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From: "vsevolod.livinskij at frtk dot ru" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/103037] New: [11/12 Regression] Wrong code
 with -O2
Date: Tue, 02 Nov 2021 07:17:23 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D103037

            Bug ID: 103037
           Summary: [11/12 Regression] Wrong code with -O2
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: vsevolod.livinskij at frtk dot ru
  Target Milestone: ---

Link to the Compiler Explorer: https://godbolt.org/z/eaGzsPnax

Reproducer:
#include <stdio.h>

short var_3 =3D 2;
unsigned char var_9 =3D 23;
unsigned short var_11;
unsigned short arr_4 [23];

void test() __attribute__((noipa));

const unsigned short &min(unsigned short &d, const unsigned short &e) {
  return e < d ? e : d;
}

void test() {
  for (int a =3D 0; a < var_9; a +=3D 3)
      var_11 =3D min(arr_4[a], 1) / (arr_4[a] ? arr_4[a] : var_3);
}


int main() {
    for (size_t i_0 =3D 0; i_0 < 23; ++i_0)
        arr_4 [i_0] =3D 2;
    test();
    printf("%hu\n", var_11);
    if (var_11 !=3D 0)
        __builtin_abort();

}

Error:
>$ g++ driver.cpp -O0 && ./a.out
0
>$ g++ driver.cpp -O2 && ./a.out
1

GCC version:
Using built-in specs.
COLLECT_GCC=3Dg++
COLLECT_LTO_WRAPPER=3D/testing/gcc/bin_master/libexec/gcc/x86_64-pc-linux-g=
nu/12.0.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: /testing/gcc/gcc_src_master/configure --enable-multilib
--prefix=3D/testing/gcc/bin_master --disable-bootstrap
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 12.0.0 20211101 (679652a77da60078392a834ed4b6b910127dbf24) (GCC=
)=