From 461382ae941e235ad75a6b3d00e05e5369baa98a Mon Sep 17 00:00:00 2001
From: Andrew Kelley <andrew@ziglang.org>
Date: Fri, 31 May 2019 01:08:16 -0400
Subject: [PATCH] no-copy semantics for function call init var and literal

```zig
export fn entry() void {
    var x = foo();
}
const Foo = struct {
    x: i32,
};
fn foo() Foo {
    return Foo{
        .x = 1234,
    };
}
```

```llvm
define void @entry() #2 !dbg !35 {
Entry:
  %x = alloca %Foo, align 4
  call fastcc void @foo(%Foo* sret %x), !dbg !45
  call void @llvm.dbg.declare(metadata %Foo* %x, metadata !39, metadata !DIExpression()), !dbg !46
  ret void, !dbg !47
}
define internal fastcc void @foo(%Foo* nonnull sret) unnamed_addr #2 !dbg !48 {
Entry:
  %1 = bitcast %Foo* %0 to i8*, !dbg !52
  call void @llvm.memcpy.p0i8.p0i8.i64(i8* align 4 %1, i8* align 4 bitcast (%Foo* @0 to i8*), i64 4, i1 false), !dbg !52
  ret void, !dbg !52
}
```
---
 src/ir.cpp | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/src/ir.cpp b/src/ir.cpp
index 9c45542b5b..f700404f29 100644
--- a/src/ir.cpp
+++ b/src/ir.cpp
@@ -14365,11 +14365,11 @@ static IrInstruction *ir_resolve_result(IrAnalyze *ira, ResultLoc *result_loc, Z
             assert(result_loc->source_instruction->id == IrInstructionIdAllocaSrc);
             IrInstructionAllocaSrc *alloca_src =
                 reinterpret_cast<IrInstructionAllocaSrc *>(result_loc->source_instruction);
-            bool is_comptime = value != nullptr && value->value.special != ConstValSpecialRuntime &&
-                result_loc_var->var->gen_is_const;
             if (alloca_src->base.child == nullptr) {
                 uint32_t align = 0; // TODO
                 bool force_comptime = false; // TODO
+                bool is_comptime = value != nullptr && value->value.special != ConstValSpecialRuntime &&
+                    result_loc_var->var->gen_is_const;
                 IrInstruction *alloca_gen;
                 if (is_comptime) {
                     alloca_gen = ir_get_ref(ira, result_loc->source_instruction, value, true, false);
@@ -14378,10 +14378,13 @@ static IrInstruction *ir_resolve_result(IrAnalyze *ira, ResultLoc *result_loc, Z
                             alloca_src->name_hint, force_comptime);
                 }
                 alloca_src->base.child = alloca_gen;
+                return is_comptime ? nullptr : alloca_src->base.child;
             }
-            return is_comptime ? nullptr : alloca_src->base.child;
+            return nullptr;
         }
         case ResultLocIdReturn: {
+            bool is_comptime = value != nullptr && value->value.special != ConstValSpecialRuntime;
+            if (is_comptime) return nullptr;
             ZigType *ptr_return_type = get_pointer_to_type(ira->codegen, ira->explicit_return_type, false);
             return ir_build_return_ptr(ira, result_loc->source_instruction, ptr_return_type);
         }