[openacc, parloops] Fix SIGSEGV in oacc_entry_exit_ok_1

When compiling the test-case with r268755, we run into a SIGSEGV in
oacc_entry_exit_ok_1 when trying to dereference a NULL red:
...
                      struct reduction_info *red;
                      red = reduction_phi (reduction_list, use_stmt);
                      tree val = PHI_RESULT (red->keep_res);
...

Fix this by handling ref == NULL.

Bootstrapped and reg-tested on x86_64.
Build and reg-tested on x86_64 with nvptx accelerator.

2019-06-16  Tom de Vries  <tdevries@suse.de>

	PR tree-optimization/89376
	* tree-parloops.c (oacc_entry_exit_ok_1): Handle red == NULL.

	* testsuite/libgomp.oacc-c-c++-common/pr89376.c: New test.

From-SVN: r272338

gcc/ChangeLog

@@ -1,3 +1,8 @@
+2019-06-16  Tom de Vries  <tdevries@suse.de>
+
+	PR tree-optimization/89376
+	* tree-parloops.c (oacc_entry_exit_ok_1): Handle red == NULL.
+
 2019-06-15  Maya Rashish  <coypu@sdf.org>
 
 	* doc/invoke.texi (Spec Files): Update location of the

gcc/tree-parloops.c

@@ -3052,11 +3052,11 @@ oacc_entry_exit_ok_1 (bitmap in_loop_bbs, vec<basic_block> region_bbs,
 		{
 		  use_operand_p use_p;
 		  gimple *use_stmt;
+		  struct reduction_info *red;
 		  single_imm_use (lhs, &use_p, &use_stmt);
-		  if (gimple_code (use_stmt) == GIMPLE_PHI)
+		  if (gimple_code (use_stmt) == GIMPLE_PHI
+		      && (red = reduction_phi (reduction_list, use_stmt)))
 		    {
-		      struct reduction_info *red;
-		      red = reduction_phi (reduction_list, use_stmt);
 		      tree val = PHI_RESULT (red->keep_res);
 		      if (has_single_use (val))
 			{

libgomp/ChangeLog

@@ -1,3 +1,8 @@
+2019-06-16  Tom de Vries  <tdevries@suse.de>
+
+	PR tree-optimization/89376
+	* testsuite/libgomp.oacc-c-c++-common/pr89376.c: New test.
+
 2019-06-15  Tom de Vries  <tdevries@suse.de>
 
 	PR tree-optimization/89713

libgomp/testsuite/libgomp.oacc-c-c++-common/pr89376.c

@@ -0,0 +1,15 @@
+/* { dg-do run } */
+/* { dg-additional-options "-fno-tree-ch -fno-tree-dce -fno-tree-vrp" } */
+
+int
+main (void)
+{
+  int fa;
+
+  #pragma acc kernels
+  for (int rw = 0; rw < 1; ++rw)
+    fa = 0;
+
+  return 0;
+}
+