[flang] SET_EXPONENT(-0.0) should return -0.0

[PeteSteinfeld]

Summary

Section 16.9.171 says:

If X has the value zero, the result has the same value as X

So if X is -0.0, SET_EXPONENT should return -0.0.

[klausler]

flang/runtime/numeric.cpp

125

There's a typo in that comment.

[PeteSteinfeld]

Responding to Peter's commend.

flang/runtime/numeric.cpp

125

Thanks for catching this. Corrected in the latest version.

flang/runtime/numeric.cpp

 
 // SET_EXPONENT (16.9.171)
 template <typename T> inline T SetExponent(T x, std::int64_t p) {
   if (std::isnan(x)) {
     return x; // NaN -> same NaN
   } else if (std::isinf(x)) {
     return std::numeric_limits<T>::quiet_NaN(); // +/-Inf -> NaN
   } else if (x == 0) {
-    return 0; // 0 -> 0
+    return x; // return negative zero if x is negative zero
   } else {
     int expo{std::ilogb(x) + 1};
     auto ip{static_cast<int>(p - expo)};
     if (ip != p - expo) {
       ip = p < 0 ? std::numeric_limits<int>::min()
                  : std::numeric_limits<int>::max();
     }
     return std::ldexp(x, ip); // x*2**(p-e)