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From: "haoxintu at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/103209] New: [12 Regression] wrong code at
 -O1 on x86_64-linux-gnu
Date: Fri, 12 Nov 2021 12:17:28 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D103209

            Bug ID: 103209
           Summary: [12 Regression] wrong code at -O1 on x86_64-linux-gnu
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Keywords: wrong-code
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: haoxintu at gmail dot com
  Target Milestone: ---

Hi all.

It seems to be a recent regression issue.

$cat small.c
#include <stdio.h>
#include <stdint.h>

int32_t a[6];
int64_t b;
int32_t *c;
int32_t **d =3D &c;
int64_t *e =3D &b;
int32_t **const *f =3D &d;
int32_t **const **g =3D &f;
int32_t *h();
static int16_t j();
static uint32_t k(int8_t, const int32_t *, int64_t);
static uint32_t l() {
  int32_t *m =3D &a[3];
  int32_t n =3D 0;
  int8_t o =3D 0;
  int32_t *p[] =3D {&n, &n, &n, &n};
  uint32_t q[6][1][2] =3D {};
  for (o =3D 0; o <=3D 1; o =3D 6)
    if (h(j(k(3, 0, q[2][0][0]), &n), n) =3D=3D p[3])
      *m =3D *e;
  return 0;
}
int32_t *h(uint32_t, int32_t) { return ***g; }
int16_t j(uint32_t, int32_t *r) { **f =3D r; }
uint32_t k(int8_t, const int32_t *, int64_t) { *e =3D 3; return 0;}
int main() {
  int i =3D 0;
  l();
  for (i =3D 0; i < 6; i++){
    if (i =3D=3D 3)
        printf("%d\n", a[i]);
  }
  return 0;
}

$gcc -O1 small.c ; ./a.out
0

$gcc -O0 small.c ; ./a.out
3

$gcc -O2 small.c ; ./a.out
3

$gcc -v
Using built-in specs.
COLLECT_GCC=3Dgcc
COLLECT_LTO_WRAPPER=3D/home/haoxin/haoxin-data/compilers/gcc/build/libexec/=
gcc/x86_64-pc-linux-gnu/12.0.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with:../configure
--prefix=3D/home/haoxin/haoxin-data/compilers/gcc/build/ --enable-bootstrap
--enable-checking=3Drelease --enable-languages=3Dc,c++ --enable-multilib :
(reconfigured) ../configure
--prefix=3D/home/haoxin/haoxin-data/compilers/gcc/build/ --enable-bootstrap
--enable-checking=3Drelease --enable-multilib --enable-languages=3Dc,c++,lto
--no-create --no-recursion
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 12.0.0 20211112 (experimental) (GCC)=20

Thanks,
Haoxin=