tree-loop-distribution.c: Add general explanantion on the pass.

	* tree-loop-distribution.c: Add general explanantion on the pass.
	(generate_loops_for_partition): Mark distributed loop.
	(pg_add_dependence_edges): New parameter.  Handle alias data
	dependence specially and record it in the parameter if asked.
	(struct pg_vdata, pg_edata, pg_edge_callback_data): New structs.
	(init_partition_graph_vertices, add_partition_graph_edge): New.
	(pg_skip_alias_edge, free_partition_graph_edata_cb): New.
	(free_partition_graph_vdata, build_partition_graph): New.
	(sort_partitions_by_post_order, merge_dep_scc_partitions): New.
	(pg_collect_alias_ddrs, break_alias_scc_partitions): New.
	(data_ref_segment_size, latch_dominated_by_data_ref): New.
	(compute_alias_check_pairs, version_loop_by_alias_check): New.
	(version_for_distribution_p, finalize_partitions): New.
	(distribute_loop): Handle alias data dependence specially.  Factor
	out loop fusion code as functions and call these functions.

	gcc/testsuite
	* gcc.dg/tree-ssa/ldist-4.c: Adjust test string.
	* gcc.dg/tree-ssa/ldist-12.c: Ditto.
	* gcc.dg/tree-ssa/ldist-13.c: Ditto.
	* gcc.dg/tree-ssa/ldist-14.c: Ditto.

From-SVN: r249994

gcc/ChangeLog

 2017-07-05  Bin Cheng  <bin.cheng@arm.com>
 
+	* tree-loop-distribution.c: Add general explanantion on the pass.
+	(generate_loops_for_partition): Mark distributed loop.
+	(pg_add_dependence_edges): New parameter.  Handle alias data
+	dependence specially and record it in the parameter if asked.
+	(struct pg_vdata, pg_edata, pg_edge_callback_data): New structs.
+	(init_partition_graph_vertices, add_partition_graph_edge): New.
+	(pg_skip_alias_edge, free_partition_graph_edata_cb): New.
+	(free_partition_graph_vdata, build_partition_graph): New.
+	(sort_partitions_by_post_order, merge_dep_scc_partitions): New.
+	(pg_collect_alias_ddrs, break_alias_scc_partitions): New.
+	(data_ref_segment_size, latch_dominated_by_data_ref): New.
+	(compute_alias_check_pairs, version_loop_by_alias_check): New.
+	(version_for_distribution_p, finalize_partitions): New.
+	(distribute_loop): Handle alias data dependence specially.  Factor
+	out loop fusion code as functions and call these functions.
+
+2017-07-05  Bin Cheng  <bin.cheng@arm.com>
+
 	* tree-loop-distribution.c (classify_partition): New parameter and
 	better handle reduction statement.
 	(rdg_build_partitions): Revise comment.

gcc/testsuite/ChangeLog

 2017-07-05  Bin Cheng  <bin.cheng@arm.com>
 
+	* gcc.dg/tree-ssa/ldist-4.c: Adjust test string.
+	* gcc.dg/tree-ssa/ldist-12.c: Ditto.
+	* gcc.dg/tree-ssa/ldist-13.c: Ditto.
+	* gcc.dg/tree-ssa/ldist-14.c: Ditto.
+
+2017-07-05  Bin Cheng  <bin.cheng@arm.com>
+
 	* gcc.dg/tree-ssa/ldist-26.c: New test.
 
 2017-07-05  Bin Cheng  <bin.cheng@arm.com>

gcc/testsuite/gcc.dg/tree-ssa/ldist-12.c

@@ -18,4 +18,5 @@ int foo (int * __restrict__ ia,
   return oya[22] + oyb[21];
 }
 
-/* { dg-final { scan-tree-dump-times "distributed: split to 2 loops" 1 "ldist" } } */
+/* Distributing the loop doesn't expose more parallelism.  */
+/* { dg-final { scan-tree-dump-times "distributed: split to 2 loops" 0 "ldist" } } */

gcc/testsuite/gcc.dg/tree-ssa/ldist-13.c

@@ -16,6 +16,5 @@ float foo (int n)
   return tmp;
 }
 
-/* We should apply loop distribution.  */
-
-/* { dg-final { scan-tree-dump "Loop 1 distributed: split to 2 loops" "ldist" } } */
+/* Distributing the loop doesn't expose more parallelism.  */
+/* { dg-final { scan-tree-dump-not "Loop 1 distributed: split to 2 loops" "ldist" } } */

gcc/testsuite/gcc.dg/tree-ssa/ldist-14.c

@@ -21,6 +21,5 @@ float foo (int n)
   return tmp;
 }
 
-/* We should apply loop distribution.  */
-
-/* { dg-final { scan-tree-dump "Loop 1 distributed: split to 2 loops" "ldist" } } */
+/* Distributing the loop doesn't expose more parallelism.  */
+/* { dg-final { scan-tree-dump-not "Loop 1 distributed: split to 2 loops" "ldist" } } */

gcc/testsuite/gcc.dg/tree-ssa/ldist-4.c

@@ -20,7 +20,5 @@ int loop1 (int k)
   return b[100-1][1];
 }
 
-/* The current cost model fuses the two partitions because they have
-   similar memory accesses.  */
-/* { dg-final { scan-tree-dump "similar memory accesses" "ldist" } } */
+/* Distributing inner loop doesn't expose more parallelism.  */
 /* { dg-final { scan-tree-dump-times "distributed: split to 2 loops" 0 "ldist" } } */