[PATCH 2/2] ipa-cp: Improve updating behavior when profile counts have gone bad

[Martin Jambor]

Hi,

Looking into the behavior of profile count updating in PR 107925, I
noticed that an option not considered possible was actually happening,
and - with the guesswork in place to distribute unexplained counts -
it simply can happen.  Currently it is handled by dropping the counts
to local estimated zero, whereas it is probably better to leave the
count as they are but drop the category to GUESSED_GLOBAL0 - which is
what profile_count::combine_with_ipa_count in a similar case (or so I
hope :-)

Profiled-LTO-bootstrapped and normally bootstrapped and tested on an
x86_64-linux.  OK for master once stage1 opens up?  Or perhaps even now?

Thanks,

Martin


gcc/ChangeLog:

2023-02-20  Martin Jambor  <mjam...@suse.cz>

        PR ipa/107925
        * ipa-cp.cc (update_profiling_info): Drop counts of orig_node to
        global0 instead of zeroing when it does not have as many counts as
        it should.
---
 gcc/ipa-cp.cc | 29 ++++++++++++++++++++++-------
 1 file changed, 22 insertions(+), 7 deletions(-)

diff --git a/gcc/ipa-cp.cc b/gcc/ipa-cp.cc
index 5a6b41cf2d6..6477bb840e5 100644
--- a/gcc/ipa-cp.cc
+++ b/gcc/ipa-cp.cc
@@ -4969,10 +4969,20 @@ update_profiling_info (struct cgraph_node *orig_node,
                                              false);
   new_sum = stats.count_sum;
 
+  bool orig_edges_processed = false;
   if (new_sum > orig_node_count)
     {
-      /* TODO: Perhaps this should be gcc_unreachable ()?  */
-      remainder = profile_count::zero ().guessed_local ();
+      /* TODO: Profile has alreay gone astray, keep what we have but lower it
+        to global0 category.  */
+      remainder = orig_node->count.global0 ();
+
+      for (cgraph_edge *cs = orig_node->callees; cs; cs = cs->next_callee)
+       cs->count = cs->count.global0 ();
+      for (cgraph_edge *cs = orig_node->indirect_calls;
+          cs;
+          cs = cs->next_callee)
+       cs->count = cs->count.global0 ();
+      orig_edges_processed = true;
     }
   else if (stats.rec_count_sum.nonzero_p ())
     {
@@ -5070,11 +5080,16 @@ update_profiling_info (struct cgraph_node *orig_node,
   for (cgraph_edge *cs = new_node->indirect_calls; cs; cs = cs->next_callee)
     cs->count = cs->count.apply_scale (new_sum, orig_new_node_count);
 
-  profile_count::adjust_for_ipa_scaling (&remainder, &orig_node_count);
-  for (cgraph_edge *cs = orig_node->callees; cs; cs = cs->next_callee)
-    cs->count = cs->count.apply_scale (remainder, orig_node_count);
-  for (cgraph_edge *cs = orig_node->indirect_calls; cs; cs = cs->next_callee)
-    cs->count = cs->count.apply_scale (remainder, orig_node_count);
+  if (!orig_edges_processed)
+    {
+      profile_count::adjust_for_ipa_scaling (&remainder, &orig_node_count);
+      for (cgraph_edge *cs = orig_node->callees; cs; cs = cs->next_callee)
+       cs->count = cs->count.apply_scale (remainder, orig_node_count);
+      for (cgraph_edge *cs = orig_node->indirect_calls;
+          cs;
+          cs = cs->next_callee)
+       cs->count = cs->count.apply_scale (remainder, orig_node_count);
+    }
 
   if (dump_file)
     {
-- 
2.39.1