From f0b3c57ea6b87f51eb0a9bfd7c4438625cb7ed17 Mon Sep 17 00:00:00 2001
From: Jan Hubicka <hubicka@ucw.cz>
Date: Mon, 30 Jun 2025 09:14:46 +0200
Subject: [PATCH] Re-add logic to mitigate some afdo profile inconsistencies

This patch re-adds logic to increase counts of annotated basic blocks if otherwise
the Kirhoff law can not be solved.  This is done only in easy cases where total
count of in or out edges is smaller than the count of BB or when BB has single
exit which is annotated by small count.

This helps to solve problems seen i.e. in parest where header of loops gets too
low count because vectorizer replaced the IV condiitonal and did not preserved
debug info.  We should solve the debug info issues as well, and simiar problems
can now be tracked by in afdo debug dumps.

gcc/ChangeLog:

	* auto-profile.cc (autofdo_source_profile::offline_external_functions):
	Add missing newline in dump.
	(afdo_propagate_edge): If annotated BB or edge has too small count
	bump it up to mitigate profile imprecisions caused by vectorizer.
	(afdo_propagate): Increase number of iteraitons and fix dump
---
 gcc/auto-profile.cc | 43 ++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 40 insertions(+), 3 deletions(-)

diff --git a/gcc/auto-profile.cc b/gcc/auto-profile.cc
index 44e7faa8fee..d78f2cb42b5 100644
--- a/gcc/auto-profile.cc
+++ b/gcc/auto-profile.cc
@@ -1308,7 +1308,7 @@ autofdo_source_profile::offline_external_functions ()
 	      if (dump_file)
 		fprintf (dump_file,
 			 "string table in auto-profile contains"
-			 " duplicated name %s", n1);
+			 " duplicated name %s\n", n1);
 	      to_symbol_name.put (i, index);
 	    }
 	  continue;
@@ -2491,6 +2491,21 @@ afdo_propagate_edge (bool is_succ, bb_set *annotated_bb)
 	set_bb_annotated (bb, annotated_bb);
 	changed = true;
       }
+    else if (is_bb_annotated (bb, *annotated_bb)
+	     && bb->count < total_known_count)
+      {
+	if (dump_file)
+	  {
+	    fprintf (dump_file, "  Increasing bb %i count from ",
+		     bb->index);
+	    bb->count.dump (dump_file);
+	    fprintf (dump_file, " to ");
+	    total_known_count.dump (dump_file);
+	    fprintf (dump_file, " hoping to mitigate afdo inconsistency\n");
+	  }
+	bb->count = total_known_count;
+	changed = true;
+      }
     else if (num_unknown_edges == 1 && is_bb_annotated (bb, *annotated_bb))
       {
 	if (bb->count > total_known_count)
@@ -2533,6 +2548,27 @@ afdo_propagate_edge (bool is_succ, bb_set *annotated_bb)
 	      }
 	  }
       }
+    else if (num_unknown_edges == 0
+	     && is_bb_annotated (bb, *annotated_bb)
+	     && (is_succ ? single_succ_p (bb) : single_pred_p (bb)))
+      {
+	edge e = is_succ ? single_succ_edge (bb) : single_pred_edge (bb);
+	if (AFDO_EINFO (e)->is_annotated ()
+	    && AFDO_EINFO (e)->get_count () < bb->count)
+	  {
+	    if (dump_file)
+	      {
+		fprintf (dump_file, "  Increasing edge %i->%i count from ",
+			 e->src->index, e->dest->index);
+		AFDO_EINFO (e)->get_count ().dump (dump_file);
+		fprintf (dump_file, " to ");
+		bb->count.dump (dump_file);
+		fprintf (dump_file, " hoping to mitigate afdo inconsistency\n");
+	      }
+	    AFDO_EINFO (e)->set_count (bb->count);
+	    changed = true;
+	  }
+      }
   }
   return changed;
 }
@@ -2662,10 +2698,11 @@ afdo_propagate (bb_set *annotated_bb)
 		     ((basic_block)bb->aux)->index,
 		     bb->index);
 	    bb->count.dump (dump_file);
+	    fprintf (dump_file, "\n");
 	  }
       }
 
-  while (changed && i++ < 10)
+  while (changed && i++ < 100)
     {
       changed = false;
 
@@ -2676,7 +2713,7 @@ afdo_propagate (bb_set *annotated_bb)
       afdo_propagate_circuit (*annotated_bb);
     }
   if (dump_file)
-    fprintf (dump_file, "Propated in %i iterations %s\n",
+    fprintf (dump_file, "Propagation took %i iterations %s\n",
 	     i, changed ? "; iteration limit reached\n" : "");
 }
 
-- 
2.47.2