result location semantics for `@bitCast`

```zig
export fn entry() void {
    var x = @bitCast(f32, foo());
}
```

```llvm
define void @entry() #2 !dbg !35 {
Entry:
  %x = alloca float, align 4
  %0 = bitcast float* %x to %Foo*, !dbg !42
  call fastcc void @foo(%Foo* sret %0), !dbg !42
  call void @llvm.dbg.declare(metadata float* %x, metadata !39, metadata !DIExpression()), !dbg !43
  ret void, !dbg !44
}
```
17b1ac5d03Andrew Kelley committed on 6/10/2019, 4:24:19 PMparent1a51bf6
5 files changedLine totals unavailable