re PR rtl-optimization/84872 (ICE in create_preheader, at cfgloopmanip.c:1536)

	PR rtl-optimization/84872
	* cfgloopmanip.c (create_preheader): Use make_forwarder_block even if
	nentry == 1 when CP_FALLTHRU_PREHEADERS and single_entry is
	EDGE_CROSSING edge.

	* gcc.dg/graphite/pr84872.c: New test.

From-SVN: r259182

gcc/ChangeLog

+2018-04-06  Jakub Jelinek  <jakub@redhat.com>
+
+	PR rtl-optimization/84872
+	* cfgloopmanip.c (create_preheader): Use make_forwarder_block even if
+	nentry == 1 when CP_FALLTHRU_PREHEADERS and single_entry is
+	EDGE_CROSSING edge.
+
 2018-04-06  Tamar Christina  <tamar.christina@arm.com>
 
 	* expr.c (copy_blkmode_to_reg): Revert 254862.

gcc/cfgloopmanip.c

@@ -1494,7 +1494,9 @@ create_preheader (struct loop *loop, int flags)
 
   mfb_kj_edge = loop_latch_edge (loop);
   latch_edge_was_fallthru = (mfb_kj_edge->flags & EDGE_FALLTHRU) != 0;
-  if (nentry == 1)
+  if (nentry == 1
+      && ((flags & CP_FALLTHRU_PREHEADERS) == 0
+  	  || (single_entry->flags & EDGE_CROSSING) == 0))
     dummy = split_edge (single_entry);
   else
     {

gcc/testsuite/ChangeLog

 2018-04-06  Jakub Jelinek  <jakub@redhat.com>
 
+	PR rtl-optimization/84872
+	* gcc.dg/graphite/pr84872.c: New test.
+
 	PR c++/85210
 	* g++.dg/cpp1z/decomp42.C: New test.
 

gcc/testsuite/gcc.dg/graphite/pr84872.c

+/* PR rtl-optimization/84872 */
+/* { dg-do compile { target pthread } } */
+/* { dg-options "-O1 -floop-parallelize-all -freorder-blocks-and-partition -fschedule-insns2 -fselective-scheduling2 -fsel-sched-pipelining -fno-tree-dce" } */
+
+void
+foo (int x)
+{
+  int a[2];
+  int b, c = 0;
+
+  for (b = 0; b < 2; ++b)
+    a[b] = 0;
+  for (b = 0; b < 2; ++b)
+    a[b] = 0;
+
+  while (c < 1)
+    while (x < 1)
+      ++x;
+}