[Bug target/113832] New: [14 Regression] 6% exec time regression of 464.h264ref on aarch64

[Bug target/113832] New: [14 Regression] 6% exec time regression of 464.h264ref on aarch64

[fkastl at suse dot cz]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113832

            Bug ID: 113832
           Summary: [14 Regression] 6% exec time regression of 464.h264ref
                    on aarch64
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Keywords: needs-bisection
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: fkastl at suse dot cz
  Target Milestone: ---
              Host: aarch64-gnu-linux
            Target: aarch64-gnu-linux

As seen here

https://lnt.opensuse.org/db_default/v4/SPEC/graph?plot.0=586.220.0

between commits

g:cc7aebff74d89675
g:314cbfe2980b32f5

there is a 6% slowdown of the 464.h264ref 2006 SPEC benchmark. Compiler options
are:

-Ofast -march=native -flto PGO

The CPU is Ampere Altra - Neoverse N1.

[Bug target/113832] [14 Regression] 6% exec time regression of 464.h264ref on aarch64

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113832

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |pinskia at gcc dot gnu.org
   Target Milestone|---                         |14.0

[Bug target/113832] [14 Regression] 6% exec time regression of 464.h264ref on aarch64

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113832

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Maybe
https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=2f14c0dbb789852947cb58fdf7d3162413f053fa

[Bug target/113832] [14 Regression] 6% exec time regression of 464.h264ref on aarch64

[roger at nextmovesoftware dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113832

Roger Sayle <roger at nextmovesoftware dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |roger at nextmovesoftware dot com

--- Comment #2 from Roger Sayle <roger at nextmovesoftware dot com> ---
Adding myself to Cc list (in case this is confirmed to be a widening multiply
issue).

[Bug target/113832] [14 Regression] 6% exec time regression of 464.h264ref on aarch64

[law at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113832

Jeffrey A. Law <law at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P2
                 CC|                            |law at gcc dot gnu.org

[Bug target/113832] [14 Regression] 6% exec time regression of 464.h264ref on aarch64

[pheeck at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113832

--- Comment #3 from Filip Kastl <pheeck at gcc dot gnu.org> ---
It seems that the benchmark runtime returned to normal for a while but then
went back to 6% slowdown.

Somewhere between these two commits the benchmark sped up
g:eb7a8f213d59e0cf
g:15d1dae0d4d1be88

And between these two commits the benchmark regressed once again
g:c7a9883663a88861
g:84fc8f4f3263d665

[Bug target/113832] [14/15 Regression] 6% exec time regression of 464.h264ref on aarch64

[pheeck at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113832

--- Comment #4 from Filip Kastl <pheeck at gcc dot gnu.org> ---
There was another speedup followed by a slowdown.

speedup somewhere between
g:4b8e7b57d952a103
g:839bc42772ba7af6

slowdown
g:7924e352523b3715
g:f3fdcf4a37a7be07

---

Btw, here is a plot also showing GCC 13

https://lnt.opensuse.org/db_default/v4/SPEC/graph?plot.7=868.220.0&plot.8=586.220.0&

[Bug target/113832] [14/15 Regression] 6% exec time regression of 464.h264ref on aarch64

[roger at nextmovesoftware dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113832

--- Comment #5 from Roger Sayle <roger at nextmovesoftware dot com> ---
I'm trying to confirm that there are actually widening multiplications in
464.h264ref (on aarch64), but if anyone's already done an analysis of what
might be causing these performance swings, please do post (a pointer here).

[Bug target/113832] [14/15 Regression] 6% exec time regression of 464.h264ref on aarch64

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113832

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|14.0                        |14.2

--- Comment #6 from Richard Biener <rguenth at gcc dot gnu.org> ---
GCC 14.1 is being released, retargeting bugs to GCC 14.2.