142 lines · c
1//===-- Implementation header for exp10f16 ----------------------*- 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-exception6//7//===----------------------------------------------------------------------===//8 9#ifndef LLVM_LIBC_SRC___SUPPORT_MATH_EXP10F16_H10#define LLVM_LIBC_SRC___SUPPORT_MATH_EXP10F16_H11 12#include "include/llvm-libc-macros/float16-macros.h"13 14#ifdef LIBC_TYPES_HAS_FLOAT1615 16#include "exp10f16_utils.h"17#include "src/__support/FPUtil/FEnvImpl.h"18#include "src/__support/FPUtil/FPBits.h"19#include "src/__support/FPUtil/cast.h"20#include "src/__support/FPUtil/except_value_utils.h"21#include "src/__support/FPUtil/rounding_mode.h"22#include "src/__support/macros/config.h"23#include "src/__support/macros/optimization.h"24#include "src/__support/macros/properties/cpu_features.h"25 26namespace LIBC_NAMESPACE_DECL {27 28namespace math {29 30#ifndef LIBC_MATH_HAS_SKIP_ACCURATE_PASS31#ifdef LIBC_TARGET_CPU_HAS_FMA_FLOAT32static constexpr size_t N_EXP10F16_EXCEPTS = 5;33#else34static constexpr size_t N_EXP10F16_EXCEPTS = 8;35#endif36 37static constexpr fputil::ExceptValues<float16, N_EXP10F16_EXCEPTS>38 EXP10F16_EXCEPTS = {{39 // x = 0x1.8f4p-2, exp10f16(x) = 0x1.3ap+1 (RZ)40 {0x363dU, 0x40e8U, 1U, 0U, 1U},41 // x = 0x1.95cp-2, exp10f16(x) = 0x1.3ecp+1 (RZ)42 {0x3657U, 0x40fbU, 1U, 0U, 0U},43 // x = -0x1.018p-4, exp10f16(x) = 0x1.bbp-1 (RZ)44 {0xac06U, 0x3aecU, 1U, 0U, 0U},45 // x = -0x1.c28p+0, exp10f16(x) = 0x1.1ccp-6 (RZ)46 {0xbf0aU, 0x2473U, 1U, 0U, 0U},47 // x = -0x1.e1cp+1, exp10f16(x) = 0x1.694p-13 (RZ)48 {0xc387U, 0x09a5U, 1U, 0U, 0U},49#ifndef LIBC_TARGET_CPU_HAS_FMA_FLOAT50 // x = 0x1.0cp+1, exp10f16(x) = 0x1.f04p+6 (RZ)51 {0x4030U, 0x57c1U, 1U, 0U, 1U},52 // x = 0x1.1b8p+1, exp10f16(x) = 0x1.47cp+7 (RZ)53 {0x406eU, 0x591fU, 1U, 0U, 1U},54 // x = 0x1.1b8p+2, exp10f16(x) = 0x1.a4p+14 (RZ)55 {0x446eU, 0x7690U, 1U, 0U, 1U},56#endif57 }};58#endif // !LIBC_MATH_HAS_SKIP_ACCURATE_PASS59 60LIBC_INLINE static constexpr float16 exp10f16(float16 x) {61 using FPBits = fputil::FPBits<float16>;62 FPBits x_bits(x);63 64 uint16_t x_u = x_bits.uintval();65 uint16_t x_abs = x_u & 0x7fffU;66 67 // When |x| >= 5, or x is NaN.68 if (LIBC_UNLIKELY(x_abs >= 0x4500U)) {69 // exp10(NaN) = NaN70 if (x_bits.is_nan()) {71 if (x_bits.is_signaling_nan()) {72 fputil::raise_except_if_required(FE_INVALID);73 return FPBits::quiet_nan().get_val();74 }75 76 return x;77 }78 79 // When x >= 5.80 if (x_bits.is_pos()) {81 // exp10(+inf) = +inf82 if (x_bits.is_inf())83 return FPBits::inf().get_val();84 85 switch (fputil::quick_get_round()) {86 case FE_TONEAREST:87 case FE_UPWARD:88 fputil::set_errno_if_required(ERANGE);89 fputil::raise_except_if_required(FE_OVERFLOW);90 return FPBits::inf().get_val();91 default:92 return FPBits::max_normal().get_val();93 }94 }95 96 // When x <= -8.97 if (x_u >= 0xc800U) {98 // exp10(-inf) = +099 if (x_bits.is_inf())100 return FPBits::zero().get_val();101 102 fputil::set_errno_if_required(ERANGE);103 fputil::raise_except_if_required(FE_UNDERFLOW | FE_INEXACT);104 105 if (fputil::fenv_is_round_up())106 return FPBits::min_subnormal().get_val();107 return FPBits::zero().get_val();108 }109 }110 111 // When x is 1, 2, 3, or 4. These are hard-to-round cases with exact results.112 if (LIBC_UNLIKELY((x_u & ~(0x3c00U | 0x4000U | 0x4200U | 0x4400U)) == 0)) {113 switch (x_u) {114 case 0x3c00U: // x = 1.0f16115 return fputil::cast<float16>(10.0);116 case 0x4000U: // x = 2.0f16117 return fputil::cast<float16>(100.0);118 case 0x4200U: // x = 3.0f16119 return fputil::cast<float16>(1'000.0);120 case 0x4400U: // x = 4.0f16121 return fputil::cast<float16>(10'000.0);122 }123 }124 125#ifndef LIBC_MATH_HAS_SKIP_ACCURATE_PASS126 if (auto r = EXP10F16_EXCEPTS.lookup(x_u); LIBC_UNLIKELY(r.has_value()))127 return r.value();128#endif // !LIBC_MATH_HAS_SKIP_ACCURATE_PASS129 130 // 10^x = 2^((hi + mid) * log2(10)) * 10^lo131 auto [exp2_hi_mid, exp10_lo] = exp10_range_reduction(x);132 return fputil::cast<float16>(exp2_hi_mid * exp10_lo);133}134 135} // namespace math136 137} // namespace LIBC_NAMESPACE_DECL138 139#endif // LIBC_TYPES_HAS_FLOAT16140 141#endif // LLVM_LIBC_SRC___SUPPORT_MATH_EXP10F16_H142