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From: "kugan at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/114653] New: Not vectoring the loop with openmp
 reduction.
Date: Tue, 09 Apr 2024 09:53:59 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D114653

            Bug ID: 114653
           Summary: Not vectoring the loop with openmp reduction.
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: kugan at gcc dot gnu.org
  Target Milestone: ---

Created attachment 57910
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=3D57910&action=3Dedit
testcase

Main loop in the attached test case is not vectorized with -fopenmp. It gets
vectorized with -fopenmp-simd.

In the case of -fopenmp reduction variables lax,lay,laz gets assigned to an
array. data reference calculation for this seem to fail. See:

        offset from base address: (ssizetype) ((sizetype) _20 * 4)
        constant offset from base address: 0
        step: 0
        base alignment: 16
        base misalignment: 0
        offset alignment: 4
        step alignment: 128
        base_object: D.4806[_20]
Creating dr for D.4808[_20]
analyze_innermost: Applying pattern match.pd:219, generic-match-1.cc:3190
test.cpp:37:9: missed:  failed: evolution of offset is not affine.


command used:=20
 test.cpp -Ofast -fopenmp -mcpu=3Dneoverse-v2


gcc -v:
Using built-in specs.
COLLECT_GCC=3D/home/kvivekananda/install/bin/gcc
COLLECT_LTO_WRAPPER=3D/home/kvivekananda/install/libexec/gcc/aarch64-unknow=
n-linux-gnu/14.0.1/lto-wrapper
Target: aarch64-unknown-linux-gnu
Configured with: ../gcc/configure --enable-multiarch=3Dyes
--enable-languages=3Dc,c++,fortran,lto --disable-bootstrap
--prefix=3D/home/kvivekananda/install
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 14.0.1 20240314 (experimental) (GCC)=