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/optimization.h" // LIBC_UNLIKELY
12#include "src/math/generic/explogxf.h"
13
14namespace LIBC_NAMESPACE {
15
16LLVM_LIBC_FUNCTION(float, atanhf, (float x)) {
17 using FPBits = typename fputil::FPBits<float>;
18
19 FPBits xbits(x);
20 Sign sign = xbits.sign();
21 uint32_t x_abs = xbits.abs().uintval();
22
23 // |x| >= 1.0
24 if (LIBC_UNLIKELY(x_abs >= 0x3F80'0000U)) {
25 if (xbits.is_nan()) {
26 return x;
27 }
28 // |x| == 1.0
29 if (x_abs == 0x3F80'0000U) {
30 fputil::set_errno_if_required(ERANGE);
31 fputil::raise_except_if_required(FE_DIVBYZERO);
32 return FPBits::inf(sign).get_val();
33 } else {
34 fputil::set_errno_if_required(EDOM);
35 fputil::raise_except_if_required(FE_INVALID);
36 return FPBits::quiet_nan().get_val();
37 }
38 }
39
40 // |x| < ~0.10
41 if (LIBC_UNLIKELY(x_abs <= 0x3dcc'0000U)) {
42 // |x| <= 2^-26
43 if (LIBC_UNLIKELY(x_abs <= 0x3280'0000U)) {
44 return static_cast<float>(LIBC_UNLIKELY(x_abs == 0)
45 ? x
46 : (x + 0x1.5555555555555p-2 * x * x * x));
47 }
48
49 double xdbl = x;
50 double x2 = xdbl * xdbl;
51 // Pure Taylor series.
52 double pe = fputil::polyeval(x: x2, a0: 0.0, a: 0x1.5555555555555p-2,
53 a: 0x1.999999999999ap-3, a: 0x1.2492492492492p-3,
54 a: 0x1.c71c71c71c71cp-4, a: 0x1.745d1745d1746p-4);
55 return static_cast<float>(fputil::multiply_add(x: xdbl, y: pe, z: xdbl));
56 }
57 double xdbl = x;
58 return static_cast<float>(0.5 * log_eval(x: (xdbl + 1.0) / (xdbl - 1.0)));
59}
60
61} // namespace LIBC_NAMESPACE
62

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