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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/109130] New: 464.h264ref regressed by 6.5% on a
 Neoverse-N1 CPU with PGO, LTO, -Ofast and -march=native
Date: Tue, 14 Mar 2023 17:03:42 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D109130

            Bug ID: 109130
           Summary: 464.h264ref regressed by 6.5% on a Neoverse-N1 CPU
                    with PGO, LTO, -Ofast and -march=3Dnative
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jamborm at gcc dot gnu.org
                CC: tnfchris at gcc dot gnu.org
            Blocks: 26163
  Target Milestone: ---
              Host: aarch64-suse-linux
            Target: aarch64-suse-linux

LNT shows what looks like a clear recent 6.5% regression on the
464.h264ref benchmark from SPEC 2006 CPU suite when compiled with
PGO, LTO, -Ofast and -march=3Dnative on a Neoverse-N1 CPU:

  https://lnt.opensuse.org/db_default/v4/SPEC/graph?plot.0=3D586.220.0

In the same time period, I cannot (immediately) see any similar
regressions on any other CPU (all others that we monitor are x86_64)
or option combination.

Unfortunately I don't have the time and resources to further
investigate, but the commit range bad177e848787258..2fc55f51f9953b45
includes 8e26ac4749c (AArch64: Fix codegen regressions around tbz),
among other things.


Referenced Bugs:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D26163
[Bug 26163] [meta-bug] missed optimization in SPEC (2k17, 2k and 2k6 and 95=
)=