[Bug tree-optimization/115450] New: cpu2017 502.gcc runtime miscompute

[Bug tree-optimization/115450] New: cpu2017 502.gcc runtime miscompute

[kugan at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115450

            Bug ID: 115450
           Summary: cpu2017 502.gcc runtime miscompute
           Product: gcc
           Version: 15.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: kugan at gcc dot gnu.org
  Target Milestone: ---

5022.gcc is meicompiling for aarch64 with -O3 -Wl,-z,muldefs -lm
-fallow-argument-mismatch -fpermissive -fstack-arrays -flto
-Wl,--sort-section=name -fno-strict-aliasing -fgnu89-inline -march=native
-mcpu=neoverse-v2 -msve-vector-bits=128

gcc -v
Using built-in specs.
COLLECT_GCC=/home/kvivekananda/install_base/bin/gcc
COLLECT_LTO_WRAPPER=/home/kvivekananda/install_base/libexec/gcc/aarch64-unknown-linux-gnu/15.0.0/lto-wrapper
Target: aarch64-unknown-linux-gnu
Configured with: ../gcc_base/configure --enable-multiarch=yes
--enable-languages=c,c++,fortran,lto --disable-bootstrap
--prefix=/home/kvivekananda/install_base : (reconfigured) ../gcc_base/configure
--enable-multiarch=yes --disable-bootstrap
--prefix=/home/kvivekananda/install_base --enable-languages=c,c++,fortran,lto
--no-create --no-recursion
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 15.0.0 20240607 (experimental) (GCC) 


Bisect points to:
[d93353e6423ecaaae9fa47d0935caafd9abfe4de] Do single-lane SLP discovery for
reductions

[Bug tree-optimization/115450] cpu2017 502.gcc runtime miscompute

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115450

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
>[r15-1006-gd93353e6423eca] Do single-lane SLP discovery for reductions


Interesting because PR 115256 bisect it to an earlier patch.

[Bug tree-optimization/115450] [15 Regression] cpu2017 502.gcc runtime miscompute on aarch64 with SVE since r15-1006-gd93353e6423eca

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115450

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |pinskia at gcc dot gnu.org
             Target|                            |aarch64-linux-gnu
           Keywords|                            |wrong-code
            Summary|cpu2017 502.gcc runtime     |[15 Regression] cpu2017
                   |miscompute                  |502.gcc runtime miscompute
                   |                            |on aarch64 with SVE since
                   |                            |r15-1006-gd93353e6423eca
   Target Milestone|---                         |15.0
             Blocks|                            |26163


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)

[Bug tree-optimization/115450] [15 Regression] cpu2017 502.gcc runtime miscompute on aarch64 with SVE since r15-1006-gd93353e6423eca

[kugan at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115450

--- Comment #2 from kugan at gcc dot gnu.org ---
(In reply to Andrew Pinski from comment #1)
> >[r15-1006-gd93353e6423eca] Do single-lane SLP discovery for reductions
> 
> 
> Interesting because PR 115256 bisect it to an earlier patch.
I believe this is a new issue.

[Bug tree-optimization/115450] [15 Regression] cpu2017 502.gcc runtime miscompute on aarch64 with SVE since r15-1006-gd93353e6423eca

[vineetg at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115450

Vineet Gupta <vineetg at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jeffreyalaw at gmail dot com,
                   |                            |vineetg at gcc dot gnu.org

--- Comment #3 from Vineet Gupta <vineetg at gcc dot gnu.org> ---
Bisected RISC-V SPEC 502.gcc runtime failure to same commit as well.

[Bug tree-optimization/115450] [15 Regression] cpu2017 502.gcc runtime miscompute on aarch64 with SVE since r15-1006-gd93353e6423eca

[vineetg at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115450

--- Comment #4 from Vineet Gupta <vineetg at gcc dot gnu.org> ---
-Ofast -flto=auto -march=rv64gcv_zvl256b_zba_zbb_zbs_zicond_zfa
-ftree-vectorize -mrvv-vector-bits=zvl

For RISC-V issue only happens in a LTO build

[Bug tree-optimization/115450] [15 Regression] cpu2017 502.gcc runtime miscompute on aarch64 with SVE since r15-1006-gd93353e6423eca

[liuhongt at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115450

Hongtao Liu <liuhongt at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |liuhongt at gcc dot gnu.org

--- Comment #5 from Hongtao Liu <liuhongt at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #1)
> >[r15-1006-gd93353e6423eca] Do single-lane SLP discovery for reductions
> 
> 
> Interesting because PR 115256 bisect it to an earlier patch.

For PR 115256, the issue is fixed after adding -fno-strict-aliasing.