Fix profile updating bug in tree-ssa-threadupdate

[Jan Hubicka <hubicka@ucw.cz>]

Hi,
ssa_fix_duplicate_block_edges later calls update_profile to correct profile after threading.
In the testcase this does not work since we lose track of the duplicated edge.  This 
happens because redirect_edge_and_branch returns NULL if the edge already has correct
destination which is the case.

Bootstrapped/regtesed x86_64-linux, comitted.

gcc/ChangeLog:

	* tree-ssa-threadupdate.cc (ssa_fix_duplicate_block_edges): Fix profile update.

gcc/testsuite/ChangeLog:

	* gcc.dg/tree-ssa/phi_on_compare-1.c: Check profile consistency.

diff --git a/gcc/testsuite/gcc.dg/tree-ssa/phi_on_compare-1.c b/gcc/testsuite/gcc.dg/tree-ssa/phi_on_compare-1.c
index be504ddb11a..923497f7896 100644
--- a/gcc/testsuite/gcc.dg/tree-ssa/phi_on_compare-1.c
+++ b/gcc/testsuite/gcc.dg/tree-ssa/phi_on_compare-1.c
@@ -1,5 +1,5 @@
 /* { dg-do compile } */
-/* { dg-options "-Ofast -fdump-tree-dom2" } */
+/* { dg-options "-Ofast -fdump-tree-dom2 -fdump-tree-optimized-details-blocks" } */
 
 void g (int);
 void g1 (int);
@@ -33,3 +33,4 @@ f (long a, long b, long c, long d, long x)
    optimization in the backward threader before killing the forward
    threader.  Similarly for the other phi_on_compare-*.c tests.  */
 /* { dg-final { scan-tree-dump-times "Removing basic block" 1 "dom2" } } */
+/* { dg-final { scan-tree-dump-not "Invalid sum" "optimized" } } */
diff --git a/gcc/tree-ssa-threadupdate.cc b/gcc/tree-ssa-threadupdate.cc
index d5416b21a78..a5b9a002a8a 100644
--- a/gcc/tree-ssa-threadupdate.cc
+++ b/gcc/tree-ssa-threadupdate.cc
@@ -1059,14 +1059,19 @@ ssa_fix_duplicate_block_edges (struct redirection_data *rd,
 	     threading path.  */
 	  if (!any_remaining_duplicated_blocks (path, i))
 	    {
-	      e2 = redirect_edge_and_branch (victim, elast->dest);
-	      /* If we redirected the edge, then we need to copy PHI arguments
-		 at the target.  If the edge already existed (e2 != victim
-		 case), then the PHIs in the target already have the correct
-		 arguments.  */
-	      if (e2 == victim)
-		copy_phi_args (e2->dest, elast, e2,
-			       path, multi_incomings ? 0 : i);
+	      if (victim->dest != elast->dest)
+		{
+		  e2 = redirect_edge_and_branch (victim, elast->dest);
+		  /* If we redirected the edge, then we need to copy PHI arguments
+		     at the target.  If the edge already existed (e2 != victim
+		     case), then the PHIs in the target already have the correct
+		     arguments.  */
+		  if (e2 == victim)
+		    copy_phi_args (e2->dest, elast, e2,
+				   path, multi_incomings ? 0 : i);
+		}
+	      else
+		e2 = victim;
 	    }
 	  else
 	    {