cmd/cc: fix uint right shift in constant evaluation

        Fixes #3664.

R=golang-dev, bradfitz, rsc
CC=golang-dev
https://golang.org/cl/6249048

diff --git a/src/cmd/cc/scon.c b/src/cmd/cc/scon.c
index 193331f774d476fbb6a25fdd71741a717b6c3f05..f6031a5be7ebe096e788070fe421399aa1780ea8 100644 (file)
--- a/src/cmd/cc/scon.c
+++ b/src/cmd/cc/scon.c
@@ -175,7 +175,10 @@ evconst(Node *n)
                break;
 
        case OLSHR:
-               v = (uvlong)l->vconst >> r->vconst;
+               if(l->type->width != sizeof(uvlong))
+                       v = ((uvlong)l->vconst & 0xffffffffULL) >> r->vconst;
+               else
+                       v = (uvlong)l->vconst >> r->vconst;
                break;
 
        case OASHR: