[Bug target/115966] New: [15 Regression] Miscompilation of 403.gcc with -Ofast -march=native on x86_64

[pheeck at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115966

            Bug ID: 115966
           Summary: [15 Regression] Miscompilation of 403.gcc with -Ofast
                    -march=native on x86_64
           Product: gcc
           Version: 15.0
            Status: UNCONFIRMED
          Keywords: needs-bisection, wrong-code
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: pheeck at gcc dot gnu.org
            Blocks: 26163
  Target Milestone: ---
              Host: x86_64-linux
            Target: x86_64-linux

Compiling the 403.gcc CPU SPEC 2006 benchmark with -g -Ofast -march=native
-fpermissive (403.gcc no longer compiles without -fpermissive) on an x86_64
machine results in a miscompilation. Here is what the benchmark reports:

*** Miscompare of scilab.s; for details see
   
/home/gcc/buildworker/source/cpu2006/benchspec/CPU2006/403.gcc/run/run_peak_ref_amd64-m64-mine.0000/scilab.s.mis
157474:         .long   1764174565
                .long   1248582442
                 ^
157475:         .long   1072684140
                .long   1072430610
                    ^
157476:         .long   103477976
                .long   3882853149
                ^
157477:         .long   1072638526
                .long   1072384995
                    ^
157478:         .long   2763002310
                .long   3786780864
                ^
157479:         .long   1072546777
                .long   1072746777
                    ^
157484:         .long   579723672
                .long   1095315795
                ^
157485:         .long   1072020921
                .long   1072274451
                    ^
157486:         .long   1075822880
                .long   1120461514
                 ^
157487:         .long   1071776283
                .long   1071400834
                    ^

I've seen this on AMD Zen4, Zen3 and Zen2 machines and on an Intel Ice Lake
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)