I got more feedback for the patch from Gabriel Ravier and Jakub Jelinek in https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96674 and re-worked it accordingly.
The changes from the previous patch are:
1. Switched the tests to use __attribute__((noipa)) instead of
__attribute__((noinline)) .
2. Fixed a type in the pattern comment.
3. Added :c for top-level bit_ior expression.
4. Added :s for the subexpressions.
5. Added a pattern for the negated expression:
x >= y && y != XXX_MIN --> x > y - 1
and the corresponding tests.
The new patch is attached.
Eugene
-----Original Message-----
From: Richard Biener <richard.guent...@gmail.com>
Sent: Tuesday, January 5, 2021 4:21 AM
To: Eugene Rozenfeld <eugene.rozenf...@microsoft.com>
Cc: gcc-patches@gcc.gnu.org
Subject: [EXTERNAL] Re: [PATCH][tree-optimization]Optimize combination of
comparisons to dec+compare
On Mon, Jan 4, 2021 at 9:50 PM Eugene Rozenfeld
<eugene.rozenf...@microsoft.com> wrote:
>
> Ping.
>
> -----Original Message-----
> From: Eugene Rozenfeld
> Sent: Tuesday, December 22, 2020 3:01 PM
> To: Richard Biener <richard.guent...@gmail.com>;
> gcc-patches@gcc.gnu.org
> Subject: RE: Optimize combination of comparisons to dec+compare
>
> Re-sending my question and re-attaching the patch.
>
> Richard, can you please clarify your feedback?
Hmm, OK.
The patch is OK.
Thanks,
Richard.
> Thanks,
>
> Eugene
>
> -----Original Message-----
> From: Gcc-patches <gcc-patches-boun...@gcc.gnu.org> On Behalf Of
> Eugene Rozenfeld via Gcc-patches
> Sent: Tuesday, December 15, 2020 2:06 PM
> To: Richard Biener <richard.guent...@gmail.com>
> Cc: gcc-patches@gcc.gnu.org
> Subject: [EXTERNAL] Re: Optimize combination of comparisons to
> dec+compare
>
> Richard,
>
> > Do we already handle x < y || x <= CST to x <= y - CST?
>
> That is an invalid transformation: e.g., consider x=3, y=4, CST=2.
> Can you please clarify?
>
> Thanks,
>
> Eugene
>
> -----Original Message-----
> From: Richard Biener <richard.guent...@gmail.com>
> Sent: Thursday, December 10, 2020 12:21 AM
> To: Eugene Rozenfeld <eugene.rozenf...@microsoft.com>
> Cc: gcc-patches@gcc.gnu.org
> Subject: Re: Optimize combination of comparisons to dec+compare
>
> On Thu, Dec 10, 2020 at 1:52 AM Eugene Rozenfeld via Gcc-patches
> <gcc-patches@gcc.gnu.org> wrote:
> >
> > This patch adds a pattern for optimizing x < y || x == XXX_MIN to x
> > <=
> > y-1 if y is an integer with TYPE_OVERFLOW_WRAPS.
>
> Do we already handle x < y || x <= CST to x <= y - CST?
> That is, the XXX_MIN case is just a special-case of generic anti-range
> testing? For anti-range testing with signed types we pun to unsigned when
> possible.
>
> > This fixes pr96674.
> >
> > Tested on x86_64-pc-linux-gnu.
> >
> > For this function
> >
> > bool f(unsigned a, unsigned b)
> > {
> > return (b == 0) | (a < b);
> > }
> >
> > the code without the patch is
> >
> > test esi,esi
> > sete al
> > cmp esi,edi
> > seta dl
> > or eax,edx
> > ret
> >
> > the code with the patch is
> >
> > sub esi,0x1
> > cmp esi,edi
> > setae al
> > ret
> >
> > Eugene
> >
> > gcc/
> > PR tree-optimization/96674
> > * match.pd: New pattern x < y || x == XXX_MIN --> x <= y - 1
> >
> > gcc/testsuite
> > * gcc.dg/pr96674.c: New test.
> >
0002-Optimize-combination-of-comparisons-to-dec-compare.patch
Description: 0002-Optimize-combination-of-comparisons-to-dec-compare.patch
