Handle CONSTRUCTOR in operand_equal_p

[Richard Biener]

On October 14, 2015 6:27:02 PM GMT+02:00, Jan Hubicka <hubicka@ucw.cz> wrote:
>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.  */

The comment is wrong (or at least odd),
On gimple an empty vector constructor should be folded to a VECTOR_CST.

>+	return (!vec_safe_length (CONSTRUCTOR_ELTS (arg0))
>+		&& !vec_safe_length (CONSTRUCTOR_ELTS (arg1)));
>       default:
> 	break;
>       }