r12-4526 cancelled jump thread path rotates loop. It exposes a issue in
profile-estimate when predict_extra_loop_exits, outer loop's exit edge
is marked as inner loop's extra loop exit and set with incorrect
prediction, then a hot inner loop will become cold loop finally through
optimizations, this patch ignores the EDGE_DFS_BACK edge when searching
extra exit edges to avoid unexpected predict_edge.
gcc/ChangeLog:
PR middle-end/103270
* predict.c (predict_extra_loop_exits): Ignore EDGE_DFS_BACK edge.
gcc/ChangeLog:
PR middle-end/103270
* predict.c (predict_extra_loop_exits): New.
---
gcc/predict.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/gcc/predict.c b/gcc/predict.c
index 68b11135680..1ae8ccff72c 100644
--- a/gcc/predict.c
+++ b/gcc/predict.c
@@ -1910,6 +1910,10 @@ predict_extra_loop_exits (edge exit_edge)
continue;
if ((check_value_one ^ integer_onep (val)) == 1)
continue;
+#if 0
+ if (e->flags & EDGE_DFS_BACK)
+ continue;
+#endif
if (EDGE_COUNT (e->src->succs) != 1)
{
predict_paths_leading_to_edge (e, PRED_LOOP_EXTRA_EXIT, NOT_TAKEN);
--
2.25.1
