Don't tail-merge blocks from different loops

2017-07-03  Tom de Vries  <tom@codesourcery.com>

	PR tree-optimization/81192
	* tree-ssa-tail-merge.c (same_succ_hash): Use bb->loop_father->num in
	hash.
	(same_succ::equal): Don't find bbs to be equal if bb->loop_father
	differs.
	(find_same_succ_bb): Remove obsolete test on bb->loop_father->latch.

	* gcc.dg/pr81192.c: Update.

From-SVN: r249894

gcc/ChangeLog

 2017-07-03  Tom de Vries  <tom@codesourcery.com>
 
 	PR tree-optimization/81192
+	* tree-ssa-tail-merge.c (same_succ_hash): Use bb->loop_father->num in
+	hash.
+	(same_succ::equal): Don't find bbs to be equal if bb->loop_father
+	differs.
+	(find_same_succ_bb): Remove obsolete test on bb->loop_father->latch.
+
+2017-07-03  Tom de Vries  <tom@codesourcery.com>
+
+	PR tree-optimization/81192
 	* tree-ssa-tail-merge.c (same_succ_flush_bb): Handle
 	BB_SAME_SUCC (bb) == NULL.
 

gcc/testsuite/ChangeLog

 2017-07-03  Tom de Vries  <tom@codesourcery.com>
 
 	PR tree-optimization/81192
+	* gcc.dg/pr81192.c: Update.
+
+2017-07-03  Tom de Vries  <tom@codesourcery.com>
+
+	PR tree-optimization/81192
 	* gcc.dg/pr81192.c: New test.
 
 2017-07-02  Thomas Koenig  <tkoenig@gcc.gnu.org>

gcc/testsuite/gcc.dg/pr81192.c

@@ -19,4 +19,4 @@ fn2 (void)
       ;
 }
 
-/* { dg-final { scan-tree-dump-times "(?n)find_duplicates: <bb .*> duplicate of <bb .*>" 1 "pre" } } */
+/* { dg-final { scan-tree-dump-not "(?n)find_duplicates: <bb .*> duplicate of <bb .*>" "pre" } } */

gcc/tree-ssa-tail-merge.c

@@ -479,6 +479,8 @@ same_succ_hash (const same_succ *e)
   hstate.add_int (size);
   BB_SIZE (bb) = size;
 
+  hstate.add_int (bb->loop_father->num);
+
   for (i = 0; i < e->succ_flags.length (); ++i)
     {
       flags = e->succ_flags[i];
@@ -568,6 +570,9 @@ same_succ::equal (const same_succ *e1, const same_succ *e2)
   if (BB_SIZE (bb1) != BB_SIZE (bb2))
     return 0;
 
+  if (bb1->loop_father != bb2->loop_father)
+    return 0;
+
   gsi1 = gsi_start_nondebug_bb (bb1);
   gsi2 = gsi_start_nondebug_bb (bb2);
   gsi_advance_fw_nondebug_nonlocal (&gsi1);
@@ -695,15 +700,7 @@ find_same_succ_bb (basic_block bb, same_succ **same_p)
   edge_iterator ei;
   edge e;
 
-  if (bb == NULL
-      /* Be conservative with loop structure.  It's not evident that this test
-	 is sufficient.  Before tail-merge, we've just called
-	 loop_optimizer_finalize, and LOOPS_MAY_HAVE_MULTIPLE_LATCHES is now
-	 set, so there's no guarantee that the loop->latch value is still valid.
-	 But we assume that, since we've forced LOOPS_HAVE_SIMPLE_LATCHES at the
-	 start of pre, we've kept that property intact throughout pre, and are
-	 keeping it throughout tail-merge using this test.  */
-      || bb->loop_father->latch == bb)
+  if (bb == NULL)
     return;
   bitmap_set_bit (same->bbs, bb->index);
   FOR_EACH_EDGE (e, ei, bb->succs)