1//===-- Single-precision atanh 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
9#include "src/math/atanhf.h"
10#include "src/__support/FPUtil/FPBits.h"
11#include "src/__support/macros/config.h"
12#include "src/__support/macros/optimization.h" // LIBC_UNLIKELY
13#include "src/math/generic/explogxf.h"
14
15namespace LIBC_NAMESPACE_DECL {
16
17LLVM_LIBC_FUNCTION(float, atanhf, (float x)) {
18 using FPBits = typename fputil::FPBits<float>;
19
20 FPBits xbits(x);
21 Sign sign = xbits.sign();
22 uint32_t x_abs = xbits.abs().uintval();
23
24 // |x| >= 1.0
25 if (LIBC_UNLIKELY(x_abs >= 0x3F80'0000U)) {
26 if (xbits.is_nan()) {
27 if (xbits.is_signaling_nan()) {
28 fputil::raise_except_if_required(FE_INVALID);
29 return FPBits::quiet_nan().get_val();
30 }
31 return x;
32 }
33 // |x| == 1.0
34 if (x_abs == 0x3F80'0000U) {
35 fputil::set_errno_if_required(ERANGE);
36 fputil::raise_except_if_required(FE_DIVBYZERO);
37 return FPBits::inf(sign).get_val();
38 } else {
39 fputil::set_errno_if_required(EDOM);
40 fputil::raise_except_if_required(FE_INVALID);
41 return FPBits::quiet_nan().get_val();
42 }
43 }
44
45 // |x| < ~0.10
46 if (LIBC_UNLIKELY(x_abs <= 0x3dcc'0000U)) {
47 // |x| <= 2^-26
48 if (LIBC_UNLIKELY(x_abs <= 0x3280'0000U)) {
49 return static_cast<float>(LIBC_UNLIKELY(x_abs == 0)
50 ? x
51 : (x + 0x1.5555555555555p-2 * x * x * x));
52 }
53
54 double xdbl = x;
55 double x2 = xdbl * xdbl;
56 // Pure Taylor series.
57 double pe = fputil::polyeval(x2, 0.0, 0x1.5555555555555p-2,
58 0x1.999999999999ap-3, 0x1.2492492492492p-3,
59 0x1.c71c71c71c71cp-4, 0x1.745d1745d1746p-4);
60 return static_cast<float>(fputil::multiply_add(xdbl, pe, xdbl));
61 }
62 double xdbl = x;
63 return static_cast<float>(0.5 * log_eval((xdbl + 1.0) / (xdbl - 1.0)));
64}
65
66} // namespace LIBC_NAMESPACE_DECL
67

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