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1//===-- Division of IEEE 754 floating-point numbers -------------*- 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_GENERIC_DIV_H
10#define LLVM_LIBC_SRC___SUPPORT_FPUTIL_GENERIC_DIV_H
11
12#include "hdr/errno_macros.h"
13#include "hdr/fenv_macros.h"
14#include "src/__support/CPP/bit.h"
15#include "src/__support/CPP/type_traits.h"
16#include "src/__support/FPUtil/BasicOperations.h"
17#include "src/__support/FPUtil/FEnvImpl.h"
18#include "src/__support/FPUtil/FPBits.h"
19#include "src/__support/FPUtil/dyadic_float.h"
20#include "src/__support/macros/attributes.h"
21#include "src/__support/macros/config.h"
22#include "src/__support/macros/optimization.h"
23
24namespace LIBC_NAMESPACE_DECL {
25namespace fputil::generic {
26
27template <typename OutType, typename InType>
28LIBC_INLINE cpp::enable_if_t<cpp::is_floating_point_v<OutType> &&
29 cpp::is_floating_point_v<InType> &&
30 sizeof(OutType) <= sizeof(InType),
31 OutType>
32div(InType x, InType y) {
33 using OutFPBits = FPBits<OutType>;
34 using OutStorageType = typename OutFPBits::StorageType;
35 using InFPBits = FPBits<InType>;
36 using InStorageType = typename InFPBits::StorageType;
37 using DyadicFloat =
38 DyadicFloat<cpp::bit_ceil(static_cast<size_t>(InFPBits::SIG_LEN + 1))>;
39
40 InFPBits x_bits(x);
41 InFPBits y_bits(y);
42
43 Sign result_sign = x_bits.sign() == y_bits.sign() ? Sign::POS : Sign::NEG;
44
45 if (LIBC_UNLIKELY(x_bits.is_inf_or_nan() || y_bits.is_inf_or_nan() ||
46 x_bits.is_zero() || y_bits.is_zero())) {
47 if (x_bits.is_nan() || y_bits.is_nan()) {
48 if (x_bits.is_signaling_nan() || y_bits.is_signaling_nan())
49 raise_except_if_required(FE_INVALID);
50
51 if (x_bits.is_quiet_nan()) {
52 InStorageType x_payload = x_bits.get_mantissa();
53 x_payload >>= InFPBits::FRACTION_LEN - OutFPBits::FRACTION_LEN;
54 return OutFPBits::quiet_nan(x_bits.sign(),
55 static_cast<OutStorageType>(x_payload))
56 .get_val();
57 }
58
59 if (y_bits.is_quiet_nan()) {
60 InStorageType y_payload = y_bits.get_mantissa();
61 y_payload >>= InFPBits::FRACTION_LEN - OutFPBits::FRACTION_LEN;
62 return OutFPBits::quiet_nan(y_bits.sign(),
63 static_cast<OutStorageType>(y_payload))
64 .get_val();
65 }
66
67 return OutFPBits::quiet_nan().get_val();
68 }
69
70 if (x_bits.is_inf()) {
71 if (y_bits.is_inf()) {
72 set_errno_if_required(EDOM);
73 raise_except_if_required(FE_INVALID);
74 return OutFPBits::quiet_nan().get_val();
75 }
76
77 return OutFPBits::inf(result_sign).get_val();
78 }
79
80 if (y_bits.is_inf())
81 return OutFPBits::inf(result_sign).get_val();
82
83 if (y_bits.is_zero()) {
84 if (x_bits.is_zero()) {
85 raise_except_if_required(FE_INVALID);
86 return OutFPBits::quiet_nan().get_val();
87 }
88
89 raise_except_if_required(FE_DIVBYZERO);
90 return OutFPBits::inf(result_sign).get_val();
91 }
92
93 if (x_bits.is_zero())
94 return OutFPBits::zero(result_sign).get_val();
95 }
96
97 DyadicFloat xd(x);
98 DyadicFloat yd(y);
99
100 // Number of iterations = full output precision + 1 rounding bit + 1 potential
101 // leading 0.
102 constexpr int NUM_ITERS = OutFPBits::FRACTION_LEN + 3;
103 int result_exp = xd.exponent - yd.exponent - (NUM_ITERS - 1);
104
105 InStorageType q = 0;
106 InStorageType r = static_cast<InStorageType>(xd.mantissa >> 2);
107 InStorageType yd_mant_in = static_cast<InStorageType>(yd.mantissa >> 1);
108
109 for (int i = 0; i < NUM_ITERS; ++i) {
110 q <<= 1;
111 r <<= 1;
112 if (r >= yd_mant_in) {
113 q += 1;
114 r -= yd_mant_in;
115 }
116 }
117
118 DyadicFloat result(result_sign, result_exp, q);
119 result.mantissa |= static_cast<unsigned int>(r != 0);
120 return result.template as<OutType, /*ShouldSignalExceptions=*/true>();
121}
122
123} // namespace fputil::generic
124} // namespace LIBC_NAMESPACE_DECL
125
126#endif // LLVM_LIBC_SRC___SUPPORT_FPUTIL_GENERIC_DIV_H
127

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source code of libc/src/__support/FPUtil/generic/div.h