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, 10 insertions, 2 deletions

diff --git a/gcc/cfghooks.c b/gcc/cfghooks.c
index d65cce9..1fa3aa7 100644
--- a/gcc/cfghooks.c
+++ b/gcc/cfghooks.c
@@ -378,6 +378,10 @@ redirect_edge_and_branch_force (edge e, basic_block dest)
     rescan_loop_exit (e, false, true);
 
   ret = cfg_hooks->redirect_edge_and_branch_force (e, dest);
+  if (ret != NULL
+      && dom_info_available_p (CDI_DOMINATORS))
+    set_immediate_dominator (CDI_DOMINATORS, ret, src);
+
   if (current_loops != NULL)
     {
       if (ret != NULL)
@@ -724,7 +728,8 @@ make_forwarder_block (basic_block bb, bool (*redirect_edge_p) (edge),
 	fallthru->count = 0;
 
       jump = redirect_edge_and_branch_force (e, bb);
-      if (jump)
+      if (jump != NULL
+	  && new_bb_cbk != NULL)
 	new_bb_cbk (jump);
     }
 
@@ -742,9 +747,12 @@ make_forwarder_block (basic_block bb, bool (*redirect_edge_p) (edge),
       /* If we do not split a loop header, then both blocks belong to the
 	 same loop.  In case we split loop header and do not redirect the
 	 latch edge to DUMMY, then DUMMY belongs to the outer loop, and
-	 BB becomes the new header.  */
+	 BB becomes the new header.  If latch is not recorded for the loop,
+	 we leave this updating on the caller (this may only happen during
+	 loop analysis).  */
       loop = dummy->loop_father;
       if (loop->header == dummy
+	  && loop->latch != NULL
 	  && find_edge (loop->latch, dummy) == NULL)
 	{
 	  remove_bb_from_loops (dummy);