diff --git a/src/cmd/acme/regx.c b/src/cmd/acme/regx.c
index a76f617..3a3e78c 100644
--- a/src/cmd/acme/regx.c
+++ b/src/cmd/acme/regx.c
@@ -521,56 +521,26 @@
 }
 
 /*
- * Add inst to the list [l, l+NLIST), but only if it is not there already.
- * These work lists are stored and processed in increasing
- * order of sep->p[0], so if the inst is there already, the one 
- * there already is a more left match and takes priority.
- * (This works for backward searches too, because there
- * is no explicit comparison.)
+ * Note optimization in addinst:
+ * 	*l must be pending when addinst called; if *l has been looked
+ *		at already, the optimization is a bug.
  */
-Ilist*
-addinst1(Ilist *l, Inst *inst, Rangeset *sep)
-{
-	Ilist *p;
-
-	for(p = l; p->inst; p++)
-		if(p->inst==inst)
-			return 0;
-	
-	if(p == l+NLIST)
-		return l+NLIST;
-	
-	p->inst = inst;
-	p->se = *sep;
-	(p+1)->inst = 0;
-	return p;
-}
-
 int
 addinst(Ilist *l, Inst *inst, Rangeset *sep)
 {
-	Ilist *ap;
-	
-	ap = addinst1(l, inst, sep);
-	if(ap == 0)
-		return 0;
-	if(ap == l+NLIST)
-		return -1;
-	
-	/*
-	 * Added inst to list at ap.
-	 * Expand any ORs right now, so that entire 
-	 * work list ends up being sorted by increasing sep->p[0].
-	 */
-	for(; ap->inst; ap++){
-		if(ap->inst->type == OR){
-			if(addinst1(l, ap->inst->u1.left, &ap->se) == l+NLIST)
-				return -1;
-			if(addinst1(l, ap->inst->u.right, &ap->se) == l+NLIST)
-				return -1;
+	Ilist *p;
+
+	for(p = l; p->inst; p++){
+		if(p->inst==inst){
+			if((sep)->r[0].q0 < p->se.r[0].q0)
+				p->se= *sep;	/* this would be bug */
+			return 0;	/* It's already there */
 		}
 	}
-	return 0;
+	p->inst = inst;
+	p->se= *sep;
+	(p+1)->inst = nil;
+	return 1;
 }
 
 int
@@ -587,6 +557,7 @@
 	Inst *inst;
 	Ilist *tlp;
 	uint p;
+	int nnl, ntl;
 	int nc, c;
 	int wrapped;
 	int startchar;
@@ -595,6 +566,7 @@
 	p = startp;
 	startchar = 0;
 	wrapped = 0;
+	nnl = 0;
 	if(startinst->type<OPERATOR)
 		startchar = startinst->type;
 	list[0][0].inst = list[1][0].inst = nil;
@@ -604,7 +576,6 @@
 	else
 		nc = runestrlen(r);
 	/* Execute machine once for each character */
-	nl = list[0];
 	for(;;p++){
 	doloop:
 		if(p>=eof || p>=nc){
@@ -623,7 +594,7 @@
 			}
 			c = 0;
 		}else{
-			if(((wrapped && p>=startp) || sel.r[0].q0>0) && nl->inst==0)
+			if(((wrapped && p>=startp) || sel.r[0].q0>0) && nnl==0)
 				break;
 			if(t != nil)
 				c = textreadc(t, p);
@@ -631,15 +602,18 @@
 				c = r[p];
 		}
 		/* fast check for first char */
-		if(startchar && nl->inst==0 && c!=startchar)
+		if(startchar && nnl==0 && c!=startchar)
 			continue;
 		tl = list[flag];
 		nl = list[flag^=1];
 		nl->inst = nil;
+		ntl = nnl;
+		nnl = 0;
 		if(sel.r[0].q0<0 && (!wrapped || p<startp || startp==eof)){
 			/* Add first instruction to this list */
 			sempty.r[0].q0 = p;
-			if(addinst(tl, startinst, &sempty) < 0){
+			if(addinst(tl, startinst, &sempty))
+			if(++ntl >= NLIST){
 	Overflow:
 				warning(nil, "regexp list overflow\n");
 				sel.r[0].q0 = -1;
@@ -653,7 +627,8 @@
 			default:	/* regular character */
 				if(inst->type==c){
 	Addinst:
-					if(addinst(nl, inst->u1.next, &tlp->se) < 0)
+					if(addinst(nl, inst->u1.next, &tlp->se))
+					if(++nnl >= NLIST)
 						goto Overflow;
 				}
 				break;
@@ -691,8 +666,13 @@
 					goto Addinst;
 				break;
 			case OR:
-				/* already expanded; just a placeholder */
-				break;
+				/* evaluate right choice later */
+				if(addinst(tl, inst->u.right, &tlp->se))
+				if(++ntl >= NLIST)
+					goto Overflow;
+				/* efficiency: advance and re-evaluate */
+				inst = inst->u1.left;
+				goto Switchstmt;
 			case END:	/* Match! */
 				tlp->se.r[0].q1 = p;
 				newmatch(&tlp->se);
@@ -720,11 +700,13 @@
 	Inst *inst;
 	Ilist *tlp;
 	int p;
+	int nnl, ntl;
 	int c;
 	int wrapped;
 	int startchar;
 
 	flag = 0;
+	nnl = 0;
 	wrapped = 0;
 	p = startp;
 	startchar = 0;
@@ -733,7 +715,6 @@
 	list[0][0].inst = list[1][0].inst = nil;
 	sel.r[0].q0= -1;
 	/* Execute machine once for each character, including terminal NUL */
-	nl = list[0];
 	for(;;--p){
 	doloop:
 		if(p <= 0){
@@ -753,20 +734,24 @@
 			}
 			c = 0;
 		}else{
-			if(((wrapped && p<=startp) || sel.r[0].q0>0) && nl->inst==0)
+			if(((wrapped && p<=startp) || sel.r[0].q0>0) && nnl==0)
 				break;
 			c = textreadc(t, p-1);
 		}
 		/* fast check for first char */
-		if(startchar && nl->inst==0 && c!=startchar)
+		if(startchar && nnl==0 && c!=startchar)
 			continue;
 		tl = list[flag];
 		nl = list[flag^=1];
 		nl->inst = nil;
+		ntl = nnl;
+		nnl = 0;
 		if(sel.r[0].q0<0 && (!wrapped || p>startp)){
 			/* Add first instruction to this list */
-			sempty.r[0].q0 = p;
-			if(addinst(tl, bstartinst, &sempty) < 0){
+			/* the minus is so the optimizations in addinst work */
+			sempty.r[0].q0 = -p;
+			if(addinst(tl, bstartinst, &sempty))
+			if(++ntl >= NLIST){
 	Overflow:
 				warning(nil, "regexp list overflow\n");
 				sel.r[0].q0 = -1;
@@ -780,7 +765,8 @@
 			default:	/* regular character */
 				if(inst->type == c){
 	Addinst:
-					if(addinst(nl, inst->u1.next, &tlp->se) < 0)
+					if(addinst(nl, inst->u1.next, &tlp->se))
+					if(++nnl >= NLIST)
 						goto Overflow;
 				}
 				break;
@@ -818,9 +804,15 @@
 					goto Addinst;
 				break;
 			case OR:
-				/* already expanded; just a placeholder */
-				break;
+				/* evaluate right choice later */
+				if(addinst(tl, inst->u.right, &tlp->se))
+				if(++ntl >= NLIST)
+					goto Overflow;
+				/* efficiency: advance and re-evaluate */
+				inst = inst->u1.left;
+				goto Switchstmt;
 			case END:	/* Match! */
+				tlp->se.r[0].q0 = -tlp->se.r[0].q0; /* minus sign */
 				tlp->se.r[0].q1 = p;
 				bnewmatch(&tlp->se);
 				break;