Re: Handle CONSTRUCTOR in operand_equal_p

[Richard Biener <rguenther@suse.de>]

On October 15, 2015 1:55:09 AM GMT+02:00, Jan Hubicka <hubicka@ucw.cz> wrote:
>> 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.

Yes we do, but then the comment should refer to aggregate types.

>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;
>> >       }
>>