From f31276858a7182663abc0f91fd8961231191b9ed Mon Sep 17 00:00:00 2001
From: Jeff Law <law@redhat.com>
Date: Thu, 6 Oct 2016 10:23:22 -0600
Subject: [PATCH] re PR tree-optimization/71661 (wrong code at -O3)

	PR tree-optimization/71661
	* tree-cfgcleanup.c (remove_forwarder_block_with_phi): Handle case when
	removal of a forwarder exposes a new natural loop.

	PR tree-optimization/71661
	* gcc.dg/tree-ssa/pr71661.c: New test.

From-SVN: r240836
---
 gcc/ChangeLog                           |  6 +++++
 gcc/testsuite/ChangeLog                 |  5 ++++
 gcc/testsuite/gcc.dg/tree-ssa/pr71661.c | 31 +++++++++++++++++++++++++
 gcc/tree-cfgcleanup.c                   |  5 ++++
 4 files changed, 47 insertions(+)
 create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/pr71661.c

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 6b8acef79bc..0092be861e8 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2016-10-05  Jeff Law  <law@redhat.com>
+
+	PR tree-optimization/71661
+	* tree-cfgcleanup.c (remove_forwarder_block_with_phi): Handle case when
+	removal of a forwarder exposes a new natural loop.
+
 2016-10-06  Uros Bizjak  <ubizjak@gmail.com>
 
 	* config/i386/sse.md (andnot<mode>3): Add FALLTHRU comments.
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index e180375cd7c..56f1c8dbd40 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2016-10-06  Jeff Law  <law@redhat.com>
+
+	PR tree-optimization/71661
+	* gcc.dg/tree-ssa/pr71661.c: New test.
+
 2016-10-06  Richard Biener  <rguenther@suse.de>
 
 	PR tree-optimization/77855
diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr71661.c b/gcc/testsuite/gcc.dg/tree-ssa/pr71661.c
new file mode 100644
index 00000000000..c273ea1afd6
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr71661.c
@@ -0,0 +1,31 @@
+/* { dg-do run } */
+/* { dg-options "-O3 -fdisable-tree-ethread" } */
+
+extern void exit (int);
+
+int a, b;
+
+void
+fn1 ()
+{
+  unsigned c = 0;
+  int d;
+  b = a;
+  if (a < 0)
+    goto L1;
+  for (; a < 1; a++)
+    d = 0;
+  for (; d < 2; d++)
+    {
+      for (c = 0; c < 3; c++)
+      L1:
+        a = 2;
+    }
+}
+
+int
+main ()
+{
+  fn1 ();
+  exit (0);
+}
diff --git a/gcc/tree-cfgcleanup.c b/gcc/tree-cfgcleanup.c
index 6052872cb57..21873f8d516 100644
--- a/gcc/tree-cfgcleanup.c
+++ b/gcc/tree-cfgcleanup.c
@@ -840,6 +840,11 @@ remove_forwarder_block_with_phi (basic_block bb)
   if (dest == bb)
     return false;
 
+  /* Removal of forwarders may expose new natural loops and thus
+     a block may turn into a loop header.  */
+  if (current_loops && bb_loop_header_p (bb))
+    return false;
+
   /* If the destination block consists of a nonlocal label, do not
      merge it.  */
   label = first_stmt (dest);
-- 
2.30.2