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From: "asolokha at gmx dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug debug/106955] New: [13 Regression] '-fcompare-debug' failure w/
 -std=c++20 -O1 -ftree-parallelize-loops=2 -fno-ipa-sra --param
 ggc-min-expand=55
Date: Fri, 16 Sep 2022 10:31:31 +0000
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: debug
X-Bugzilla-Version: 13.0
X-Bugzilla-Keywords: compare-debug-failure
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X-Bugzilla-Who: asolokha at gmx dot com
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D106955

            Bug ID: 106955
           Summary: [13 Regression] '-fcompare-debug' failure w/
                    -std=3Dc++20 -O1 -ftree-parallelize-loops=3D2 -fno-ipa-=
sra
                    --param ggc-min-expand=3D55
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Keywords: compare-debug-failure
          Severity: normal
          Priority: P3
         Component: debug
          Assignee: unassigned at gcc dot gnu.org
          Reporter: asolokha at gmx dot com
  Target Milestone: ---

Created attachment 53582
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=3D53582&action=3Dedit
gkd diff

g++ 13.0.0 20220911 snapshot (g:0ea5e3f4542832b8da016b152695e64a2a386309) f=
ails
-fcompare-debug check when compiling the following testcase, reduced from
test/std/containers/sequences/forwardlist/forwardlist.ops/sort.pass.cpp from
the libc++ 14.0.6 test suite, w/ -std=3Dc++20 -O1 -ftree-parallelize-loops=
=3D2
-fno-ipa-sra --param ggc-min-expand=3D55:

#include <forward_list>
#include <iterator>
#include <algorithm>
#include <vector>

void
test_stable ()
{
  std::vector<int> v;

  for (int i =3D 0; i < 1000; ++i)
    v.push_back (i);

  for (int i =3D 0; i < 1000; ++i)
    v[i] =3D i;
}

% g++-13.0.0 -std=3Dc++20 -O1 -fcompare-debug -ftree-parallelize-loops=3D2
-fno-ipa-sra --param ggc-min-expand=3D55 -c dfptqjrz.cpp
g++-13.0.0: error: dfptqjrz.cpp: '-fcompare-debug' failure

gkd diff attached.

Preprocessed testcase is still being reduced, currently at
06:43:08 INFO (66.7%, 468334 bytes, 7781 lines)
I'll post it here once the reducer yields something meaningful under several
kilobytes in size.=