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 // TODO: Add optimization for known good targets with fast
22 // float to float16 conversion:
23 // https://github.com/llvm/llvm-project/issues/133517
24 template <typename OutType, typename InType>
25 LIBC_INLINE constexpr cpp::enable_if_t<cpp::is_floating_point_v<OutType> &&
26 cpp::is_floating_point_v<InType>,
27 OutType>
cast(InType x)28 cast(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
33 // bfloat16 is always defined (for now)
34 if constexpr (cpp::is_same_v<OutType, bfloat16> ||
35 cpp::is_same_v<InType, bfloat16>
36 #if defined(LIBC_TYPES_HAS_FLOAT16) && !defined(__LIBC_USE_FLOAT16_CONVERSION)
37 || cpp::is_same_v<OutType, float16> ||
38 cpp::is_same_v<InType, float16>
39 #endif
40 ) {
41 using InFPBits = FPBits<InType>;
42 using InStorageType = typename InFPBits::StorageType;
43 using OutFPBits = FPBits<OutType>;
44 using OutStorageType = typename OutFPBits::StorageType;
45
46 InFPBits x_bits(x);
47
48 if (x_bits.is_nan()) {
49 if (x_bits.is_signaling_nan()) {
50 raise_except_if_required(FE_INVALID);
51 return OutFPBits::quiet_nan().get_val();
52 }
53
54 InStorageType x_mant = x_bits.get_mantissa();
55 if (InFPBits::FRACTION_LEN > OutFPBits::FRACTION_LEN)
56 x_mant >>= InFPBits::FRACTION_LEN - OutFPBits::FRACTION_LEN;
57 return OutFPBits::quiet_nan(x_bits.sign(),
58 static_cast<OutStorageType>(x_mant))
59 .get_val();
60 }
61
62 if (x_bits.is_inf())
63 return OutFPBits::inf(x_bits.sign()).get_val();
64
65 constexpr size_t MAX_FRACTION_LEN =
66 cpp::max(OutFPBits::FRACTION_LEN, InFPBits::FRACTION_LEN);
67 DyadicFloat<cpp::bit_ceil(MAX_FRACTION_LEN)> xd(x);
68 return xd.template as<OutType, /*ShouldSignalExceptions=*/true>();
69 }
70
71 return static_cast<OutType>(x);
72 }
73
74 } // namespace LIBC_NAMESPACE::fputil
75
76 #endif // LLVM_LIBC_SRC___SUPPORT_FPUTIL_CAST_H
77