[libc-commits] [libc] [libc][NFC] unify nextafter and nexttoward code (PR #73698)

[Nishant Mittal via libc-commits]

================
@@ -144,59 +144,26 @@ LIBC_INLINE T ldexp(T x, int exp) {
   return normal;
 }
 
-template <typename T, cpp::enable_if_t<cpp::is_floating_point_v<T>, int> = 0>
-LIBC_INLINE T nextafter(T from, T to) {
-  FPBits<T> from_bits(from);
-  if (from_bits.is_nan())
-    return from;
-
-  FPBits<T> to_bits(to);
-  if (to_bits.is_nan())
-    return to;
-
-  if (from == to)
-    return to;
-
-  using UIntType = typename FPBits<T>::UIntType;
-  UIntType int_val = from_bits.uintval();
-  UIntType sign_mask = (UIntType(1) << (sizeof(T) * 8 - 1));
-  if (from != T(0.0)) {
-    if ((from < to) == (from > T(0.0))) {
-      ++int_val;
-    } else {
-      --int_val;
-    }
-  } else {
-    int_val = (to_bits.uintval() & sign_mask) + UIntType(1);
-  }
-
-  UIntType exponent_bits = int_val & FloatProperties<T>::EXPONENT_MASK;
-  if (exponent_bits == UIntType(0))
-    raise_except_if_required(FE_UNDERFLOW | FE_INEXACT);
-  else if (exponent_bits == FloatProperties<T>::EXPONENT_MASK)
-    raise_except_if_required(FE_OVERFLOW | FE_INEXACT);
-
-  return cpp::bit_cast<T>(int_val);
-}
-
-template <typename T>
-LIBC_INLINE cpp::enable_if_t<cpp::is_floating_point_v<T>, T>
-nexttoward(T from, long double to) {
+template <
+    typename T, typename U,
+    cpp::enable_if_t<cpp::is_floating_point_v<T> && cpp::is_floating_point_v<U>,
+                     int> = 0>
+LIBC_INLINE T nextafter(T from, U to) {
   FPBits<T> from_bits(from);
   if (from_bits.is_nan())
     return from;
 
-  FPBits<long double> to_bits(to);
+  FPBits<U> to_bits(to);
   if (to_bits.is_nan())
-    return to;
+    return static_cast<T>(to);
 
-  if ((long double)from == to)
-    return to;
+  if (static_cast<U>(from) == to)
----------------
nishantwrp wrote:

Just a side note: This would work only if U is equal or higher precision than T. (Which is OK for our usecase but should we add a comment or maybe some condition in `enable_if` that ensures this?)

https://github.com/llvm/llvm-project/pull/73698