[Bug target/116039] New: [15] rv64gc miscompile at -O3 with -fno-strict-aliasing since r15-1901-g98914f9eba5

[patrick at rivosinc dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116039

            Bug ID: 116039
           Summary: [15] rv64gc miscompile at -O3 with
                    -fno-strict-aliasing since r15-1901-g98914f9eba5
           Product: gcc
           Version: 15.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: patrick at rivosinc dot com
  Target Milestone: ---

Testcase:
int c[12];
char d[12];
int *f = c;
int *z = (int *)1;
long long y;
int main() {
  c[9] = 0xff;
  for (int i = 0; i < 12; i += 3)
    d[9] = z ? f[i] : 0;
  for (long i = 0; i < 12; ++i)
    y ^= d[i];
  __builtin_printf("%llu\n", y);
}

Commands:
> /scratch/tc-testing/tc-compiler-fuzz-trunk/build-gcv/bin/riscv64-unknown-linux-gnu-gcc
>  -O3 red.c -o user-config.out -fsigned-char -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,zve64f=true
>  timeout --verbose -k 0.1 4 
> /scratch/tc-testing/tc-compiler-fuzz-trunk/build-gcv/bin/qemu-riscv64 
> user-config.out
255
> /scratch/tc-testing/tc-compiler-fuzz-trunk/build-gcv/bin/riscv64-unknown-linux-gnu-gcc
>  -O2 red.c -o user-config.out -fsigned-char -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,zve64f=true
>  timeout --verbose -k 0.1 4 
> /scratch/tc-testing/tc-compiler-fuzz-trunk/build-gcv/bin/qemu-riscv64 
> user-config.out
18446744073709551615

First bad commit: r15-1901-g98914f9eba5

Found via fuzzer.