2017-06-27  Segher Boessenkool  <segher@kernel.crashing.org>

	Backport from trunk
	2017-05-17  Segher Boessenkool  <segher@kernel.crashing.org>

	PR middle-end/80692
	* real.c (do_compare): Give decimal_do_compare preference over
	comparing just the signs.

	* gcc.c-torture/execute/pr80692.c: New testcase.

--- gcc/real.c
+++ gcc/real.c
@@ -950,12 +950,12 @@ do_compare (const REAL_VALUE_TYPE *a, const REAL_VALUE_TYPE *b,
       gcc_unreachable ();
     }
 
-  if (a->sign != b->sign)
-    return -a->sign - -b->sign;
-
   if (a->decimal || b->decimal)
     return decimal_do_compare (a, b, nan_result);
 
+  if (a->sign != b->sign)
+    return -a->sign - -b->sign;
+
   if (REAL_EXP (a) > REAL_EXP (b))
     ret = 1;
   else if (REAL_EXP (a) < REAL_EXP (b))
--- /dev/null
+++ gcc/testsuite/gcc.c-torture/execute/pr80692.c
@@ -0,0 +1,11 @@
+int main () {
+	_Decimal64 d64 = -0.DD;
+
+	if (d64 != 0.DD)
+		__builtin_abort ();
+
+	if (d64 != -0.DD)
+		__builtin_abort ();
+
+	return 0;
+}
--- /dev/null
+++ gcc/testsuite/gcc.c-torture/execute/pr80692.x
@@ -0,0 +1,7 @@
+load_lib target-supports.exp
+
+if { ! [check_effective_target_dfp] } {
+        return 1
+}
+
+return 0