gc: fix order of operations for f() < g().

Also, 6g was passing uninitialized
Node &n2 to regalloc, causing non-deterministic
register collisions (but only when both left and
right hand side of comparison had function calls).

Fixes #1728.

R=ken2
CC=golang-dev
https://golang.org/cl/4425070

1 files changed, 29 insertions, 0 deletions

diff --git a/test/func7.go b/test/func7.go
new file mode 100644
index 0000000000..e38b008cc0
--- /dev/null
+++ b/test/func7.go
@@ -0,0 +1,29 @@
+// $G $D/$F.go && $L $F.$A && ./$A.out
+
+// Copyright 2011 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 calledf = false
+
+func f() int {
+	calledf = true
+	return 1
+}
+
+func g() int {
+	if !calledf {
+		println("BUG: func7 - called g before f")
+	}
+	return 0
+}
+
+func main() {
+	// 6g, 8g, 5g all used to evaluate g() before f().
+	if f() < g() {
+		panic("wrong answer")
+	}
+}
+