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* [gcc r12-5717] [PR103437] Use long long multiplication as backup for overflow processing
@ 2021-12-02 16:01 Vladimir Makarov
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From: Vladimir Makarov @ 2021-12-02 16:01 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:7d02c8bf75980fa2468f4167a82dd3a619e35cb4
commit r12-5717-g7d02c8bf75980fa2468f4167a82dd3a619e35cb4
Author: Vladimir N. Makarov <vmakarov@redhat.com>
Date: Thu Dec 2 10:55:59 2021 -0500
[PR103437] Use long long multiplication as backup for overflow processing
__builtin_smul_overflow can be unavailable for some C++ compilers.
Add long long multiplication as backup for overflow processing.
gcc/ChangeLog:
PR rtl-optimization/103437
* ira-color.c (setup_allocno_priorities): Use long long
multiplication as backup for overflow processing.
Diff:
---
gcc/ira-color.c | 17 +++++++++++++++++
1 file changed, 17 insertions(+)
diff --git a/gcc/ira-color.c b/gcc/ira-color.c
index 1f80cbea0e2..3b19a58e1f0 100644
--- 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;
+ }
allocno_priorities[ALLOCNO_NUM (a)] = priority;
if (priority < 0)
priority = -priority;
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