https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114666
Bug ID: 114666
Summary: [14 Regression] Signed single bit comparison
miscompile at -O2
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: middle-end
Assignee: unassigned at gcc dot gnu.org
Reporter: patrick at rivosinc dot com
Target Milestone: ---
Testcase:
struct {
signed a : 1;
} b = {-1};
char c;
int main()
{
if ((b.a ^ 1UL) < 3)
__builtin_abort();
}
Commands:
> /scratch/tc-testing/tc-apr-9/build-rv64gcv/bin/riscv64-unknown-linux-gnu-gcc
> -O2 red.c -o red.out
> /scratch/tc-testing/tc-apr-9/build-rv64gcv/bin/qemu-riscv64 red.out
zsh: IOT instruction (core dumped)
/scratch/tc-testing/tc-apr-9/build-rv64gcv/bin/qemu-riscv64 red.out
> /scratch/tc-testing/tc-apr-9/build-rv64gcv/bin/riscv64-unknown-linux-gnu-gcc
> -O1 red.c -o red.out
> /scratch/tc-testing/tc-apr-9/build-rv64gcv/bin/qemu-riscv64 red.out
> echo $?
0
Godbolt showing the same issue on x86: https://godbolt.org/z/1dx8YKG3e
Discovered/tested using r14-9877-g1f719aa7c0d (not bisected)
Found via fuzzer.
