[PATCH] Update bb count and freq when merging two blocks

[Dehao Chen]

This patch makes sure max count is used when merging two basic blocks.

Bootstrapped and testing on-going.

OK for trunk if test is ok?

Thanks,
Dehao

gcc/ChangeLog:
2014-05-16  Dehao Chen  <de...@google.com>

        * tree-cfg.c (gimple_merge_blocks): Updates bb count with max count.

Index: gcc/tree-cfg.c
===================================================================
--- gcc/tree-cfg.c (revision 210531)
+++ gcc/tree-cfg.c (working copy)
@@ -1877,6 +1877,15 @@ gimple_merge_blocks (basic_block a, basic_block b)
  }
     }

+  /* When merging two BBs, if their counts are different, the larger count
+     is selected as the new bb count. This is to handle inconsistent
+     profiles.  */
+  if (a->count != b->count)
+    {
+      a->count = MAX (a->count, b->count);
+      a->frequency = MAX (a->frequency, b->frequency);
+    }
+
   /* Merge the sequences.  */
   last = gsi_last_bb (a);
   gsi_insert_seq_after (&last, bb_seq (b), GSI_NEW_STMT);