bug in shift of longer operand

by a shorter operand. the bits
in the difference were not cheared.

R=r
OCL=27705
CL=27705

diff --git a/src/cmd/6g/gen.c b/src/cmd/6g/gen.c
index 8e047b8d0399d207bb309f87d5e4f14ade70ce84..cdb76bc693f9c0d37f0d67b4c63dd7942392744b 100644 (file)
--- a/src/cmd/6g/gen.c
+++ b/src/cmd/6g/gen.c
@@ -549,7 +549,7 @@ void
 cgen_shift(int op, Node *nl, Node *nr, Node *res)
 {
        Node n1, n2, n3;
-       int a, rcl;
+       int a;
        Prog *p1;
 
        a = optoas(op, nl->type);
@@ -569,23 +569,26 @@ cgen_shift(int op, Node *nl, Node *nr, Node *res)
                goto ret;
        }
 
-       rcl = reg[D_CX];
-
-       nodreg(&n1, types[TINT64], D_CX);
-       regalloc(&n1, nr->type, &n1);
+       nodreg(&n1, types[TUINT32], D_CX);
+       regalloc(&n1, nr->type, &n1);           // to hold the shift type in CX
+       regalloc(&n3, types[TUINT64], &n1);     // to clear high bits of CX
 
        regalloc(&n2, nl->type, res);
        if(nl->ullman >= nr->ullman) {
                cgen(nl, &n2);
                cgen(nr, &n1);
+               gmove(&n1, &n3);
        } else {
                cgen(nr, &n1);
+               gmove(&n1, &n3);
                cgen(nl, &n2);
        }
+       regfree(&n3);
+
        // test and fix up large shifts
-       nodconst(&n3, types[TUINT32], nl->type->width*8);
-       gins(optoas(OCMP, types[TUINT32]), &n1, &n3);
-       p1 = gbranch(optoas(OLT, types[TUINT32]), T);
+       nodconst(&n3, types[TUINT64], nl->type->width*8);
+       gins(optoas(OCMP, types[TUINT64]), &n1, &n3);
+       p1 = gbranch(optoas(OLT, types[TUINT64]), T);
        if(op == ORSH && issigned[nl->type->etype]) {
                nodconst(&n3, types[TUINT32], nl->type->width*8-1);
                gins(a, &n3, &n2);