) ", [" else "[";
-            try stream.print("{s}[{s}=", .{ prefix, field_name });
-            try self.writeInstRef(stream, item.data.init);
-            try stream.writeAll("]");
-        }
-        try stream.writeAll(") ");
-        try self.writeSrc(stream, inst_data.src());
-    }
-
-    fn writeFieldType(self: *Writer, stream: anytype, inst: Inst.Index) !void {
-        const inst_data = self.code.instructions.items(.data)[inst].pl_node;
-        const extra = self.code.extraData(Inst.FieldType, inst_data.payload_index).data;
-        try self.writeInstRef(stream, extra.container_type);
-        const field_name = self.code.nullTerminatedString(extra.name_start);
-        try stream.print(", {s}) ", .{field_name});
-        try self.writeSrc(stream, inst_data.src());
-    }
-
-    fn writeFieldTypeRef(self: *Writer, stream: anytype, inst: Inst.Index) !void {
-        const inst_data = self.code.instructions.items(.data)[inst].pl_node;
-        const extra = self.code.extraData(Inst.FieldTypeRef, inst_data.payload_index).data;
-        try self.writeInstRef(stream, extra.container_type);
-        try stream.writeAll(", ");
-        try self.writeInstRef(stream, extra.field_name);
-        try stream.writeAll(") ");
-        try self.writeSrc(stream, inst_data.src());
-    }
-
-    fn writeNodeMultiOp(self: *Writer, stream: anytype, extended: Inst.Extended.InstData) !void {
-        const extra = self.code.extraData(Inst.NodeMultiOp, extended.operand);
-        const src: LazySrcLoc = .{ .node_offset = extra.data.src_node };
-        const operands = self.code.refSlice(extra.end, extended.small);
-
-        for (operands) |operand, i| {
-            if (i != 0) try stream.writeAll(", ");
-            try self.writeInstRef(stream, operand);
-        }
-        try stream.writeAll(")) ");
-        try self.writeSrc(stream, src);
-    }
-
-    fn writeAsm(self: *Writer, stream: anytype, extended: Inst.Extended.InstData) !void {
-        const extra = self.code.extraData(Inst.Asm, extended.operand);
-        const src: LazySrcLoc = .{ .node_offset = extra.data.src_node };
-        const outputs_len = @truncate(u5, extended.small);
-        const inputs_len = @truncate(u5, extended.small >> 5);
-        const clobbers_len = @truncate(u5, extended.small >> 10);
-        const is_volatile = @truncate(u1, extended.small >> 15) != 0;
-        const asm_source = self.code.nullTerminatedString(extra.data.asm_source);
-
-        try self.writeFlag(stream, "volatile, ", is_volatile);
-        try stream.print("\"{}\", ", .{std.zig.fmtEscapes(asm_source)});
-        try stream.writeAll(", ");
-
-        var extra_i: usize = extra.end;
-        var output_type_bits = extra.data.output_type_bits;
-        {
-            var i: usize = 0;
-            while (i < outputs_len) : (i += 1) {
-                const output = self.code.extraData(Inst.Asm.Output, extra_i);
-                extra_i = output.end;
-
-                const is_type = @truncate(u1, output_type_bits) != 0;
-                output_type_bits >>= 1;
-
-                const name = self.code.nullTerminatedString(output.data.name);
-                const constraint = self.code.nullTerminatedString(output.data.constraint);
-                try stream.print("output({}, \"{}\", ", .{
-                    std.zig.fmtId(name), std.zig.fmtEscapes(constraint),
-                });
-                try self.writeFlag(stream, "->", is_type);
-                try self.writeInstRef(stream, output.data.operand);
-                try stream.writeAll(")");
-                if (i + 1 < outputs_len) {
-                    try stream.writeAll("), ");
-                }
-            }
-        }
-        {
-            var i: usize = 0;
-            while (i < inputs_len) : (i += 1) {
-                const input = self.code.extraData(Inst.Asm.Input, extra_i);
-                extra_i = input.end;
-
-                const name = self.code.nullTerminatedString(input.data.name);
-                const constraint = self.code.nullTerminatedString(input.data.constraint);
-                try stream.print("input({}, \"{}\", ", .{
-                    std.zig.fmtId(name), std.zig.fmtEscapes(constraint),
-                });
-                try self.writeInstRef(stream, input.data.operand);
-                try stream.writeAll(")");
-                if (i + 1 < inputs_len) {
-                    try stream.writeAll(", ");
-                }
-            }
-        }
-        {
-            var i: usize = 0;
-            while (i < clobbers_len) : (i += 1) {
-                const str_index = self.code.extra[extra_i];
-                extra_i += 1;
-                const clobber = self.code.nullTerminatedString(str_index);
-                try stream.print("{}", .{std.zig.fmtId(clobber)});
-                if (i + 1 < clobbers_len) {
-                    try stream.writeAll(", ");
-                }
-            }
-        }
-        try stream.writeAll(")) ");
-        try self.writeSrc(stream, src);
-    }
-
-    fn writeOverflowArithmetic(self: *Writer, stream: anytype, extended: Inst.Extended.InstData) !void {
-        const extra = self.code.extraData(Zir.Inst.OverflowArithmetic, extended.operand).data;
-        const src: LazySrcLoc = .{ .node_offset = extra.node };
-
-        try self.writeInstRef(stream, extra.lhs);
-        try stream.writeAll(", ");
-        try self.writeInstRef(stream, extra.rhs);
-        try stream.writeAll(", ");
-        try self.writeInstRef(stream, extra.ptr);
-        try stream.writeAll(")) ");
-        try self.writeSrc(stream, src);
-    }
-
-    fn writeSaturatingArithmetic(self: *Writer, stream: anytype, extended: Inst.Extended.InstData) !void {
-        const extra = self.code.extraData(Zir.Inst.SaturatingArithmetic, extended.operand).data;
-        const src: LazySrcLoc = .{ .node_offset = extra.node };
-
-        try self.writeInstRef(stream, extra.lhs);
-        try stream.writeAll(", ");
-        try self.writeInstRef(stream, extra.rhs);
-        try stream.writeAll(", ");
-        try stream.writeAll(") ");
-        try self.writeSrc(stream, src);
-    }
-
-    fn writePlNodeCall(self: *Writer, stream: anytype, inst: Inst.Index) !void {
-        const inst_data = self.code.instructions.items(.data)[inst].pl_node;
-        const extra = self.code.extraData(Inst.Call, inst_data.payload_index);
-        const args = self.code.refSlice(extra.end, extra.data.args_len);
-
-        try self.writeInstRef(stream, extra.data.callee);
-        try stream.writeAll(", [");
-        for (args) |arg, i| {
-            if (i != 0) try stream.writeAll(", ");
-            try self.writeInstRef(stream, arg);
-        }
-        try stream.writeAll("]) ");
-        try self.writeSrc(stream, inst_data.src());
-    }
-
-    fn writePlNodeBlock(self: *Writer, stream: anytype, inst: Inst.Index) !void {
-        const inst_data = self.code.instructions.items(.data)[inst].pl_node;
-        try self.writePlNodeBlockWithoutSrc(stream, inst);
-        try self.writeSrc(stream, inst_data.src());
-    }
-
-    fn writePlNodeBlockWithoutSrc(self: *Writer, stream: anytype, inst: Inst.Index) !void {
-        const inst_data = self.code.instructions.items(.data)[inst].pl_node;
-        const extra = self.code.extraData(Inst.Block, inst_data.payload_index);
-        const body = self.code.extra[extra.end..][0..extra.data.body_len];
-        try stream.writeAll("{\n");
-        self.indent += 2;
-        try self.writeBody(stream, body);
-        self.indent -= 2;
-        try stream.writeByteNTimes(' ', self.indent);
-        try stream.writeAll("}) ");
-    }
-
-    fn writePlNodeCondBr(self: *Writer, stream: anytype, inst: Inst.Index) !void {
-        const inst_data = self.code.instructions.items(.data)[inst].pl_node;
-        const extra = self.code.extraData(Inst.CondBr, inst_data.payload_index);
-        const then_body = self.code.extra[extra.end..][0..extra.data.then_body_len];
-        const else_body = self.code.extra[extra.end + then_body.len ..][0..extra.data.else_body_len];
-        try self.writeInstRef(stream, extra.data.condition);
-        try stream.writeAll(", {\n");
-        self.indent += 2;
-        try self.writeBody(stream, then_body);
-        self.indent -= 2;
-        try stream.writeByteNTimes(' ', self.indent);
-        try stream.writeAll("}, {\n");
-        self.indent += 2;
-        try self.writeBody(stream, else_body);
-        self.indent -= 2;
-        try stream.writeByteNTimes(' ', self.indent);
-        try stream.writeAll("}) ");
-        try self.writeSrc(stream, inst_data.src());
-    }
-
-    fn writeStructDecl(self: *Writer, stream: anytype, extended: Inst.Extended.InstData) !void {
-        const small = @bitCast(Inst.StructDecl.Small, extended.small);
-
-        var extra_index: usize = extended.operand;
-
-        const src_node: ?i32 = if (small.has_src_node) blk: {
-            const src_node = @bitCast(i32, self.code.extra[extra_index]);
-            extra_index += 1;
-            break :blk src_node;
-        } else null;
-
-        const body_len = if (small.has_body_len) blk: {
-            const body_len = self.code.extra[extra_index];
-            extra_index += 1;
-            break :blk body_len;
-        } else 0;
-
-        const fields_len = if (small.has_fields_len) blk: {
-            const fields_len = self.code.extra[extra_index];
-            extra_index += 1;
-            break :blk fields_len;
-        } else 0;
-
-        const decls_len = if (small.has_decls_len) blk: {
-            const decls_len = self.code.extra[extra_index];
-            extra_index += 1;
-            break :blk decls_len;
-        } else 0;
-
-        try self.writeFlag(stream, "known_has_bits, ", small.known_has_bits);
-        try stream.print("{s}, {s}, ", .{
-            @tagName(small.name_strategy), @tagName(small.layout),
-        });
-
-        if (decls_len == 0) {
-            try stream.writeAll("{}, ");
-        } else {
-            try stream.writeAll("{\n");
-            self.indent += 2;
-            extra_index = try self.writeDecls(stream, decls_len, extra_index);
-            self.indent -= 2;
-            try stream.writeByteNTimes(' ', self.indent);
-            try stream.writeAll("}, ");
-        }
-
-        const body = self.code.extra[extra_index..][0..body_len];
-        extra_index += body.len;
-
-        if (fields_len == 0) {
-            assert(body.len == 0);
-            try stream.writeAll("{}, {})");
-        } else {
-            const prev_parent_decl_node = self.parent_decl_node;
-            if (src_node) |off| self.parent_decl_node = self.relativeToNodeIndex(off);
-            self.indent += 2;
-            if (body.len == 0) {
-                try stream.writeAll("{}, {\n");
-            } else {
-                try stream.writeAll("{\n");
-                try self.writeBody(stream, body);
-
-                try stream.writeByteNTimes(' ', self.indent - 2);
-                try stream.writeAll("}, {\n");
-            }
-
-            const bits_per_field = 4;
-            const fields_per_u32 = 32 / bits_per_field;
-            const bit_bags_count = std.math.divCeil(usize, fields_len, fields_per_u32) catch unreachable;
-            var bit_bag_index: usize = extra_index;
-            extra_index += bit_bags_count;
-            var cur_bit_bag: u32 = undefined;
-            var field_i: u32 = 0;
-            while (field_i < fields_len) : (field_i += 1) {
-                if (field_i % fields_per_u32 == 0) {
-                    cur_bit_bag = self.code.extra[bit_bag_index];
-                    bit_bag_index += 1;
-                }
-                const has_align = @truncate(u1, cur_bit_bag) != 0;
-                cur_bit_bag >>= 1;
-                const has_default = @truncate(u1, cur_bit_bag) != 0;
-                cur_bit_bag >>= 1;
-                const is_comptime = @truncate(u1, cur_bit_bag) != 0;
-                cur_bit_bag >>= 1;
-                const unused = @truncate(u1, cur_bit_bag) != 0;
-                cur_bit_bag >>= 1;
-
-                _ = unused;
-
-                const field_name = self.code.nullTerminatedString(self.code.extra[extra_index]);
-                extra_index += 1;
-                const field_type = @intToEnum(Inst.Ref, self.code.extra[extra_index]);
-                extra_index += 1;
-
-                try stream.writeByteNTimes(' ', self.indent);
-                try self.writeFlag(stream, "comptime ", is_comptime);
-                try stream.print("{}: ", .{std.zig.fmtId(field_name)});
-                try self.writeInstRef(stream, field_type);
-
-                if (has_align) {
-                    const align_ref = @intToEnum(Inst.Ref, self.code.extra[extra_index]);
-                    extra_index += 1;
-
-                    try stream.writeAll(" align(");
-                    try self.writeInstRef(stream, align_ref);
-                    try stream.writeAll(")");
-                }
-                if (has_default) {
-                    const default_ref = @intToEnum(Inst.Ref, self.code.extra[extra_index]);
-                    extra_index += 1;
-
-                    try stream.writeAll(" = ");
-                    try self.writeInstRef(stream, default_ref);
-                }
-                try stream.writeAll(",\n");
-            }
-
-            self.parent_decl_node = prev_parent_decl_node;
-            self.indent -= 2;
-            try stream.writeByteNTimes(' ', self.indent);
-            try stream.writeAll("})");
-        }
-        try self.writeSrcNode(stream, src_node);
-    }
-
-    fn writeUnionDecl(self: *Writer, stream: anytype, extended: Inst.Extended.InstData) !void {
-        const small = @bitCast(Inst.UnionDecl.Small, extended.small);
-
-        var extra_index: usize = extended.operand;
-
-        const src_node: ?i32 = if (small.has_src_node) blk: {
-            const src_node = @bitCast(i32, self.code.extra[extra_index]);
-            extra_index += 1;
-            break :blk src_node;
-        } else null;
-
-        const tag_type_ref = if (small.has_tag_type) blk: {
-            const tag_type_ref = @intToEnum(Zir.Inst.Ref, self.code.extra[extra_index]);
-            extra_index += 1;
-            break :blk tag_type_ref;
-        } else .none;
-
-        const body_len = if (small.has_body_len) blk: {
-            const body_len = self.code.extra[extra_index];
-            extra_index += 1;
-            break :blk body_len;
-        } else 0;
-
-        const fields_len = if (small.has_fields_len) blk: {
-            const fields_len = self.code.extra[extra_index];
-            extra_index += 1;
-            break :blk fields_len;
-        } else 0;
-
-        const decls_len = if (small.has_decls_len) blk: {
-            const decls_len = self.code.extra[extra_index];
-            extra_index += 1;
-            break :blk decls_len;
-        } else 0;
-
-        try stream.print("{s}, {s}, ", .{
-            @tagName(small.name_strategy), @tagName(small.layout),
-        });
-        try self.writeFlag(stream, "autoenum, ", small.auto_enum_tag);
-
-        if (decls_len == 0) {
-            try stream.writeAll("{}, ");
-        } else {
-            try stream.writeAll("{\n");
-            self.indent += 2;
-            extra_index = try self.writeDecls(stream, decls_len, extra_index);
-            self.indent -= 2;
-            try stream.writeByteNTimes(' ', self.indent);
-            try stream.writeAll("}, ");
-        }
-
-        assert(fields_len != 0);
-
-        if (tag_type_ref != .none) {
-            try self.writeInstRef(stream, tag_type_ref);
-            try stream.writeAll(", ");
-        }
-
-        const body = self.code.extra[extra_index..][0..body_len];
-        extra_index += body.len;
-
-        const prev_parent_decl_node = self.parent_decl_node;
-        if (src_node) |off| self.parent_decl_node = self.relativeToNodeIndex(off);
-        self.indent += 2;
-        if (body.len == 0) {
-            try stream.writeAll("{}, {\n");
-        } else {
-            try stream.writeAll("{\n");
-            try self.writeBody(stream, body);
-
-            try stream.writeByteNTimes(' ', self.indent - 2);
-            try stream.writeAll("}, {\n");
-        }
-
-        const bits_per_field = 4;
-        const fields_per_u32 = 32 / bits_per_field;
-        const bit_bags_count = std.math.divCeil(usize, fields_len, fields_per_u32) catch unreachable;
-        const body_end = extra_index;
-        extra_index += bit_bags_count;
-        var bit_bag_index: usize = body_end;
-        var cur_bit_bag: u32 = undefined;
-        var field_i: u32 = 0;
-        while (field_i < fields_len) : (field_i += 1) {
-            if (field_i % fields_per_u32 == 0) {
-                cur_bit_bag = self.code.extra[bit_bag_index];
-                bit_bag_index += 1;
-            }
-            const has_type = @truncate(u1, cur_bit_bag) != 0;
-            cur_bit_bag >>= 1;
-            const has_align = @truncate(u1, cur_bit_bag) != 0;
-            cur_bit_bag >>= 1;
-            const has_value = @truncate(u1, cur_bit_bag) != 0;
-            cur_bit_bag >>= 1;
-            const unused = @truncate(u1, cur_bit_bag) != 0;
-            cur_bit_bag >>= 1;
-
-            _ = unused;
-
-            const field_name = self.code.nullTerminatedString(self.code.extra[extra_index]);
-            extra_index += 1;
-            try stream.writeByteNTimes(' ', self.indent);
-            try stream.print("{}", .{std.zig.fmtId(field_name)});
-
-            if (has_type) {
-                const field_type = @intToEnum(Inst.Ref, self.code.extra[extra_index]);
-                extra_index += 1;
-
-                try stream.writeAll(": ");
-                try self.writeInstRef(stream, field_type);
-            }
-            if (has_align) {
-                const align_ref = @intToEnum(Inst.Ref, self.code.extra[extra_index]);
-                extra_index += 1;
-
-                try stream.writeAll(" align(");
-                try self.writeInstRef(stream, align_ref);
-                try stream.writeAll(")");
-            }
-            if (has_value) {
-                const default_ref = @intToEnum(Inst.Ref, self.code.extra[extra_index]);
-                extra_index += 1;
-
-                try stream.writeAll(" = ");
-                try self.writeInstRef(stream, default_ref);
-            }
-            try stream.writeAll(",\n");
-        }
-
-        self.parent_decl_node = prev_parent_decl_node;
-        self.indent -= 2;
-        try stream.writeByteNTimes(' ', self.indent);
-        try stream.writeAll("})");
-        try self.writeSrcNode(stream, src_node);
-    }
-
-    fn writeDecls(self: *Writer, stream: anytype, decls_len: u32, extra_start: usize) !usize {
-        const parent_decl_node = self.parent_decl_node;
-        const bit_bags_count = std.math.divCeil(usize, decls_len, 8) catch unreachable;
-        var extra_index = extra_start + bit_bags_count;
-        var bit_bag_index: usize = extra_start;
-        var cur_bit_bag: u32 = undefined;
-        var decl_i: u32 = 0;
-        while (decl_i < decls_len) : (decl_i += 1) {
-            if (decl_i % 8 == 0) {
-                cur_bit_bag = self.code.extra[bit_bag_index];
-                bit_bag_index += 1;
-            }
-            const is_pub = @truncate(u1, cur_bit_bag) != 0;
-            cur_bit_bag >>= 1;
-            const is_exported = @truncate(u1, cur_bit_bag) != 0;
-            cur_bit_bag >>= 1;
-            const has_align = @truncate(u1, cur_bit_bag) != 0;
-            cur_bit_bag >>= 1;
-            const has_section = @truncate(u1, cur_bit_bag) != 0;
-            cur_bit_bag >>= 1;
-
-            const sub_index = extra_index;
-
-            const hash_u32s = self.code.extra[extra_index..][0..4];
-            extra_index += 4;
-            const line = self.code.extra[extra_index];
-            extra_index += 1;
-            const decl_name_index = self.code.extra[extra_index];
-            extra_index += 1;
-            const decl_index = self.code.extra[extra_index];
-            extra_index += 1;
-            const align_inst: Inst.Ref = if (!has_align) .none else inst: {
-                const inst = @intToEnum(Inst.Ref, self.code.extra[extra_index]);
-                extra_index += 1;
-                break :inst inst;
-            };
-            const section_inst: Inst.Ref = if (!has_section) .none else inst: {
-                const inst = @intToEnum(Inst.Ref, self.code.extra[extra_index]);
-                extra_index += 1;
-                break :inst inst;
-            };
-
-            const pub_str = if (is_pub) "pub " else "";
-            const hash_bytes = @bitCast([16]u8, hash_u32s.*);
-            try stream.writeByteNTimes(' ', self.indent);
-            if (decl_name_index == 0) {
-                const name = if (is_exported) "usingnamespace" else "comptime";
-                try stream.writeAll(pub_str);
-                try stream.writeAll(name);
-            } else if (decl_name_index == 1) {
-                try stream.writeAll("test");
-            } else {
-                const raw_decl_name = self.code.nullTerminatedString(decl_name_index);
-                const decl_name = if (raw_decl_name.len == 0)
-                    self.code.nullTerminatedString(decl_name_index + 1)
-                else
-                    raw_decl_name;
-                const test_str = if (raw_decl_name.len == 0) "test " else "";
-                const export_str = if (is_exported) "export " else "";
-                try stream.print("[{d}] {s}{s}{s}{}", .{
-                    sub_index, pub_str, test_str, export_str, std.zig.fmtId(decl_name),
-                });
-                if (align_inst != .none) {
-                    try stream.writeAll(" align(");
-                    try self.writeInstRef(stream, align_inst);
-                    try stream.writeAll(")");
-                }
-                if (section_inst != .none) {
-                    try stream.writeAll(" linksection(");
-                    try self.writeInstRef(stream, section_inst);
-                    try stream.writeAll(")");
-                }
-            }
-            const tag = self.code.instructions.items(.tag)[decl_index];
-            try stream.print(" line({d}) hash({}): %{d} = {s}(", .{
-                line, std.fmt.fmtSliceHexLower(&hash_bytes), decl_index, @tagName(tag),
-            });
-
-            const decl_block_inst_data = self.code.instructions.items(.data)[decl_index].pl_node;
-            const sub_decl_node_off = decl_block_inst_data.src_node;
-            self.parent_decl_node = self.relativeToNodeIndex(sub_decl_node_off);
-            try self.writePlNodeBlockWithoutSrc(stream, decl_index);
-            self.parent_decl_node = parent_decl_node;
-            try self.writeSrc(stream, decl_block_inst_data.src());
-            try stream.writeAll("\n");
-        }
-        return extra_index;
-    }
-
-    fn writeEnumDecl(self: *Writer, stream: anytype, extended: Inst.Extended.InstData) !void {
-        const small = @bitCast(Inst.EnumDecl.Small, extended.small);
-        var extra_index: usize = extended.operand;
-
-        const src_node: ?i32 = if (small.has_src_node) blk: {
-            const src_node = @bitCast(i32, self.code.extra[extra_index]);
-            extra_index += 1;
-            break :blk src_node;
-        } else null;
-
-        const tag_type_ref = if (small.has_tag_type) blk: {
-            const tag_type_ref = @intToEnum(Zir.Inst.Ref, self.code.extra[extra_index]);
-            extra_index += 1;
-            break :blk tag_type_ref;
-        } else .none;
-
-        const body_len = if (small.has_body_len) blk: {
-            const body_len = self.code.extra[extra_index];
-            extra_index += 1;
-            break :blk body_len;
-        } else 0;
-
-        const fields_len = if (small.has_fields_len) blk: {
-            const fields_len = self.code.extra[extra_index];
-            extra_index += 1;
-            break :blk fields_len;
-        } else 0;
-
-        const decls_len = if (small.has_decls_len) blk: {
-            const decls_len = self.code.extra[extra_index];
-            extra_index += 1;
-            break :blk decls_len;
-        } else 0;
-
-        try stream.print("{s}, ", .{@tagName(small.name_strategy)});
-        try self.writeFlag(stream, "nonexhaustive, ", small.nonexhaustive);
-
-        if (decls_len == 0) {
-            try stream.writeAll("{}, ");
-        } else {
-            try stream.writeAll("{\n");
-            self.indent += 2;
-            extra_index = try self.writeDecls(stream, decls_len, extra_index);
-            self.indent -= 2;
-            try stream.writeByteNTimes(' ', self.indent);
-            try stream.writeAll("}, ");
-        }
-
-        if (tag_type_ref != .none) {
-            try self.writeInstRef(stream, tag_type_ref);
-            try stream.writeAll(", ");
-        }
-
-        const body = self.code.extra[extra_index..][0..body_len];
-        extra_index += body.len;
-
-        if (fields_len == 0) {
-            assert(body.len == 0);
-            try stream.writeAll("{}, {})");
-        } else {
-            const prev_parent_decl_node = self.parent_decl_node;
-            if (src_node) |off| self.parent_decl_node = self.relativeToNodeIndex(off);
-            self.indent += 2;
-            if (body.len == 0) {
-                try stream.writeAll("{}, {\n");
-            } else {
-                try stream.writeAll("{\n");
-                try self.writeBody(stream, body);
-
-                try stream.writeByteNTimes(' ', self.indent - 2);
-                try stream.writeAll("}, {\n");
-            }
-
-            const bit_bags_count = std.math.divCeil(usize, fields_len, 32) catch unreachable;
-            const body_end = extra_index;
-            extra_index += bit_bags_count;
-            var bit_bag_index: usize = body_end;
-            var cur_bit_bag: u32 = undefined;
-            var field_i: u32 = 0;
-            while (field_i < fields_len) : (field_i += 1) {
-                if (field_i % 32 == 0) {
-                    cur_bit_bag = self.code.extra[bit_bag_index];
-                    bit_bag_index += 1;
-                }
-                const has_tag_value = @truncate(u1, cur_bit_bag) != 0;
-                cur_bit_bag >>= 1;
-
-                const field_name = self.code.nullTerminatedString(self.code.extra[extra_index]);
-                extra_index += 1;
-
-                try stream.writeByteNTimes(' ', self.indent);
-                try stream.print("{}", .{std.zig.fmtId(field_name)});
-
-                if (has_tag_value) {
-                    const tag_value_ref = @intToEnum(Inst.Ref, self.code.extra[extra_index]);
-                    extra_index += 1;
-
-                    try stream.writeAll(" = ");
-                    try self.writeInstRef(stream, tag_value_ref);
-                }
-                try stream.writeAll(",\n");
-            }
-            self.parent_decl_node = prev_parent_decl_node;
-            self.indent -= 2;
-            try stream.writeByteNTimes(' ', self.indent);
-            try stream.writeAll("})");
-        }
-        try self.writeSrcNode(stream, src_node);
-    }
-
-    fn writeOpaqueDecl(
-        self: *Writer,
-        stream: anytype,
-        inst: Inst.Index,
-        name_strategy: Inst.NameStrategy,
-    ) !void {
-        const inst_data = self.code.instructions.items(.data)[inst].pl_node;
-        const extra = self.code.extraData(Inst.OpaqueDecl, inst_data.payload_index);
-        const decls_len = extra.data.decls_len;
-
-        try stream.print("{s}, ", .{@tagName(name_strategy)});
-
-        if (decls_len == 0) {
-            try stream.writeAll("}) ");
-        } else {
-            try stream.writeAll("\n");
-            self.indent += 2;
-            _ = try self.writeDecls(stream, decls_len, extra.end);
-            self.indent -= 2;
-            try stream.writeByteNTimes(' ', self.indent);
-            try stream.writeAll("}) ");
-        }
-        try self.writeSrc(stream, inst_data.src());
-    }
-
-    fn writeErrorSetDecl(
-        self: *Writer,
-        stream: anytype,
-        inst: Inst.Index,
-        name_strategy: Inst.NameStrategy,
-    ) !void {
-        const inst_data = self.code.instructions.items(.data)[inst].pl_node;
-        const extra = self.code.extraData(Inst.ErrorSetDecl, inst_data.payload_index);
-        const fields = self.code.extra[extra.end..][0..extra.data.fields_len];
-
-        try stream.print("{s}, ", .{@tagName(name_strategy)});
-
-        try stream.writeAll("{\n");
-        self.indent += 2;
-        for (fields) |str_index| {
-            const name = self.code.nullTerminatedString(str_index);
-            try stream.writeByteNTimes(' ', self.indent);
-            try stream.print("{},\n", .{std.zig.fmtId(name)});
-        }
-        self.indent -= 2;
-        try stream.writeByteNTimes(' ', self.indent);
-        try stream.writeAll("}) ");
-
-        try self.writeSrc(stream, inst_data.src());
-    }
-
-    fn writePlNodeSwitchBr(
-        self: *Writer,
-        stream: anytype,
-        inst: Inst.Index,
-        special_prong: SpecialProng,
-    ) !void {
-        const inst_data = self.code.instructions.items(.data)[inst].pl_node;
-        const extra = self.code.extraData(Inst.SwitchBlock, inst_data.payload_index);
-        const special: struct {
-            body: []const Inst.Index,
-            end: usize,
-        } = switch (special_prong) {
-            .none => .{ .body = &.{}, .end = extra.end },
-            .under, .@"else" => blk: {
-                const body_len = self.code.extra[extra.end];
-                const extra_body_start = extra.end + 1;
-                break :blk .{
-                    .body = self.code.extra[extra_body_start..][0..body_len],
-                    .end = extra_body_start + body_len,
-                };
-            },
-        };
-
-        try self.writeInstRef(stream, extra.data.operand);
-
-        if (special.body.len != 0) {
-            const prong_name = switch (special_prong) {
-                .@"else" => "else",
-                .under => "_",
-                else => unreachable,
-            };
-            try stream.print(", {s} => {{\n", .{prong_name});
-            self.indent += 2;
-            try self.writeBody(stream, special.body);
-            self.indent -= 2;
-            try stream.writeByteNTimes(' ', self.indent);
-            try stream.writeAll("}");
-        }
-
-        var extra_index: usize = special.end;
-        {
-            var scalar_i: usize = 0;
-            while (scalar_i < extra.data.cases_len) : (scalar_i += 1) {
-                const item_ref = @intToEnum(Inst.Ref, self.code.extra[extra_index]);
-                extra_index += 1;
-                const body_len = self.code.extra[extra_index];
-                extra_index += 1;
-                const body = self.code.extra[extra_index..][0..body_len];
-                extra_index += body_len;
-
-                try stream.writeAll(", ");
-                try self.writeInstRef(stream, item_ref);
-                try stream.writeAll(" => {\n");
-                self.indent += 2;
-                try self.writeBody(stream, body);
-                self.indent -= 2;
-                try stream.writeByteNTimes(' ', self.indent);
-                try stream.writeAll("}");
-            }
-        }
-        try stream.writeAll(") ");
-        try self.writeSrc(stream, inst_data.src());
-    }
-
-    fn writePlNodeSwitchBlockMulti(
-        self: *Writer,
-        stream: anytype,
-        inst: Inst.Index,
-        special_prong: SpecialProng,
-    ) !void {
-        const inst_data = self.code.instructions.items(.data)[inst].pl_node;
-        const extra = self.code.extraData(Inst.SwitchBlockMulti, inst_data.payload_index);
-        const special: struct {
-            body: []const Inst.Index,
-            end: usize,
-        } = switch (special_prong) {
-            .none => .{ .body = &.{}, .end = extra.end },
-            .under, .@"else" => blk: {
-                const body_len = self.code.extra[extra.end];
-                const extra_body_start = extra.end + 1;
-                break :blk .{
-                    .body = self.code.extra[extra_body_start..][0..body_len],
-                    .end = extra_body_start + body_len,
-                };
-            },
-        };
-
-        try self.writeInstRef(stream, extra.data.operand);
-
-        if (special.body.len != 0) {
-            const prong_name = switch (special_prong) {
-                .@"else" => "else",
-                .under => "_",
-                else => unreachable,
-            };
-            try stream.print(", {s} => {{\n", .{prong_name});
-            self.indent += 2;
-            try self.writeBody(stream, special.body);
-            self.indent -= 2;
-            try stream.writeByteNTimes(' ', self.indent);
-            try stream.writeAll("}");
-        }
-
-        var extra_index: usize = special.end;
-        {
-            var scalar_i: usize = 0;
-            while (scalar_i < extra.data.scalar_cases_len) : (scalar_i += 1) {
-                const item_ref = @intToEnum(Inst.Ref, self.code.extra[extra_index]);
-                extra_index += 1;
-                const body_len = self.code.extra[extra_index];
-                extra_index += 1;
-                const body = self.code.extra[extra_index..][0..body_len];
-                extra_index += body_len;
-
-                try stream.writeAll(", ");
-                try self.writeInstRef(stream, item_ref);
-                try stream.writeAll(" => {\n");
-                self.indent += 2;
-                try self.writeBody(stream, body);
-                self.indent -= 2;
-                try stream.writeByteNTimes(' ', self.indent);
-                try stream.writeAll("}");
-            }
-        }
-        {
-            var multi_i: usize = 0;
-            while (multi_i < extra.data.multi_cases_len) : (multi_i += 1) {
-                const items_len = self.code.extra[extra_index];
-                extra_index += 1;
-                const ranges_len = self.code.extra[extra_index];
-                extra_index += 1;
-                const body_len = self.code.extra[extra_index];
-                extra_index += 1;
-                const items = self.code.refSlice(extra_index, items_len);
-                extra_index += items_len;
-
-                for (items) |item_ref| {
-                    try stream.writeAll(", ");
-                    try self.writeInstRef(stream, item_ref);
-                }
-
-                var range_i: usize = 0;
-                while (range_i < ranges_len) : (range_i += 1) {
-                    const item_first = @intToEnum(Inst.Ref, self.code.extra[extra_index]);
-                    extra_index += 1;
-                    const item_last = @intToEnum(Inst.Ref, self.code.extra[extra_index]);
-                    extra_index += 1;
-
-                    try stream.writeAll(", ");
-                    try self.writeInstRef(stream, item_first);
-                    try stream.writeAll("...");
-                    try self.writeInstRef(stream, item_last);
-                }
-
-                const body = self.code.extra[extra_index..][0..body_len];
-                extra_index += body_len;
-                try stream.writeAll(" => {\n");
-                self.indent += 2;
-                try self.writeBody(stream, body);
-                self.indent -= 2;
-                try stream.writeByteNTimes(' ', self.indent);
-                try stream.writeAll("}");
-            }
-        }
-        try stream.writeAll(") ");
-        try self.writeSrc(stream, inst_data.src());
-    }
-
-    fn writePlNodeField(self: *Writer, stream: anytype, inst: Inst.Index) !void {
-        const inst_data = self.code.instructions.items(.data)[inst].pl_node;
-        const extra = self.code.extraData(Inst.Field, inst_data.payload_index).data;
-        const name = self.code.nullTerminatedString(extra.field_name_start);
-        try self.writeInstRef(stream, extra.lhs);
-        try stream.print(", \"{}\") ", .{std.zig.fmtEscapes(name)});
-        try self.writeSrc(stream, inst_data.src());
-    }
-
-    fn writeAs(self: *Writer, stream: anytype, inst: Inst.Index) !void {
-        const inst_data = self.code.instructions.items(.data)[inst].pl_node;
-        const extra = self.code.extraData(Inst.As, inst_data.payload_index).data;
-        try self.writeInstRef(stream, extra.dest_type);
-        try stream.writeAll(", ");
-        try self.writeInstRef(stream, extra.operand);
-        try stream.writeAll(") ");
-        try self.writeSrc(stream, inst_data.src());
-    }
-
-    fn writeNode(
-        self: *Writer,
-        stream: anytype,
-        inst: Inst.Index,
-    ) (@TypeOf(stream).Error || error{OutOfMemory})!void {
-        const src_node = self.code.instructions.items(.data)[inst].node;
-        const src: LazySrcLoc = .{ .node_offset = src_node };
-        try stream.writeAll(") ");
-        try self.writeSrc(stream, src);
-    }
-
-    fn writeStrTok(
-        self: *Writer,
-        stream: anytype,
-        inst: Inst.Index,
-    ) (@TypeOf(stream).Error || error{OutOfMemory})!void {
-        const inst_data = self.code.instructions.items(.data)[inst].str_tok;
-        const str = inst_data.get(self.code);
-        try stream.print("\"{}\") ", .{std.zig.fmtEscapes(str)});
-        try self.writeSrc(stream, inst_data.src());
-    }
-
-    fn writeFunc(
-        self: *Writer,
-        stream: anytype,
-        inst: Inst.Index,
-        inferred_error_set: bool,
-    ) !void {
-        const inst_data = self.code.instructions.items(.data)[inst].pl_node;
-        const src = inst_data.src();
-        const extra = self.code.extraData(Inst.Func, inst_data.payload_index);
-        var extra_index = extra.end;
-
-        const ret_ty_body = self.code.extra[extra_index..][0..extra.data.ret_body_len];
-        extra_index += ret_ty_body.len;
-
-        const body = self.code.extra[extra_index..][0..extra.data.body_len];
-        extra_index += body.len;
-
-        var src_locs: Zir.Inst.Func.SrcLocs = undefined;
-        if (body.len != 0) {
-            src_locs = self.code.extraData(Zir.Inst.Func.SrcLocs, extra_index).data;
-        }
-        return self.writeFuncCommon(
-            stream,
-            ret_ty_body,
-            inferred_error_set,
-            false,
-            false,
-            .none,
-            .none,
-            body,
-            src,
-            src_locs,
-        );
-    }
-
-    fn writeFuncExtended(self: *Writer, stream: anytype, extended: Inst.Extended.InstData) !void {
-        const extra = self.code.extraData(Inst.ExtendedFunc, extended.operand);
-        const src: LazySrcLoc = .{ .node_offset = extra.data.src_node };
-        const small = @bitCast(Inst.ExtendedFunc.Small, extended.small);
-
-        var extra_index: usize = extra.end;
-        if (small.has_lib_name) {
-            const lib_name = self.code.nullTerminatedString(self.code.extra[extra_index]);
-            extra_index += 1;
-            try stream.print("lib_name=\"{}\", ", .{std.zig.fmtEscapes(lib_name)});
-        }
-        try self.writeFlag(stream, "test, ", small.is_test);
-        const cc: Inst.Ref = if (!small.has_cc) .none else blk: {
-            const cc = @intToEnum(Zir.Inst.Ref, self.code.extra[extra_index]);
-            extra_index += 1;
-            break :blk cc;
-        };
-        const align_inst: Inst.Ref = if (!small.has_align) .none else blk: {
-            const align_inst = @intToEnum(Zir.Inst.Ref, self.code.extra[extra_index]);
-            extra_index += 1;
-            break :blk align_inst;
-        };
-
-        const ret_ty_body = self.code.extra[extra_index..][0..extra.data.ret_body_len];
-        extra_index += ret_ty_body.len;
-
-        const body = self.code.extra[extra_index..][0..extra.data.body_len];
-        extra_index += body.len;
-
-        var src_locs: Zir.Inst.Func.SrcLocs = undefined;
-        if (body.len != 0) {
-            src_locs = self.code.extraData(Zir.Inst.Func.SrcLocs, extra_index).data;
-        }
-        return self.writeFuncCommon(
-            stream,
-            ret_ty_body,
-            small.is_inferred_error,
-            small.is_var_args,
-            small.is_extern,
-            cc,
-            align_inst,
-            body,
-            src,
-            src_locs,
-        );
-    }
-
-    fn writeVarExtended(self: *Writer, stream: anytype, extended: Inst.Extended.InstData) !void {
-        const extra = self.code.extraData(Inst.ExtendedVar, extended.operand);
-        const small = @bitCast(Inst.ExtendedVar.Small, extended.small);
-
-        try self.writeInstRef(stream, extra.data.var_type);
-
-        var extra_index: usize = extra.end;
-        if (small.has_lib_name) {
-            const lib_name = self.code.nullTerminatedString(self.code.extra[extra_index]);
-            extra_index += 1;
-            try stream.print(", lib_name=\"{}\"", .{std.zig.fmtEscapes(lib_name)});
-        }
-        const align_inst: Inst.Ref = if (!small.has_align) .none else blk: {
-            const align_inst = @intToEnum(Zir.Inst.Ref, self.code.extra[extra_index]);
-            extra_index += 1;
-            break :blk align_inst;
-        };
-        const init_inst: Inst.Ref = if (!small.has_init) .none else blk: {
-            const init_inst = @intToEnum(Zir.Inst.Ref, self.code.extra[extra_index]);
-            extra_index += 1;
-            break :blk init_inst;
-        };
-        try self.writeFlag(stream, ", is_extern", small.is_extern);
-        try self.writeOptionalInstRef(stream, ", align=", align_inst);
-        try self.writeOptionalInstRef(stream, ", init=", init_inst);
-        try stream.writeAll("))");
-    }
-
-    fn writeBoolBr(self: *Writer, stream: anytype, inst: Inst.Index) !void {
-        const inst_data = self.code.instructions.items(.data)[inst].bool_br;
-        const extra = self.code.extraData(Inst.Block, inst_data.payload_index);
-        const body = self.code.extra[extra.end..][0..extra.data.body_len];
-        try self.writeInstRef(stream, inst_data.lhs);
-        try stream.writeAll(", {\n");
-        self.indent += 2;
-        try self.writeBody(stream, body);
-        self.indent -= 2;
-        try stream.writeByteNTimes(' ', self.indent);
-        try stream.writeAll("})");
-    }
-
-    fn writeIntType(self: *Writer, stream: anytype, inst: Inst.Index) !void {
-        const int_type = self.code.instructions.items(.data)[inst].int_type;
-        const prefix: u8 = switch (int_type.signedness) {
-            .signed => 'i',
-            .unsigned => 'u',
-        };
-        try stream.print("{c}{d}) ", .{ prefix, int_type.bit_count });
-        try self.writeSrc(stream, int_type.src());
-    }
-
-    fn writeBreak(self: *Writer, stream: anytype, inst: Inst.Index) !void {
-        const inst_data = self.code.instructions.items(.data)[inst].@"break";
-
-        try self.writeInstIndex(stream, inst_data.block_inst);
-        try stream.writeAll(", ");
-        try self.writeInstRef(stream, inst_data.operand);
-        try stream.writeAll(")");
-    }
-
-    fn writeUnreachable(self: *Writer, stream: anytype, inst: Inst.Index) !void {
-        const inst_data = self.code.instructions.items(.data)[inst].@"unreachable";
-        const safety_str = if (inst_data.safety) "safe" else "unsafe";
-        try stream.print("{s}) ", .{safety_str});
-        try self.writeSrc(stream, inst_data.src());
-    }
-
-    fn writeFuncCommon(
-        self: *Writer,
-        stream: anytype,
-        ret_ty_body: []const Inst.Index,
-        inferred_error_set: bool,
-        var_args: bool,
-        is_extern: bool,
-        cc: Inst.Ref,
-        align_inst: Inst.Ref,
-        body: []const Inst.Index,
-        src: LazySrcLoc,
-        src_locs: Zir.Inst.Func.SrcLocs,
-    ) !void {
-        if (ret_ty_body.len == 0) {
-            try stream.writeAll("ret_ty=void");
-        } else {
-            try stream.writeAll("ret_ty={\n");
-            self.indent += 2;
-            try self.writeBody(stream, ret_ty_body);
-            self.indent -= 2;
-            try stream.writeByteNTimes(' ', self.indent);
-            try stream.writeAll("}");
-        }
-
-        try self.writeOptionalInstRef(stream, ", cc=", cc);
-        try self.writeOptionalInstRef(stream, ", align=", align_inst);
-        try self.writeFlag(stream, ", vargs", var_args);
-        try self.writeFlag(stream, ", extern", is_extern);
-        try self.writeFlag(stream, ", inferror", inferred_error_set);
-
-        if (body.len == 0) {
-            try stream.writeAll(", body={}) ");
-        } else {
-            try stream.writeAll(", body={\n");
-            self.indent += 2;
-            try self.writeBody(stream, body);
-            self.indent -= 2;
-            try stream.writeByteNTimes(' ', self.indent);
-            try stream.writeAll("}) ");
-        }
-        if (body.len != 0) {
-            try stream.print("(lbrace={d}:{d},rbrace={d}:{d}) ", .{
-                src_locs.lbrace_line, @truncate(u16, src_locs.columns),
-                src_locs.rbrace_line, @truncate(u16, src_locs.columns >> 16),
-            });
-        }
-        try self.writeSrc(stream, src);
-    }
-
-    fn writeSwitchCapture(self: *Writer, stream: anytype, inst: Inst.Index) !void {
-        const inst_data = self.code.instructions.items(.data)[inst].switch_capture;
-        try self.writeInstIndex(stream, inst_data.switch_inst);
-        try stream.print(", {d})", .{inst_data.prong_index});
-    }
-
-    fn writeDbgStmt(self: *Writer, stream: anytype, inst: Inst.Index) !void {
-        const inst_data = self.code.instructions.items(.data)[inst].dbg_stmt;
-        try stream.print("{d}, {d})", .{ inst_data.line, inst_data.column });
-    }
-
-    fn writeInstRef(self: *Writer, stream: anytype, ref: Inst.Ref) !void {
-        var i: usize = @enumToInt(ref);
-
-        if (i < Inst.Ref.typed_value_map.len) {
-            return stream.print("@{}", .{ref});
-        }
-        i -= Inst.Ref.typed_value_map.len;
-
-        return self.writeInstIndex(stream, @intCast(Inst.Index, i));
-    }
-
-    fn writeInstIndex(self: *Writer, stream: anytype, inst: Inst.Index) !void {
-        _ = self;
-        return stream.print("%{d}", .{inst});
-    }
-
-    fn writeOptionalInstRef(
-        self: *Writer,
-        stream: anytype,
-        prefix: []const u8,
-        inst: Inst.Ref,
-    ) !void {
-        if (inst == .none) return;
-        try stream.writeAll(prefix);
-        try self.writeInstRef(stream, inst);
-    }
-
-    fn writeFlag(
-        self: *Writer,
-        stream: anytype,
-        name: []const u8,
-        flag: bool,
-    ) !void {
-        _ = self;
-        if (!flag) return;
-        try stream.writeAll(name);
-    }
-
-    fn writeSrc(self: *Writer, stream: anytype, src: LazySrcLoc) !void {
-        const tree = self.file.tree;
-        const src_loc: Module.SrcLoc = .{
-            .file_scope = self.file,
-            .parent_decl_node = self.parent_decl_node,
-            .lazy = src,
-        };
-        // Caller must ensure AST tree is loaded.
-        const abs_byte_off = src_loc.byteOffset(self.gpa) catch unreachable;
-        const delta_line = std.zig.findLineColumn(tree.source, abs_byte_off);
-        try stream.print("{s}:{d}:{d}", .{
-            @tagName(src), delta_line.line + 1, delta_line.column + 1,
-        });
-    }
-
-    fn writeSrcNode(self: *Writer, stream: anytype, src_node: ?i32) !void {
-        const node_offset = src_node orelse return;
-        const src: LazySrcLoc = .{ .node_offset = node_offset };
-        try stream.writeAll(" ");
-        return self.writeSrc(stream, src);
-    }
-
-    fn writeBody(self: *Writer, stream: anytype, body: []const Inst.Index) !void {
-        for (body) |inst| {
-            try stream.writeByteNTimes(' ', self.indent);
-            try stream.print("%{d} ", .{inst});
-            try self.writeInstToStream(stream, inst);
-            try stream.writeByte('\n');
-        }
-    }
-};
-
 pub const DeclIterator = struct {
     extra_index: usize,
     bit_bag_index: usize,
diff --git a/src/main.zig b/src/main.zig
index b7b5d06264..74bf45b62c 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -4132,7 +4132,7 @@ pub fn cmdAstCheck(
         // zig fmt: on
     }
 
-    return Zir.renderAsTextToFile(gpa, &file, io.getStdOut());
+    return @import("print_zir.zig").renderAsTextToFile(gpa, &file, io.getStdOut());
 }
 
 /// This is only enabled for debug builds.
diff --git a/src/print_zir.zig b/src/print_zir.zig
new file mode 100644
index 0000000000..911cf05baf
--- /dev/null
+++ b/src/print_zir.zig
@@ -0,0 +1,1868 @@
+const std = @import("std");
+const mem = std.mem;
+const Allocator = std.mem.Allocator;
+const assert = std.debug.assert;
+const Ast = std.zig.Ast;
+
+const Zir = @import("Zir.zig");
+const Module = @import("Module.zig");
+const LazySrcLoc = Module.LazySrcLoc;
+
+/// Write human-readable, debug formatted ZIR code to a file.
+pub fn renderAsTextToFile(
+    gpa: *Allocator,
+    scope_file: *Module.Scope.File,
+    fs_file: std.fs.File,
+) !void {
+    var arena = std.heap.ArenaAllocator.init(gpa);
+    defer arena.deinit();
+
+    var writer: Writer = .{
+        .gpa = gpa,
+        .arena = &arena.allocator,
+        .file = scope_file,
+        .code = scope_file.zir,
+        .indent = 0,
+        .parent_decl_node = 0,
+    };
+
+    const main_struct_inst = scope_file.zir.getMainStruct();
+    try fs_file.writer().print("%{d} ", .{main_struct_inst});
+    try writer.writeInstToStream(fs_file.writer(), main_struct_inst);
+    try fs_file.writeAll("\n");
+    const imports_index = scope_file.zir.extra[@enumToInt(Zir.ExtraIndex.imports)];
+    if (imports_index != 0) {
+        try fs_file.writeAll("Imports:\n");
+
+        const extra = scope_file.zir.extraData(Zir.Inst.Imports, imports_index);
+        var import_i: u32 = 0;
+        var extra_index = extra.end;
+
+        while (import_i < extra.data.imports_len) : (import_i += 1) {
+            const item = scope_file.zir.extraData(Zir.Inst.Imports.Item, extra_index);
+            extra_index = item.end;
+
+            const src: LazySrcLoc = .{ .token_abs = item.data.token };
+            const import_path = scope_file.zir.nullTerminatedString(item.data.name);
+            try fs_file.writer().print("  @import(\"{}\") ", .{
+                std.zig.fmtEscapes(import_path),
+            });
+            try writer.writeSrc(fs_file.writer(), src);
+            try fs_file.writer().writeAll("\n");
+        }
+    }
+}
+
+const Writer = struct {
+    gpa: *Allocator,
+    arena: *Allocator,
+    file: *Module.Scope.File,
+    code: Zir,
+    indent: u32,
+    parent_decl_node: u32,
+
+    fn relativeToNodeIndex(self: *Writer, offset: i32) Ast.Node.Index {
+        return @bitCast(Ast.Node.Index, offset + @bitCast(i32, self.parent_decl_node));
+    }
+
+    fn writeInstToStream(
+        self: *Writer,
+        stream: anytype,
+        inst: Zir.Inst.Index,
+    ) (@TypeOf(stream).Error || error{OutOfMemory})!void {
+        const tags = self.code.instructions.items(.tag);
+        const tag = tags[inst];
+        try stream.print("= {s}(", .{@tagName(tags[inst])});
+        switch (tag) {
+            .array_type,
+            .as,
+            .coerce_result_ptr,
+            .elem_ptr,
+            .elem_val,
+            .store,
+            .store_to_block_ptr,
+            .store_to_inferred_ptr,
+            .field_ptr_type,
+            => try self.writeBin(stream, inst),
+
+            .alloc,
+            .alloc_mut,
+            .alloc_comptime,
+            .indexable_ptr_len,
+            .anyframe_type,
+            .bit_not,
+            .bool_not,
+            .negate,
+            .negate_wrap,
+            .load,
+            .ensure_result_used,
+            .ensure_result_non_error,
+            .ret_node,
+            .ret_load,
+            .resolve_inferred_alloc,
+            .optional_type,
+            .optional_payload_safe,
+            .optional_payload_unsafe,
+            .optional_payload_safe_ptr,
+            .optional_payload_unsafe_ptr,
+            .err_union_payload_safe,
+            .err_union_payload_unsafe,
+            .err_union_payload_safe_ptr,
+            .err_union_payload_unsafe_ptr,
+            .err_union_code,
+            .err_union_code_ptr,
+            .is_non_null,
+            .is_non_null_ptr,
+            .is_non_err,
+            .is_non_err_ptr,
+            .typeof,
+            .typeof_elem,
+            .struct_init_empty,
+            .type_info,
+            .size_of,
+            .bit_size_of,
+            .typeof_log2_int_type,
+            .log2_int_type,
+            .ptr_to_int,
+            .error_to_int,
+            .int_to_error,
+            .compile_error,
+            .set_eval_branch_quota,
+            .enum_to_int,
+            .align_of,
+            .bool_to_int,
+            .embed_file,
+            .error_name,
+            .panic,
+            .set_align_stack,
+            .set_cold,
+            .set_float_mode,
+            .set_runtime_safety,
+            .sqrt,
+            .sin,
+            .cos,
+            .exp,
+            .exp2,
+            .log,
+            .log2,
+            .log10,
+            .fabs,
+            .floor,
+            .ceil,
+            .trunc,
+            .round,
+            .tag_name,
+            .reify,
+            .type_name,
+            .frame_type,
+            .frame_size,
+            .clz,
+            .ctz,
+            .pop_count,
+            .byte_swap,
+            .bit_reverse,
+            .elem_type,
+            .@"resume",
+            .@"await",
+            .await_nosuspend,
+            .fence,
+            => try self.writeUnNode(stream, inst),
+
+            .ref,
+            .ret_coerce,
+            .ensure_err_payload_void,
+            => try self.writeUnTok(stream, inst),
+
+            .bool_br_and,
+            .bool_br_or,
+            => try self.writeBoolBr(stream, inst),
+
+            .array_type_sentinel => try self.writeArrayTypeSentinel(stream, inst),
+            .param_type => try self.writeParamType(stream, inst),
+            .ptr_type_simple => try self.writePtrTypeSimple(stream, inst),
+            .ptr_type => try self.writePtrType(stream, inst),
+            .int => try self.writeInt(stream, inst),
+            .int_big => try self.writeIntBig(stream, inst),
+            .float => try self.writeFloat(stream, inst),
+            .float128 => try self.writeFloat128(stream, inst),
+            .str => try self.writeStr(stream, inst),
+            .int_type => try self.writeIntType(stream, inst),
+
+            .@"break",
+            .break_inline,
+            => try self.writeBreak(stream, inst),
+
+            .elem_ptr_node,
+            .elem_val_node,
+            .field_ptr_named,
+            .field_val_named,
+            .slice_start,
+            .slice_end,
+            .slice_sentinel,
+            .array_init,
+            .array_init_anon,
+            .array_init_ref,
+            .array_init_anon_ref,
+            .union_init_ptr,
+            .shuffle,
+            .select,
+            .mul_add,
+            .builtin_call,
+            .field_parent_ptr,
+            .memcpy,
+            .memset,
+            .builtin_async_call,
+            => try self.writePlNode(stream, inst),
+
+            .struct_init,
+            .struct_init_ref,
+            => try self.writeStructInit(stream, inst),
+
+            .cmpxchg_strong, .cmpxchg_weak => try self.writeCmpxchg(stream, inst),
+            .atomic_store => try self.writeAtomicStore(stream, inst),
+            .atomic_rmw => try self.writeAtomicRmw(stream, inst),
+
+            .struct_init_anon,
+            .struct_init_anon_ref,
+            => try self.writeStructInitAnon(stream, inst),
+
+            .field_type => try self.writeFieldType(stream, inst),
+            .field_type_ref => try self.writeFieldTypeRef(stream, inst),
+
+            .add,
+            .addwrap,
+            .array_cat,
+            .array_mul,
+            .mul,
+            .mulwrap,
+            .sub,
+            .subwrap,
+            .cmp_lt,
+            .cmp_lte,
+            .cmp_eq,
+            .cmp_gte,
+            .cmp_gt,
+            .cmp_neq,
+            .div,
+            .has_decl,
+            .has_field,
+            .mod_rem,
+            .shl,
+            .shl_exact,
+            .shr,
+            .shr_exact,
+            .xor,
+            .store_node,
+            .error_union_type,
+            .merge_error_sets,
+            .bit_and,
+            .bit_or,
+            .float_to_int,
+            .int_to_float,
+            .int_to_ptr,
+            .int_to_enum,
+            .float_cast,
+            .int_cast,
+            .err_set_cast,
+            .ptr_cast,
+            .truncate,
+            .align_cast,
+            .div_exact,
+            .div_floor,
+            .div_trunc,
+            .mod,
+            .rem,
+            .bit_offset_of,
+            .offset_of,
+            .splat,
+            .reduce,
+            .atomic_load,
+            .bitcast,
+            .bitcast_result_ptr,
+            .vector_type,
+            .maximum,
+            .minimum,
+            => try self.writePlNodeBin(stream, inst),
+
+            .@"export" => try self.writePlNodeExport(stream, inst),
+
+            .call,
+            .call_chkused,
+            .call_compile_time,
+            .call_nosuspend,
+            .call_async,
+            => try self.writePlNodeCall(stream, inst),
+
+            .block,
+            .block_inline,
+            .suspend_block,
+            .loop,
+            .validate_struct_init_ptr,
+            .validate_array_init_ptr,
+            .c_import,
+            => try self.writePlNodeBlock(stream, inst),
+
+            .condbr,
+            .condbr_inline,
+            => try self.writePlNodeCondBr(stream, inst),
+
+            .opaque_decl => try self.writeOpaqueDecl(stream, inst, .parent),
+            .opaque_decl_anon => try self.writeOpaqueDecl(stream, inst, .anon),
+            .opaque_decl_func => try self.writeOpaqueDecl(stream, inst, .func),
+
+            .error_set_decl => try self.writeErrorSetDecl(stream, inst, .parent),
+            .error_set_decl_anon => try self.writeErrorSetDecl(stream, inst, .anon),
+            .error_set_decl_func => try self.writeErrorSetDecl(stream, inst, .func),
+
+            .switch_block => try self.writePlNodeSwitchBr(stream, inst, .none),
+            .switch_block_else => try self.writePlNodeSwitchBr(stream, inst, .@"else"),
+            .switch_block_under => try self.writePlNodeSwitchBr(stream, inst, .under),
+            .switch_block_ref => try self.writePlNodeSwitchBr(stream, inst, .none),
+            .switch_block_ref_else => try self.writePlNodeSwitchBr(stream, inst, .@"else"),
+            .switch_block_ref_under => try self.writePlNodeSwitchBr(stream, inst, .under),
+
+            .switch_block_multi => try self.writePlNodeSwitchBlockMulti(stream, inst, .none),
+            .switch_block_else_multi => try self.writePlNodeSwitchBlockMulti(stream, inst, .@"else"),
+            .switch_block_under_multi => try self.writePlNodeSwitchBlockMulti(stream, inst, .under),
+            .switch_block_ref_multi => try self.writePlNodeSwitchBlockMulti(stream, inst, .none),
+            .switch_block_ref_else_multi => try self.writePlNodeSwitchBlockMulti(stream, inst, .@"else"),
+            .switch_block_ref_under_multi => try self.writePlNodeSwitchBlockMulti(stream, inst, .under),
+
+            .field_ptr,
+            .field_val,
+            => try self.writePlNodeField(stream, inst),
+
+            .as_node => try self.writeAs(stream, inst),
+
+            .breakpoint,
+            .repeat,
+            .repeat_inline,
+            .alloc_inferred,
+            .alloc_inferred_mut,
+            .alloc_inferred_comptime,
+            => try self.writeNode(stream, inst),
+
+            .error_value,
+            .enum_literal,
+            .decl_ref,
+            .decl_val,
+            .import,
+            .ret_err_value,
+            .ret_err_value_code,
+            .param_anytype,
+            .param_anytype_comptime,
+            => try self.writeStrTok(stream, inst),
+
+            .param, .param_comptime => try self.writeParam(stream, inst),
+
+            .func => try self.writeFunc(stream, inst, false),
+            .func_inferred => try self.writeFunc(stream, inst, true),
+
+            .@"unreachable" => try self.writeUnreachable(stream, inst),
+
+            .switch_capture,
+            .switch_capture_ref,
+            .switch_capture_multi,
+            .switch_capture_multi_ref,
+            .switch_capture_else,
+            .switch_capture_else_ref,
+            => try self.writeSwitchCapture(stream, inst),
+
+            .dbg_stmt => try self.writeDbgStmt(stream, inst),
+
+            .extended => try self.writeExtended(stream, inst),
+        }
+    }
+
+    fn writeExtended(self: *Writer, stream: anytype, inst: Zir.Inst.Index) !void {
+        const extended = self.code.instructions.items(.data)[inst].extended;
+        try stream.print("{s}(", .{@tagName(extended.opcode)});
+        switch (extended.opcode) {
+            .ret_ptr,
+            .ret_type,
+            .this,
+            .ret_addr,
+            .error_return_trace,
+            .frame,
+            .frame_address,
+            .builtin_src,
+            => try self.writeExtNode(stream, extended),
+
+            .@"asm" => try self.writeAsm(stream, extended),
+            .func => try self.writeFuncExtended(stream, extended),
+            .variable => try self.writeVarExtended(stream, extended),
+
+            .compile_log,
+            .typeof_peer,
+            => try self.writeNodeMultiOp(stream, extended),
+
+            .add_with_overflow,
+            .sub_with_overflow,
+            .mul_with_overflow,
+            .shl_with_overflow,
+            => try self.writeOverflowArithmetic(stream, extended),
+
+            .add_with_saturation,
+            .sub_with_saturation,
+            .mul_with_saturation,
+            .shl_with_saturation,
+            => try self.writeSaturatingArithmetic(stream, extended),
+            .struct_decl => try self.writeStructDecl(stream, extended),
+            .union_decl => try self.writeUnionDecl(stream, extended),
+            .enum_decl => try self.writeEnumDecl(stream, extended),
+
+            .alloc,
+            .builtin_extern,
+            .c_undef,
+            .c_include,
+            .c_define,
+            .wasm_memory_size,
+            .wasm_memory_grow,
+            => try stream.writeAll("TODO))"),
+        }
+    }
+
+    fn writeExtNode(self: *Writer, stream: anytype, extended: Zir.Inst.Extended.InstData) !void {
+        const src: LazySrcLoc = .{ .node_offset = @bitCast(i32, extended.operand) };
+        try stream.writeAll(")) ");
+        try self.writeSrc(stream, src);
+    }
+
+    fn writeBin(self: *Writer, stream: anytype, inst: Zir.Inst.Index) !void {
+        const inst_data = self.code.instructions.items(.data)[inst].bin;
+        try self.writeInstRef(stream, inst_data.lhs);
+        try stream.writeAll(", ");
+        try self.writeInstRef(stream, inst_data.rhs);
+        try stream.writeByte(')');
+    }
+
+    fn writeUnNode(
+        self: *Writer,
+        stream: anytype,
+        inst: Zir.Inst.Index,
+    ) (@TypeOf(stream).Error || error{OutOfMemory})!void {
+        const inst_data = self.code.instructions.items(.data)[inst].un_node;
+        try self.writeInstRef(stream, inst_data.operand);
+        try stream.writeAll(") ");
+        try self.writeSrc(stream, inst_data.src());
+    }
+
+    fn writeUnTok(
+        self: *Writer,
+        stream: anytype,
+        inst: Zir.Inst.Index,
+    ) (@TypeOf(stream).Error || error{OutOfMemory})!void {
+        const inst_data = self.code.instructions.items(.data)[inst].un_tok;
+        try self.writeInstRef(stream, inst_data.operand);
+        try stream.writeAll(") ");
+        try self.writeSrc(stream, inst_data.src());
+    }
+
+    fn writeArrayTypeSentinel(
+        self: *Writer,
+        stream: anytype,
+        inst: Zir.Inst.Index,
+    ) (@TypeOf(stream).Error || error{OutOfMemory})!void {
+        const inst_data = self.code.instructions.items(.data)[inst].array_type_sentinel;
+        _ = inst_data;
+        try stream.writeAll("TODO)");
+    }
+
+    fn writeParamType(
+        self: *Writer,
+        stream: anytype,
+        inst: Zir.Inst.Index,
+    ) (@TypeOf(stream).Error || error{OutOfMemory})!void {
+        const inst_data = self.code.instructions.items(.data)[inst].param_type;
+        try self.writeInstRef(stream, inst_data.callee);
+        try stream.print(", {d})", .{inst_data.param_index});
+    }
+
+    fn writePtrTypeSimple(
+        self: *Writer,
+        stream: anytype,
+        inst: Zir.Inst.Index,
+    ) (@TypeOf(stream).Error || error{OutOfMemory})!void {
+        const inst_data = self.code.instructions.items(.data)[inst].ptr_type_simple;
+        const str_allowzero = if (inst_data.is_allowzero) "allowzero, " else "";
+        const str_const = if (!inst_data.is_mutable) "const, " else "";
+        const str_volatile = if (inst_data.is_volatile) "volatile, " else "";
+        try self.writeInstRef(stream, inst_data.elem_type);
+        try stream.print(", {s}{s}{s}{s})", .{
+            str_allowzero,
+            str_const,
+            str_volatile,
+            @tagName(inst_data.size),
+        });
+    }
+
+    fn writePtrType(
+        self: *Writer,
+        stream: anytype,
+        inst: Zir.Inst.Index,
+    ) (@TypeOf(stream).Error || error{OutOfMemory})!void {
+        const inst_data = self.code.instructions.items(.data)[inst].ptr_type;
+        _ = inst_data;
+        try stream.writeAll("TODO)");
+    }
+
+    fn writeInt(self: *Writer, stream: anytype, inst: Zir.Inst.Index) !void {
+        const inst_data = self.code.instructions.items(.data)[inst].int;
+        try stream.print("{d})", .{inst_data});
+    }
+
+    fn writeIntBig(self: *Writer, stream: anytype, inst: Zir.Inst.Index) !void {
+        const inst_data = self.code.instructions.items(.data)[inst].str;
+        const byte_count = inst_data.len * @sizeOf(std.math.big.Limb);
+        const limb_bytes = self.code.string_bytes[inst_data.start..][0..byte_count];
+        // limb_bytes is not aligned properly; we must allocate and copy the bytes
+        // in order to accomplish this.
+        const limbs = try self.gpa.alloc(std.math.big.Limb, inst_data.len);
+        defer self.gpa.free(limbs);
+
+        mem.copy(u8, mem.sliceAsBytes(limbs), limb_bytes);
+        const big_int: std.math.big.int.Const = .{
+            .limbs = limbs,
+            .positive = true,
+        };
+        const as_string = try big_int.toStringAlloc(self.gpa, 10, .lower);
+        defer self.gpa.free(as_string);
+        try stream.print("{s})", .{as_string});
+    }
+
+    fn writeFloat(self: *Writer, stream: anytype, inst: Zir.Inst.Index) !void {
+        const number = self.code.instructions.items(.data)[inst].float;
+        try stream.print("{d})", .{number});
+    }
+
+    fn writeFloat128(self: *Writer, stream: anytype, inst: Zir.Inst.Index) !void {
+        const inst_data = self.code.instructions.items(.data)[inst].pl_node;
+        const extra = self.code.extraData(Zir.Inst.Float128, inst_data.payload_index).data;
+        const src = inst_data.src();
+        const number = extra.get();
+        // TODO improve std.format to be able to print f128 values
+        try stream.print("{d}) ", .{@floatCast(f64, number)});
+        try self.writeSrc(stream, src);
+    }
+
+    fn writeStr(
+        self: *Writer,
+        stream: anytype,
+        inst: Zir.Inst.Index,
+    ) (@TypeOf(stream).Error || error{OutOfMemory})!void {
+        const inst_data = self.code.instructions.items(.data)[inst].str;
+        const str = inst_data.get(self.code);
+        try stream.print("\"{}\")", .{std.zig.fmtEscapes(str)});
+    }
+
+    fn writePlNode(self: *Writer, stream: anytype, inst: Zir.Inst.Index) !void {
+        const inst_data = self.code.instructions.items(.data)[inst].pl_node;
+        try stream.writeAll("TODO) ");
+        try self.writeSrc(stream, inst_data.src());
+    }
+
+    fn writeParam(self: *Writer, stream: anytype, inst: Zir.Inst.Index) !void {
+        const inst_data = self.code.instructions.items(.data)[inst].pl_tok;
+        const extra = self.code.extraData(Zir.Inst.Param, inst_data.payload_index);
+        const body = self.code.extra[extra.end..][0..extra.data.body_len];
+        try stream.print("\"{}\", ", .{
+            std.zig.fmtEscapes(self.code.nullTerminatedString(extra.data.name)),
+        });
+        try stream.writeAll("{\n");
+        self.indent += 2;
+        try self.writeBody(stream, body);
+        self.indent -= 2;
+        try stream.writeByteNTimes(' ', self.indent);
+        try stream.writeAll("}) ");
+        try self.writeSrc(stream, inst_data.src());
+    }
+
+    fn writePlNodeBin(self: *Writer, stream: anytype, inst: Zir.Inst.Index) !void {
+        const inst_data = self.code.instructions.items(.data)[inst].pl_node;
+        const extra = self.code.extraData(Zir.Inst.Bin, inst_data.payload_index).data;
+        try self.writeInstRef(stream, extra.lhs);
+        try stream.writeAll(", ");
+        try self.writeInstRef(stream, extra.rhs);
+        try stream.writeAll(") ");
+        try self.writeSrc(stream, inst_data.src());
+    }
+
+    fn writePlNodeExport(self: *Writer, stream: anytype, inst: Zir.Inst.Index) !void {
+        const inst_data = self.code.instructions.items(.data)[inst].pl_node;
+        const extra = self.code.extraData(Zir.Inst.Export, inst_data.payload_index).data;
+        const decl_name = self.code.nullTerminatedString(extra.decl_name);
+
+        try self.writeInstRef(stream, extra.namespace);
+        try stream.print(", {}, ", .{std.zig.fmtId(decl_name)});
+        try self.writeInstRef(stream, extra.options);
+        try stream.writeAll(") ");
+        try self.writeSrc(stream, inst_data.src());
+    }
+
+    fn writeStructInit(self: *Writer, stream: anytype, inst: Zir.Inst.Index) !void {
+        const inst_data = self.code.instructions.items(.data)[inst].pl_node;
+        const extra = self.code.extraData(Zir.Inst.StructInit, inst_data.payload_index);
+        var field_i: u32 = 0;
+        var extra_index = extra.end;
+
+        while (field_i < extra.data.fields_len) : (field_i += 1) {
+            const item = self.code.extraData(Zir.Inst.StructInit.Item, extra_index);
+            extra_index = item.end;
+
+            if (field_i != 0) {
+                try stream.writeAll(", [");
+            } else {
+                try stream.writeAll("[");
+            }
+            try self.writeInstIndex(stream, item.data.field_type);
+            try stream.writeAll(", ");
+            try self.writeInstRef(stream, item.data.init);
+            try stream.writeAll("]");
+        }
+        try stream.writeAll(") ");
+        try self.writeSrc(stream, inst_data.src());
+    }
+
+    fn writeCmpxchg(self: *Writer, stream: anytype, inst: Zir.Inst.Index) !void {
+        const inst_data = self.code.instructions.items(.data)[inst].pl_node;
+        const extra = self.code.extraData(Zir.Inst.Cmpxchg, inst_data.payload_index).data;
+
+        try self.writeInstRef(stream, extra.ptr);
+        try stream.writeAll(", ");
+        try self.writeInstRef(stream, extra.expected_value);
+        try stream.writeAll(", ");
+        try self.writeInstRef(stream, extra.new_value);
+        try stream.writeAll(", ");
+        try self.writeInstRef(stream, extra.success_order);
+        try stream.writeAll(", ");
+        try self.writeInstRef(stream, extra.failure_order);
+        try stream.writeAll(") ");
+        try self.writeSrc(stream, inst_data.src());
+    }
+
+    fn writeAtomicStore(self: *Writer, stream: anytype, inst: Zir.Inst.Index) !void {
+        const inst_data = self.code.instructions.items(.data)[inst].pl_node;
+        const extra = self.code.extraData(Zir.Inst.AtomicStore, inst_data.payload_index).data;
+
+        try self.writeInstRef(stream, extra.ptr);
+        try stream.writeAll(", ");
+        try self.writeInstRef(stream, extra.operand);
+        try stream.writeAll(", ");
+        try self.writeInstRef(stream, extra.ordering);
+        try stream.writeAll(") ");
+        try self.writeSrc(stream, inst_data.src());
+    }
+
+    fn writeAtomicRmw(self: *Writer, stream: anytype, inst: Zir.Inst.Index) !void {
+        const inst_data = self.code.instructions.items(.data)[inst].pl_node;
+        const extra = self.code.extraData(Zir.Inst.AtomicRmw, inst_data.payload_index).data;
+
+        try self.writeInstRef(stream, extra.ptr);
+        try stream.writeAll(", ");
+        try self.writeInstRef(stream, extra.operation);
+        try stream.writeAll(", ");
+        try self.writeInstRef(stream, extra.operand);
+        try stream.writeAll(", ");
+        try self.writeInstRef(stream, extra.ordering);
+        try stream.writeAll(") ");
+        try self.writeSrc(stream, inst_data.src());
+    }
+
+    fn writeStructInitAnon(self: *Writer, stream: anytype, inst: Zir.Inst.Index) !void {
+        const inst_data = self.code.instructions.items(.data)[inst].pl_node;
+        const extra = self.code.extraData(Zir.Inst.StructInitAnon, inst_data.payload_index);
+        var field_i: u32 = 0;
+        var extra_index = extra.end;
+
+        while (field_i < extra.data.fields_len) : (field_i += 1) {
+            const item = self.code.extraData(Zir.Inst.StructInitAnon.Item, extra_index);
+            extra_index = item.end;
+
+            const field_name = self.code.nullTerminatedString(item.data.field_name);
+
+            const prefix = if (field_i != 0) ", [" else "[";
+            try stream.print("{s}[{s}=", .{ prefix, field_name });
+            try self.writeInstRef(stream, item.data.init);
+            try stream.writeAll("]");
+        }
+        try stream.writeAll(") ");
+        try self.writeSrc(stream, inst_data.src());
+    }
+
+    fn writeFieldType(self: *Writer, stream: anytype, inst: Zir.Inst.Index) !void {
+        const inst_data = self.code.instructions.items(.data)[inst].pl_node;
+        const extra = self.code.extraData(Zir.Inst.FieldType, inst_data.payload_index).data;
+        try self.writeInstRef(stream, extra.container_type);
+        const field_name = self.code.nullTerminatedString(extra.name_start);
+        try stream.print(", {s}) ", .{field_name});
+        try self.writeSrc(stream, inst_data.src());
+    }
+
+    fn writeFieldTypeRef(self: *Writer, stream: anytype, inst: Zir.Inst.Index) !void {
+        const inst_data = self.code.instructions.items(.data)[inst].pl_node;
+        const extra = self.code.extraData(Zir.Inst.FieldTypeRef, inst_data.payload_index).data;
+        try self.writeInstRef(stream, extra.container_type);
+        try stream.writeAll(", ");
+        try self.writeInstRef(stream, extra.field_name);
+        try stream.writeAll(") ");
+        try self.writeSrc(stream, inst_data.src());
+    }
+
+    fn writeNodeMultiOp(self: *Writer, stream: anytype, extended: Zir.Inst.Extended.InstData) !void {
+        const extra = self.code.extraData(Zir.Inst.NodeMultiOp, extended.operand);
+        const src: LazySrcLoc = .{ .node_offset = extra.data.src_node };
+        const operands = self.code.refSlice(extra.end, extended.small);
+
+        for (operands) |operand, i| {
+            if (i != 0) try stream.writeAll(", ");
+            try self.writeInstRef(stream, operand);
+        }
+        try stream.writeAll(")) ");
+        try self.writeSrc(stream, src);
+    }
+
+    fn writeAsm(self: *Writer, stream: anytype, extended: Zir.Inst.Extended.InstData) !void {
+        const extra = self.code.extraData(Zir.Inst.Asm, extended.operand);
+        const src: LazySrcLoc = .{ .node_offset = extra.data.src_node };
+        const outputs_len = @truncate(u5, extended.small);
+        const inputs_len = @truncate(u5, extended.small >> 5);
+        const clobbers_len = @truncate(u5, extended.small >> 10);
+        const is_volatile = @truncate(u1, extended.small >> 15) != 0;
+        const asm_source = self.code.nullTerminatedString(extra.data.asm_source);
+
+        try self.writeFlag(stream, "volatile, ", is_volatile);
+        try stream.print("\"{}\", ", .{std.zig.fmtEscapes(asm_source)});
+        try stream.writeAll(", ");
+
+        var extra_i: usize = extra.end;
+        var output_type_bits = extra.data.output_type_bits;
+        {
+            var i: usize = 0;
+            while (i < outputs_len) : (i += 1) {
+                const output = self.code.extraData(Zir.Inst.Asm.Output, extra_i);
+                extra_i = output.end;
+
+                const is_type = @truncate(u1, output_type_bits) != 0;
+                output_type_bits >>= 1;
+
+                const name = self.code.nullTerminatedString(output.data.name);
+                const constraint = self.code.nullTerminatedString(output.data.constraint);
+                try stream.print("output({}, \"{}\", ", .{
+                    std.zig.fmtId(name), std.zig.fmtEscapes(constraint),
+                });
+                try self.writeFlag(stream, "->", is_type);
+                try self.writeInstRef(stream, output.data.operand);
+                try stream.writeAll(")");
+                if (i + 1 < outputs_len) {
+                    try stream.writeAll("), ");
+                }
+            }
+        }
+        {
+            var i: usize = 0;
+            while (i < inputs_len) : (i += 1) {
+                const input = self.code.extraData(Zir.Inst.Asm.Input, extra_i);
+                extra_i = input.end;
+
+                const name = self.code.nullTerminatedString(input.data.name);
+                const constraint = self.code.nullTerminatedString(input.data.constraint);
+                try stream.print("input({}, \"{}\", ", .{
+                    std.zig.fmtId(name), std.zig.fmtEscapes(constraint),
+                });
+                try self.writeInstRef(stream, input.data.operand);
+                try stream.writeAll(")");
+                if (i + 1 < inputs_len) {
+                    try stream.writeAll(", ");
+                }
+            }
+        }
+        {
+            var i: usize = 0;
+            while (i < clobbers_len) : (i += 1) {
+                const str_index = self.code.extra[extra_i];
+                extra_i += 1;
+                const clobber = self.code.nullTerminatedString(str_index);
+                try stream.print("{}", .{std.zig.fmtId(clobber)});
+                if (i + 1 < clobbers_len) {
+                    try stream.writeAll(", ");
+                }
+            }
+        }
+        try stream.writeAll(")) ");
+        try self.writeSrc(stream, src);
+    }
+
+    fn writeOverflowArithmetic(self: *Writer, stream: anytype, extended: Zir.Inst.Extended.InstData) !void {
+        const extra = self.code.extraData(Zir.Inst.OverflowArithmetic, extended.operand).data;
+        const src: LazySrcLoc = .{ .node_offset = extra.node };
+
+        try self.writeInstRef(stream, extra.lhs);
+        try stream.writeAll(", ");
+        try self.writeInstRef(stream, extra.rhs);
+        try stream.writeAll(", ");
+        try self.writeInstRef(stream, extra.ptr);
+        try stream.writeAll(")) ");
+        try self.writeSrc(stream, src);
+    }
+
+    fn writeSaturatingArithmetic(self: *Writer, stream: anytype, extended: Zir.Inst.Extended.InstData) !void {
+        const extra = self.code.extraData(Zir.Inst.SaturatingArithmetic, extended.operand).data;
+        const src: LazySrcLoc = .{ .node_offset = extra.node };
+
+        try self.writeInstRef(stream, extra.lhs);
+        try stream.writeAll(", ");
+        try self.writeInstRef(stream, extra.rhs);
+        try stream.writeAll(", ");
+        try stream.writeAll(") ");
+        try self.writeSrc(stream, src);
+    }
+
+    fn writePlNodeCall(self: *Writer, stream: anytype, inst: Zir.Inst.Index) !void {
+        const inst_data = self.code.instructions.items(.data)[inst].pl_node;
+        const extra = self.code.extraData(Zir.Inst.Call, inst_data.payload_index);
+        const args = self.code.refSlice(extra.end, extra.data.args_len);
+
+        try self.writeInstRef(stream, extra.data.callee);
+        try stream.writeAll(", [");
+        for (args) |arg, i| {
+            if (i != 0) try stream.writeAll(", ");
+            try self.writeInstRef(stream, arg);
+        }
+        try stream.writeAll("]) ");
+        try self.writeSrc(stream, inst_data.src());
+    }
+
+    fn writePlNodeBlock(self: *Writer, stream: anytype, inst: Zir.Inst.Index) !void {
+        const inst_data = self.code.instructions.items(.data)[inst].pl_node;
+        try self.writePlNodeBlockWithoutSrc(stream, inst);
+        try self.writeSrc(stream, inst_data.src());
+    }
+
+    fn writePlNodeBlockWithoutSrc(self: *Writer, stream: anytype, inst: Zir.Inst.Index) !void {
+        const inst_data = self.code.instructions.items(.data)[inst].pl_node;
+        const extra = self.code.extraData(Zir.Inst.Block, inst_data.payload_index);
+        const body = self.code.extra[extra.end..][0..extra.data.body_len];
+        try stream.writeAll("{\n");
+        self.indent += 2;
+        try self.writeBody(stream, body);
+        self.indent -= 2;
+        try stream.writeByteNTimes(' ', self.indent);
+        try stream.writeAll("}) ");
+    }
+
+    fn writePlNodeCondBr(self: *Writer, stream: anytype, inst: Zir.Inst.Index) !void {
+        const inst_data = self.code.instructions.items(.data)[inst].pl_node;
+        const extra = self.code.extraData(Zir.Inst.CondBr, inst_data.payload_index);
+        const then_body = self.code.extra[extra.end..][0..extra.data.then_body_len];
+        const else_body = self.code.extra[extra.end + then_body.len ..][0..extra.data.else_body_len];
+        try self.writeInstRef(stream, extra.data.condition);
+        try stream.writeAll(", {\n");
+        self.indent += 2;
+        try self.writeBody(stream, then_body);
+        self.indent -= 2;
+        try stream.writeByteNTimes(' ', self.indent);
+        try stream.writeAll("}, {\n");
+        self.indent += 2;
+        try self.writeBody(stream, else_body);
+        self.indent -= 2;
+        try stream.writeByteNTimes(' ', self.indent);
+        try stream.writeAll("}) ");
+        try self.writeSrc(stream, inst_data.src());
+    }
+
+    fn writeStructDecl(self: *Writer, stream: anytype, extended: Zir.Inst.Extended.InstData) !void {
+        const small = @bitCast(Zir.Inst.StructDecl.Small, extended.small);
+
+        var extra_index: usize = extended.operand;
+
+        const src_node: ?i32 = if (small.has_src_node) blk: {
+            const src_node = @bitCast(i32, self.code.extra[extra_index]);
+            extra_index += 1;
+            break :blk src_node;
+        } else null;
+
+        const body_len = if (small.has_body_len) blk: {
+            const body_len = self.code.extra[extra_index];
+            extra_index += 1;
+            break :blk body_len;
+        } else 0;
+
+        const fields_len = if (small.has_fields_len) blk: {
+            const fields_len = self.code.extra[extra_index];
+            extra_index += 1;
+            break :blk fields_len;
+        } else 0;
+
+        const decls_len = if (small.has_decls_len) blk: {
+            const decls_len = self.code.extra[extra_index];
+            extra_index += 1;
+            break :blk decls_len;
+        } else 0;
+
+        try self.writeFlag(stream, "known_has_bits, ", small.known_has_bits);
+        try stream.print("{s}, {s}, ", .{
+            @tagName(small.name_strategy), @tagName(small.layout),
+        });
+
+        if (decls_len == 0) {
+            try stream.writeAll("{}, ");
+        } else {
+            try stream.writeAll("{\n");
+            self.indent += 2;
+            extra_index = try self.writeDecls(stream, decls_len, extra_index);
+            self.indent -= 2;
+            try stream.writeByteNTimes(' ', self.indent);
+            try stream.writeAll("}, ");
+        }
+
+        const body = self.code.extra[extra_index..][0..body_len];
+        extra_index += body.len;
+
+        if (fields_len == 0) {
+            assert(body.len == 0);
+            try stream.writeAll("{}, {})");
+        } else {
+            const prev_parent_decl_node = self.parent_decl_node;
+            if (src_node) |off| self.parent_decl_node = self.relativeToNodeIndex(off);
+            self.indent += 2;
+            if (body.len == 0) {
+                try stream.writeAll("{}, {\n");
+            } else {
+                try stream.writeAll("{\n");
+                try self.writeBody(stream, body);
+
+                try stream.writeByteNTimes(' ', self.indent - 2);
+                try stream.writeAll("}, {\n");
+            }
+
+            const bits_per_field = 4;
+            const fields_per_u32 = 32 / bits_per_field;
+            const bit_bags_count = std.math.divCeil(usize, fields_len, fields_per_u32) catch unreachable;
+            var bit_bag_index: usize = extra_index;
+            extra_index += bit_bags_count;
+            var cur_bit_bag: u32 = undefined;
+            var field_i: u32 = 0;
+            while (field_i < fields_len) : (field_i += 1) {
+                if (field_i % fields_per_u32 == 0) {
+                    cur_bit_bag = self.code.extra[bit_bag_index];
+                    bit_bag_index += 1;
+                }
+                const has_align = @truncate(u1, cur_bit_bag) != 0;
+                cur_bit_bag >>= 1;
+                const has_default = @truncate(u1, cur_bit_bag) != 0;
+                cur_bit_bag >>= 1;
+                const is_comptime = @truncate(u1, cur_bit_bag) != 0;
+                cur_bit_bag >>= 1;
+                const unused = @truncate(u1, cur_bit_bag) != 0;
+                cur_bit_bag >>= 1;
+
+                _ = unused;
+
+                const field_name = self.code.nullTerminatedString(self.code.extra[extra_index]);
+                extra_index += 1;
+                const field_type = @intToEnum(Zir.Inst.Ref, self.code.extra[extra_index]);
+                extra_index += 1;
+
+                try stream.writeByteNTimes(' ', self.indent);
+                try self.writeFlag(stream, "comptime ", is_comptime);
+                try stream.print("{}: ", .{std.zig.fmtId(field_name)});
+                try self.writeInstRef(stream, field_type);
+
+                if (has_align) {
+                    const align_ref = @intToEnum(Zir.Inst.Ref, self.code.extra[extra_index]);
+                    extra_index += 1;
+
+                    try stream.writeAll(" align(");
+                    try self.writeInstRef(stream, align_ref);
+                    try stream.writeAll(")");
+                }
+                if (has_default) {
+                    const default_ref = @intToEnum(Zir.Inst.Ref, self.code.extra[extra_index]);
+                    extra_index += 1;
+
+                    try stream.writeAll(" = ");
+                    try self.writeInstRef(stream, default_ref);
+                }
+                try stream.writeAll(",\n");
+            }
+
+            self.parent_decl_node = prev_parent_decl_node;
+            self.indent -= 2;
+            try stream.writeByteNTimes(' ', self.indent);
+            try stream.writeAll("})");
+        }
+        try self.writeSrcNode(stream, src_node);
+    }
+
+    fn writeUnionDecl(self: *Writer, stream: anytype, extended: Zir.Inst.Extended.InstData) !void {
+        const small = @bitCast(Zir.Inst.UnionDecl.Small, extended.small);
+
+        var extra_index: usize = extended.operand;
+
+        const src_node: ?i32 = if (small.has_src_node) blk: {
+            const src_node = @bitCast(i32, self.code.extra[extra_index]);
+            extra_index += 1;
+            break :blk src_node;
+        } else null;
+
+        const tag_type_ref = if (small.has_tag_type) blk: {
+            const tag_type_ref = @intToEnum(Zir.Inst.Ref, self.code.extra[extra_index]);
+            extra_index += 1;
+            break :blk tag_type_ref;
+        } else .none;
+
+        const body_len = if (small.has_body_len) blk: {
+            const body_len = self.code.extra[extra_index];
+            extra_index += 1;
+            break :blk body_len;
+        } else 0;
+
+        const fields_len = if (small.has_fields_len) blk: {
+            const fields_len = self.code.extra[extra_index];
+            extra_index += 1;
+            break :blk fields_len;
+        } else 0;
+
+        const decls_len = if (small.has_decls_len) blk: {
+            const decls_len = self.code.extra[extra_index];
+            extra_index += 1;
+            break :blk decls_len;
+        } else 0;
+
+        try stream.print("{s}, {s}, ", .{
+            @tagName(small.name_strategy), @tagName(small.layout),
+        });
+        try self.writeFlag(stream, "autoenum, ", small.auto_enum_tag);
+
+        if (decls_len == 0) {
+            try stream.writeAll("{}, ");
+        } else {
+            try stream.writeAll("{\n");
+            self.indent += 2;
+            extra_index = try self.writeDecls(stream, decls_len, extra_index);
+            self.indent -= 2;
+            try stream.writeByteNTimes(' ', self.indent);
+            try stream.writeAll("}, ");
+        }
+
+        assert(fields_len != 0);
+
+        if (tag_type_ref != .none) {
+            try self.writeInstRef(stream, tag_type_ref);
+            try stream.writeAll(", ");
+        }
+
+        const body = self.code.extra[extra_index..][0..body_len];
+        extra_index += body.len;
+
+        const prev_parent_decl_node = self.parent_decl_node;
+        if (src_node) |off| self.parent_decl_node = self.relativeToNodeIndex(off);
+        self.indent += 2;
+        if (body.len == 0) {
+            try stream.writeAll("{}, {\n");
+        } else {
+            try stream.writeAll("{\n");
+            try self.writeBody(stream, body);
+
+            try stream.writeByteNTimes(' ', self.indent - 2);
+            try stream.writeAll("}, {\n");
+        }
+
+        const bits_per_field = 4;
+        const fields_per_u32 = 32 / bits_per_field;
+        const bit_bags_count = std.math.divCeil(usize, fields_len, fields_per_u32) catch unreachable;
+        const body_end = extra_index;
+        extra_index += bit_bags_count;
+        var bit_bag_index: usize = body_end;
+        var cur_bit_bag: u32 = undefined;
+        var field_i: u32 = 0;
+        while (field_i < fields_len) : (field_i += 1) {
+            if (field_i % fields_per_u32 == 0) {
+                cur_bit_bag = self.code.extra[bit_bag_index];
+                bit_bag_index += 1;
+            }
+            const has_type = @truncate(u1, cur_bit_bag) != 0;
+            cur_bit_bag >>= 1;
+            const has_align = @truncate(u1, cur_bit_bag) != 0;
+            cur_bit_bag >>= 1;
+            const has_value = @truncate(u1, cur_bit_bag) != 0;
+            cur_bit_bag >>= 1;
+            const unused = @truncate(u1, cur_bit_bag) != 0;
+            cur_bit_bag >>= 1;
+
+            _ = unused;
+
+            const field_name = self.code.nullTerminatedString(self.code.extra[extra_index]);
+            extra_index += 1;
+            try stream.writeByteNTimes(' ', self.indent);
+            try stream.print("{}", .{std.zig.fmtId(field_name)});
+
+            if (has_type) {
+                const field_type = @intToEnum(Zir.Inst.Ref, self.code.extra[extra_index]);
+                extra_index += 1;
+
+                try stream.writeAll(": ");
+                try self.writeInstRef(stream, field_type);
+            }
+            if (has_align) {
+                const align_ref = @intToEnum(Zir.Inst.Ref, self.code.extra[extra_index]);
+                extra_index += 1;
+
+                try stream.writeAll(" align(");
+                try self.writeInstRef(stream, align_ref);
+                try stream.writeAll(")");
+            }
+            if (has_value) {
+                const default_ref = @intToEnum(Zir.Inst.Ref, self.code.extra[extra_index]);
+                extra_index += 1;
+
+                try stream.writeAll(" = ");
+                try self.writeInstRef(stream, default_ref);
+            }
+            try stream.writeAll(",\n");
+        }
+
+        self.parent_decl_node = prev_parent_decl_node;
+        self.indent -= 2;
+        try stream.writeByteNTimes(' ', self.indent);
+        try stream.writeAll("})");
+        try self.writeSrcNode(stream, src_node);
+    }
+
+    fn writeDecls(self: *Writer, stream: anytype, decls_len: u32, extra_start: usize) !usize {
+        const parent_decl_node = self.parent_decl_node;
+        const bit_bags_count = std.math.divCeil(usize, decls_len, 8) catch unreachable;
+        var extra_index = extra_start + bit_bags_count;
+        var bit_bag_index: usize = extra_start;
+        var cur_bit_bag: u32 = undefined;
+        var decl_i: u32 = 0;
+        while (decl_i < decls_len) : (decl_i += 1) {
+            if (decl_i % 8 == 0) {
+                cur_bit_bag = self.code.extra[bit_bag_index];
+                bit_bag_index += 1;
+            }
+            const is_pub = @truncate(u1, cur_bit_bag) != 0;
+            cur_bit_bag >>= 1;
+            const is_exported = @truncate(u1, cur_bit_bag) != 0;
+            cur_bit_bag >>= 1;
+            const has_align = @truncate(u1, cur_bit_bag) != 0;
+            cur_bit_bag >>= 1;
+            const has_section = @truncate(u1, cur_bit_bag) != 0;
+            cur_bit_bag >>= 1;
+
+            const sub_index = extra_index;
+
+            const hash_u32s = self.code.extra[extra_index..][0..4];
+            extra_index += 4;
+            const line = self.code.extra[extra_index];
+            extra_index += 1;
+            const decl_name_index = self.code.extra[extra_index];
+            extra_index += 1;
+            const decl_index = self.code.extra[extra_index];
+            extra_index += 1;
+            const align_inst: Zir.Inst.Ref = if (!has_align) .none else inst: {
+                const inst = @intToEnum(Zir.Inst.Ref, self.code.extra[extra_index]);
+                extra_index += 1;
+                break :inst inst;
+            };
+            const section_inst: Zir.Inst.Ref = if (!has_section) .none else inst: {
+                const inst = @intToEnum(Zir.Inst.Ref, self.code.extra[extra_index]);
+                extra_index += 1;
+                break :inst inst;
+            };
+
+            const pub_str = if (is_pub) "pub " else "";
+            const hash_bytes = @bitCast([16]u8, hash_u32s.*);
+            try stream.writeByteNTimes(' ', self.indent);
+            if (decl_name_index == 0) {
+                const name = if (is_exported) "usingnamespace" else "comptime";
+                try stream.writeAll(pub_str);
+                try stream.writeAll(name);
+            } else if (decl_name_index == 1) {
+                try stream.writeAll("test");
+            } else {
+                const raw_decl_name = self.code.nullTerminatedString(decl_name_index);
+                const decl_name = if (raw_decl_name.len == 0)
+                    self.code.nullTerminatedString(decl_name_index + 1)
+                else
+                    raw_decl_name;
+                const test_str = if (raw_decl_name.len == 0) "test " else "";
+                const export_str = if (is_exported) "export " else "";
+                try stream.print("[{d}] {s}{s}{s}{}", .{
+                    sub_index, pub_str, test_str, export_str, std.zig.fmtId(decl_name),
+                });
+                if (align_inst != .none) {
+                    try stream.writeAll(" align(");
+                    try self.writeInstRef(stream, align_inst);
+                    try stream.writeAll(")");
+                }
+                if (section_inst != .none) {
+                    try stream.writeAll(" linksection(");
+                    try self.writeInstRef(stream, section_inst);
+                    try stream.writeAll(")");
+                }
+            }
+            const tag = self.code.instructions.items(.tag)[decl_index];
+            try stream.print(" line({d}) hash({}): %{d} = {s}(", .{
+                line, std.fmt.fmtSliceHexLower(&hash_bytes), decl_index, @tagName(tag),
+            });
+
+            const decl_block_inst_data = self.code.instructions.items(.data)[decl_index].pl_node;
+            const sub_decl_node_off = decl_block_inst_data.src_node;
+            self.parent_decl_node = self.relativeToNodeIndex(sub_decl_node_off);
+            try self.writePlNodeBlockWithoutSrc(stream, decl_index);
+            self.parent_decl_node = parent_decl_node;
+            try self.writeSrc(stream, decl_block_inst_data.src());
+            try stream.writeAll("\n");
+        }
+        return extra_index;
+    }
+
+    fn writeEnumDecl(self: *Writer, stream: anytype, extended: Zir.Inst.Extended.InstData) !void {
+        const small = @bitCast(Zir.Inst.EnumDecl.Small, extended.small);
+        var extra_index: usize = extended.operand;
+
+        const src_node: ?i32 = if (small.has_src_node) blk: {
+            const src_node = @bitCast(i32, self.code.extra[extra_index]);
+            extra_index += 1;
+            break :blk src_node;
+        } else null;
+
+        const tag_type_ref = if (small.has_tag_type) blk: {
+            const tag_type_ref = @intToEnum(Zir.Inst.Ref, self.code.extra[extra_index]);
+            extra_index += 1;
+            break :blk tag_type_ref;
+        } else .none;
+
+        const body_len = if (small.has_body_len) blk: {
+            const body_len = self.code.extra[extra_index];
+            extra_index += 1;
+            break :blk body_len;
+        } else 0;
+
+        const fields_len = if (small.has_fields_len) blk: {
+            const fields_len = self.code.extra[extra_index];
+            extra_index += 1;
+            break :blk fields_len;
+        } else 0;
+
+        const decls_len = if (small.has_decls_len) blk: {
+            const decls_len = self.code.extra[extra_index];
+            extra_index += 1;
+            break :blk decls_len;
+        } else 0;
+
+        try stream.print("{s}, ", .{@tagName(small.name_strategy)});
+        try self.writeFlag(stream, "nonexhaustive, ", small.nonexhaustive);
+
+        if (decls_len == 0) {
+            try stream.writeAll("{}, ");
+        } else {
+            try stream.writeAll("{\n");
+            self.indent += 2;
+            extra_index = try self.writeDecls(stream, decls_len, extra_index);
+            self.indent -= 2;
+            try stream.writeByteNTimes(' ', self.indent);
+            try stream.writeAll("}, ");
+        }
+
+        if (tag_type_ref != .none) {
+            try self.writeInstRef(stream, tag_type_ref);
+            try stream.writeAll(", ");
+        }
+
+        const body = self.code.extra[extra_index..][0..body_len];
+        extra_index += body.len;
+
+        if (fields_len == 0) {
+            assert(body.len == 0);
+            try stream.writeAll("{}, {})");
+        } else {
+            const prev_parent_decl_node = self.parent_decl_node;
+            if (src_node) |off| self.parent_decl_node = self.relativeToNodeIndex(off);
+            self.indent += 2;
+            if (body.len == 0) {
+                try stream.writeAll("{}, {\n");
+            } else {
+                try stream.writeAll("{\n");
+                try self.writeBody(stream, body);
+
+                try stream.writeByteNTimes(' ', self.indent - 2);
+                try stream.writeAll("}, {\n");
+            }
+
+            const bit_bags_count = std.math.divCeil(usize, fields_len, 32) catch unreachable;
+            const body_end = extra_index;
+            extra_index += bit_bags_count;
+            var bit_bag_index: usize = body_end;
+            var cur_bit_bag: u32 = undefined;
+            var field_i: u32 = 0;
+            while (field_i < fields_len) : (field_i += 1) {
+                if (field_i % 32 == 0) {
+                    cur_bit_bag = self.code.extra[bit_bag_index];
+                    bit_bag_index += 1;
+                }
+                const has_tag_value = @truncate(u1, cur_bit_bag) != 0;
+                cur_bit_bag >>= 1;
+
+                const field_name = self.code.nullTerminatedString(self.code.extra[extra_index]);
+                extra_index += 1;
+
+                try stream.writeByteNTimes(' ', self.indent);
+                try stream.print("{}", .{std.zig.fmtId(field_name)});
+
+                if (has_tag_value) {
+                    const tag_value_ref = @intToEnum(Zir.Inst.Ref, self.code.extra[extra_index]);
+                    extra_index += 1;
+
+                    try stream.writeAll(" = ");
+                    try self.writeInstRef(stream, tag_value_ref);
+                }
+                try stream.writeAll(",\n");
+            }
+            self.parent_decl_node = prev_parent_decl_node;
+            self.indent -= 2;
+            try stream.writeByteNTimes(' ', self.indent);
+            try stream.writeAll("})");
+        }
+        try self.writeSrcNode(stream, src_node);
+    }
+
+    fn writeOpaqueDecl(
+        self: *Writer,
+        stream: anytype,
+        inst: Zir.Inst.Index,
+        name_strategy: Zir.Inst.NameStrategy,
+    ) !void {
+        const inst_data = self.code.instructions.items(.data)[inst].pl_node;
+        const extra = self.code.extraData(Zir.Inst.OpaqueDecl, inst_data.payload_index);
+        const decls_len = extra.data.decls_len;
+
+        try stream.print("{s}, ", .{@tagName(name_strategy)});
+
+        if (decls_len == 0) {
+            try stream.writeAll("}) ");
+        } else {
+            try stream.writeAll("\n");
+            self.indent += 2;
+            _ = try self.writeDecls(stream, decls_len, extra.end);
+            self.indent -= 2;
+            try stream.writeByteNTimes(' ', self.indent);
+            try stream.writeAll("}) ");
+        }
+        try self.writeSrc(stream, inst_data.src());
+    }
+
+    fn writeErrorSetDecl(
+        self: *Writer,
+        stream: anytype,
+        inst: Zir.Inst.Index,
+        name_strategy: Zir.Inst.NameStrategy,
+    ) !void {
+        const inst_data = self.code.instructions.items(.data)[inst].pl_node;
+        const extra = self.code.extraData(Zir.Inst.ErrorSetDecl, inst_data.payload_index);
+        const fields = self.code.extra[extra.end..][0..extra.data.fields_len];
+
+        try stream.print("{s}, ", .{@tagName(name_strategy)});
+
+        try stream.writeAll("{\n");
+        self.indent += 2;
+        for (fields) |str_index| {
+            const name = self.code.nullTerminatedString(str_index);
+            try stream.writeByteNTimes(' ', self.indent);
+            try stream.print("{},\n", .{std.zig.fmtId(name)});
+        }
+        self.indent -= 2;
+        try stream.writeByteNTimes(' ', self.indent);
+        try stream.writeAll("}) ");
+
+        try self.writeSrc(stream, inst_data.src());
+    }
+
+    fn writePlNodeSwitchBr(
+        self: *Writer,
+        stream: anytype,
+        inst: Zir.Inst.Index,
+        special_prong: Zir.SpecialProng,
+    ) !void {
+        const inst_data = self.code.instructions.items(.data)[inst].pl_node;
+        const extra = self.code.extraData(Zir.Inst.SwitchBlock, inst_data.payload_index);
+        const special: struct {
+            body: []const Zir.Inst.Index,
+            end: usize,
+        } = switch (special_prong) {
+            .none => .{ .body = &.{}, .end = extra.end },
+            .under, .@"else" => blk: {
+                const body_len = self.code.extra[extra.end];
+                const extra_body_start = extra.end + 1;
+                break :blk .{
+                    .body = self.code.extra[extra_body_start..][0..body_len],
+                    .end = extra_body_start + body_len,
+                };
+            },
+        };
+
+        try self.writeInstRef(stream, extra.data.operand);
+
+        if (special.body.len != 0) {
+            const prong_name = switch (special_prong) {
+                .@"else" => "else",
+                .under => "_",
+                else => unreachable,
+            };
+            try stream.print(", {s} => {{\n", .{prong_name});
+            self.indent += 2;
+            try self.writeBody(stream, special.body);
+            self.indent -= 2;
+            try stream.writeByteNTimes(' ', self.indent);
+            try stream.writeAll("}");
+        }
+
+        var extra_index: usize = special.end;
+        {
+            var scalar_i: usize = 0;
+            while (scalar_i < extra.data.cases_len) : (scalar_i += 1) {
+                const item_ref = @intToEnum(Zir.Inst.Ref, self.code.extra[extra_index]);
+                extra_index += 1;
+                const body_len = self.code.extra[extra_index];
+                extra_index += 1;
+                const body = self.code.extra[extra_index..][0..body_len];
+                extra_index += body_len;
+
+                try stream.writeAll(", ");
+                try self.writeInstRef(stream, item_ref);
+                try stream.writeAll(" => {\n");
+                self.indent += 2;
+                try self.writeBody(stream, body);
+                self.indent -= 2;
+                try stream.writeByteNTimes(' ', self.indent);
+                try stream.writeAll("}");
+            }
+        }
+        try stream.writeAll(") ");
+        try self.writeSrc(stream, inst_data.src());
+    }
+
+    fn writePlNodeSwitchBlockMulti(
+        self: *Writer,
+        stream: anytype,
+        inst: Zir.Inst.Index,
+        special_prong: Zir.SpecialProng,
+    ) !void {
+        const inst_data = self.code.instructions.items(.data)[inst].pl_node;
+        const extra = self.code.extraData(Zir.Inst.SwitchBlockMulti, inst_data.payload_index);
+        const special: struct {
+            body: []const Zir.Inst.Index,
+            end: usize,
+        } = switch (special_prong) {
+            .none => .{ .body = &.{}, .end = extra.end },
+            .under, .@"else" => blk: {
+                const body_len = self.code.extra[extra.end];
+                const extra_body_start = extra.end + 1;
+                break :blk .{
+                    .body = self.code.extra[extra_body_start..][0..body_len],
+                    .end = extra_body_start + body_len,
+                };
+            },
+        };
+
+        try self.writeInstRef(stream, extra.data.operand);
+
+        if (special.body.len != 0) {
+            const prong_name = switch (special_prong) {
+                .@"else" => "else",
+                .under => "_",
+                else => unreachable,
+            };
+            try stream.print(", {s} => {{\n", .{prong_name});
+            self.indent += 2;
+            try self.writeBody(stream, special.body);
+            self.indent -= 2;
+            try stream.writeByteNTimes(' ', self.indent);
+            try stream.writeAll("}");
+        }
+
+        var extra_index: usize = special.end;
+        {
+            var scalar_i: usize = 0;
+            while (scalar_i < extra.data.scalar_cases_len) : (scalar_i += 1) {
+                const item_ref = @intToEnum(Zir.Inst.Ref, self.code.extra[extra_index]);
+                extra_index += 1;
+                const body_len = self.code.extra[extra_index];
+                extra_index += 1;
+                const body = self.code.extra[extra_index..][0..body_len];
+                extra_index += body_len;
+
+                try stream.writeAll(", ");
+                try self.writeInstRef(stream, item_ref);
+                try stream.writeAll(" => {\n");
+                self.indent += 2;
+                try self.writeBody(stream, body);
+                self.indent -= 2;
+                try stream.writeByteNTimes(' ', self.indent);
+                try stream.writeAll("}");
+            }
+        }
+        {
+            var multi_i: usize = 0;
+            while (multi_i < extra.data.multi_cases_len) : (multi_i += 1) {
+                const items_len = self.code.extra[extra_index];
+                extra_index += 1;
+                const ranges_len = self.code.extra[extra_index];
+                extra_index += 1;
+                const body_len = self.code.extra[extra_index];
+                extra_index += 1;
+                const items = self.code.refSlice(extra_index, items_len);
+                extra_index += items_len;
+
+                for (items) |item_ref| {
+                    try stream.writeAll(", ");
+                    try self.writeInstRef(stream, item_ref);
+                }
+
+                var range_i: usize = 0;
+                while (range_i < ranges_len) : (range_i += 1) {
+                    const item_first = @intToEnum(Zir.Inst.Ref, self.code.extra[extra_index]);
+                    extra_index += 1;
+                    const item_last = @intToEnum(Zir.Inst.Ref, self.code.extra[extra_index]);
+                    extra_index += 1;
+
+                    try stream.writeAll(", ");
+                    try self.writeInstRef(stream, item_first);
+                    try stream.writeAll("...");
+                    try self.writeInstRef(stream, item_last);
+                }
+
+                const body = self.code.extra[extra_index..][0..body_len];
+                extra_index += body_len;
+                try stream.writeAll(" => {\n");
+                self.indent += 2;
+                try self.writeBody(stream, body);
+                self.indent -= 2;
+                try stream.writeByteNTimes(' ', self.indent);
+                try stream.writeAll("}");
+            }
+        }
+        try stream.writeAll(") ");
+        try self.writeSrc(stream, inst_data.src());
+    }
+
+    fn writePlNodeField(self: *Writer, stream: anytype, inst: Zir.Inst.Index) !void {
+        const inst_data = self.code.instructions.items(.data)[inst].pl_node;
+        const extra = self.code.extraData(Zir.Inst.Field, inst_data.payload_index).data;
+        const name = self.code.nullTerminatedString(extra.field_name_start);
+        try self.writeInstRef(stream, extra.lhs);
+        try stream.print(", \"{}\") ", .{std.zig.fmtEscapes(name)});
+        try self.writeSrc(stream, inst_data.src());
+    }
+
+    fn writeAs(self: *Writer, stream: anytype, inst: Zir.Inst.Index) !void {
+        const inst_data = self.code.instructions.items(.data)[inst].pl_node;
+        const extra = self.code.extraData(Zir.Inst.As, inst_data.payload_index).data;
+        try self.writeInstRef(stream, extra.dest_type);
+        try stream.writeAll(", ");
+        try self.writeInstRef(stream, extra.operand);
+        try stream.writeAll(") ");
+        try self.writeSrc(stream, inst_data.src());
+    }
+
+    fn writeNode(
+        self: *Writer,
+        stream: anytype,
+        inst: Zir.Inst.Index,
+    ) (@TypeOf(stream).Error || error{OutOfMemory})!void {
+        const src_node = self.code.instructions.items(.data)[inst].node;
+        const src: LazySrcLoc = .{ .node_offset = src_node };
+        try stream.writeAll(") ");
+        try self.writeSrc(stream, src);
+    }
+
+    fn writeStrTok(
+        self: *Writer,
+        stream: anytype,
+        inst: Zir.Inst.Index,
+    ) (@TypeOf(stream).Error || error{OutOfMemory})!void {
+        const inst_data = self.code.instructions.items(.data)[inst].str_tok;
+        const str = inst_data.get(self.code);
+        try stream.print("\"{}\") ", .{std.zig.fmtEscapes(str)});
+        try self.writeSrc(stream, inst_data.src());
+    }
+
+    fn writeFunc(
+        self: *Writer,
+        stream: anytype,
+        inst: Zir.Inst.Index,
+        inferred_error_set: bool,
+    ) !void {
+        const inst_data = self.code.instructions.items(.data)[inst].pl_node;
+        const src = inst_data.src();
+        const extra = self.code.extraData(Zir.Inst.Func, inst_data.payload_index);
+        var extra_index = extra.end;
+
+        const ret_ty_body = self.code.extra[extra_index..][0..extra.data.ret_body_len];
+        extra_index += ret_ty_body.len;
+
+        const body = self.code.extra[extra_index..][0..extra.data.body_len];
+        extra_index += body.len;
+
+        var src_locs: Zir.Inst.Func.SrcLocs = undefined;
+        if (body.len != 0) {
+            src_locs = self.code.extraData(Zir.Inst.Func.SrcLocs, extra_index).data;
+        }
+        return self.writeFuncCommon(
+            stream,
+            ret_ty_body,
+            inferred_error_set,
+            false,
+            false,
+            .none,
+            .none,
+            body,
+            src,
+            src_locs,
+        );
+    }
+
+    fn writeFuncExtended(self: *Writer, stream: anytype, extended: Zir.Inst.Extended.InstData) !void {
+        const extra = self.code.extraData(Zir.Inst.ExtendedFunc, extended.operand);
+        const src: LazySrcLoc = .{ .node_offset = extra.data.src_node };
+        const small = @bitCast(Zir.Inst.ExtendedFunc.Small, extended.small);
+
+        var extra_index: usize = extra.end;
+        if (small.has_lib_name) {
+            const lib_name = self.code.nullTerminatedString(self.code.extra[extra_index]);
+            extra_index += 1;
+            try stream.print("lib_name=\"{}\", ", .{std.zig.fmtEscapes(lib_name)});
+        }
+        try self.writeFlag(stream, "test, ", small.is_test);
+        const cc: Zir.Inst.Ref = if (!small.has_cc) .none else blk: {
+            const cc = @intToEnum(Zir.Inst.Ref, self.code.extra[extra_index]);
+            extra_index += 1;
+            break :blk cc;
+        };
+        const align_inst: Zir.Inst.Ref = if (!small.has_align) .none else blk: {
+            const align_inst = @intToEnum(Zir.Inst.Ref, self.code.extra[extra_index]);
+            extra_index += 1;
+            break :blk align_inst;
+        };
+
+        const ret_ty_body = self.code.extra[extra_index..][0..extra.data.ret_body_len];
+        extra_index += ret_ty_body.len;
+
+        const body = self.code.extra[extra_index..][0..extra.data.body_len];
+        extra_index += body.len;
+
+        var src_locs: Zir.Inst.Func.SrcLocs = undefined;
+        if (body.len != 0) {
+            src_locs = self.code.extraData(Zir.Inst.Func.SrcLocs, extra_index).data;
+        }
+        return self.writeFuncCommon(
+            stream,
+            ret_ty_body,
+            small.is_inferred_error,
+            small.is_var_args,
+            small.is_extern,
+            cc,
+            align_inst,
+            body,
+            src,
+            src_locs,
+        );
+    }
+
+    fn writeVarExtended(self: *Writer, stream: anytype, extended: Zir.Inst.Extended.InstData) !void {
+        const extra = self.code.extraData(Zir.Inst.ExtendedVar, extended.operand);
+        const small = @bitCast(Zir.Inst.ExtendedVar.Small, extended.small);
+
+        try self.writeInstRef(stream, extra.data.var_type);
+
+        var extra_index: usize = extra.end;
+        if (small.has_lib_name) {
+            const lib_name = self.code.nullTerminatedString(self.code.extra[extra_index]);
+            extra_index += 1;
+            try stream.print(", lib_name=\"{}\"", .{std.zig.fmtEscapes(lib_name)});
+        }
+        const align_inst: Zir.Inst.Ref = if (!small.has_align) .none else blk: {
+            const align_inst = @intToEnum(Zir.Inst.Ref, self.code.extra[extra_index]);
+            extra_index += 1;
+            break :blk align_inst;
+        };
+        const init_inst: Zir.Inst.Ref = if (!small.has_init) .none else blk: {
+            const init_inst = @intToEnum(Zir.Inst.Ref, self.code.extra[extra_index]);
+            extra_index += 1;
+            break :blk init_inst;
+        };
+        try self.writeFlag(stream, ", is_extern", small.is_extern);
+        try self.writeOptionalInstRef(stream, ", align=", align_inst);
+        try self.writeOptionalInstRef(stream, ", init=", init_inst);
+        try stream.writeAll("))");
+    }
+
+    fn writeBoolBr(self: *Writer, stream: anytype, inst: Zir.Inst.Index) !void {
+        const inst_data = self.code.instructions.items(.data)[inst].bool_br;
+        const extra = self.code.extraData(Zir.Inst.Block, inst_data.payload_index);
+        const body = self.code.extra[extra.end..][0..extra.data.body_len];
+        try self.writeInstRef(stream, inst_data.lhs);
+        try stream.writeAll(", {\n");
+        self.indent += 2;
+        try self.writeBody(stream, body);
+        self.indent -= 2;
+        try stream.writeByteNTimes(' ', self.indent);
+        try stream.writeAll("})");
+    }
+
+    fn writeIntType(self: *Writer, stream: anytype, inst: Zir.Inst.Index) !void {
+        const int_type = self.code.instructions.items(.data)[inst].int_type;
+        const prefix: u8 = switch (int_type.signedness) {
+            .signed => 'i',
+            .unsigned => 'u',
+        };
+        try stream.print("{c}{d}) ", .{ prefix, int_type.bit_count });
+        try self.writeSrc(stream, int_type.src());
+    }
+
+    fn writeBreak(self: *Writer, stream: anytype, inst: Zir.Inst.Index) !void {
+        const inst_data = self.code.instructions.items(.data)[inst].@"break";
+
+        try self.writeInstIndex(stream, inst_data.block_inst);
+        try stream.writeAll(", ");
+        try self.writeInstRef(stream, inst_data.operand);
+        try stream.writeAll(")");
+    }
+
+    fn writeUnreachable(self: *Writer, stream: anytype, inst: Zir.Inst.Index) !void {
+        const inst_data = self.code.instructions.items(.data)[inst].@"unreachable";
+        const safety_str = if (inst_data.safety) "safe" else "unsafe";
+        try stream.print("{s}) ", .{safety_str});
+        try self.writeSrc(stream, inst_data.src());
+    }
+
+    fn writeFuncCommon(
+        self: *Writer,
+        stream: anytype,
+        ret_ty_body: []const Zir.Inst.Index,
+        inferred_error_set: bool,
+        var_args: bool,
+        is_extern: bool,
+        cc: Zir.Inst.Ref,
+        align_inst: Zir.Inst.Ref,
+        body: []const Zir.Inst.Index,
+        src: LazySrcLoc,
+        src_locs: Zir.Inst.Func.SrcLocs,
+    ) !void {
+        if (ret_ty_body.len == 0) {
+            try stream.writeAll("ret_ty=void");
+        } else {
+            try stream.writeAll("ret_ty={\n");
+            self.indent += 2;
+            try self.writeBody(stream, ret_ty_body);
+            self.indent -= 2;
+            try stream.writeByteNTimes(' ', self.indent);
+            try stream.writeAll("}");
+        }
+
+        try self.writeOptionalInstRef(stream, ", cc=", cc);
+        try self.writeOptionalInstRef(stream, ", align=", align_inst);
+        try self.writeFlag(stream, ", vargs", var_args);
+        try self.writeFlag(stream, ", extern", is_extern);
+        try self.writeFlag(stream, ", inferror", inferred_error_set);
+
+        if (body.len == 0) {
+            try stream.writeAll(", body={}) ");
+        } else {
+            try stream.writeAll(", body={\n");
+            self.indent += 2;
+            try self.writeBody(stream, body);
+            self.indent -= 2;
+            try stream.writeByteNTimes(' ', self.indent);
+            try stream.writeAll("}) ");
+        }
+        if (body.len != 0) {
+            try stream.print("(lbrace={d}:{d},rbrace={d}:{d}) ", .{
+                src_locs.lbrace_line, @truncate(u16, src_locs.columns),
+                src_locs.rbrace_line, @truncate(u16, src_locs.columns >> 16),
+            });
+        }
+        try self.writeSrc(stream, src);
+    }
+
+    fn writeSwitchCapture(self: *Writer, stream: anytype, inst: Zir.Inst.Index) !void {
+        const inst_data = self.code.instructions.items(.data)[inst].switch_capture;
+        try self.writeInstIndex(stream, inst_data.switch_inst);
+        try stream.print(", {d})", .{inst_data.prong_index});
+    }
+
+    fn writeDbgStmt(self: *Writer, stream: anytype, inst: Zir.Inst.Index) !void {
+        const inst_data = self.code.instructions.items(.data)[inst].dbg_stmt;
+        try stream.print("{d}, {d})", .{ inst_data.line, inst_data.column });
+    }
+
+    fn writeInstRef(self: *Writer, stream: anytype, ref: Zir.Inst.Ref) !void {
+        var i: usize = @enumToInt(ref);
+
+        if (i < Zir.Inst.Ref.typed_value_map.len) {
+            return stream.print("@{}", .{ref});
+        }
+        i -= Zir.Inst.Ref.typed_value_map.len;
+
+        return self.writeInstIndex(stream, @intCast(Zir.Inst.Index, i));
+    }
+
+    fn writeInstIndex(self: *Writer, stream: anytype, inst: Zir.Inst.Index) !void {
+        _ = self;
+        return stream.print("%{d}", .{inst});
+    }
+
+    fn writeOptionalInstRef(
+        self: *Writer,
+        stream: anytype,
+        prefix: []const u8,
+        inst: Zir.Inst.Ref,
+    ) !void {
+        if (inst == .none) return;
+        try stream.writeAll(prefix);
+        try self.writeInstRef(stream, inst);
+    }
+
+    fn writeFlag(
+        self: *Writer,
+        stream: anytype,
+        name: []const u8,
+        flag: bool,
+    ) !void {
+        _ = self;
+        if (!flag) return;
+        try stream.writeAll(name);
+    }
+
+    fn writeSrc(self: *Writer, stream: anytype, src: LazySrcLoc) !void {
+        const tree = self.file.tree;
+        const src_loc: Module.SrcLoc = .{
+            .file_scope = self.file,
+            .parent_decl_node = self.parent_decl_node,
+            .lazy = src,
+        };
+        // Caller must ensure AST tree is loaded.
+        const abs_byte_off = src_loc.byteOffset(self.gpa) catch unreachable;
+        const delta_line = std.zig.findLineColumn(tree.source, abs_byte_off);
+        try stream.print("{s}:{d}:{d}", .{
+            @tagName(src), delta_line.line + 1, delta_line.column + 1,
+        });
+    }
+
+    fn writeSrcNode(self: *Writer, stream: anytype, src_node: ?i32) !void {
+        const node_offset = src_node orelse return;
+        const src: LazySrcLoc = .{ .node_offset = node_offset };
+        try stream.writeAll(" ");
+        return self.writeSrc(stream, src);
+    }
+
+    fn writeBody(self: *Writer, stream: anytype, body: []const Zir.Inst.Index) !void {
+        for (body) |inst| {
+            try stream.writeByteNTimes(' ', self.indent);
+            try stream.print("%{d} ", .{inst});
+            try self.writeInstToStream(stream, inst);
+            try stream.writeByte('\n');
+        }
+    }
+};