Move tail merging pass forward

[Jan Hubicka <hubicka at ucw dot cz>]

Hi,
testcase in PR35545 shows case where profile feedback infrastructure does everything
to make the testcase optimized (fully devirutalized) but it does not happen
because tracer is run too late in the queue.

Tail duplication in general is a pass enabling more optimizations to be done
by forward propagating passes, such as constant propagation, fre or vrp.  It
makes no sense to run it afterwards.

This patch moves it shortly after loop optimization (as like loop optimization
it increases basic blocks). It may make sense to move it even further, but that
would probalby need more benchamrking.

I have profiledbootstrapped the patch with LTO at x86_64-linux and also
tested with firefox. Comitted.

Honza

	PR middle-end/35545
	* passes.def (pass_tracer): Move before last dominator pass.
	* g++.dg/tree-prof/pr35545.C: New testcase.
Index: passes.def
===================================================================
--- passes.def	(revision 215645)
+++ passes.def	(working copy)
@@ -252,6 +252,7 @@ along with GCC; see the file COPYING3.
       NEXT_PASS (pass_cse_reciprocals);
       NEXT_PASS (pass_reassoc);
       NEXT_PASS (pass_strength_reduction);
+      NEXT_PASS (pass_tracer);
       NEXT_PASS (pass_dominator);
       NEXT_PASS (pass_strlen);
       NEXT_PASS (pass_vrp);
@@ -262,7 +263,6 @@ along with GCC; see the file COPYING3.
 	 opportunities.  */
       NEXT_PASS (pass_phi_only_cprop);
       NEXT_PASS (pass_cd_dce);
-      NEXT_PASS (pass_tracer);
       NEXT_PASS (pass_dse);
       NEXT_PASS (pass_forwprop);
       NEXT_PASS (pass_phiopt);
Index: testsuite/g++.dg/tree-prof/pr35545.C
===================================================================
--- testsuite/g++.dg/tree-prof/pr35545.C	(revision 0)
+++ testsuite/g++.dg/tree-prof/pr35545.C	(revision 0)
@@ -0,0 +1,52 @@
+// devirt.cc
+/* { dg-options "-O2 -fdump-ipa-profile_estimate -fdump-tree-optimized" } */
+
+class A {
+public:
+  virtual int foo() {
+     return 1;
+  }
+
+int i;
+};
+
+class B : public A
+{
+public:
+  virtual int foo() {
+     return 2;
+  }
+
+ int b;
+} ;
+
+
+int main()
+{
+ int i;
+
+  A* ap = 0;
+
+  for (i = 0; i < 10000; i++)
+  {
+
+     if (i%7==0)
+     {
+        ap = new A();
+     }
+     else
+        ap = new B();
+
+    ap->foo();
+
+    delete ap;
+
+  }
+
+  return 0;
+
+}
+/* { dg-final-use { scan-ipa-dump "Indirect call -> direct call" "profile_estimate" } } */
+/* { dg-final-use { cleanup-ipa-dump "profile" } } */
+/* { dg-final-use { scan-ipa-dump-not "OBJ_TYPE_REF" "optimized" } } */
+/* { dg-final-use { cleanup-tree-dump "optimized" } } */