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From: "johnnybit at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug c/101262] New: GCC11 OpenMP optimization causes sigsegv on
 aligned constant array in darktable
Date: Tue, 29 Jun 2021 17:21:05 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D101262

            Bug ID: 101262
           Summary: GCC11 OpenMP optimization causes sigsegv on aligned
                    constant array in darktable
           Product: gcc
           Version: 11.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: johnnybit at gmail dot com
  Target Milestone: ---

A loop with constant length arrays with openmp and simd optimization crashes
with sigsegv when compilled with GCC11. Same code works with previous versi=
ons
and with various Clang versions

the code in question looks like

#define PIXEL_CHAN 8

static const float centers_ops[PIXEL_CHAN] DT_ALIGNED_ARRAY =3D {-56.0f / 7=
.0f,
// =3D -8.0f
                                                               -48.0f / 7.0=
f,
                                                               -40.0f / 7.0=
f,
                                                               -32.0f / 7.0=
f,
                                                               -24.0f / 7.0=
f,
                                                               -16.0f / 7.0=
f,
                                                                -8.0f / 7.0=
f,
                                                                 0.0f / 7.0=
f};

#pragma omp simd aligned(centers_ops, factors:64) safelen(PIXEL_CHAN)
reduction(+:result)
  for(int i =3D 0; i < PIXEL_CHAN; ++i)
    result +=3D gaussian_func(expo - centers_ops[i], gauss_denom) * factors=
[i];


centers_ops is static const float [PIXEL_CHAN]
factors is const float *const restric factors (which is PIXEL_CHAN length)

the crash is on

result +=3D gaussian_func(expo - centers_ops[i], gauss_denom) * factors[i];

line.

The reports in darktable are=20
https://github.com/darktable-org/darktable/issues/9340
https://github.com/darktable-org/darktable/issues/9002=