https://gcc.gnu.org/g:9399a3b5f512af6dbbe05be076e726efc91413f1
commit r16-1183-g9399a3b5f512af6dbbe05be076e726efc91413f1
Author: Jan Hubicka <hubi...@ucw.cz>
Date: Thu Jun 5 15:24:36 2025 +0200
Fix handling of GUESSED_LOCAL in auto-fdo and preserve more static profile
This patch fixes ICE where GUESSED_LOCAL was kept in autofdo profile.
It may make more sense to turn GESSED_LOCAL 0 to GUESSED 0 since it seems
bit more informative then autofdo 0 (which really means that count is below
the 2% threshold or that info was lost due to some code transformation).
The patch also modifies code setting probabilities of edge to keep reliable
predictions of 0 or 1.
gcc/ChangeLog:
* auto-profile.cc (update_count_by_afdo_count): Fix handling
of GUESSED_LOCAL.
(afdo_calculate_branch_prob): Preserve static profile for
probabilities 0 and 1.
Diff:
---
gcc/auto-profile.cc | 20 +++++++++++++++++---
1 file changed, 17 insertions(+), 3 deletions(-)
diff --git a/gcc/auto-profile.cc b/gcc/auto-profile.cc
index 215dadf87c21..91b1e97f5bb4 100644
--- a/gcc/auto-profile.cc
+++ b/gcc/auto-profile.cc
@@ -1120,7 +1120,8 @@ update_count_by_afdo_count (profile_count *count,
gcov_type c)
/* In case we have guessed profile which is already zero, preserve
quality info. */
else if (count->nonzero_p ()
- || count->quality () == GUESSED)
+ || count->quality () == GUESSED
+ || count->quality () == GUESSED_LOCAL)
*count = profile_count::zero ().afdo ();
}
@@ -1515,8 +1516,21 @@ afdo_calculate_branch_prob (bb_set *annotated_bb)
if (num_unknown_succ == 0 && total_count.nonzero_p ())
{
FOR_EACH_EDGE (e, ei, bb->succs)
- e->probability
- = AFDO_EINFO (e)->get_count ().probability_in (total_count);
+ {
+ /* If probability is 1, preserve reliable static prediction
+ (This is, for example the case of single fallthru edge
+ or single fallthru plus unlikely EH edge.) */
+ if (AFDO_EINFO (e)->get_count () == total_count ()
+ && e->probability == profile_probability::always ())
+ ;
+ else if (AFDO_EINFO (e)->get_count ().nonzero_p ())
+ e->probability
+ = AFDO_EINFO (e)->get_count ().probability_in (total_count);
+ /* If probability is zero, preserve reliable static prediction. */
+ else if (e->probability.nonzero_p ()
+ || e->probability.quality () == GUESSED)
+ e->probability = profile_probability::never ().afdo ();
+ }
}
}
FOR_ALL_BB_FN (bb, cfun)
