[PATCH][PR tree-optimization/67892] Use FSM threader to handle backedges

	PR tree-optimization/67892
	* tree-ssa-threadedge.c (simplify_controL_stmt_condition): Fix typo
	in comment.
	(thread_through_normal_block): If we have seen a backedge, then
	do nothing.  No longer call find_jump_threads_backwards here.
	(thread_across_edge): Use find_jump_threads_backwards to find
	jump threads if the old style threader was not successful.
	* tree-ssa-threadbackward.c (get_gimple_control_stmt): Use
	gsi_last_nondebug_bb.  Return NULL if the block does not end
	with a control statement.
	(find_jump_threads_backwards): Setup code moved here from
	tree-ssa-threadedge.c::thread_through_normal_block.  Accept
	single edge argument instead of name & block.
	* tree-ssa-threadbackward.h (find_jump_threads_backwards): Update
	prototype.

        PR tree-optimization/67892
	* gcc.dg/tree-ssa/pr21417: Update expected output.
	* gcc.dg/tree-ssa/ssa-dom-thread-2b.c: Likewise.

From-SVN: r229538

gcc/ChangeLog

+2015-10-29  Jeff Law  <law@redhat.com>
+
+	PR tree-optimization/67892
+	* tree-ssa-threadedge.c (simplify_controL_stmt_condition): Fix typo
+	in comment.
+	(thread_through_normal_block): If we have seen a backedge, then
+	do nothing.  No longer call find_jump_threads_backwards here.
+	(thread_across_edge): Use find_jump_threads_backwards to find
+	jump threads if the old style threader was not successful.
+	* tree-ssa-threadbackward.c (get_gimple_control_stmt): Use
+	gsi_last_nondebug_bb.  Return NULL if the block does not end
+	with a control statement.
+	(find_jump_threads_backwards): Setup code moved here from
+	tree-ssa-threadedge.c::thread_through_normal_block.  Accept
+	single edge argument instead of name & block.
+	* tree-ssa-threadbackward.h (find_jump_threads_backwards): Update
+	prototype.
+
 2015-10-29  Tom de Vries  <tom@codesourcery.com>
 
 	* fold-const.c (fold_unary_loc): Remove folding inhibition for restrict

gcc/testsuite/ChangeLog

+2015-10-29  Jeff Law  <law@redhat.com>
+
+        PR tree-optimization/67892
+	* gcc.dg/tree-ssa/pr21417: Update expected output.
+	* gcc.dg/tree-ssa/ssa-dom-thread-2b.c: Likewise.
+
 2015-10-29  Richard Biener  <rguenther@suse.de>
 
 	PR middle-end/68142

gcc/testsuite/gcc.dg/tree-ssa/pr21417.c

@@ -49,5 +49,5 @@ L23:
 /* We should thread the backedge to the top of the loop; ie we only
    execute the if (expr->common.code != 142) test once per loop
    iteration.  */
-/* { dg-final { scan-tree-dump-times "Threaded jump" 1 "dom2" } } */
+/* { dg-final { scan-tree-dump-times "FSM jump thread" 1 "dom2" } } */
 

gcc/testsuite/gcc.dg/tree-ssa/ssa-dom-thread-2b.c

@@ -25,6 +25,5 @@ void thread_latch_through_header (void)
 /* Threading the latch to a later point in the loop is safe in this
    case.  And we want to thread through the header as well.  These
    are both caught by threading in DOM.  */
-/* { dg-final { scan-tree-dump-not "Jumps threaded" "vrp1"} } */
-/* { dg-final { scan-tree-dump-times "Jumps threaded: 1" 0 "dom1"} } */
-/* { dg-final { scan-tree-dump-times "Jumps threaded: 2" 1 "dom1"} } */
+/* { dg-final { scan-tree-dump-not "Jumps threaded" "dom1"} } */
+/* { dg-final { scan-tree-dump-times "Jumps threaded: 2" 1 "vrp1"} } */

gcc/tree-ssa-threadbackward.c

@@ -37,19 +37,22 @@ along with GCC; see the file COPYING3.  If not see
 static int max_threaded_paths;
 
 /* Simple helper to get the last statement from BB, which is assumed
-   to be a control statement.  */
+   to be a control statement.   Return NULL if the last statement is
+   not a control statement.  */
+
 static gimple *
 get_gimple_control_stmt (basic_block bb)
 {
-  gimple_stmt_iterator gsi = gsi_last_bb (bb);
+  gimple_stmt_iterator gsi = gsi_last_nondebug_bb (bb);
 
   if (gsi_end_p (gsi))
     return NULL;
 
   gimple *stmt = gsi_stmt (gsi);
   enum gimple_code code = gimple_code (stmt);
-  gcc_assert (code == GIMPLE_COND || code == GIMPLE_SWITCH || code == GIMPLE_GOTO);
-  return stmt;
+  if (code == GIMPLE_COND || code == GIMPLE_SWITCH || code == GIMPLE_GOTO)
+    return stmt;
+  return NULL;
 }
 
 /* Return true if the CFG contains at least one path from START_BB to END_BB.
@@ -340,11 +343,39 @@ fsm_find_control_statement_thread_paths (tree name,
    finding a path where NAME is a constant, we can thread the path.  */
 
 void  
-find_jump_threads_backwards (tree name, basic_block bb)
+find_jump_threads_backwards (edge e)
 {     
+  if (!flag_expensive_optimizations
+      || optimize_function_for_size_p (cfun)
+      || e->dest->loop_father != e->src->loop_father
+      || loop_depth (e->dest->loop_father) == 0)
+    return;
+
+  gimple *stmt = get_gimple_control_stmt (e->dest);
+  if (!stmt)
+    return;
+
+  enum gimple_code code = gimple_code (stmt);
+  tree name = NULL;
+  if (code == GIMPLE_SWITCH)
+    name = gimple_switch_index (as_a <gswitch *> (stmt));
+  else if (code == GIMPLE_GOTO)
+    name = gimple_goto_dest (stmt);
+  else if (code == GIMPLE_COND)
+    {
+      if (TREE_CODE (gimple_cond_lhs (stmt)) == SSA_NAME
+	  && TREE_CODE (gimple_cond_rhs (stmt)) == INTEGER_CST
+	  && (INTEGRAL_TYPE_P (TREE_TYPE (gimple_cond_lhs (stmt)))
+	      || POINTER_TYPE_P (TREE_TYPE (gimple_cond_lhs (stmt)))))
+	name = gimple_cond_lhs (stmt);
+    }
+
+  if (!name || TREE_CODE (name) != SSA_NAME)
+    return;
+
   vec<basic_block, va_gc> *bb_path;
   vec_alloc (bb_path, n_basic_blocks_for_fn (cfun));
-  vec_safe_push (bb_path, bb);           
+  vec_safe_push (bb_path, e->dest);
   hash_set<basic_block> *visited_bbs = new hash_set<basic_block>;
 
   max_threaded_paths = PARAM_VALUE (PARAM_MAX_FSM_THREAD_PATHS);
@@ -352,4 +383,4 @@ find_jump_threads_backwards (tree name, basic_block bb)
 
   delete visited_bbs;
   vec_free (bb_path);
-}         
+}

gcc/tree-ssa-threadbackward.h

@@ -20,6 +20,6 @@ along with GCC; see the file COPYING3.  If not see
 #ifndef GCC_TREE_SSA_THREADFSM_H
 #define GCC_TREE_SSA_THREADFSM_H
 
-extern void find_jump_threads_backwards (tree, basic_block);
+extern void find_jump_threads_backwards (edge);
 
 #endif /* GCC_TREE_SSA_THREADFSM_H */

gcc/tree-ssa-threadedge.c

@@ -566,7 +566,7 @@ simplify_control_stmt_condition (edge e,
 
 	 It is possible to get loops in the SSA_NAME_VALUE chains
 	 (consider threading the backedge of a loop where we have
-	 a loop invariant SSA_NAME used in the condition.  */
+	 a loop invariant SSA_NAME used in the condition).  */
       if (cached_lhs)
 	{
 	  for (int i = 0; i < 2; i++)
@@ -904,12 +904,10 @@ thread_through_normal_block (edge e,
 			     bitmap visited,
 			     bool *backedge_seen_p)
 {
-  /* If we have traversed a backedge, then we do not want to look
-     at certain expressions in the table that can not be relied upon.
-     Luckily the only code that looked at those expressions is the
-     SIMPLIFY callback, which we replace if we can no longer use it.  */
+  /* If we have seen a backedge, then we rely solely on the FSM threader
+     to find jump threads.  */
   if (*backedge_seen_p)
-    simplify = dummy_simplify;
+    return 0;
 
   /* We want to record any equivalences created by traversing E.  */
   if (!handle_dominating_asserts)
@@ -1019,26 +1017,6 @@ thread_through_normal_block (edge e,
 				      backedge_seen_p);
 	  return 1;
 	}
-
-      if (!flag_expensive_optimizations
-	  || optimize_function_for_size_p (cfun)
-	  || !(TREE_CODE (cond) == SSA_NAME
-	       || (TREE_CODE_CLASS (TREE_CODE (cond)) == tcc_comparison
-		   && TREE_CODE (TREE_OPERAND (cond, 0)) == SSA_NAME
-		   && TREE_CODE (TREE_OPERAND (cond, 1)) == INTEGER_CST))
-	  || e->dest->loop_father != e->src->loop_father
-	  || loop_depth (e->dest->loop_father) == 0)
-	return 0;
-
-      /* Extract the SSA_NAME we want to trace backwards if COND is not
-	 already a bare SSA_NAME.  */
-      if (TREE_CODE (cond) != SSA_NAME)
-	cond = TREE_OPERAND (cond, 0);
-
-      /* When COND cannot be simplified, try to find paths from a control
-	 statement back through the PHI nodes which would affect that control
-	 statement.  */
-      find_jump_threads_backwards (cond, e->dest);
     }
   return 0;
 }
@@ -1118,6 +1096,8 @@ thread_across_edge (gcond *dummy_cond,
       path->release ();
       delete path;
 
+      find_jump_threads_backwards (e);
+
       /* A negative status indicates the target block was deemed too big to
 	 duplicate.  Just quit now rather than trying to use the block as
 	 a joiner in a jump threading path.
@@ -1217,6 +1197,7 @@ thread_across_edge (gcond *dummy_cond,
 	  }
 	else
 	  {
+	    find_jump_threads_backwards (path->last ()->e);
 	    delete_jump_thread_path (path);
 	  }