gc: bug281 - bad overlap in stack copy

Fixes #807.

R=ken2
CC=golang-dev
https://golang.org/cl/1283041

src/cmd/5g/cgen.c

@@ -1053,11 +1053,32 @@ stkof(Node *n)
 {
 	Type *t;
 	Iter flist;
+	int32 off;
 
 	switch(n->op) {
 	case OINDREG:
 		return n->xoffset;
 
+	case ODOT:
+		t = n->left->type;
+		if(isptr[t->etype])
+			break;
+		off = stkof(n->left);
+		if(off == -1000 || off == 1000)
+			return off;
+		return off + n->xoffset;
+
+	case OINDEX:
+		t = n->left->type;
+		if(!isfixedarray(t))
+			break;
+		off = stkof(n->left);
+		if(off == -1000 || off == 1000)
+			return off;
+		if(isconst(n->right, CTINT))
+			return off + t->type->width * mpgetfix(n->right->val.u.xval);
+		return 1000;
+		
 	case OCALLMETH:
 	case OCALLINTER:
 	case OCALLFUNC:
@@ -1106,6 +1127,17 @@ sgen(Node *n, Node *res, int32 w)
 	osrc = stkof(n);
 	odst = stkof(res);
 
+	if(osrc != -1000 && odst != -1000 && (osrc == 1000 || odst == 1000)) {
+		// osrc and odst both on stack, and at least one is in
+		// an unknown position.  Could generate code to test
+		// for forward/backward copy, but instead just copy
+		// to a temporary location first.
+		tempname(&tmp, n->type);
+		sgen(n, &tmp, w);
+		sgen(&tmp, res, w);
+		return;
+	}
+
 	if(osrc % 4 != 0 || odst %4 != 0)
 		fatal("sgen: non word(4) aligned offset src %d or dst %d", osrc, odst);
 

src/cmd/6g/cgen.c

@@ -938,11 +938,32 @@ stkof(Node *n)
 {
 	Type *t;
 	Iter flist;
+	int32 off;
 
 	switch(n->op) {
 	case OINDREG:
 		return n->xoffset;
 
+	case ODOT:
+		t = n->left->type;
+		if(isptr[t->etype])
+			break;
+		off = stkof(n->left);
+		if(off == -1000 || off == 1000)
+			return off;
+		return off + n->xoffset;
+
+	case OINDEX:
+		t = n->left->type;
+		if(!isfixedarray(t))
+			break;
+		off = stkof(n->left);
+		if(off == -1000 || off == 1000)
+			return off;
+		if(isconst(n->right, CTINT))
+			return off + t->type->width * mpgetfix(n->right->val.u.xval);
+		return 1000;
+		
 	case OCALLMETH:
 	case OCALLINTER:
 	case OCALLFUNC:
@@ -968,7 +989,7 @@ stkof(Node *n)
 void
 sgen(Node *n, Node *ns, int32 w)
 {
-	Node nodl, nodr, oldl, oldr, cx, oldcx;
+	Node nodl, nodr, oldl, oldr, cx, oldcx, tmp;
 	int32 c, q, odst, osrc;
 
 	if(debug['g']) {
@@ -989,6 +1010,16 @@ sgen(Node *n, Node *ns, int32 w)
 	osrc = stkof(n);
 	odst = stkof(ns);
 
+	if(osrc != -1000 && odst != -1000 && (osrc == 1000 || odst == 1000)) {
+		// osrc and odst both on stack, and at least one is in
+		// an unknown position.  Could generate code to test
+		// for forward/backward copy, but instead just copy
+		// to a temporary location first.
+		tempname(&tmp, n->type);
+		sgen(n, &tmp, w);
+		sgen(&tmp, ns, w);
+		return;
+	}
 
 	if(n->ullman >= ns->ullman) {
 		savex(D_SI, &nodr, &oldr, N, types[tptr]);

src/cmd/8g/cgen.c

@@ -439,7 +439,6 @@ Prog*
 cgenindex(Node *n, Node *res)
 {
 	Node tmp, lo, hi, zero;
-	Prog *p;
 
 	if(!is64(n->type)) {
 		cgen(n, res);
@@ -1043,11 +1042,32 @@ stkof(Node *n)
 {
 	Type *t;
 	Iter flist;
+	int32 off;
 
 	switch(n->op) {
 	case OINDREG:
 		return n->xoffset;
 
+	case ODOT:
+		t = n->left->type;
+		if(isptr[t->etype])
+			break;
+		off = stkof(n->left);
+		if(off == -1000 || off == 1000)
+			return off;
+		return off + n->xoffset;
+
+	case OINDEX:
+		t = n->left->type;
+		if(!isfixedarray(t))
+			break;
+		off = stkof(n->left);
+		if(off == -1000 || off == 1000)
+			return off;
+		if(isconst(n->right, CTINT))
+			return off + t->type->width * mpgetfix(n->right->val.u.xval);
+		return 1000;
+		
 	case OCALLMETH:
 	case OCALLINTER:
 	case OCALLFUNC:
@@ -1094,6 +1114,17 @@ sgen(Node *n, Node *res, int32 w)
 	osrc = stkof(n);
 	odst = stkof(res);
 	
+	if(osrc != -1000 && odst != -1000 && (osrc == 1000 || odst == 1000)) {
+		// osrc and odst both on stack, and at least one is in
+		// an unknown position.  Could generate code to test
+		// for forward/backward copy, but instead just copy
+		// to a temporary location first.
+		tempname(&tsrc, n->type);
+		sgen(n, &tsrc, w);
+		sgen(&tsrc, res, w);
+		return;
+	}
+
 	nodreg(&dst, types[tptr], D_DI);
 	nodreg(&src, types[tptr], D_SI);
 

test/fixedbugs/bug281.go

@@ -0,0 +1,55 @@
+// $G $D/$F.go && $L $F.$A && ./$A.out
+
+// Copyright 2010 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.
+
+// http://code.google.com/p/go/issues/detail?id=807
+
+package main
+
+type Point struct {
+	X, Y int64
+}
+
+type Rect struct {
+	Min, Max Point
+}
+
+func (p Point) Sub(q Point) Point {
+	return Point{p.X-q.X, p.Y-q.Y}
+}
+
+type Obj struct {
+	bbox Rect
+}
+
+func (o *Obj) Bbox() Rect {
+	return o.bbox
+}
+
+func (o *Obj) Points() [2]Point{
+	return [2]Point{o.bbox.Min, o.bbox.Max}
+}
+
+var x = 0
+
+func main() {
+	o := &Obj{Rect{Point{800, 0}, Point{}}}
+	p := Point{800, 300}
+	q := p.Sub(o.Bbox().Min)
+	if q.X != 0 || q.Y != 300 {
+		println("BUG dot: ", q.X, q.Y)
+		return
+	}
+	
+	q = p.Sub(o.Points()[0])
+	if q.X != 0 || q.Y != 300 {
+		println("BUG index const: ", q.X, q.Y)
+	}
+	
+	q = p.Sub(o.Points()[x])
+	if q.X != 0 || q.Y != 300 {
+		println("BUG index var: ", q.X, q.Y)
+	}
+}