another shift bug

R=r
OCL=19525
CL=19525

src/cmd/6g/gen.c

@@ -6,7 +6,6 @@
 #undef	EXTERN
 #define	EXTERN
 #include "gg.h"
-//#include "opt.h"
 
 enum
 {
@@ -93,11 +92,6 @@ if(throwreturn == N) {
 	gclean();
 	checklabels();
 
-//	if(debug['N']) {
-//		regopt(ptxt);
-//		debug['N'] = 0;
-//	}
-
 	if(curfn->type->outtuple != 0) {
 		gins(ACALL, N, throwreturn);
 	}
@@ -105,6 +99,11 @@ if(throwreturn == N) {
 	pc->as = ARET;	// overwrite AEND
 	pc->lineno = lineno;
 
+//	if(debug['N']) {
+//		regopt(ptxt);
+//		debug['N'] = 0;
+//	}
+
 	// fill in argument size
 	ptxt->to.offset = rnd(curfn->type->argwid, maxround);
 
@@ -1212,7 +1211,13 @@ cgen_shift(int op, Node *nl, Node *nr, Node *res)
 	if(nr->op == OLITERAL) {
 		regalloc(&n1, nl->type, res);
 		cgen(nl, &n1);
-		gins(a, nr, &n1);
+		if(mpgetfix(nr->val.u.xval) >= nl->type->width*8) {
+			// large shift gets 2 shifts by width
+			nodconst(&n3, types[TUINT32], nl->type->width*8-1);
+			gins(a, &n3, &n1);
+			gins(a, &n3, &n1);
+		} else
+			gins(a, nr, &n1);
 		gmove(&n1, res);
 		regfree(&n1);
 		goto ret;