cmd/compile: check ODEREF for safe lhs in assignment during static init

For #66585

Change-Id: Iddc407e3ef4c3b6ecf5173963b66b3e65e43c92d
Reviewed-on: https://go-review.googlesource.com/c/go/+/575336
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Keith Randall <khr@golang.org>
Auto-Submit: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>

src/cmd/compile/internal/staticinit/sched.go

@@ -881,7 +881,13 @@ func mayModifyPkgVar(n ir.Node) bool {
 	// safeLHS reports whether the assigned-to variable lhs is either a
 	// local variable or a global from another package.
 	safeLHS := func(lhs ir.Node) bool {
-		v, ok := ir.OuterValue(lhs).(*ir.Name)
+		outer := ir.OuterValue(lhs)
+		// "*p = ..." should be safe if p is a local variable.
+		// TODO: Should ir.OuterValue handle this?
+		for outer.Op() == ir.ODEREF {
+			outer = outer.(*ir.StarExpr).X
+		}
+		v, ok := outer.(*ir.Name)
 		return ok && v.Op() == ir.ONAME && !(v.Class == ir.PEXTERN && v.Sym().Pkg == types.LocalPkg)
 	}
 

test/codegen/issue66585.go

@@ -0,0 +1,24 @@
+// asmcheck
+
+// Copyright 2024 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.
+
+package p
+
+var x = func() int {
+	n := 0
+	f(&n)
+	return n
+}()
+
+func f(p *int) {
+	*p = 1
+}
+
+var y = 1
+
+// z can be static initialized.
+//
+// amd64:-"MOVQ"
+var z = y