On Thu, Dec 02, 2021 at 11:03:46AM -0500, Vladimir Makarov wrote:
> --- a/gcc/ira-color.c
> +++ b/gcc/ira-color.c
> @@ -2797,6 +2797,7 @@ static void
> setup_allocno_priorities (ira_allocno_t *consideration_allocnos, int n)
> {
> int i, length, nrefs, priority, max_priority, mult, diff;
> + bool overflow_backup_p = true;
> ira_allocno_t a;
>
> max_priority = 0;
> @@ -2811,9 +2812,25 @@ setup_allocno_priorities (ira_allocno_t
> *consideration_allocnos, int n)
> diff = ALLOCNO_MEMORY_COST (a) - ALLOCNO_CLASS_COST (a);
> /* Multiplication can overflow for very large functions.
> Check the overflow and constrain the result if necessary: */
> +#ifdef __has_builtin
> +#if __has_builtin(__builtin_smul_overflow)
> + overflow_backup_p = false;
> if (__builtin_smul_overflow (mult, diff, &priority)
> || priority <= -INT_MAX)
> priority = diff >= 0 ? INT_MAX : -INT_MAX;
> +#endif
> +#endif
> + if (overflow_backup_p)
> + {
> + static_assert
> + (sizeof (long long) >= 2 * sizeof (int),
> + "overflow code does not work for such int and long long sizes");
> + long long priorityll = (long long) mult * diff;
> + if (priorityll < -INT_MAX || priorityll > INT_MAX)
> + priority = diff >= 0 ? INT_MAX : -INT_MAX;
> + else
> + priority = priorityll;
> + }
This will require that long long is at least twice as large as int
everywhere, I thought you wanted to do that only when
__builtin_smul_overflow isn't available.
That would be
#ifdef __has_builtin
#if __has_builtin(__builtin_smul_overflow)
#define HAS_SMUL_OVERFLOW
#endif
#endif
#ifdef HAS_SMUL_OVERFLOW
if (__builtin_smul_overflow (mult, diff, &priority)
|| priority <= -INT_MAX)
priority = diff >= 0 ? INT_MAX : -INT_MAX;
#else
static_assert (sizeof (long long) >= 2 * sizeof (int),
"overflow code does not work for int wider"
"than half of long long");
long long priorityll = (long long) mult * diff;
if (priorityll < -INT_MAX || priorityll > INT_MAX)
priority = diff >= 0 ? INT_MAX : -INT_MAX;
else
priority = priorityll;
#endif
Why priority <= -INT_MAX in the first case though,
shouldn't that be < -INT_MAX ?
Jakub
