Fix APFloat mod sign

fmod specification requires the sign of the remainder is
the same as numerator in case remainder is zero.

Reviewers: gottesmm, scanon, arsenm, davide, craig.topper
Reviewed By: scanon
Subscribers: wdng, llvm-commits
Differential Revision: https://reviews.llvm.org/D39225


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@317081 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Support/APFloat.cpp

@@ -1743,6 +1743,7 @@ IEEEFloat::opStatus IEEEFloat::remainder(const IEEEFloat &rhs) {
 IEEEFloat::opStatus IEEEFloat::mod(const IEEEFloat &rhs) {
   opStatus fs;
   fs = modSpecials(rhs);
+  unsigned int origSign = sign;
 
   while (isFiniteNonZero() && rhs.isFiniteNonZero() &&
          compareAbsoluteValue(rhs) != cmpLessThan) {
@@ -1754,6 +1755,8 @@ IEEEFloat::opStatus IEEEFloat::mod(const IEEEFloat &rhs) {
     fs = subtract(V, rmNearestTiesToEven);
     assert(fs==opOK);
   }
+  if (isZero())
+    sign = origSign; // fmod requires this
   return fs;
 }