[Bug target/115342] New: [14/15 Regression] AArch64: Function multiversioning initialization incorrect

[Bug target/115342] New: [14/15 Regression] AArch64: Function multiversioning initialization incorrect

[wilco at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115342

            Bug ID: 115342
           Summary: [14/15 Regression] AArch64: Function multiversioning
                    initialization incorrect
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: wilco at gcc dot gnu.org
  Target Milestone: ---

The CPU features initialization code uses CPUID registers. It uses incorrect
comparisons so that for example SVE is not set if SVE2 is available. Using
HWCAPs for these is both simpler and works correctly. The initialization must
also be done atomically so to avoid multiple threads causing corruption due to
non-atomic RMW of the global.

[Bug target/115342] [14/15 Regression] AArch64: Function multiversioning initialization incorrect

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115342

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

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

[Bug target/115342] [14/15 Regression] AArch64: Function multiversioning initialization incorrect

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115342

--- Comment #1 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Wilco Dijkstra <wilco@gcc.gnu.org>:

https://gcc.gnu.org/g:d7cbcfe7c33645eaf95f175f19884d443817857b

commit r15-1036-gd7cbcfe7c33645eaf95f175f19884d443817857b
Author: Wilco Dijkstra <wilco.dijkstra@arm.com>
Date:   Wed Jun 5 14:04:33 2024 +0100

    AArch64: Fix cpu features initialization [PR115342]

    The CPU features initialization code uses CPUID registers (rather than
    HWCAP).  The equality comparisons it uses are incorrect: for example
FEAT_SVE
    is not set if SVE2 is available.  Using HWCAPs for these is both simpler
and
    correct.  The initialization must also be done atomically to avoid multiple
    threads causing corruption due to non-atomic RMW accesses to the global.

    libgcc:
            PR target/115342
            * config/aarch64/cpuinfo.c (__init_cpu_features_constructor):
            Use HWCAP where possible.  Use atomic write for initialization.
            Fix FEAT_PREDRES comparison.
            (__init_cpu_features_resolver): Use atomic load for correct
            initialization.
            (__init_cpu_features): Likewise.

[Bug target/115342] [14/15 Regression] AArch64: Function multiversioning initialization incorrect

[ramana at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115342

Ramana Radhakrishnan <ramana at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |ramana at gcc dot gnu.org
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2024-06-20

--- Comment #2 from Ramana Radhakrishnan <ramana at gcc dot gnu.org> ---
Confirmed ?

[Bug target/115342] [14/15 Regression] AArch64: Function multiversioning initialization incorrect

[wilco at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115342

Wilco <wilco at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED

--- Comment #3 from Wilco <wilco at gcc dot gnu.org> ---
(In reply to Ramana Radhakrishnan from comment #2)
> Confirmed ?

And fixed on trunk. Will do the backport later.

[Bug target/115342] [14/15 Regression] AArch64: Function multiversioning initialization incorrect

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115342

--- Comment #4 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-14 branch has been updated by Wilco Dijkstra
<wilco@gcc.gnu.org>:

https://gcc.gnu.org/g:9421f02916676d27e24fcda918f85e359329ac69

commit r14-10338-g9421f02916676d27e24fcda918f85e359329ac69
Author: Wilco Dijkstra <wilco.dijkstra@arm.com>
Date:   Wed Jun 5 14:04:33 2024 +0100

    AArch64: Fix cpu features initialization [PR115342]

    The CPU features initialization code uses CPUID registers (rather than
    HWCAP).  The equality comparisons it uses are incorrect: for example
FEAT_SVE
    is not set if SVE2 is available.  Using HWCAPs for these is both simpler
and
    correct.  The initialization must also be done atomically to avoid multiple
    threads causing corruption due to non-atomic RMW accesses to the global.

    libgcc:
            PR target/115342
            * config/aarch64/cpuinfo.c (__init_cpu_features_constructor):
            Use HWCAP where possible.  Use atomic write for initialization.
            Fix FEAT_PREDRES comparison.
            (__init_cpu_features_resolver): Use atomic load for correct
            initialization.
            (__init_cpu_features): Likewise.
    (cherry picked from commit d7cbcfe7c33645eaf95f175f19884d443817857b)

[Bug target/115342] [14/15 Regression] AArch64: Function multiversioning initialization incorrect

[wilco at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115342

Wilco <wilco at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |FIXED
             Status|ASSIGNED                    |RESOLVED

--- Comment #5 from Wilco <wilco at gcc dot gnu.org> ---
Fixed on trunk and gcc-14 branch.