* 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.



git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@121670 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 36 insertions, 28 deletions

diff --git a/gcc/cfgloopmanip.c b/gcc/cfgloopmanip.c
index 8e5f4c2bf38..9ca3947a0c6 100644
--- a/gcc/cfgloopmanip.c
+++ b/gcc/cfgloopmanip.c
@@ -38,11 +38,9 @@ static void loop_redirect_edge (edge, basic_block);
 static void remove_bbs (basic_block *, int);
 static bool rpe_enum_p (basic_block, void *);
 static int find_path (edge, basic_block **);
-static bool alp_enum_p (basic_block, void *);
 static void fix_loop_placements (struct loop *, bool *);
 static bool fix_bb_placement (basic_block);
 static void fix_bb_placements (basic_block, bool *);
-static void place_new_loop (struct loop *);
 static basic_block create_preheader (struct loop *, int);
 static void unloop (struct loop *, bool *);
 
@@ -395,39 +393,54 @@ remove_path (edge e)
   return true;
 }
 
-/* Predicate for enumeration in add_loop.  */
-static bool
-alp_enum_p (basic_block bb, void *alp_header)
+/* Creates place for a new LOOP in loops structure.  */
+
+static void
+place_new_loop (struct loop *loop)
 {
-  return bb != (basic_block) alp_header;
+  loop->num = number_of_loops ();
+  VEC_safe_push (loop_p, heap, current_loops->larray, loop);
 }
 
 /* Given LOOP structure with filled header and latch, find the body of the
    corresponding loop and add it to loops tree.  Insert the LOOP as a son of
    outer.  */
 
-static void
+void
 add_loop (struct loop *loop, struct loop *outer)
 {
   basic_block *bbs;
   int i, n;
+  struct loop *subloop;
 
   /* Add it to loop structure.  */
   place_new_loop (loop);
   flow_loop_tree_node_add (outer, loop);
 
   /* Find its nodes.  */
-  bbs = XCNEWVEC (basic_block, n_basic_blocks);
-  n = dfs_enumerate_from (loop->latch, 1, alp_enum_p,
-			  bbs, n_basic_blocks, loop->header);
+  bbs = XNEWVEC (basic_block, n_basic_blocks);
+  n = get_loop_body_with_size (loop, bbs, n_basic_blocks);
 
   for (i = 0; i < n; i++)
     {
-      remove_bb_from_loops (bbs[i]);
-      add_bb_to_loop (bbs[i], loop);
+      if (bbs[i]->loop_father == outer)
+	{
+	  remove_bb_from_loops (bbs[i]);
+	  add_bb_to_loop (bbs[i], loop);
+	  continue;
+	}
+
+      loop->num_nodes++;
+
+      /* If we find a direct subloop of OUTER, move it to LOOP.  */
+      subloop = bbs[i]->loop_father;
+      if (subloop->outer == outer
+	  && subloop->header == bbs[i])
+	{
+	  flow_loop_tree_node_remove (subloop);
+	  flow_loop_tree_node_add (loop, subloop);
+	}
     }
-  remove_bb_from_loops (loop->header);
-  add_bb_to_loop (loop->header, loop);
 
   free (bbs);
 }
@@ -631,14 +644,6 @@ fix_loop_placements (struct loop *loop, bool *irred_invalidated)
     }
 }
 
-/* Creates place for a new LOOP in loops structure.  */
-static void
-place_new_loop (struct loop *loop)
-{
-  loop->num = number_of_loops ();
-  VEC_safe_push (loop_p, heap, current_loops->larray, loop);
-}
-
 /* Copies copy of LOOP as subloop of TARGET loop, placing newly
    created loop into loops structure.  */
 struct loop *
@@ -1115,12 +1120,15 @@ create_preheader (struct loop *loop, int flags)
   gcc_assert (nentry);
   if (nentry == 1)
     {
-      /* Get an edge that is different from the one from loop->latch
-	 to loop->header.  */
-      e = EDGE_PRED (loop->header,
-		     EDGE_PRED (loop->header, 0)->src == loop->latch);
-
-      if (!(flags & CP_SIMPLE_PREHEADERS) || single_succ_p (e->src))
+      e = loop_preheader_edge (loop);
+
+      if (/* We do not allow entry block to be the loop preheader, since we
+	     cannot emit code there.  */
+	  e->src != ENTRY_BLOCK_PTR
+	  /* If we want simple preheaders, also force the preheader to have
+	     just a single successor.  */
+	  && !((flags & CP_SIMPLE_PREHEADERS)
+	       && !single_succ_p (e->src)))
 	return NULL;
     }