Optimize expand_omp_for_static_chunk for chunk_size one

2015-08-24  Tom de Vries  <tom@codesourcery.com>

	PR tree-optimization/65468
	* omp-low.c (expand_omp_for_static_chunk): Remove inner loop if
	chunk_size is one.

	* gcc.dg/gomp/static-chunk-size-one.c: New test.

	* testsuite/libgomp.c/static-chunk-size-one.c: New test.

From-SVN: r227124

6 files changed, 65 insertions, 3 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 7d25402..d1a9e3a 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2015-08-24  Tom de Vries  <tom@codesourcery.com>
+
+	PR tree-optimization/65468
+	* omp-low.c (expand_omp_for_static_chunk): Remove inner loop if
+	chunk_size is one.
+
 2015-08-24  Nathan Sidwell  <nathan@acm.org>
 
 	* config/nvptx/nvptx.c (walk_args_for_param): Revert previous
diff --git a/gcc/omp-low.c b/gcc/omp-low.c
index d181101..19f34ec 100644
--- a/gcc/omp-low.c
+++ b/gcc/omp-low.c
@@ -7204,9 +7204,14 @@ expand_omp_for_static_chunk (struct omp_region *region,
 	  assign_stmt = gimple_build_assign (vback, t);
 	  gsi_insert_before (&gsi, assign_stmt, GSI_SAME_STMT);
 
-	  t = build2 (fd->loop.cond_code, boolean_type_node,
-		      DECL_P (vback) && TREE_ADDRESSABLE (vback)
-		      ? t : vback, e);
+	  if (tree_int_cst_equal (fd->chunk_size, integer_one_node))
+	    t = build2 (EQ_EXPR, boolean_type_node,
+			build_int_cst (itype, 0),
+			build_int_cst (itype, 1));
+	  else
+	    t = build2 (fd->loop.cond_code, boolean_type_node,
+			DECL_P (vback) && TREE_ADDRESSABLE (vback)
+			? t : vback, e);
 	  gsi_insert_before (&gsi, gimple_build_cond_empty (t), GSI_SAME_STMT);
 	}
 
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 6235844..36fc88f 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2015-08-24  Tom de Vries  <tom@codesourcery.com>
+
+	PR tree-optimization/65468
+	* gcc.dg/gomp/static-chunk-size-one.c: New test.
+
 2015-08-23  Francois-Xavier Coudert  <fxcoudert@gcc.gnu.org>
 
 	PR libfortran/54572
diff --git a/gcc/testsuite/gcc.dg/gomp/static-chunk-size-one.c b/gcc/testsuite/gcc.dg/gomp/static-chunk-size-one.c
new file mode 100644
index 0000000..e82de77
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/gomp/static-chunk-size-one.c
@@ -0,0 +1,18 @@
+/* { dg-do compile } */
+/* { dg-options "-fopenmp -O2 -fdump-tree-optimized -fno-tree-pre" } */
+
+int
+bar ()
+{
+  int a = 0, i;
+
+#pragma omp parallel for num_threads (3) reduction (+:a) schedule(static, 1)
+  for (i = 0; i < 10; i++)
+    a += i;
+
+  return a;
+}
+
+/* Two phis for reduction, one in loop header, one in loop exit.  One phi for iv
+   in loop header.  */
+/* { dg-final { scan-tree-dump-times "PHI" 3 "optimized" } } */
diff --git a/libgomp/ChangeLog b/libgomp/ChangeLog
index bd9111b..43aaa52 100644
--- a/libgomp/ChangeLog
+++ b/libgomp/ChangeLog
@@ -1,3 +1,8 @@
+2015-08-24  Tom de Vries  <tom@codesourcery.com>
+
+	PR tree-optimization/65468
+	* testsuite/libgomp.c/static-chunk-size-one.c: New test.
+
 2015-08-24  Joost VandeVondele  <vondele@gnu.gcc.org>
 
 	PR libgomp/66761
diff --git a/libgomp/testsuite/libgomp.c/static-chunk-size-one.c b/libgomp/testsuite/libgomp.c/static-chunk-size-one.c
new file mode 100644
index 0000000..9ed7b83
--- /dev/null
+++ b/libgomp/testsuite/libgomp.c/static-chunk-size-one.c
@@ -0,0 +1,23 @@
+extern void abort ();
+
+int
+bar ()
+{
+  int a = 0, i;
+
+#pragma omp parallel for num_threads (3) reduction (+:a) schedule(static, 1)
+  for (i = 0; i < 10; i++)
+    a += i;
+
+  return a;
+}
+
+int
+main (void)
+{
+  int res;
+  res = bar ();
+  if (res != 45)
+    abort ();
+  return 0;
+}