Handle CONSTRUCTOR in operand_equal_p

[Jan Hubicka]

Hi,
this patch adds the CONSTRUCTOR case discussed while back.  Only empty
constructors are matched, as those are only appearing in gimple operand.
I tested that during bootstrap about 7500 matches are for empty ctors.
There are couple hundred for non-empty probably used on generic. 

Bootstrapped/regtested x86_64-linux, OK?

Honza

        * fold-const.c (operand_equal_p): Match empty constructors.
Index: fold-const.c
===================================================================
--- fold-const.c        (revision 228735)
+++ fold-const.c        (working copy)
@@ -2890,6 +2891,11 @@ operand_equal_p (const_tree arg0, const_
        return operand_equal_p (TREE_OPERAND (arg0, 0), TREE_OPERAND (arg1, 0),
                                flags | OEP_ADDRESS_OF
                                | OEP_CONSTANT_ADDRESS_OF);
+      case CONSTRUCTOR:
+       /* In GIMPLE empty constructors are allowed in initializers of
+          vector types.  */
+       return (!vec_safe_length (CONSTRUCTOR_ELTS (arg0))
+               && !vec_safe_length (CONSTRUCTOR_ELTS (arg1)));
       default:
        break;
       }