patch: CSE bug when narrowing constants

[Gary Funck <gary at intrepid dot com>]

Although this bug hasn't been confirmed yet:
  http://gcc.gnu.org/ml/gcc/2008-11/msg00360.html
this patch fixes the problem:

Index: cse.c
===================================================================
RCS file: /eng/cvs/pub/upc/gcc-upc-4-2/gcc/cse.c,v
retrieving revision 1.1.1.4
diff -u -p -r1.1.1.4 cse.c
--- cse.c       22 Apr 2008 16:34:51 -0000      1.1.1.4
+++ cse.c       29 Nov 2008 01:18:13 -0000
@@ -1452,6 +1452,8 @@ lookup_as_function (rtx x, enum rtx_code
 static rtx
 lookup_as_function (rtx x, enum rtx_code code)
 {
+  int narrowing = 0;
+  enum machine_mode mode = GET_MODE (x);
   struct table_elt *p
     = lookup (x, SAFE_HASH (x, VOIDmode), GET_MODE (x));
 
@@ -1459,8 +1461,9 @@ lookup_as_function (rtx x, enum rtx_code
      long as we are narrowing.  So if we looked in vain for a mode narrower
      than word_mode before, look for word_mode now.  */
   if (p == 0 && code == CONST_INT
-      && GET_MODE_SIZE (GET_MODE (x)) < GET_MODE_SIZE (word_mode))
+      && GET_MODE_SIZE (mode) < GET_MODE_SIZE (word_mode))
     {
+      narrowing = 1;
       x = copy_rtx (x);
       PUT_MODE (x, word_mode);
       p = lookup (x, SAFE_HASH (x, VOIDmode), word_mode);
@@ -1473,7 +1476,12 @@ lookup_as_function (rtx x, enum rtx_code
     if (GET_CODE (p->exp) == code
        /* Make sure this is a valid entry in the table.  */
        && exp_equiv_p (p->exp, p->exp, 1, false))
-      return p->exp;
+     {
+       rtx result = p->exp;
+       if (narrowing)
+         result = gen_lowpart (mode, result);
+       return result;
+     }
 
   return 0;
 }