[llvm-bugs] [Bug 142004] [RISC-V] Miscompile on -O[1-3]

[LLVM Bugs via llvm-bugs]

Issue	142004
Summary	[RISC-V] Miscompile on -O[1-3]
Labels	new issue
Assignees
Reporter	ewlu

    Testcase:
```c
unsigned short b;
long long n;
long d;
long f;
int i;
unsigned short a = 293;
int main() {
  a = a < ((unsigned short)((unsigned char)~f | (d ?: 0)));
  b = i;
  n ^= a;
  n ^= b;
  __builtin_printf("%llu\n", n);
}
```

Commands:
```
# O3
$ /scratch/ewlu/daily-upstream-build/build-gcv/bin/clang -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/ewlu/daily-upstream-build/build-gcv/bin/qemu-riscv64 user-config.out 1
1

# O2
$ /scratch/ewlu/daily-upstream-build/build-gcv/bin/clang -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/ewlu/daily-upstream-build/build-gcv/bin/qemu-riscv64 user-config.out 1
1

# O1 
$ /scratch/ewlu/daily-upstream-build/build-gcv/bin/clang -O1 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/ewlu/daily-upstream-build/build-gcv/bin/qemu-riscv64 user-config.out 1
1

# O0 
$ /scratch/ewlu/daily-upstream-build/build-gcv/bin/clang -O0 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/ewlu/daily-upstream-build/build-gcv/bin/qemu-riscv64 user-config.out 1
0
```

First detected 5/23/2025. I haven't been able to bisect the commit which caused the error. Went back several release versions with my bisect script and error kept appearing. I'm hoping it's not an environment thing?

Found via fuzzer.

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