libc/src/__support/FPUtil/cast.h

   1 //===-- Conversion between floating-point types -----------------*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #ifndef LLVM_LIBC_SRC___SUPPORT_FPUTIL_CAST_H
  10 #define LLVM_LIBC_SRC___SUPPORT_FPUTIL_CAST_H
  11
  12 #include "FPBits.h"
  13 #include "dyadic_float.h"
  14 #include "hdr/fenv_macros.h"
  15 #include "src/__support/CPP/algorithm.h"
  16 #include "src/__support/CPP/type_traits.h"
  17 #include "src/__support/macros/properties/types.h"
  18
  19 namespace LIBC_NAMESPACE::fputil {
  20
  21 template <typename OutType, typename InType>
  22 LIBC_INLINE constexpr cpp::enable_if_t<cpp::is_floating_point_v<OutType> &&
  23                                            cpp::is_floating_point_v<InType>,
  24                                        OutType>
  25 cast(InType x) {
  26 #if defined(LIBC_TYPES_HAS_FLOAT16) && !defined(__LIBC_USE_FLOAT16_CONVERSION)
  27   if constexpr (cpp::is_same_v<OutType, float16> ||
  28                 cpp::is_same_v<InType, float16>) {
  29     using InFPBits = FPBits<InType>;
  30     using InStorageType = typename InFPBits::StorageType;
  31     using OutFPBits = FPBits<OutType>;
  32     using OutStorageType = typename OutFPBits::StorageType;
  33
  34     InFPBits x_bits(x);
  35
  36     if (x_bits.is_nan()) {
  37       if (x_bits.is_signaling_nan()) {
  38         raise_except_if_required(FE_INVALID);
  39         return OutFPBits::quiet_nan().get_val();
  40       }
  41
  42       InStorageType x_mant = x_bits.get_mantissa();
  43       if (InFPBits::FRACTION_LEN > OutFPBits::FRACTION_LEN)
  44         x_mant >>= InFPBits::FRACTION_LEN - OutFPBits::FRACTION_LEN;
  45       return OutFPBits::quiet_nan(x_bits.sign(),
  46                                   static_cast<OutStorageType>(x_mant))
  47           .get_val();
  48     }
  49
  50     if (x_bits.is_inf())
  51       return OutFPBits::inf(x_bits.sign()).get_val();
  52
  53     constexpr size_t MAX_FRACTION_LEN =
  54         cpp::max(OutFPBits::FRACTION_LEN, InFPBits::FRACTION_LEN);
  55     DyadicFloat<cpp::bit_ceil(MAX_FRACTION_LEN)> xd(x);
  56     return xd.template as<OutType, /*ShouldSignalExceptions=*/true>();
  57   }
  58 #endif
  59
  60   return static_cast<OutType>(x);
  61 }
  62
  63 } // namespace LIBC_NAMESPACE::fputil
  64
  65 #endif // LLVM_LIBC_SRC___SUPPORT_FPUTIL_CAST_H