gc: function argument ordering bug

Fixes #370.

R=ken2
https://golang.org/cl/163097

src/cmd/gc/walk.c

@@ -1875,7 +1875,7 @@ reorder1(NodeList *all)
 {
 	Node *f, *a, *n;
 	NodeList *l, *r, *g;
-	int c, t;
+	int c, d, t;
 
 	c = 0;	// function calls
 	t = 0;	// total parameters
@@ -1891,17 +1891,17 @@ reorder1(NodeList *all)
 		return all;
 
 	g = nil;	// fncalls assigned to tempnames
-	f = N;	// one fncall assigned to stack
+	f = N;	// last fncall assigned to stack
 	r = nil;	// non fncalls and tempnames assigned to stack
-
+	d = 0;
 	for(l=all; l; l=l->next) {
 		n = l->n;
-		ullmancalc(n);
 		if(n->ullman < UINF) {
 			r = list(r, n);
 			continue;
 		}
-		if(f == N) {
+		d++;
+		if(d == c) {
 			f = n;
 			continue;
 		}

test/fixedbugs/bug221.go

+// $G $D/$F.go && $L $F.$A && ./$A.out
+
+// Copyright 2009 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.
+
+// function call arg reordering was picking out 1 call that
+// didn't need to be in a temporary, but it was picking
+// out the first call instead of the last call.
+// http://code.google.com/p/go/issues/detail?id=370
+
+package main
+
+var gen = 'a'
+func f(n int) string {
+	s := string(gen) + string(n+'A'-1);
+	gen++;
+	return s;
+}
+
+func g(x, y string) string {
+	return x + y
+}
+
+func main() {
+	s := f(1) + f(2);
+	if s != "aAbB" {
+		panic("BUG: bug221a: ", s);
+	}
+	s = g(f(3), f(4));
+	if s != "cCdD" {
+		panic("BUG: bug221b: ", s);
+	}
+	s = f(5) + f(6) + f(7) + f(8) + f(9);
+	if s != "eEfFgGhHiI" {
+		panic("BUG: bug221c: ", s);
+	}
+}