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no-copy semantics for if optional and if error union

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if expressions no longer introduce a stack allocation.

```zig
export fn entry() void {
    var x: anyerror!i32 = 1234;
    if (x) |i| {} else |e| {}
}
```

```llvm
define void @entry() #2 !dbg !39 {
Entry:
  %x = alloca { i16, i32 }, align 4
  %0 = bitcast { i16, i32 }* %x to i8*, !dbg !52
  call void @llvm.memcpy.p0i8.p0i8.i64(i8* align 4 %0, i8* align 4 bitcast ({ i16, i32 }* @0 to i8*), i64 8, i1 false), !dbg !52
  call void @llvm.dbg.declare(metadata { i16, i32 }* %x, metadata !43, metadata !DIExpression()), !dbg !52
  %1 = getelementptr inbounds { i16, i32 }, { i16, i32 }* %x, i32 0, i32 0, !dbg !53
  %2 = load i16, i16* %1, align 2, !dbg !53
  %3 = icmp ne i16 %2, 0, !dbg !53
  br i1 %3, label %TryElse, label %TryOk, !dbg !53

TryOk:                                            ; preds = %Entry
  %4 = getelementptr inbounds { i16, i32 }, { i16, i32 }* %x, i32 0, i32 1, !dbg !53
  call void @llvm.dbg.declare(metadata i32* %4, metadata !50, metadata !DIExpression()), !dbg !53
  br label %TryEnd, !dbg !53

TryElse:                                          ; preds = %Entry
  %5 = getelementptr inbounds { i16, i32 }, { i16, i32 }* %x, i32 0, i32 0, !dbg !53
  call void @llvm.dbg.declare(metadata i16* %5, metadata !51, metadata !DIExpression()), !dbg !53
  br label %TryEnd, !dbg !53

TryEnd:                                           ; preds = %TryElse, %TryOk
  ret void, !dbg !54
}
```
This commit is contained in:
Andrew Kelley 2019-06-03 21:53:32 -04:00
parent 143d6ada8f
commit a32abcd365
No known key found for this signature in database
GPG Key ID: 7C5F548F728501A9
1 changed files with 7 additions and 6 deletions
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13
src/ir.cpp
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@ -6373,9 +6373,9 @@ static IrInstruction *ir_gen_if_optional_expr(IrBuilder *irb, Scope *scope, AstN
ZigVar *var = ir_create_var(irb, node, subexpr_scope,
var_symbol, is_const, is_const, is_shadowable, is_comptime);
IrInstruction *var_ptr_value = ir_build_optional_unwrap_ptr(irb, subexpr_scope, node, maybe_val_ptr, false);
IrInstruction *var_value = var_is_ptr ? var_ptr_value : ir_build_load_ptr(irb, subexpr_scope, node, var_ptr_value);
ir_build_var_decl_src(irb, subexpr_scope, node, var, nullptr, var_value);
IrInstruction *payload_ptr = ir_build_optional_unwrap_ptr(irb, subexpr_scope, node, maybe_val_ptr, false);
IrInstruction *var_ptr = var_is_ptr ? ir_build_ref(irb, subexpr_scope, node, payload_ptr, true, false) : payload_ptr;
ir_build_var_decl_src(irb, subexpr_scope, node, var, nullptr, var_ptr);
var_scope = var->child_scope;
} else {
var_scope = subexpr_scope;
@ -6447,9 +6447,10 @@ static IrInstruction *ir_gen_if_err_expr(IrBuilder *irb, Scope *scope, AstNode *
ZigVar *var = ir_create_var(irb, node, subexpr_scope,
var_symbol, var_is_const, var_is_const, is_shadowable, var_is_comptime);
IrInstruction *var_ptr_value = ir_build_unwrap_err_payload(irb, subexpr_scope, node, err_val_ptr, false);
IrInstruction *var_value = var_is_ptr ? var_ptr_value : ir_build_load_ptr(irb, subexpr_scope, node, var_ptr_value);
ir_build_var_decl_src(irb, subexpr_scope, node, var, nullptr, var_value);
IrInstruction *payload_ptr = ir_build_unwrap_err_payload(irb, subexpr_scope, node, err_val_ptr, false);
IrInstruction *var_ptr = var_is_ptr ?
ir_build_ref(irb, subexpr_scope, node, payload_ptr, true, false) : payload_ptr;
ir_build_var_decl_src(irb, subexpr_scope, node, var, nullptr, var_ptr);
var_scope = var->child_scope;
} else {
var_scope = subexpr_scope;