[HIP] cmath demote long double args to double

[ashi1]

Summary

Since there is no ROCm Device Library support for
long double, demote them to double, and use the fp64
math functions.

[ashi1]

There are applications calling functions such as fmod(long double x, long double y), but this produces a "call is ambiguous" error.

[tra]

LGTM in general. Will defer to Sam as it's HIP.

Nit:

long double, promote them to double, and use the fp64

I'd say long double -> double qualifies as a demotion.

[yaxunl]

LGTM. Thanks.

[ashi1]

In D92130#2423801, @tra wrote:

LGTM in general. Will defer to Sam as it's HIP.

Nit:

long double, promote them to double, and use the fp64

I'd say long double -> double qualifies as a demotion.

Thanks, I've changed the commit description to demote.

clang/lib/Headers/__clang_hip_cmath.h

template <class _Tp> struct __numeric_type {
   static double __test(char);
   static double __test(int);
   static double __test(unsigned);
   static double __test(long);
   static double __test(unsigned long);
   static double __test(long long);
   static double __test(unsigned long long);
   static double __test(double);
+  // No support for long double, use double instead.
+  static double __test(long double);
 
   typedef decltype(__test(std::declval<_Tp>())) type;
   static const bool value = !std::is_same<type, void>::value;
 };
 
 template <> struct __numeric_type<void> { static const bool value = true; };
 
 template <class _A1, class _A2 = void, class _A3 = void,