tree-vrp.c (finalize_jump_threads): Do not care about dominance info.

	* tree-vrp.c (finalize_jump_threads): Do not care about dominance info.
	(execute_vrp): Preserve loops through jump threading.
	* tree-ssa-threadupdate.c (thread_single_edge,
	dbds_continue_enumeration_p, determine_bb_domination_status,
	thread_through_loop_header): New functions.
	(create_edge_and_update_destination_phis,
	create_edge_and_update_destination_phis): Set loops for the new blocks.
	(prune_undesirable_thread_requests): Removed.
	(redirect_edges): Do not pretend that redirect_edge_and_branch can
	create new blocks.
	(thread_block): Do not call prune_undesirable_thread_requests.
	Update loops.
	(mark_threaded_blocks): Select edges to thread here.
	(thread_through_all_blocks): Take may_peel_loop_headers argument.
	Thread edges through loop headers independently.
	* cfgloopmanip.c (create_preheader, mfb_keep_just): Export.
	* tree-pass.h (TODO_mark_first_instance): New.
	(first_pass_instance): Declare.
	* cfghooks.c (duplicate_block): Put the block to the original loop
	if copy is not specified.
	* tree-ssa-dom.c (tree_ssa_dominator_optimize): Preserve loops through
	jump threading.  Pass may_peel_loop_headers to
	thread_through_all_blocks according to first_pass_instance.
	* cfgloop.h (create_preheader): Declare.
	* tree-flow.h (thread_through_all_blocks): Declaration changed.
	* basic-block.h (mfb_keep_just, mfb_kj_edge): Declare.
	* passes.c (first_pass_instance): New variable.
	(next_pass_1): Set TODO_mark_first_instance.
	(execute_todo): Set first_pass_instance.

	* gcc.dg/tree-ssa/ssa-dom-thread-2.c: New test.
	* gcc.dg/vect/vect-102.c, gcc.dg/vect/vect-103.c,
	gcc.dg/vect/vect-104.c: Use more complex construction to prevent vectorizing.
	* gcc.dg/tree-ssa/pr21559.c: Update outcome.

From-SVN: r124786

1 files changed, 11 insertions, 17 deletions

diff --git a/gcc/tree-ssa-dom.c b/gcc/tree-ssa-dom.c
index 7a14615..87270fc 100644
--- a/gcc/tree-ssa-dom.c
+++ b/gcc/tree-ssa-dom.c
@@ -277,25 +277,17 @@ tree_ssa_dominator_optimize (void)
   calculate_dominance_info (CDI_DOMINATORS);
   cfg_altered = false;
 
-  /* We need to know which edges exit loops so that we can
-     aggressively thread through loop headers to an exit
-     edge.  */
-  loop_optimizer_init (AVOID_CFG_MODIFICATIONS);
-  if (current_loops)
-    {
-      mark_loop_exit_edges ();
-      loop_optimizer_finalize ();
-    }
-
-  /* Clean up the CFG so that any forwarder blocks created by loop
-     canonicalization are removed.  */
-  cleanup_tree_cfg ();
-  calculate_dominance_info (CDI_DOMINATORS);
+  /* We need to know loop structures in order to avoid destroying them
+     in jump threading.  Note that we still can e.g. thread through loop
+     headers to an exit edge, or through loop header to the loop body, assuming
+     that we update the loop info.  */
+  loop_optimizer_init (LOOPS_HAVE_SIMPLE_LATCHES);
 
   /* We need accurate information regarding back edges in the CFG
-     for jump threading.  */
+     for jump threading; this may include back edes that are not part of
+     a single loop.  */
   mark_dfs_back_edges ();
-
+      
   /* Recursively walk the dominator tree optimizing statements.  */
   walk_dominator_tree (&walk_data, ENTRY_BLOCK_PTR);
 
@@ -319,7 +311,7 @@ tree_ssa_dominator_optimize (void)
   free_all_edge_infos ();
 
   /* Thread jumps, creating duplicate blocks as needed.  */
-  cfg_altered |= thread_through_all_blocks ();
+  cfg_altered |= thread_through_all_blocks (first_pass_instance);
 
   if (cfg_altered)
     free_dominance_info (CDI_DOMINATORS);
@@ -353,6 +345,8 @@ tree_ssa_dominator_optimize (void)
   if (dump_file && (dump_flags & TDF_STATS))
     dump_dominator_optimization_stats (dump_file);
 
+  loop_optimizer_finalize ();
+
   /* Delete our main hashtable.  */
   htab_delete (avail_exprs);