1//===-- Implementation of hypotf function ---------------------------------===//
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#include "src/math/hypotf.h"
9#include "src/__support/FPUtil/FEnvImpl.h"
10#include "src/__support/FPUtil/FPBits.h"
11#include "src/__support/FPUtil/double_double.h"
12#include "src/__support/FPUtil/multiply_add.h"
13#include "src/__support/FPUtil/sqrt.h"
14#include "src/__support/common.h"
15#include "src/__support/macros/config.h"
16#include "src/__support/macros/optimization.h"
17
18namespace LIBC_NAMESPACE_DECL {
19
20LLVM_LIBC_FUNCTION(float, hypotf, (float x, float y)) {
21 using DoubleBits = fputil::FPBits<double>;
22 using FPBits = fputil::FPBits<float>;
23
24 FPBits x_abs = FPBits(x).abs();
25 FPBits y_abs = FPBits(y).abs();
26
27 bool x_abs_larger = x_abs.uintval() >= y_abs.uintval();
28
29 FPBits a_bits = x_abs_larger ? x_abs : y_abs;
30 FPBits b_bits = x_abs_larger ? y_abs : x_abs;
31
32 uint32_t a_u = a_bits.uintval();
33 uint32_t b_u = b_bits.uintval();
34
35 // Note: replacing `a_u >= FPBits::EXP_MASK` with `a_bits.is_inf_or_nan()`
36 // generates extra exponent bit masking instructions on x86-64.
37 if (LIBC_UNLIKELY(a_u >= FPBits::EXP_MASK)) {
38 // x or y is inf or nan
39 if (a_bits.is_signaling_nan() || b_bits.is_signaling_nan()) {
40 fputil::raise_except_if_required(FE_INVALID);
41 return FPBits::quiet_nan().get_val();
42 }
43 if (a_bits.is_inf() || b_bits.is_inf())
44 return FPBits::inf().get_val();
45 return a_bits.get_val();
46 }
47
48 if (LIBC_UNLIKELY(a_u - b_u >=
49 static_cast<uint32_t>((FPBits::FRACTION_LEN + 2)
50 << FPBits::FRACTION_LEN)))
51 return x_abs.get_val() + y_abs.get_val();
52
53 double ad = static_cast<double>(a_bits.get_val());
54 double bd = static_cast<double>(b_bits.get_val());
55
56 // These squares are exact.
57 double a_sq = ad * ad;
58#ifdef LIBC_TARGET_CPU_HAS_FMA_DOUBLE
59 double sum_sq = fputil::multiply_add(bd, bd, a_sq);
60#else
61 double b_sq = bd * bd;
62 double sum_sq = a_sq + b_sq;
63#endif
64
65 // Take sqrt in double precision.
66 DoubleBits result(fputil::sqrt<double>(sum_sq));
67 uint64_t r_u = result.uintval();
68
69 // If any of the sticky bits of the result are non-zero, except the LSB, then
70 // the rounded result is correct.
71 if (LIBC_UNLIKELY(((r_u + 1) & 0x0000'0000'0FFF'FFFE) == 0)) {
72 double r_d = result.get_val();
73
74 // Perform rounding correction.
75#ifdef LIBC_TARGET_CPU_HAS_FMA_DOUBLE
76 double sum_sq_lo = fputil::multiply_add(bd, bd, a_sq - sum_sq);
77 double err = sum_sq_lo - fputil::multiply_add(r_d, r_d, -sum_sq);
78#else
79 fputil::DoubleDouble r_sq = fputil::exact_mult(r_d, r_d);
80 double sum_sq_lo = b_sq - (sum_sq - a_sq);
81 double err = (sum_sq - r_sq.hi) + (sum_sq_lo - r_sq.lo);
82#endif
83
84 if (err > 0) {
85 r_u |= 1;
86 } else if ((err < 0) && (r_u & 1) == 0) {
87 r_u -= 1;
88 } else if ((r_u & 0x0000'0000'1FFF'FFFF) == 0) {
89 // The rounded result is exact.
90 fputil::clear_except_if_required(FE_INEXACT);
91 }
92 return static_cast<float>(DoubleBits(r_u).get_val());
93 }
94
95 return static_cast<float>(result.get_val());
96}
97
98} // namespace LIBC_NAMESPACE_DECL
99

source code of libc/src/math/generic/hypotf.cpp