2011-09-27 Tom de Vries <tom@codesourcery.com>

	PR middle-end/43864
	* tree-ssa-tail-merge.c: New file.
	(struct same_succ_def): Define.
	(same_succ, const_same_succ): New typedef.
	(struct bb_cluster_def): Define.
	(bb_cluster, const_bb_cluster): New typedef.
	(struct aux_bb_info): Define.
	(BB_SIZE, BB_SAME_SUCC, BB_CLUSTER, BB_VOP_AT_EXIT): Define.
	(gvn_uses_equal): New function.
	(same_succ_print, same_succ_print_traverse, update_dep_bb)
	(stmt_update_dep_bb, local_def, same_succ_hash)
	(inverse_flags, same_succ_equal, same_succ_alloc, same_succ_delete)
	(same_succ_reset): New function.
	(same_succ_htab, same_succ_edge_flags)
	(deleted_bbs, deleted_bb_preds): New var.
	(debug_same_succ): New function.
	(worklist): New var.
	(print_worklist, add_to_worklist, find_same_succ_bb, find_same_succ)
	(init_worklist, delete_worklist, delete_basic_block_same_succ)
	(same_succ_flush_bbs, purge_bbs, update_worklist): New function.
	(print_cluster, debug_cluster, update_rep_bb)
	(add_bb_to_cluster, new_cluster, delete_cluster): New function.
	(all_clusters): New var.
	(alloc_cluster_vectors, reset_cluster_vectors, delete_cluster_vectors)
	(merge_clusters, set_cluster): New function.
	(gimple_equal_p, gsi_advance_bw_nondebug_nonlocal, find_duplicate)
	(same_phi_alternatives_1, same_phi_alternatives, bb_has_non_vop_phi)
	(deps_ok_for_redirect_from_bb_to_bb, deps_ok_for_redirect)
	(find_clusters_1, find_clusters): New function.
	(update_vuses, vop_phi, vop_at_entry, replace_block_by): New function.
	(update_bbs): New var.
	(apply_clusters): New function.
	(update_debug_stmt, update_debug_stmts): New function.
	(tail_merge_optimize): New function.
	tree-pass.h (tail_merge_optimize): Declare.
	* tree-ssa-pre.c (execute_pre): Use tail_merge_optimize.
	* Makefile.in (OBJS-common): Add tree-ssa-tail-merge.o.
	(tree-ssa-tail-merge.o): New rule.
	* opts.c (default_options_table): Set OPT_ftree_tail_merge by default at
	OPT_LEVELS_2_PLUS.
	* tree-ssa-sccvn.c (vn_valueize): Move to ...
	* tree-ssa-sccvn.h (vn_valueize): Here.
	* timevar.def (TV_TREE_TAIL_MERGE): New timevar.
	* common.opt (ftree-tail-merge): New switch.
	* params.def (PARAM_MAX_TAIL_MERGE_COMPARISONS)
	(PARAM_MAX_TAIL_MERGE_ITERATIONS): New parameter.
	* doc/invoke.texi (Optimization Options, -O2): Add -ftree-tail-merge.
	(-ftree-tail-merge, max-tail-merge-comparisons)
	(max-tail-merge-iterations): New item.


git-svn-id: https://gcc.gnu.org/svn/gcc/trunk@179275 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 11 insertions, 1 deletions

diff --git a/gcc/tree-ssa-pre.c b/gcc/tree-ssa-pre.c
index 5c112c080a6..a7f6cee35d8 100644
--- a/gcc/tree-ssa-pre.c
+++ b/gcc/tree-ssa-pre.c
@@ -4915,7 +4915,6 @@ execute_pre (bool do_fre)
   statistics_counter_event (cfun, "Constified", pre_stats.constified);
 
   clear_expression_ids ();
-  free_scc_vn ();
   if (!do_fre)
     {
       remove_dead_inserted_code ();
@@ -4925,6 +4924,17 @@ execute_pre (bool do_fre)
   scev_finalize ();
   fini_pre (do_fre);
 
+  if (!do_fre)
+    /* TODO: tail_merge_optimize may merge all predecessors of a block, in which
+       case we can merge the block with the remaining predecessor of the block.
+       It should either:
+       - call merge_blocks after each tail merge iteration
+       - call merge_blocks after all tail merge iterations
+       - mark TODO_cleanup_cfg when necessary
+       - share the cfg cleanup with fini_pre.  */
+    todo |= tail_merge_optimize (todo);
+  free_scc_vn ();
+
   return todo;
 }