bug in 6g optimizer

8g still needs fixing

R=rsc
https://golang.org/cl/176057

src/cmd/6g/gsubr.c

@@ -1049,6 +1049,7 @@ naddr(Node *n, Addr *a, int canemitcode)
 	case OLEN:
 		// len of string or slice
 		naddr(n->left, a, canemitcode);
+		a->etype = TUINT;
 		a->offset += Array_nel;
 		if(a->offset >= unmappedzero && a->offset-Array_nel < unmappedzero)
 			checkoffset(a, canemitcode);
@@ -1057,6 +1058,7 @@ naddr(Node *n, Addr *a, int canemitcode)
 	case OCAP:
 		// cap of string or slice
 		naddr(n->left, a, canemitcode);
+		a->etype = TUINT;
 		a->offset += Array_cap;
 		if(a->offset >= unmappedzero && a->offset-Array_cap < unmappedzero)
 			checkoffset(a, canemitcode);

src/cmd/6g/reg.c

@@ -67,7 +67,7 @@ rcmp(const void *a1, const void *a2)
 	return p2->varno - p1->varno;
 }
 
-void
+static void
 setoutvar(void)
 {
 	Type *t;
@@ -91,6 +91,13 @@ setoutvar(void)
 //print("ovars = %Q\n", &ovar);
 }
 
+static void
+setaddrs(Bits bit)
+{
+	if(bany(&bit))
+		var[bnum(bit)].addr = 1;
+}
+
 void
 regopt(Prog *firstp)
 {
@@ -181,8 +188,7 @@ regopt(Prog *firstp)
 		 */
 		case ALEAL:
 		case ALEAQ:
-			for(z=0; z<BITS; z++)
-				addrs.b[z] |= bit.b[z];
+			setaddrs(bit);
 			break;
 
 		/*
@@ -378,8 +384,7 @@ regopt(Prog *firstp)
 		 * funny
 		 */
 		case ACALL:
-			for(z=0; z<BITS; z++)
-				addrs.b[z] |= bit.b[z];
+			setaddrs(bit);
 			break;
 		}
 
@@ -453,6 +458,18 @@ regopt(Prog *firstp)
 	if(firstr == R)
 		return;
 
+	for(i=0; i<nvar; i++) {
+		Var *v = var+i;
+		if(v->addr) {
+			bit = blsh(i);
+			for(z=0; z<BITS; z++)
+				addrs.b[z] |= bit.b[z];
+		}
+
+//		print("bit=%2d addr=%d et=%-6E w=%-2d s=%S + %lld\n",
+//			i, v->addr, v->etype, v->width, v->sym, v->offset);
+	}
+
 	if(debug['R'] && debug['v'])
 		dumpit("pass1", firstr);
 
@@ -768,31 +785,16 @@ doregbits(int r)
 }
 
 static int
-overlap(Var *v, int o2, int w2)
+overlap(int32 o1, int w1, int32 o2, int w2)
 {
-	int o1, w1, t1, t2, z;
-	Bits bit;
+	int32 t1, t2;
 
-	o1 = v->offset;
-	w1 = v->width;
 	t1 = o1+w1;
 	t2 = o2+w2;
+
 	if(!(t1 > o2 && t2 > o1))
 		return 0;
 
-	// set to max extent
-	if(o2 < o1)
-		v->offset = o2;
-	if(t1 > t2)
-		v->width = t1-v->offset;
-	else
-		v->width = t2-v->offset;
-
-	// and dont registerize
-	bit = blsh(v-var);
-	for(z=0; z<BITS; z++)
-		addrs.b[z] |= bit.b[z];
-
 	return 1;
 }
 
@@ -809,6 +811,9 @@ mkvar(Reg *r, Adr *a)
 	 * mark registers used
 	 */
 	t = a->type;
+	if(t == D_NONE)
+		goto none;
+
 	if(r != R) {
 		r->regu |= doregbits(t);
 		r->regu |= doregbits(a->index);
@@ -817,14 +822,15 @@ mkvar(Reg *r, Adr *a)
 	switch(t) {
 	default:
 		goto none;
+
 	case D_ADDR:
 		a->type = a->index;
 		bit = mkvar(r, a);
-		for(z=0; z<BITS; z++)
-			addrs.b[z] |= bit.b[z];
+		setaddrs(bit);
 		a->type = t;
 		ostats.naddr++;
 		goto none;
+
 	case D_EXTERN:
 	case D_STATIC:
 	case D_PARAM:
@@ -840,32 +846,30 @@ mkvar(Reg *r, Adr *a)
 	et = a->etype;
 	o = a->offset;
 	w = a->width;
-	v = var;
 
 	flag = 0;
 	for(i=0; i<nvar; i++) {
-		if(s == v->sym)
-		if(n == v->name) {
+		v = var+i;
+		if(v->sym == s && v->name == n) {
+			if(v->offset == o) {
 				// if it is the same, use it
-			if(v->etype == et)
-			if(v->width == w)
-			if(v->offset == o)
-				goto out;
-
-			// if it overlaps, set max
-			// width and dont registerize
-			if(overlap(v, o, w))
+				if(v->etype != et||
+			   	   v->width != w)
+					v->addr = 1;
+				return blsh(i);
+			}
+
+			// if it overlaps, disable bothj
+			if(overlap(v->offset, v->width, o, w)) {
+				v->addr = 1;
 				flag = 1;
 			}
-		v++;
 		}
-	if(flag)
-		goto none;
+	}
 
 	switch(et) {
 	case 0:
 	case TFUNC:
-	case TARRAY:
 		goto none;
 	}
 
@@ -874,9 +878,10 @@ mkvar(Reg *r, Adr *a)
 			fatal("variable not optimized: %D", a);
 		goto none;
 	}
+
 	i = nvar;
 	nvar++;
-	v = &var[i];
+	v = var+i;
 	v->sym = s;
 	v->offset = o;
 	v->name = n;
@@ -884,24 +889,10 @@ mkvar(Reg *r, Adr *a)
 	v->etype = et;
 	v->width = w;
 	if(debug['R'])
-		print("bit=%2d et=%2d w=%d %D\n", i, et, w, a);
+		print("bit=%2d et=%2d w=%d %S %D\n", i, et, w, s, a);
 	ostats.nvar++;
 
-out:
 	bit = blsh(i);
-
-	// funny punning
-	if(v->etype != et) {
-		if(debug['R'])
-			print("pun et=%d/%d w=%d/%d o=%d/%d %D\n",
-				v->etype, et,
-				v->width, w,
-				v->offset, o, a);
-		for(z=0; z<BITS; z++)
-			addrs.b[z] |= bit.b[z];
-		goto none;
-	}
-
 	if(n == D_EXTERN || n == D_STATIC)
 		for(z=0; z<BITS; z++)
 			externs.b[z] |= bit.b[z];
@@ -909,6 +900,10 @@ out:
 		for(z=0; z<BITS; z++)
 			params.b[z] |= bit.b[z];
 
+	// funny punning
+	if(flag)
+		v->addr = 1;
+
 	return bit;
 
 none:

src/cmd/8g/gsubr.c

@@ -1769,6 +1769,7 @@ naddr(Node *n, Addr *a, int canemitcode)
 	case OLEN:
 		// len of string or slice
 		naddr(n->left, a, canemitcode);
+		a->etype = TUINT;
 		a->offset += Array_nel;
 		if(a->offset >= unmappedzero && a->offset-Array_nel < unmappedzero)
 			checkoffset(a, canemitcode);
@@ -1777,6 +1778,7 @@ naddr(Node *n, Addr *a, int canemitcode)
 	case OCAP:
 		// cap of string or slice
 		naddr(n->left, a, canemitcode);
+		a->etype = TUINT;
 		a->offset += Array_cap;
 		if(a->offset >= unmappedzero && a->offset-Array_nel < unmappedzero)
 			checkoffset(a, canemitcode);

src/cmd/gc/go.h

@@ -513,6 +513,7 @@ struct	Var
 	int	width;
 	char	name;
 	char	etype;
+	char	addr;
 };
 
 EXTERN	Var	var[NVAR];