diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 0796cda55b6..f52e26008a2 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,12 @@
+2017-07-03  Tom de Vries  <tom@codesourcery.com>
+
+	backport from mainline:
+	PR tree-optimization/81192
+	2017-07-03  Tom de Vries  <tom@codesourcery.com>
+
+	* tree-ssa-tail-merge.c (same_succ_flush_bb): Handle
+	BB_SAME_SUCC (bb) == NULL.
+
 2017-06-29  Michael Meissner  <meissner@linux.vnet.ibm.com>
 
 	Backport from mainline
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 5c0235104fc..6b7ed023f33 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,11 @@
+2017-07-03  Tom de Vries  <tom@codesourcery.com>
+
+	backport from mainline:
+	PR tree-optimization/81192
+	2017-07-03  Tom de Vries  <tom@codesourcery.com>
+
+	* gcc.dg/pr81192.c: New test.
+
 2017-06-29  Michael Meissner  <meissner@linux.vnet.ibm.com>
 
 	Backport from mainline
diff --git a/gcc/testsuite/gcc.dg/pr81192.c b/gcc/testsuite/gcc.dg/pr81192.c
new file mode 100644
index 00000000000..57eb4781d4d
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr81192.c
@@ -0,0 +1,22 @@
+/* { dg-options "-Os -fdump-tree-pre-details" } */
+
+unsigned a;
+int b, c;
+
+static int
+fn1 (int p1, int p2)
+{
+  return p1 > 2147483647 - p2 ? p1 : p1 + p2;
+}
+
+void
+fn2 (void)
+{
+  int j;
+  a = 30;
+  for (; a;)
+    for (; c; b = fn1 (j, 1))
+      ;
+}
+
+/* { dg-final { scan-tree-dump-times "(?n)find_duplicates: <bb .*> duplicate of <bb .*>" 1 "pre" } } */
diff --git a/gcc/tree-ssa-tail-merge.c b/gcc/tree-ssa-tail-merge.c
index 71f874d3123..01c25d43e0d 100644
--- a/gcc/tree-ssa-tail-merge.c
+++ b/gcc/tree-ssa-tail-merge.c
@@ -808,6 +808,9 @@ static void
 same_succ_flush_bb (basic_block bb)
 {
   same_succ *same = BB_SAME_SUCC (bb);
+  if (! same)
+    return;
+
   BB_SAME_SUCC (bb) = NULL;
   if (bitmap_single_bit_set_p (same->bbs))
     same_succ_htab->remove_elt_with_hash (same, same->hashval);