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From: "patrick at rivosinc dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/114668] New: [14] RISC-V rv64gcv: miscompile at -O3
Date: Tue, 09 Apr 2024 21:55:46 +0000
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X-Bugzilla-Version: 14.0
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D114668

            Bug ID: 114668
           Summary: [14] RISC-V rv64gcv: miscompile at -O3
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: patrick at rivosinc dot com
  Target Milestone: ---

Testcase:
char a;
int b;
short e[14];
char f[4][12544];
_Bool c[4][5];
int main() {
  for (int i =3D 0; i < 4; ++i)
    for (int l =3D 0; l < 15; ++l)
      for (int m =3D 0; m < 15; ++m)
        f[i][l * m] =3D 3;
  for (int j =3D 0; j < 4; j +=3D 1)
    for (int k =3D 3; k < 13; k +=3D 3)
      for (_Bool l =3D 0; l < 1; l =3D 1)
        for (int m =3D 0; m < 4; m +=3D 1) {
          a =3D 0;
          b -=3D e[k];
          c[j][m] =3D f[j][6];
        }
  for (long i =3D 2; i < 4; ++i)
    __builtin_printf("%X\n", c[3][3]);
}

Commands:
> /scratch/tc-testing/tc-apr-9/build-rv64gcv/bin/riscv64-unknown-linux-gnu-=
gcc -march=3Drv64gcv -O3 red.c -o red.out
> /scratch/tc-testing/tc-apr-9/build-rv64gcv/bin/qemu-riscv64 red.out
1
FF

> /scratch/tc-testing/tc-apr-9/build-rv64gcv/bin/riscv64-unknown-linux-gnu-=
gcc -march=3Drv64gcv -O2 red.c -o red.out
> /scratch/tc-testing/tc-apr-9/build-rv64gcv/bin/qemu-riscv64 red.out
1
1

Adjusting the f array to its minimal size of f[4][255] makes the issue go a=
way.

Looks similar to pr114665 so this might be a duplicate/related. Submitting =
this
bug in case it's easier to understand the root cause.

Found via fuzzer.=