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Re: [PATCH] Make VRP recognize range tests (unsigned)a + CST <= CST2
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