Handle CONSTRUCTOR in operand_equal_p

[Jan Hubicka <hubicka@ucw.cz>]

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;
       }