[Bug tree-optimization/120749] New: [16 Regression] 5% slowdown of 548.exchange2_r on Aarch64

[pheeck at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120749

            Bug ID: 120749
           Summary: [16 Regression] 5% slowdown of 548.exchange2_r on
                    Aarch64
           Product: gcc
           Version: 16.0
            Status: UNCONFIRMED
          Keywords: missed-optimization, needs-bisection
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pheeck at gcc dot gnu.org
            Blocks: 26163
  Target Milestone: ---
              Host: aarch64-gnu-linux
            Target: aarch64-gnu-linux

As seen here

https://lnt.opensuse.org/db_default/v4/SPEC/graph?plot.0=589.407.0

there was a 5% exec time slowdown of 548.exchange2_r SPEC 2017 benchmark
between commits

r16-1360-gfce42e15063e76 (2025-06-10)
r16-1494-g59fbc99f8ee35f (2025-06-13)

when run with -Ofast -march=native -flto -fprofile-use on an Ampere Altra
(Neoverse N1) machine.


Referenced Bugs:

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