forsyth: better constant detection, better incomplete ptr detection

Reference: /n/atom/patch/applied/ccconstopt
Date: Sun Aug 16 00:24:35 CES 2015
Signed-off-by: quanstro@quanstro.net

--- /sys/src/cmd/cc/sub.c	Sun Aug 16 00:24:26 2015
+++ /sys/src/cmd/cc/sub.c	Sun Aug 16 00:24:27 2015
@@ -662,7 +662,7 @@
 	Type *t1, *t2;
 	int i, j, k;
 	Node *n1;
-	long w;
+	long w, x;
 
 	t1 = n->left->type;
 	if(n->right == Z)
@@ -692,7 +692,19 @@
 	if(n->op == OSUB)
 	if(i == TIND && j == TIND) {
 		w = n->right->type->link->width;
-		if(w < 1 || n->left->type->link == T || n->left->type->link->width < 1)
+		if(w < 1) {
+			snap(n->right->type->link);
+			w = n->right->type->link->width;
+		}
+		x = 0;
+		if(n->left->type->link != T) {
+			x = n->left->type->link->width;
+			if(x < 1) {
+				snap(n->left->type->link);
+				x = n->left->type->link->width;
+			}
+		}
+		if(w < 1 || x < 1)
 			goto bad;
 		n->type = types[ewidth[TIND] <= ewidth[TLONG]? TLONG: TVLONG];
 		if(1 && ewidth[TIND] > ewidth[TLONG]){
@@ -917,6 +929,10 @@
 	case ONOT:
 	case OADDR:
 	case OIND:
+	case OCOM:
+	case ONEG:
+	case OPOS:
+	case OTST:
 		n = n->left;
 		goto loop;