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
19namespace LIBC_NAMESPACE::fputil {
20
21// TODO: Add optimization for known good targets with fast
22// float to float16 conversion:
23// https://github.com/llvm/llvm-project/issues/133517
24template <typename OutType, typename InType>
25LIBC_INLINE constexpr cpp::enable_if_t<cpp::is_floating_point_v<OutType> &&
26 cpp::is_floating_point_v<InType>,
27 OutType>
28cast(InType x) {
29 // Casting to the same type is a no-op.
30 if constexpr (cpp::is_same_v<InType, OutType>) {
31 return x;
32 } else {
33 if constexpr (cpp::is_same_v<OutType, bfloat16> ||
34 cpp::is_same_v<InType, bfloat16> ||
35 cpp::is_same_v<OutType, Float128> ||
36 cpp::is_same_v<InType, Float128>
37#if defined(LIBC_TYPES_HAS_FLOAT16) && !defined(__LIBC_USE_FLOAT16_CONVERSION)
38 || cpp::is_same_v<OutType, float16> ||
39 cpp::is_same_v<InType, float16>
40#endif
41 ) {
42 using InFPBits = FPBits<InType>;
43 using InStorageType = typename InFPBits::StorageType;
44 using OutFPBits = FPBits<OutType>;
45 using OutStorageType = typename OutFPBits::StorageType;
46
47 InFPBits x_bits(x);
48
49 if (x_bits.is_nan()) {
50 if (x_bits.is_signaling_nan()) {
51 raise_except_if_required(FE_INVALID);
52 return OutFPBits::quiet_nan().get_val();
53 }
54
55 InStorageType x_mant = x_bits.get_mantissa();
56 if (InFPBits::FRACTION_LEN > OutFPBits::FRACTION_LEN)
57 x_mant >>= InFPBits::FRACTION_LEN - OutFPBits::FRACTION_LEN;
58 return OutFPBits::quiet_nan(x_bits.sign(),
59 static_cast<OutStorageType>(x_mant))
60 .get_val();
61 }
62
63 if (x_bits.is_inf())
64 return OutFPBits::inf(x_bits.sign()).get_val();
65
66 constexpr size_t MAX_FRACTION_LEN =
67 cpp::max(OutFPBits::FRACTION_LEN, InFPBits::FRACTION_LEN);
68 DyadicFloat<cpp::bit_ceil(value: MAX_FRACTION_LEN)> xd(x);
69 return xd.template as<OutType, /*ShouldSignalExceptions=*/true>();
70 } else {
71 return static_cast<OutType>(x);
72 }
73 }
74}
75
76} // namespace LIBC_NAMESPACE::fputil
77
78#endif // LLVM_LIBC_SRC___SUPPORT_FPUTIL_CAST_H
79