From d9242f7a8c29aa17201cd66d29cdd20916c2de60 Mon Sep 17 00:00:00 2001 From: Cherry Mui Date: Wed, 18 May 2022 11:58:53 -0400 Subject: [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 Run-TryBot: Cherry Mui TryBot-Result: Gopher Robot Reviewed-by: Michael Knyszek (cherry picked from commit 1c77137d4fdfbb3e7e8d9efaab3bab5ee736a19d) Reviewed-on: https://go-review.googlesource.com/c/go/+/419451 Reviewed-by: Matthew Dempsky --- src/cmd/compile/internal/walk/complit.go | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) (limited to 'src/cmd/compile/internal/walk/complit.go') diff --git a/src/cmd/compile/internal/walk/complit.go b/src/cmd/compile/internal/walk/complit.go index abd920d646..1f288d21c1 100644 --- a/src/cmd/compile/internal/walk/complit.go +++ b/src/cmd/compile/internal/walk/complit.go @@ -621,6 +621,12 @@ func oaslit(n *ir.AssignStmt, init *ir.Nodes) bool { // 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: @@ -629,7 +635,7 @@ func oaslit(n *ir.AssignStmt, init *ir.Nodes) bool { 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) -- cgit v1.2.3-54-g00ecf