2013-10-02 Teresa Johnson <tejohnson@google.com>

	* predict.c (probably_never_executed): New function.
	(probably_never_executed_bb_p): Invoke probably_never_executed.
	(probably_never_executed_edge_p): Ditto.
	* bb-reorder.c (find_rarely_executed_basic_blocks_and_crossing_edges):
	Treat profile insanities conservatively.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@203152 138bc75d-0d04-0410-961f-82ee72b054a4

3 files changed, 43 insertions, 14 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index e614e8ee7ed..1a3aff53ed5 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,11 @@
+2013-10-02  Teresa Johnson  <tejohnson@google.com>
+
+	* predict.c (probably_never_executed): New function.
+	(probably_never_executed_bb_p): Invoke probably_never_executed.
+	(probably_never_executed_edge_p): Ditto.
+	* bb-reorder.c (find_rarely_executed_basic_blocks_and_crossing_edges):
+	Treat profile insanities conservatively.
+
 2013-10-02  John David Anglin  <danglin@gcc.gnu.org>
 
 	* config.gcc (hppa*64*-*-linux*): Don't add pa/t-linux to tmake_file.
diff --git a/gcc/bb-reorder.c b/gcc/bb-reorder.c
index b89f9855e77..c5a42d359dc 100644
--- a/gcc/bb-reorder.c
+++ b/gcc/bb-reorder.c
@@ -1564,8 +1564,24 @@ find_rarely_executed_basic_blocks_and_crossing_edges (void)
   /* Mark which partition (hot/cold) each basic block belongs in.  */
   FOR_EACH_BB (bb)
     {
+      bool cold_bb = false;
+
       if (probably_never_executed_bb_p (cfun, bb))
         {
+          /* Handle profile insanities created by upstream optimizations
+             by also checking the incoming edge weights. If there is a non-cold
+             incoming edge, conservatively prevent this block from being split
+             into the cold section.  */
+          cold_bb = true;
+          FOR_EACH_EDGE (e, ei, bb->preds)
+            if (!probably_never_executed_edge_p (cfun, e))
+              {
+                cold_bb = false;
+                break;
+              }
+        }
+      if (cold_bb)
+        {
           BB_SET_PARTITION (bb, BB_COLD_PARTITION);
           cold_bb_count++;
         }
diff --git a/gcc/predict.c b/gcc/predict.c
index 4815e75248e..2909117ef6b 100644
--- a/gcc/predict.c
+++ b/gcc/predict.c
@@ -226,23 +226,26 @@ maybe_hot_edge_p (edge e)
 }
 
 
-/* Return true in case BB is probably never executed.  */
 
-bool
-probably_never_executed_bb_p (struct function *fun, const_basic_block bb)
+/* Return true if profile COUNT and FREQUENCY, or function FUN static
+   node frequency reflects never being executed.  */
+   
+static bool
+probably_never_executed (struct function *fun,
+                         gcov_type count, int frequency)
 {
   gcc_checking_assert (fun);
   if (profile_status_for_function (fun) == PROFILE_READ)
     {
-      if ((bb->count * 4 + profile_info->runs / 2) / profile_info->runs > 0)
+      if ((count * 4 + profile_info->runs / 2) / profile_info->runs > 0)
 	return false;
-      if (!bb->frequency)
+      if (!frequency)
 	return true;
       if (!ENTRY_BLOCK_PTR->frequency)
 	return false;
       if (ENTRY_BLOCK_PTR->count && ENTRY_BLOCK_PTR->count < REG_BR_PROB_BASE)
 	{
-	  return (RDIV (bb->frequency * ENTRY_BLOCK_PTR->count,
+	  return (RDIV (frequency * ENTRY_BLOCK_PTR->count,
 		        ENTRY_BLOCK_PTR->frequency)
 		  < REG_BR_PROB_BASE / 4);
 	}
@@ -256,19 +259,21 @@ probably_never_executed_bb_p (struct function *fun, const_basic_block bb)
 }
 
 
+/* Return true in case BB is probably never executed.  */
+
+bool
+probably_never_executed_bb_p (struct function *fun, const_basic_block bb)
+{
+  return probably_never_executed (fun, bb->count, bb->frequency);
+}
+
+
 /* Return true in case edge E is probably never executed.  */
 
 bool
 probably_never_executed_edge_p (struct function *fun, edge e)
 {
-  gcc_checking_assert (fun);
-  if (profile_info && flag_branch_probabilities)
-    return ((e->count + profile_info->runs / 2) / profile_info->runs) == 0;
-  if ((!profile_info || !flag_branch_probabilities)
-      && (cgraph_get_node (fun->decl)->frequency
-	  == NODE_FREQUENCY_UNLIKELY_EXECUTED))
-    return true;
-  return false;
+  return probably_never_executed (fun, e->count, EDGE_FREQUENCY (e));
 }
 
 /* Return true if NODE should be optimized for size.  */