stage2: improved handling of store_to_block_ptr

 * AstGen: remove the setBlockBodyEliding function. This is no longer
   needed after 63788b2a511eb87974065a052e2436b0c6202544.
 * Sema: store_to_block_ptr instruction is handled as
   store_to_inferred_ptr or store, as necessary.

6 files changed, 90 insertions, 87 deletions

diff --git a/src/AstGen.zig b/src/AstGen.zig
index dbb998dc71..74e3ae17b1 100644
--- a/src/AstGen.zig
+++ b/src/AstGen.zig
@@ -1964,11 +1964,7 @@ fn labeledBlockExpr(
         },
         .break_operand => {
             // All break operands are values that did not use the result location pointer.
-            if (strat.elide_store_to_block_ptr_instructions) {
-                try block_scope.setBlockBodyEliding(block_inst);
-            } else {
-                try block_scope.setBlockBody(block_inst);
-            }
+            try block_scope.setBlockBody(block_inst);
             const block_ref = indexToRef(block_inst);
             switch (rl) {
                 .ref => return block_ref,
@@ -9734,32 +9730,6 @@ const GenZir = struct {
         gz.unstack();
     }
 
-    /// Same as `setBlockBody` except we don't copy instructions which are
-    /// `store_to_block_ptr` instructions with lhs set to .none.
-    /// Assumes nothing stacked on `gz`. Unstacks `gz`.
-    fn setBlockBodyEliding(gz: *GenZir, inst: Zir.Inst.Index) !void {
-        const gpa = gz.astgen.gpa;
-        const body = gz.instructionsSlice();
-        try gz.astgen.extra.ensureUnusedCapacity(gpa, @typeInfo(Zir.Inst.Block).Struct.fields.len + body.len);
-        const zir_datas = gz.astgen.instructions.items(.data);
-        const zir_tags = gz.astgen.instructions.items(.tag);
-        const block_pl_index = gz.astgen.addExtraAssumeCapacity(Zir.Inst.Block{
-            .body_len = @intCast(u32, body.len),
-        });
-        zir_datas[inst].pl_node.payload_index = block_pl_index;
-        for (body) |sub_inst| {
-            if (zir_tags[sub_inst] == .store_to_block_ptr and
-                zir_datas[sub_inst].bin.lhs == .none)
-            {
-                // Decrement `body_len`.
-                gz.astgen.extra.items[block_pl_index] -= 1;
-                continue;
-            }
-            gz.astgen.extra.appendAssumeCapacity(sub_inst);
-        }
-        gz.unstack();
-    }
-
     /// Supports `body_gz` stacked on `ret_gz` stacked on `gz`. Unstacks `body_gz` and `ret_gz`.
     fn addFunc(gz: *GenZir, args: struct {
         src_node: Ast.Node.Index,
diff --git a/src/Sema.zig b/src/Sema.zig
index b79414002a..3ba9761cd8 100644
--- a/src/Sema.zig
+++ b/src/Sema.zig
@@ -3247,22 +3247,31 @@ fn zirStoreToBlockPtr(sema: *Sema, block: *Block, inst: Zir.Inst.Index) CompileE
     defer tracy.end();
 
     const bin_inst = sema.code.instructions.items(.data)[inst].bin;
-    const ptr = sema.inst_map.get(@enumToInt(bin_inst.lhs) - @as(u32, Zir.Inst.Ref.typed_value_map.len)) orelse {
+    const ptr = sema.inst_map.get(Zir.refToIndex(bin_inst.lhs).?) orelse {
         // This is an elided instruction, but AstGen was unable to omit it.
         return;
     };
-    const value = sema.resolveInst(bin_inst.rhs);
-    const ptr_ty = try Type.ptr(sema.arena, .{
-        .pointee_type = sema.typeOf(value),
-        // TODO figure out which address space is appropriate here
-        .@"addrspace" = target_util.defaultAddressSpace(sema.mod.getTarget(), .local),
-    });
-    // TODO detect when this store should be done at compile-time. For example,
-    // if expressions should force it when the condition is compile-time known.
-    const src: LazySrcLoc = .unneeded;
-    try sema.requireRuntimeBlock(block, src);
-    const bitcasted_ptr = try block.addBitCast(ptr_ty, ptr);
-    return sema.storePtr(block, src, bitcasted_ptr, value);
+    const operand = sema.resolveInst(bin_inst.rhs);
+    const src: LazySrcLoc = sema.src;
+    blk: {
+        const ptr_inst = Air.refToIndex(ptr) orelse break :blk;
+        if (sema.air_instructions.items(.tag)[ptr_inst] != .constant) break :blk;
+        const air_datas = sema.air_instructions.items(.data);
+        const ptr_val = sema.air_values.items[air_datas[ptr_inst].ty_pl.payload];
+        switch (ptr_val.tag()) {
+            .inferred_alloc_comptime => {
+                const iac = ptr_val.castTag(.inferred_alloc_comptime).?;
+                return sema.storeToInferredAllocComptime(block, src, operand, iac);
+            },
+            .inferred_alloc => {
+                const inferred_alloc = ptr_val.castTag(.inferred_alloc).?;
+                return sema.storeToInferredAlloc(block, src, ptr, operand, inferred_alloc);
+            },
+            else => break :blk,
+        }
+    }
+
+    return sema.storePtr(block, src, ptr, operand);
 }
 
 fn zirStoreToInferredPtr(sema: *Sema, block: *Block, inst: Zir.Inst.Index) CompileError!void {
@@ -3273,46 +3282,71 @@ fn zirStoreToInferredPtr(sema: *Sema, block: *Block, inst: Zir.Inst.Index) Compi
     const bin_inst = sema.code.instructions.items(.data)[inst].bin;
     const ptr = sema.resolveInst(bin_inst.lhs);
     const operand = sema.resolveInst(bin_inst.rhs);
-    const operand_ty = sema.typeOf(operand);
     const ptr_inst = Air.refToIndex(ptr).?;
     assert(sema.air_instructions.items(.tag)[ptr_inst] == .constant);
     const air_datas = sema.air_instructions.items(.data);
     const ptr_val = sema.air_values.items[air_datas[ptr_inst].ty_pl.payload];
 
-    if (ptr_val.castTag(.inferred_alloc_comptime)) |iac| {
-        // There will be only one store_to_inferred_ptr because we are running at comptime.
-        // The alloc will turn into a Decl.
-        if (try sema.resolveMaybeUndefValAllowVariables(block, src, operand)) |operand_val| {
-            if (operand_val.tag() == .variable) {
-                return sema.failWithNeededComptime(block, src);
-            }
-            var anon_decl = try block.startAnonDecl(src);
-            defer anon_decl.deinit();
-            iac.data.decl = try anon_decl.finish(
-                try operand_ty.copy(anon_decl.arena()),
-                try operand_val.copy(anon_decl.arena()),
-            );
-            // TODO set the alignment on the decl
-            return;
-        } else {
-            return sema.failWithNeededComptime(block, src);
-        }
+    switch (ptr_val.tag()) {
+        .inferred_alloc_comptime => {
+            const iac = ptr_val.castTag(.inferred_alloc_comptime).?;
+            return sema.storeToInferredAllocComptime(block, src, operand, iac);
+        },
+        .inferred_alloc => {
+            const inferred_alloc = ptr_val.castTag(.inferred_alloc).?;
+            return sema.storeToInferredAlloc(block, src, ptr, operand, inferred_alloc);
+        },
+        else => unreachable,
     }
+}
 
-    if (ptr_val.castTag(.inferred_alloc)) |inferred_alloc| {
-        // Add the stored instruction to the set we will use to resolve peer types
-        // for the inferred allocation.
-        try inferred_alloc.data.stored_inst_list.append(sema.arena, operand);
-        // Create a runtime bitcast instruction with exactly the type the pointer wants.
-        const ptr_ty = try Type.ptr(sema.arena, .{
-            .pointee_type = operand_ty,
-            .@"align" = inferred_alloc.data.alignment,
-            .@"addrspace" = target_util.defaultAddressSpace(sema.mod.getTarget(), .local),
-        });
-        const bitcasted_ptr = try block.addBitCast(ptr_ty, ptr);
-        return sema.storePtr(block, src, bitcasted_ptr, operand);
+fn storeToInferredAlloc(
+    sema: *Sema,
+    block: *Block,
+    src: LazySrcLoc,
+    ptr: Air.Inst.Ref,
+    operand: Air.Inst.Ref,
+    inferred_alloc: *Value.Payload.InferredAlloc,
+) CompileError!void {
+    const operand_ty = sema.typeOf(operand);
+    // Add the stored instruction to the set we will use to resolve peer types
+    // for the inferred allocation.
+    try inferred_alloc.data.stored_inst_list.append(sema.arena, operand);
+    // Create a runtime bitcast instruction with exactly the type the pointer wants.
+    const ptr_ty = try Type.ptr(sema.arena, .{
+        .pointee_type = operand_ty,
+        .@"align" = inferred_alloc.data.alignment,
+        .@"addrspace" = target_util.defaultAddressSpace(sema.mod.getTarget(), .local),
+    });
+    const bitcasted_ptr = try block.addBitCast(ptr_ty, ptr);
+    return sema.storePtr(block, src, bitcasted_ptr, operand);
+}
+
+fn storeToInferredAllocComptime(
+    sema: *Sema,
+    block: *Block,
+    src: LazySrcLoc,
+    operand: Air.Inst.Ref,
+    iac: *Value.Payload.InferredAllocComptime,
+) CompileError!void {
+    const operand_ty = sema.typeOf(operand);
+    // There will be only one store_to_inferred_ptr because we are running at comptime.
+    // The alloc will turn into a Decl.
+    if (try sema.resolveMaybeUndefValAllowVariables(block, src, operand)) |operand_val| {
+        if (operand_val.tag() == .variable) {
+            return sema.failWithNeededComptime(block, src);
+        }
+        var anon_decl = try block.startAnonDecl(src);
+        defer anon_decl.deinit();
+        iac.data.decl = try anon_decl.finish(
+            try operand_ty.copy(anon_decl.arena()),
+            try operand_val.copy(anon_decl.arena()),
+        );
+        // TODO set the alignment on the decl
+        return;
+    } else {
+        return sema.failWithNeededComptime(block, src);
     }
-    unreachable;
 }
 
 fn zirSetEvalBranchQuota(sema: *Sema, block: *Block, inst: Zir.Inst.Index) CompileError!void {
diff --git a/src/Zir.zig b/src/Zir.zig
index 49541283d3..c74b2c1d8f 100644
--- a/src/Zir.zig
+++ b/src/Zir.zig
@@ -518,11 +518,14 @@ pub const Inst = struct {
         /// Same as `store` except provides a source location.
         /// Uses the `pl_node` union field. Payload is `Bin`.
         store_node,
-        /// Same as `store` but the type of the value being stored will be used to infer
-        /// the block type. The LHS is the pointer to store to.
-        /// Uses the `bin` union field.
-        /// If the pointer is none, it means this instruction has been elided in
-        /// AstGen, but AstGen was unable to actually omit it from the ZIR code.
+        /// This instruction is not really supposed to be emitted from AstGen; nevetheless it
+        /// is sometimes emitted due to deficiencies in AstGen. When Sema sees this instruction,
+        /// it must clean up after AstGen's mess by looking at various context clues and
+        /// then treating it as one of the following:
+        ///  * no-op
+        ///  * store_to_inferred_ptr
+        ///  * store
+        /// Uses the `bin` union field with LHS as the pointer to store to.
         store_to_block_ptr,
         /// Same as `store` but the type of the value being stored will be used to infer
         /// the pointer type.
diff --git a/test/behavior.zig b/test/behavior.zig
index 2425348ac8..ed2012281c 100644
--- a/test/behavior.zig
+++ b/test/behavior.zig
@@ -124,6 +124,7 @@ test {
             _ = @import("behavior/bugs/421.zig");
             _ = @import("behavior/bugs/726.zig");
             _ = @import("behavior/bugs/1421.zig");
+            _ = @import("behavior/bugs/1442.zig");
             _ = @import("behavior/bugs/2114.zig");
             _ = @import("behavior/bugs/3742.zig");
             _ = @import("behavior/struct_contains_null_ptr_itself.zig");
@@ -144,7 +145,6 @@ test {
                 _ = @import("behavior/bugs/828.zig");
                 _ = @import("behavior/bugs/920.zig");
                 _ = @import("behavior/bugs/1120.zig");
-                _ = @import("behavior/bugs/1442.zig");
                 _ = @import("behavior/bugs/1607.zig");
                 _ = @import("behavior/bugs/1851.zig");
                 _ = @import("behavior/bugs/3384.zig");
diff --git a/test/behavior/bugs/1442.zig b/test/behavior/bugs/1442.zig
index f0d524006c..69af0a9f4c 100644
--- a/test/behavior/bugs/1442.zig
+++ b/test/behavior/bugs/1442.zig
@@ -7,8 +7,6 @@ const Union = union(enum) {
 };
 
 test "const error union field alignment" {
-    if (builtin.zig_backend != .stage1) return error.SkipZigTest;
-
     var union_or_err: anyerror!Union = Union{ .Color = 1234 };
     try std.testing.expect((union_or_err catch unreachable).Color == 1234);
 }
diff --git a/test/behavior/eval.zig b/test/behavior/eval.zig
index 5c8afeb9d4..40e2377aea 100644
--- a/test/behavior/eval.zig
+++ b/test/behavior/eval.zig
@@ -495,7 +495,7 @@ test "@tagName of @typeInfo" {
 }
 
 test "static eval list init" {
-    if (builtin.zig_backend != .stage1) return error.SkipZigTest; // TODO
+    if (builtin.zig_backend == .stage2_c) return error.SkipZigTest; // TODO
 
     try expect(static_vec3.data[2] == 1.0);
     try expect(vec3(0.0, 0.0, 3.0).data[2] == 3.0);
@@ -511,8 +511,6 @@ pub fn vec3(x: f32, y: f32, z: f32) Vec3 {
 }
 
 test "inlined loop has array literal with elided runtime scope on first iteration but not second iteration" {
-    if (builtin.zig_backend != .stage1) return error.SkipZigTest; // TODO
-
     var runtime = [1]i32{3};
     comptime var i: usize = 0;
     inline while (i < 2) : (i += 1) {