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6c: MOVL xxx, r; MOVLQZX r, r -> MOVL xxx, r

eleminate MOVLQXZ instructions after MOVL as MOVL implicitely
zero extends the result.

--- a/sys/src/cmd/6c/peep.c

+++ b/sys/src/cmd/6c/peep.c

@@ -100,14 +100,27 @@

 		case AMOVQ:

 		case AMOVSS:

 		case AMOVSD:

-			if(regtyp(&p->to))

+			if(!regtyp(&p->to))

+				break;

 			if(regtyp(&p->from)) {

 				if(copyprop(r)) {

 					excise(r);

 					t++;

-				} else

+					break;

+				}

 				if(subprop(r) && copyprop(r)) {

 					excise(r);

+					t++;

+					break;

+				}

+			}

+			if(p->as != AMOVL)

+				break;

+			r1 = rnops(uniqs(r));

+			if(r1 != R){

+				p1 = r1->prog;

+				if(p1->as == AMOVLQZX && p1->from.type == p->to.type && p1->to.type == p->to.type){

+					excise(r1);

 					t++;

 				}

 			}