Make profile update in inlining more robust

Make profile update in inlining more robust

[Jan Hubicka]

Hi,
when inlining last copy of function, we assume that the counts are already correct,
because all other execution paths has been inlined earlier.  While this is true in
simple cases of static functions, it can be wrong for comdats where we optimize
out the last copy but during training run we may have collected execution counts
from other units.  This could then resuit in quite large profile inconsistencies
and thus it is better to fix.

Of course this is not perfect if some offline copy of function is later produced,
because that one will have zero counts.  I do not think there is easy solution
for this problem except for LTO or possibly arranging profile counts of different
copies of same comdat to be shared which we don't have infrastructure for.

Bootstrapped/regtested x86_64-linux,
comitted.

Honza

	* ipa-inline-transform.c (update_noncloned_frequencies): Update also
	counts.
	(clone_inlined_nodes): Update.
Index: ipa-inline-transform.c
===================================================================
--- ipa-inline-transform.c	(revision 249227)
+++ ipa-inline-transform.c	(working copy)
@@ -54,10 +54,12 @@ int nfunctions_inlined;
 /* Scale frequency of NODE edges by FREQ_SCALE.  */
 
 static void
-update_noncloned_frequencies (struct cgraph_node *node,
-			      int freq_scale)
+update_noncloned_frequencies (struct cgraph_node *node, 
+			      int freq_scale, profile_count num,
+			      profile_count den)
 {
   struct cgraph_edge *e;
+  bool scale = (num == profile_count::zero () || den > 0);
 
   /* We do not want to ignore high loop nest after freq drops to 0.  */
   if (!freq_scale)
@@ -68,14 +70,20 @@ update_noncloned_frequencies (struct cgr
       if (e->frequency > CGRAPH_FREQ_MAX)
         e->frequency = CGRAPH_FREQ_MAX;
       if (!e->inline_failed)
-        update_noncloned_frequencies (e->callee, freq_scale);
+        update_noncloned_frequencies (e->callee, freq_scale, num, den);
+      if (scale)
+	e->count = e->count.apply_scale (num, den);
     }
   for (e = node->indirect_calls; e; e = e->next_callee)
     {
       e->frequency = e->frequency * (gcov_type) freq_scale / CGRAPH_FREQ_BASE;
       if (e->frequency > CGRAPH_FREQ_MAX)
         e->frequency = CGRAPH_FREQ_MAX;
+      if (scale)
+	e->count = e->count.apply_scale (num, den);
     }
+  if (scale)
+    node->count = node->count.apply_scale (num, den);
 }
 
 /* We removed or are going to remove the last call to NODE.
@@ -212,7 +220,8 @@ clone_inlined_nodes (struct cgraph_edge
 	    }
 	  duplicate = false;
 	  e->callee->externally_visible = false;
-          update_noncloned_frequencies (e->callee, e->frequency);
+          update_noncloned_frequencies (e->callee, e->frequency,
+					e->count, e->callee->count);
 
 	  dump_callgraph_transformation (e->callee, inlining_into,
 					 "inlining to");