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From: "jamborm at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/101296] New: Addition of  x86 addsub SLP patterned
 slowed down 433.milc by 12% on znver2 with -Ofast -flto
Date: Fri, 02 Jul 2021 12:17:46 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D101296

            Bug ID: 101296
           Summary: Addition of  x86 addsub SLP patterned slowed down
                    433.milc by 12% on znver2 with -Ofast -flto
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jamborm at gcc dot gnu.org
                CC: rguenth at gcc dot gnu.org
  Target Milestone: ---
              Host: x86_64-linux
            Target: x86_64-linux

Commit g:7a6c31f0f84 (Add x86 addsub SLP pattern) has slowed down
433.milc from SPECFP 2006 by 12% on a znver2 based machine when
compiled with -Ofast -flto -march=3Dnative.

Note however that the master branch has afterwards recovered some of
these losses and today's bc8f0ed7042 is only 6% slower than what it
was before the addsub addition.  Nevertheless, this effect of this
particular change may be worth looking at.

LNT tracking graph is available for example here:
https://lnt.opensuse.org/db_default/v4/SPEC/graph?plot.0=3D289.70.0=