Richard Guenther - Re: [PATCH] Make VRP recognize range tests (unsigned)a + CST <= CST2 (original) (raw)

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• From: Richard Guenther
• To: Jeffrey Law
• Cc: Diego Novillo , gcc-patches at gcc dot gnu dot org
• Date: Mon, 12 Feb 2007 20:45:43 +0100 (CET)
• Subject: Re: [PATCH] Make VRP recognize range tests (unsigned)a + CST <= CST2
• References: <Pine.LNX.4.64.0702061352470.3994@zhemvz.fhfr.qr> <45CB68E1.8030705@redhat.com> <Pine.LNX.4.64.0702091017410.3994@zhemvz.fhfr.qr> <1171300620.4134.100.camel@sweet.slc.redhat.com>

On Mon, 12 Feb 2007, Jeffrey Law wrote:

On Fri, 2007-02-09 at 10:32 +0100, Richard Guenther wrote:

On Thu, 8 Feb 2007, Diego Novillo wrote:

Richard Guenther wrote on 02/06/07 07:56:

This patch makes VRP recognize range and anti-range tests. It does so by allowing more flexible ASSERT_EXPRs (which is neccessary for the anti-range case) like

ASSERT_EXPR <a_1, (unsigned)a_1 + 5 > 13>

and derive ranges and anti-ranges from such directly.

I don't really like where this is going. VRP does not need more complexity. Though it triggers 30,000 times more, are there any perceivable benefits in runtime or code size?

See my followup mail - no earthshaking improvements. But one would need to test with bounds-checking code. I must have missed the follow-up. What exactly do you mean by 30k triggers? Is that 30k asserts generated or 30k transformations using the result of the new asserts? The latter would definitely be in the "wow" category.

Heh, no ;) It generates 30k asserts. The followup said the patch results in 0.003% overall size reduction of stage2 gcc/*.o. I expect this to slightly improve with followup patches improving the handling of anti-ranges.

Richard.

-- Richard Guenther rguenther@suse.de Novell / SUSE Labs

• References:
  • [PATCH] Make VRP recognize range tests (unsigned)a + CST <= CST2
    * From: Richard Guenther
  • Re: [PATCH] Make VRP recognize range tests (unsigned)a + CST <= CST2
    * From: Diego Novillo
  • Re: [PATCH] Make VRP recognize range tests (unsigned)a + CST <= CST2
    * From: Richard Guenther
  • Re: [PATCH] Make VRP recognize range tests (unsigned)a + CST <= CST2
    * From: Jeffrey Law