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. > >