[Bug tree-optimization/118154] New: [15 Regression] RISC-V: Miscompile with -march=rv64gcv -O3 since 15-5117-g0b27a7dd050

[patrick at rivosinc dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=118154

            Bug ID: 118154
           Summary: [15 Regression] RISC-V: Miscompile with -march=rv64gcv
                    -O3 since 15-5117-g0b27a7dd050
           Product: gcc
           Version: 15.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: patrick at rivosinc dot com
  Target Milestone: ---

Testcase:
long a;
signed char b;
long long d;
signed char c[22][22][484];
void m(long long *l, int n) { *l ^= n + (*l >> 2); }
int main() {
  signed char l = 35;
  for (signed char f = 4; f; f++) {
    for (signed g = 0; g < 022; g += 4)
      for (signed char h = 0; h < 022; h++) {
        c[9][g][h * 22 + h] = l;
        a = ({ a > 4095 ? a : 4095; });
      }
    for (int i = 0; i < 22; i += 3)
      for (signed char j = 1; j; j++)
        for (signed char k = 0; k < 022; k++)
          b = ({ b > 19 ? b : 19; });
  }
  for (long f = 0; f < 22; ++f)
    for (long g = 0; g < 22; ++g)
      for (long h = 0; h < 22; ++h)
        for (long i = 0; i < 22; ++i)
          m(&d, c[f][g][h * 2 + i]);
  if (d != 38)
    return 1;
}

Commands:
/scratch/tc-testing/tc-compiler-fuzz-bisect/build-rv64gcv/bin/riscv64-unknown-linux-gnu-gcc
-march=rv64gcv -O3 test.c -o user-config.out -fno-strict-aliasing -fwrapv
QEMU_CPU=rv64,vlen=128,rvv_ta_all_1s=true,rvv_ma_all_1s=true,v=true,vext_spec=v1.0,zve32f=true,zve32x=true,zve64d=true,zve64f=true,zve64x=true
timeout --verbose -k 0.1 4
/scratch/tc-testing/tc-compiler-fuzz-trunk/build-gcv/bin/qemu-riscv64
user-config.out

Found via fuzzer

First bad commit: r15-5117-g0b27a7dd050