loop.texi: Document possibility not to perform disambiguation of loops with multiple latches.

	* doc/loop.texi: Document possibility not to perform disambiguation
	of loops with multiple latches.
	* cfgloopmanip.c (alp_enum_p): Removed.
	(add_loop): Handle subloops.  Use get_loop_body_with_size.
	(create_preheader): Do not allow ENTRY_BLOCK_PTR to be preheader.
	* cfghooks.c (redirect_edge_and_branch_force): Set dominator for
	the new forwarder block.
	(make_forwarder_block): Only call new_bb_cbk if it is not NULL.
	Handle the case latch is NULL.
	* tree-ssa-dom.c (tree_ssa_dominator_optimize): Avoid cfg modifications
	when marking loop exits.
	* ifcvt.c (if_convert): Ditto.  Mark loop exits even if cfg cannot
	be modified.
	* loop-init.c (loop_optimizer_init): Do not modify cfg.  Call
	disambiguate_loops_with_multiple_latches.
	* tree-cfgcleanup.c (cleanup_tree_cfg_loop): Calculate dominators
	before fix_loop_structure.
	* cfgloop.c: Include pointer-set.h and output.h.
	(canonicalize_loop_headers, HEADER_BLOCK, LATCH_EDGE,
	update_latch_info, mfb_keep_just, mfb_keep_nonlatch): Removed.
	(get_loop_latch_edges, find_subloop_latch_edge_by_profile,
	find_subloop_latch_edge_by_ivs, find_subloop_latch_edge,
	mfb_redirect_edges_in_set, form_subloop, merge_latch_edges,
	disambiguate_multiple_latches, get_loop_body_with_size,
	disambiguate_loops_with_multiple_latches): New functions.
	(flow_loop_dump): Dump multiple latch edges.
	(flow_loop_nodes_find): Handle loops with multiple latches.
	(flow_loops_find): Ditto. Do not call canonicalize_loop_headers.
	(glb_enum_p): Modified.
	(get_loop_body): Use get_loop_body_with_size.
	* cfgloop.h (LOOPS_HAVE_RECORDED_EXITS): New flag.
	(AVOID_CFG_MODIFICATIONS): New constant.
	(disambiguate_loops_with_multiple_latches, add_loop,
	get_loop_body_with_size): Declare.
	* Makefile.in (cfgloop.o): Add pointer-set.h and output.h.

	* gcc.dg/tree-ssa/loop-25.c: New test.

From-SVN: r121670

1 files changed, 13 insertions, 11 deletions

diff --git a/gcc/loop-init.c b/gcc/loop-init.c
index 2c7f37a..3e6d342 100644
--- a/gcc/loop-init.c
+++ b/gcc/loop-init.c
@@ -40,22 +40,11 @@ Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA
 void
 loop_optimizer_init (unsigned flags)
 {
-  edge e;
-  edge_iterator ei;
   struct loops *loops;
 
   gcc_assert (!current_loops);
   loops = XCNEW (struct loops);
 
-  /* Avoid annoying special cases of edges going to exit
-     block.  */
-
-  for (ei = ei_start (EXIT_BLOCK_PTR->preds); (e = ei_safe_edge (ei)); )
-    if ((e->flags & EDGE_FALLTHRU) && !single_succ_p (e->src))
-      split_edge (e);
-    else
-      ei_next (&ei);
-
   /* Find the loops.  */
 
   flow_loops_find (loops);
@@ -69,6 +58,19 @@ loop_optimizer_init (unsigned flags)
       return;
     }
 
+  if (flags & LOOPS_MAY_HAVE_MULTIPLE_LATCHES)
+    {
+      /* If the loops may have multiple latches, we cannot canonicalize
+	 them further (and most of the loop manipulation functions will
+	 not work).  However, we avoid modifying cfg, which some
+	 passes may want.  */
+      gcc_assert ((flags & ~(LOOPS_MAY_HAVE_MULTIPLE_LATCHES
+			     | LOOPS_HAVE_RECORDED_EXITS)) == 0);
+      current_loops->state = LOOPS_MAY_HAVE_MULTIPLE_LATCHES;
+    }
+  else
+    disambiguate_loops_with_multiple_latches ();
+
   /* Create pre-headers.  */
   if (flags & LOOPS_HAVE_PREHEADERS)
     create_preheaders (CP_SIMPLE_PREHEADERS);