107 lines · cpp
1//===-- Single-precision tanpi 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-exception6//7//===----------------------------------------------------------------------===//8 9#include "src/math/tanpif.h"10#include "src/__support/FPUtil/FEnvImpl.h"11#include "src/__support/FPUtil/FPBits.h"12#include "src/__support/FPUtil/cast.h"13#include "src/__support/FPUtil/except_value_utils.h"14#include "src/__support/FPUtil/multiply_add.h"15#include "src/__support/common.h"16#include "src/__support/macros/config.h"17#include "src/__support/macros/optimization.h" // LIBC_UNLIKELY18#include "src/__support/math/sincosf_utils.h"19 20namespace LIBC_NAMESPACE_DECL {21 22#ifndef LIBC_MATH_HAS_SKIP_ACCURATE_PASS23constexpr size_t N_EXCEPTS = 3;24 25constexpr fputil::ExceptValues<float, N_EXCEPTS> TANPIF_EXCEPTS{{26 // (input, RZ output, RU offset, RD offset, RN offset)27 {0x38F26685, 0x39BE6182, 1, 0, 0},28 {0x3E933802, 0x3FA267DD, 1, 0, 0},29 {0x3F3663FF, 0xBFA267DD, 0, 1, 0},30}};31#endif // !LIBC_MATH_HAS_SKIP_ACCURATE_PASS32 33LLVM_LIBC_FUNCTION(float, tanpif, (float x)) {34 using FPBits = typename fputil::FPBits<float>;35 FPBits xbits(x);36 37 uint32_t x_u = xbits.uintval();38 uint32_t x_abs = x_u & 0x7fff'ffffU;39 double xd = static_cast<double>(xbits.get_val());40 41 // Handle exceptional values42 if (LIBC_UNLIKELY(x_abs <= 0x3F3663FF)) {43 if (LIBC_UNLIKELY(x_abs == 0U))44 return x;45 46#ifndef LIBC_MATH_HAS_SKIP_ACCURATE_PASS47 bool x_sign = x_u >> 31;48 49 if (auto r = TANPIF_EXCEPTS.lookup_odd(x_abs, x_sign);50 LIBC_UNLIKELY(r.has_value()))51 return r.value();52#endif // !LIBC_MATH_HAS_SKIP_ACCURATE_PASS53 }54 55 // Numbers greater or equal to 2^23 are always integers, or infinity, or NaN56 if (LIBC_UNLIKELY(x_abs >= 0x4B00'0000)) {57 // x is inf or NaN.58 if (LIBC_UNLIKELY(x_abs >= 0x7f80'0000U)) {59 if (xbits.is_signaling_nan()) {60 fputil::raise_except_if_required(FE_INVALID);61 return FPBits::quiet_nan().get_val();62 }63 64 if (x_abs == 0x7f80'0000U) {65 fputil::set_errno_if_required(EDOM);66 fputil::raise_except_if_required(FE_INVALID);67 }68 69 return x + FPBits::quiet_nan().get_val();70 }71 72 return FPBits::zero(xbits.sign()).get_val();73 }74 75 // Range reduction:76 // For |x| > 1/32, we perform range reduction as follows:77 // Find k and y such that:78 // x = (k + y) * 1/3279 // k is an integer80 // |y| < 0.581 //82 // This is done by performing:83 // k = round(x * 32)84 // y = x * 32 - k85 //86 // Once k and y are computed, we then deduce the answer by the formula:87 // tan(x) = sin(x) / cos(x)88 // = (sin_y * cos_k + cos_y * sin_k) / (cos_y * cos_k - sin_y * sin_k)89 double sin_k, cos_k, sin_y, cosm1_y;90 sincospif_eval(xd, sin_k, cos_k, sin_y, cosm1_y);91 92 if (LIBC_UNLIKELY(sin_y == 0 && cos_k == 0)) {93 fputil::set_errno_if_required(EDOM);94 fputil::raise_except_if_required(FE_DIVBYZERO);95 96 int32_t x_mp5_i = static_cast<int32_t>(xd - 0.5);97 return FPBits::inf((x_mp5_i & 0x1) ? Sign::NEG : Sign::POS).get_val();98 }99 100 using fputil::multiply_add;101 return fputil::cast<float>(102 multiply_add(sin_y, cos_k, multiply_add(cosm1_y, sin_k, sin_k)) /103 multiply_add(sin_y, -sin_k, multiply_add(cosm1_y, cos_k, cos_k)));104}105 106} // namespace LIBC_NAMESPACE_DECL107