cmd/compile: use generated temps in bool codegen

Bool codegen was generating a temp for function calls
and other complex expressions, but was not using it.

This was a refactoring bug introduced by CL 7853.
The cmp code used to do (in short):

	l, r := &n1, &n2

It was changed to:

	l, r := nl, nr

But the requisite assignments:

	nl, nr = &n1, &n2

were only introduced on one of two code paths.

Fixes #10654.

Change-Id: Ie8de0b3a333842a048d4308e02911bb10c6915ce
Reviewed-on: https://go-review.googlesource.com/10844
Reviewed-by: Minux Ma <minux@golang.org>
Run-TryBot: Minux Ma <minux@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/cmd/compile/internal/gc/cgen.go

@@ -2007,6 +2007,7 @@ func bgenx(n, res *Node, wantTrue bool, likely int, to *obj.Prog) {
 		var n1 Node
 		Regalloc(&n1, nl.Type, nil)
 		Cgen(nl, &n1)
+		nl = &n1
 
 		var tmp Node
 		Tempname(&tmp, nl.Type)
@@ -2016,6 +2017,7 @@ func bgenx(n, res *Node, wantTrue bool, likely int, to *obj.Prog) {
 		var n2 Node
 		Regalloc(&n2, nr.Type, nil)
 		Cgen(nr, &n2)
+		nr = &n2
 		Regfree(&n2)
 
 		Regalloc(&n1, nl.Type, nil)

test/fixedbugs/issue10654.go

@@ -0,0 +1,17 @@
+// compile
+
+// Copyright 2015 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.
+
+// Issue 10654: Failure to use generated temps
+// for function calls etc. in boolean codegen.
+
+package main
+
+var s string
+
+func main() {
+	if (s == "this") != (s == "that") {
+	}
+}