cmd/compile: put constants before variables in initialization order

Fixes #66575

Change-Id: I03f4d4577b88ad0a92b260b2efd0cb9fe5082b2f
Reviewed-on: https://go-review.googlesource.com/c/go/+/575075
Reviewed-by: Robert Griesemer <gri@google.com>
Reviewed-by: Keith Randall <khr@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

diff --git a/src/cmd/compile/internal/types2/initorder.go b/src/cmd/compile/internal/types2/initorder.go
index 0d28495542cf6111218058f00bcf988dda6b6776..86cb9036c4cd93595d5a7fc8ded0d6b66fe69014 100644 (file)
--- a/src/cmd/compile/internal/types2/initorder.go
+++ b/src/cmd/compile/internal/types2/initorder.go
@@ -309,6 +309,14 @@ func (a nodeQueue) Swap(i, j int) {
 
 func (a nodeQueue) Less(i, j int) bool {
        x, y := a[i], a[j]
+
+       // Prioritize all constants before non-constants. See go.dev/issue/66575/.
+       _, xConst := x.obj.(*Const)
+       _, yConst := y.obj.(*Const)
+       if xConst != yConst {
+               return xConst
+       }
+
        // nodes are prioritized by number of incoming dependencies (1st key)
        // and source order (2nd key)
        return x.ndeps < y.ndeps || x.ndeps == y.ndeps && x.obj.order() < y.obj.order()

diff --git a/src/go/types/initorder.go b/src/go/types/initorder.go
index 70d2a713bdc0da1bb1462cd62d5c56a99993aefd..d23844027938ae2f4c6ae976723f377d9f3ca3c2 100644 (file)
--- a/src/go/types/initorder.go
+++ b/src/go/types/initorder.go
@@ -311,6 +311,14 @@ func (a nodeQueue) Swap(i, j int) {
 
 func (a nodeQueue) Less(i, j int) bool {
        x, y := a[i], a[j]
+
+       // Prioritize all constants before non-constants. See go.dev/issue/66575/.
+       _, xConst := x.obj.(*Const)
+       _, yConst := y.obj.(*Const)
+       if xConst != yConst {
+               return xConst
+       }
+
        // nodes are prioritized by number of incoming dependencies (1st key)
        // and source order (2nd key)
        return x.ndeps < y.ndeps || x.ndeps == y.ndeps && x.obj.order() < y.obj.order()

diff --git a/test/fixedbugs/issue66575.go b/test/fixedbugs/issue66575.go
new file mode 100644 (file)
index 0000000..1ad6ca0
--- /dev/null
+++ b/test/fixedbugs/issue66575.go
@@ -0,0 +1,31 @@
+// run
+
+// 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 main
+
+var (
+       v0 = initv0()
+       v1 = initv1()
+)
+
+const c = "c"
+
+func initv0() string {
+       println("initv0")
+       if c != "" { // have a dependency on c
+               return ""
+       }
+       return ""
+}
+
+func initv1() string {
+       println("initv1")
+       return ""
+}
+
+func main() {
+       // do nothing
+}

diff --git a/test/fixedbugs/issue66575.out b/test/fixedbugs/issue66575.out
new file mode 100644 (file)
index 0000000..36d1f17
--- /dev/null
+++ b/test/fixedbugs/issue66575.out
@@ -0,0 +1,2 @@
+initv0
+initv1