On Wed, Jan 20, 2021 at 01:15:12PM +0100, Richard Biener wrote:
> OK, fixed. Guess we could also use __builtin_mul_overflow directly
> if supported via a GCC_VERSION check. Looks like it's present
> since GCC 5 at least. So sth like (incremental)
>
> diff --git a/gcc/hwint.h b/gcc/hwint.h
> index 53f4ed5dcad..6d2d491acfa 100644
> --- a/gcc/hwint.h
> +++ b/gcc/hwint.h
> @@ -354,12 +354,19 @@ add_hwi (HOST_WIDE_INT a, HOST_WIDE_INT b, bool
> *overflow)
> inline HOST_WIDE_INT
> mul_hwi (HOST_WIDE_INT a, HOST_WIDE_INT b, bool *overflow)
> {
> +#if GCC_VERSION < 5001
> unsigned HOST_WIDE_INT result = a * (unsigned HOST_WIDE_INT)b;
> - if (a != 0 && (HOST_WIDE_INT)result / a != b)
> + if ((a == -1 && b == HOST_WIDE_INT_MIN)
> + || (a != 0 && (HOST_WIDE_INT)result / a != b))
> *overflow = true;
> else
> *overflow = false;
> return result;
> +#else
> + HOST_WIDE_INT result;
> + *overflow = __builtin_mul_overflow (a, b, &result);
> + return result;
> +#endif
> }
>
> for the add case we should match all of the function I guess.
Yeah, sure.
Maybe bump somewhat the GCC_VERSION number in there, we've had bugs in
__builtin_mul_overflow expansion too.
Jakub
