Re: Handle CONSTRUCTOR in operand_equal_p

[Jan Hubicka <hubicka@ucw.cz>]

> 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.

Hmm, I tought we have a={} i.e. for clearing whole structure.
If we never have constructors appearing as gimple operands, I guess we don't
really need the code at gimple level (because at least so far ipa-icf has
separate path to compare constructors).

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