Fix numeric of exp(complex) at inf

[zasdfgbnm]

Summary

This fixes the bug that exp({501, 0}) returns {inf, nan} instead of {inf, 0}

[ldionne]

The CI failures are unrelated.

libcxx/include/complex

 
 // exp
 
 template<class _Tp>
 complex<_Tp>
 exp(const complex<_Tp>& __x)
 {
     _Tp __i = __x.imag();
+    if (__i == 0) {
+        return complex<_Tp>(exp(__x.real()), copysign(_Tp(0), __x.imag()));
+    }
     if (__libcpp_isinf_or_builtin(__x.real()))
     {
         if (__x.real() < _Tp(0))
         {
             if (!__libcpp_isfinite_or_builtin(__i))
                 __i = _Tp(1);
         }
         else if (__i == 0 || !__libcpp_isfinite_or_builtin(__i))
         {
             if (__libcpp_isinf_or_builtin(__i))
                 __i = _Tp(NAN);
             return complex<_Tp>(__x.real(), __i);
         }
     }
-    else if (__libcpp_isnan_or_builtin(__x.real()) && __x.imag() == 0)
-        return __x;
     _Tp __e = exp(__x.real());
     return complex<_Tp>(__e * cos(__i), __e * sin(__i));
 }
 
 // pow
 
 template<class _Tp>
 inline _LIBCPP_INLINE_VISIBILITY

libcxx/test/std/numerics/complex.number/cases.h

const std::complex<double> testcases[] =
     std::complex<double>(-1.e-6, -1.e+6),
     std::complex<double>( 1.e-6, -1.e+6),
 
     std::complex<double>( 1.e+6,  1.e+6),
     std::complex<double>(-1.e+6,  1.e+6),
     std::complex<double>(-1.e+6, -1.e+6),
     std::complex<double>( 1.e+6, -1.e+6),
 
+    std::complex<double>(-0, -1.e-6),
+    std::complex<double>(-0,  1.e-6),
+    std::complex<double>(-0,  1.e+6),
+    std::complex<double>(-0, -1.e+6),
+    std::complex<double>( 0, -1.e-6),
+    std::complex<double>( 0,  1.e-6),
+    std::complex<double>( 0,  1.e+6),
+    std::complex<double>( 0, -1.e+6),
+
+    std::complex<double>(-1.e-6, -0),
+    std::complex<double>( 1.e-6, -0),
+    std::complex<double>( 1.e+6, -0),
+    std::complex<double>(-1.e+6, -0),
+    std::complex<double>(-1.e-6,  0),
+    std::complex<double>( 1.e-6,  0),
+    std::complex<double>( 1.e+6,  0),
+    std::complex<double>(-1.e+6,  0),
+
     std::complex<double>(NAN, NAN),
     std::complex<double>(-INFINITY, NAN),
     std::complex<double>(-2, NAN),
     std::complex<double>(-1, NAN),
     std::complex<double>(-0.5, NAN),
     std::complex<double>(-0., NAN),
     std::complex<double>(+0., NAN),
     std::complex<double>(0.5, NAN),

libcxx/test/std/numerics/complex.number/complex.transcendentals/exp.pass.cpp

for (unsigned i = 0; i < N; ++i)
             assert(std::isnan(r.real()));
             assert(std::isnan(r.imag()));
         }
         else if (std::isfinite(testcases[i].imag()) && std::abs(testcases[i].imag()) <= 1)
         {
             assert(!std::signbit(r.real()));
             assert(std::signbit(r.imag()) == std::signbit(testcases[i].imag()));
         }
+        else if (std::isinf(r.real()) && testcases[i].imag() == 0) {
+            assert(r.imag() == 0);
+            assert(std::signbit(testcases[i].imag()) == std::signbit(r.imag()));
+        }
     }
 }
 
 int main(int, char**)
 {
     test<float>();
     test<double>();
     test<long double>();
     test_edges();
 
     return 0;
 }