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[release-branch.go1.17] 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). Updates #52953. Fixes #52960. 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> (cherry picked from commit 1c77137d4fdfbb3e7e8d9efaab3bab5ee736a19d) Reviewed-on: https://go-review.googlesource.com/c/go/+/419451 Reviewed-by: Matthew Dempsky <mdempsky@google.com>
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@ -621,6 +621,12 @@ func oaslit(n *ir.AssignStmt, init *ir.Nodes) bool {
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// not a special composite literal assignment
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// not a special composite literal assignment
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return false
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return false
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}
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}
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if x.Addrtaken() {
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// If x is address-taken, the RHS may (implicitly) uses LHS.
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// Not safe to do a special composite literal assignment
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// (which may expand to multiple assignments).
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return false
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}
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switch n.Y.Op() {
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switch n.Y.Op() {
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default:
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default:
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@ -629,7 +635,7 @@ func oaslit(n *ir.AssignStmt, init *ir.Nodes) bool {
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case ir.OSTRUCTLIT, ir.OARRAYLIT, ir.OSLICELIT, ir.OMAPLIT:
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case ir.OSTRUCTLIT, ir.OARRAYLIT, ir.OSLICELIT, ir.OMAPLIT:
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if ir.Any(n.Y, func(y ir.Node) bool { return ir.Uses(y, x) }) {
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if ir.Any(n.Y, func(y ir.Node) bool { return ir.Uses(y, x) }) {
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// not a special composite literal assignment
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// not safe to do a special composite literal assignment if RHS uses LHS.
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return false
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return false
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}
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}
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anylit(n.Y, n.X, init)
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anylit(n.Y, n.X, init)
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29
test/fixedbugs/issue52953.go
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29
test/fixedbugs/issue52953.go
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@ -0,0 +1,29 @@
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// run
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// Copyright 2022 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Issue 52953: miscompilation for composite literal assignment
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// when LHS is address-taken.
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package main
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type T struct {
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Field1 bool
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}
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func main() {
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var ret T
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ret.Field1 = true
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var v *bool = &ret.Field1
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ret = T{Field1: *v}
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check(ret.Field1)
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}
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//go:noinline
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func check(b bool) {
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if !b {
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panic("FAIL")
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}
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}
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