cmd/compile: do not use special literal assignment if LHS is address-taken
A composite literal assignment
x = T{field: v}
may be compiled to
x = T{}
x.field = v
We already do not use this form is RHS uses LHS. If LHS is
address-taken, RHS may uses LHS implicitly, e.g.
v = &x.field
x = T{field: *v}
The lowering above would change the value of RHS (*v).
Fixes #52953.
Change-Id: I3f798e00598aaa550b8c17182c7472fef440d483
Reviewed-on: https://go-review.googlesource.com/c/go/+/407014
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Run-TryBot: Cherry Mui <cherryyz@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
diff --git a/src/cmd/compile/internal/walk/complit.go b/src/cmd/compile/internal/walk/complit.go
index 748a53d..595fe85 100644
--- a/src/cmd/compile/internal/walk/complit.go
+++ b/src/cmd/compile/internal/walk/complit.go
@@ -618,6 +618,12 @@
// not a special composite literal assignment
return false
}
+ if x.Addrtaken() {
+ // If x is address-taken, the RHS may (implicitly) uses LHS.
+ // Not safe to do a special composite literal assignment
+ // (which may expand to multiple assignments).
+ return false
+ }
switch n.Y.Op() {
default:
@@ -626,7 +632,7 @@
case ir.OSTRUCTLIT, ir.OARRAYLIT, ir.OSLICELIT, ir.OMAPLIT:
if ir.Any(n.Y, func(y ir.Node) bool { return ir.Uses(y, x) }) {
- // not a special composite literal assignment
+ // not safe to do a special composite literal assignment if RHS uses LHS.
return false
}
anylit(n.Y, n.X, init)
diff --git a/test/fixedbugs/issue52953.go b/test/fixedbugs/issue52953.go
new file mode 100644
index 0000000..2085e4e
--- /dev/null
+++ b/test/fixedbugs/issue52953.go
@@ -0,0 +1,29 @@
+// run
+
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Issue 52953: miscompilation for composite literal assignment
+// when LHS is address-taken.
+
+package main
+
+type T struct {
+ Field1 bool
+}
+
+func main() {
+ var ret T
+ ret.Field1 = true
+ var v *bool = &ret.Field1
+ ret = T{Field1: *v}
+ check(ret.Field1)
+}
+
+//go:noinline
+func check(b bool) {
+ if !b {
+ panic("FAIL")
+ }
+}
