diff --git a/gcc/c/ChangeLog b/gcc/c/ChangeLog
index 20492cfbbfe..011a8a0825f 100644
--- a/gcc/c/ChangeLog
+++ b/gcc/c/ChangeLog
@@ -1,3 +1,12 @@
+2017-12-10  Tom de Vries  <tom@codesourcery.com>
+
+	backport from trunk:
+	PR c/81875
+	2017-09-16  Tom de Vries  <tom@codesourcery.com>
+
+	* c-parser.c (c_parser_omp_for_loop): Fold only operands of cond, not
+	cond itself.
+
 2017-09-30  Jakub Jelinek  <jakub@redhat.com>
 
 	Backported from mainline
diff --git a/gcc/c/c-parser.c b/gcc/c/c-parser.c
index 988369e4193..101afb8e35f 100644
--- a/gcc/c/c-parser.c
+++ b/gcc/c/c-parser.c
@@ -15032,7 +15032,14 @@ c_parser_omp_for_loop (location_t loc, c_parser *parser, enum tree_code code,
 
 	  cond = cond_expr.value;
 	  cond = c_objc_common_truthvalue_conversion (cond_loc, cond);
-	  cond = c_fully_fold (cond, false, NULL);
+	  if (COMPARISON_CLASS_P (cond))
+	    {
+	      tree op0 = TREE_OPERAND (cond, 0), op1 = TREE_OPERAND (cond, 1);
+	      op0 = c_fully_fold (op0, false, NULL);
+	      op1 = c_fully_fold (op1, false, NULL);
+	      TREE_OPERAND (cond, 0) = op0;
+	      TREE_OPERAND (cond, 1) = op1;
+	    }
 	  switch (cond_expr.original_code)
 	    {
 	    case GT_EXPR:
diff --git a/libgomp/ChangeLog b/libgomp/ChangeLog
index 59a2ff88b0e..09604ca7413 100644
--- a/libgomp/ChangeLog
+++ b/libgomp/ChangeLog
@@ -1,3 +1,11 @@
+2017-12-10  Tom de Vries  <tom@codesourcery.com>
+
+	backport from trunk:
+	PR c/81875
+	2017-09-16  Tom de Vries  <tom@codesourcery.com>
+
+	* testsuite/libgomp.c/pr81875.c: New test.
+
 2017-09-15  Jakub Jelinek  <jakub@redhat.com>
 
 	Backported from mainline
diff --git a/libgomp/testsuite/libgomp.c/pr81875.c b/libgomp/testsuite/libgomp.c/pr81875.c
new file mode 100644
index 00000000000..3067d49a492
--- /dev/null
+++ b/libgomp/testsuite/libgomp.c/pr81875.c
@@ -0,0 +1,46 @@
+/* { dg-do run } */
+
+extern
+#ifdef __cplusplus
+"C"
+#endif
+void abort (void);
+
+#define N 32ULL
+int a[N];
+
+const unsigned long long c = 0x7fffffffffffffffULL;
+
+void
+f2_tpf_static32 (void)
+{
+  unsigned long long i;
+  #pragma omp for
+  for (i = c + N; i > c; i -= 1ULL)
+    a[i - 1ULL - c] -= 4;
+}
+
+__attribute__((noinline, noclone)) int
+test_tpf_static32 (void)
+{
+  int i, j, k;
+  for (i = 0; i < N; i++)
+    a[i] = i - 25;
+
+  f2_tpf_static32 ();
+
+  for (i = 0; i < N; i++)
+    if (a[i] != i - 29)
+      return 1;
+
+  return 0;
+}
+
+int
+main ()
+{
+  if (test_tpf_static32 ())
+    abort ();
+
+  return 0;
+}