[committed] Restore fold checking

[Richard Sandiford]

Noticed after making yes,rtl,df,fold my default --enable-checking option
(the rtl and df bits being long overdue).  Bootstrapped & regression-tested
on x86_64-linux-gnu and installed as obvious.

Richard


gcc/
        * fold-const.c (fold_checksum_tree): Fix VECTOR_CST case.

Index: gcc/fold-const.c
===================================================================
--- gcc/fold-const.c    2012-04-21 18:50:37.000000000 +0100
+++ gcc/fold-const.c    2012-04-21 18:50:37.559865589 +0100
@@ -14391,7 +14391,8 @@ fold_checksum_tree (const_tree expr, str
          fold_checksum_tree (TREE_IMAGPART (expr), ctx, ht);
          break;
        case VECTOR_CST:
-         fold_checksum_tree (TREE_VECTOR_CST_ELTS (expr), ctx, ht);
+         for (i = 0; i < (int) VECTOR_CST_NELTS (expr); ++i)
+           fold_checksum_tree (VECTOR_CST_ELT (expr, i), ctx, ht);
          break;
        default:
          break;