cfgbuild.c (find_bb_boundaries): Initialize profile of split blocks.

	* cfgbuild.c (find_bb_boundaries): Initialize profile of split blocks.
	(compute_outgoing_frequencies): Also initialize zero counts.
	(find_many_sub_basic_blocks): Do not produce uninitialized profile
	around loops; preserve more of profile when nothing changes.

From-SVN: r248945

1 files changed, 47 insertions, 4 deletions

diff --git a/gcc/cfgbuild.c b/gcc/cfgbuild.c
index a4004f8..f4a4d08 100644
--- a/gcc/cfgbuild.c
+++ b/gcc/cfgbuild.c
@@ -475,6 +475,10 @@ find_bb_boundaries (basic_block bb)
 
 	  bb = fallthru->dest;
 	  remove_edge (fallthru);
+	  /* BB is unreachable at this point - we need to determine its profile
+	     once edges are built.  */
+	  bb->frequency = 0;
+	  bb->count = profile_count::uninitialized ();
 	  flow_transfer_insn = NULL;
 	  if (code == CODE_LABEL && LABEL_ALT_ENTRY_P (insn))
 	    make_edge (ENTRY_BLOCK_PTR_FOR_FN (cfun), bb, 0);
@@ -577,7 +581,7 @@ compute_outgoing_frequencies (basic_block b)
         guess_outgoing_edge_probabilities (b);
     }
 
-  if (b->count > profile_count::zero ())
+  if (b->count.initialized_p ())
     FOR_EACH_EDGE (e, ei, b->succs)
       e->count = b->count.apply_probability (e->probability);
 }
@@ -590,6 +594,9 @@ void
 find_many_sub_basic_blocks (sbitmap blocks)
 {
   basic_block bb, min, max;
+  bool found = false;
+  auto_vec<unsigned int> n_succs;
+  n_succs.safe_grow_cleared (last_basic_block_for_fn (cfun));
 
   FOR_EACH_BB_FN (bb, cfun)
     SET_STATE (bb,
@@ -597,11 +604,24 @@ find_many_sub_basic_blocks (sbitmap blocks)
 
   FOR_EACH_BB_FN (bb, cfun)
     if (STATE (bb) == BLOCK_TO_SPLIT)
-      find_bb_boundaries (bb);
+      {
+	int n = last_basic_block_for_fn (cfun);
+	unsigned int ns = EDGE_COUNT (bb->succs);
+
+        find_bb_boundaries (bb);
+	if (n == last_basic_block_for_fn (cfun) && ns == EDGE_COUNT (bb->succs))
+	  n_succs[bb->index] = EDGE_COUNT (bb->succs);
+      }
 
   FOR_EACH_BB_FN (bb, cfun)
     if (STATE (bb) != BLOCK_ORIGINAL)
-      break;
+      {
+	found = true;
+        break;
+      }
+
+  if (!found)
+    return;
 
   min = max = bb;
   for (; bb != EXIT_BLOCK_PTR_FOR_FN (cfun); bb = bb->next_bb)
@@ -624,14 +644,37 @@ find_many_sub_basic_blocks (sbitmap blocks)
 	  continue;
 	if (STATE (bb) == BLOCK_NEW)
 	  {
+	    bool initialized_src = false, uninitialized_src = false;
 	    bb->count = profile_count::zero ();
 	    bb->frequency = 0;
 	    FOR_EACH_EDGE (e, ei, bb->preds)
 	      {
-		bb->count += e->count;
+		if (e->count.initialized_p ())
+		  {
+		    bb->count += e->count;
+		    initialized_src = true;
+		  }
+		else
+		  uninitialized_src = false;
 		bb->frequency += EDGE_FREQUENCY (e);
 	      }
+	    /* When some edges are missing with read profile, this is
+	       most likely because RTL expansion introduced loop.
+	       When profile is guessed we may have BB that is reachable
+	       from unlikely path as well as from normal path.
+
+	       TODO: We should handle loops created during BB expansion
+	       correctly here.  For now we assume all those loop to cycle
+	       precisely once.  */
+	    if (!initialized_src
+		|| (uninitialized_src
+		     && profile_status_for_fn (cfun) != PROFILE_READ))
+	      bb->count = profile_count::uninitialized ();
 	  }
+	else
+	  /* If nothing changed, there is no need to create new BBs.  */
+	  if (EDGE_COUNT (bb->succs) == n_succs[bb->index])
+	    continue;
 
 	compute_outgoing_frequencies (bb);
       }