gc: fix div bug

R=ken2
CC=golang-dev
https://golang.org/cl/4950052

src/cmd/6g/ggen.c

@@ -448,8 +448,8 @@ dodiv(int op, Node *nl, Node *nr, Node *res)
 {
 	int a, check;
 	Node n3, n4, n5;
-	Type *t;
+	Type *t, *t0;
-	Node ax, dx, oldax, olddx;
+	Node ax, dx, ax1, n31, oldax, olddx;
 	Prog *p1, *p2, *p3;
 
 	// Have to be careful about handling
@@ -461,6 +461,7 @@ dodiv(int op, Node *nl, Node *nr, Node *res)
 	// For int32 and int64, use explicit test.
 	// Could use int64 hw for int32.
 	t = nl->type;
+	t0 = t;
 	check = 0;
 	if(issigned[t->etype]) {
 		check = 1;
@@ -478,18 +479,28 @@ dodiv(int op, Node *nl, Node *nr, Node *res)
 	}
 	a = optoas(op, t);
 
-	regalloc(&n3, t, N);
+	regalloc(&n3, t0, N);
 	if(nl->ullman >= nr->ullman) {
-		savex(D_AX, &ax, &oldax, res, t);
+		savex(D_AX, &ax, &oldax, res, t0);
 		cgen(nl, &ax);
-		regalloc(&ax, t, &ax);	// mark ax live during cgen
+		regalloc(&ax, t0, &ax);	// mark ax live during cgen
 		cgen(nr, &n3);
 		regfree(&ax);
 	} else {
 		cgen(nr, &n3);
-		savex(D_AX, &ax, &oldax, res, t);
+		savex(D_AX, &ax, &oldax, res, t0);
 		cgen(nl, &ax);
 	}
+	if(t != t0) {
+		// Convert
+		ax1 = ax;
+		n31 = n3;
+		ax.type = t;
+		n3.type = t;
+		gmove(&ax1, &ax);
+		gmove(&n31, &n3);
+	}
+
 	p3 = P;
 	if(check) {
 		nodconst(&n4, t, -1);

src/cmd/8g/ggen.c

@@ -484,8 +484,8 @@ void
 dodiv(int op, Node *nl, Node *nr, Node *res, Node *ax, Node *dx)
 {
 	int check;
-	Node n1, t1, t2, n4, nz;
+	Node n1, t1, t2, t3, t4, n4, nz;
-	Type *t;
+	Type *t, *t0;
 	Prog *p1, *p2, *p3;
 
 	// Have to be careful about handling
@@ -497,6 +497,7 @@ dodiv(int op, Node *nl, Node *nr, Node *res, Node *ax, Node *dx)
 	// For int32 and int64, use explicit test.
 	// Could use int64 hw for int32.
 	t = nl->type;
+	t0 = t;
 	check = 0;
 	if(issigned[t->etype]) {
 		check = 1;
@@ -515,8 +516,18 @@ dodiv(int op, Node *nl, Node *nr, Node *res, Node *ax, Node *dx)
 
 	tempname(&t1, t);
 	tempname(&t2, t);
-	cgen(nl, &t1);
+	if(t0 != t) {
-	cgen(nr, &t2);
+		tempname(&t3, t0);
+		tempname(&t4, t0);
+		cgen(nl, &t3);
+		cgen(nr, &t4);
+		// Convert.
+		gmove(&t3, &t1);
+		gmove(&t4, &t2);
+	} else {
+		cgen(nl, &t1);
+		cgen(nr, &t2);
+	}
 
 	if(!samereg(ax, res) && !samereg(dx, res))
 		regalloc(&n1, t, res);

test/fixedbugs/bug366.go

@@ -0,0 +1,37 @@
+// $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.
+
+// Issue 2206.  Incorrect sign extension of div arguments.
+
+package main
+
+func five(x int64) {
+	if x != 5 {
+		panic(x)
+	}
+}
+
+func main() {
+       // 5
+       five(int64(5 / (5 / 3)))
+
+       // 5
+       five(int64(byte(5) / (byte(5) / byte(3))))
+
+       // 5
+       var a, b byte = 5, 3
+       five(int64(a / (a / b)))
+       
+       // integer divide by zero in golang.org sandbox
+       // 0 on windows/amd64
+       x := [3]byte{2, 3, 5}
+       five(int64(x[2] / (x[2] / x[1])))
+
+       // integer divide by zero in golang.org sandbox
+       // crash on windows/amd64
+       y := x[1:3]
+       five(int64(y[1] / (y[1] / y[0])))
+}