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[libc][math] Refactor exp2m1f16 implementation to header-only in src/__support/math folder.
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9 files changed

+250
-167
lines changed

9 files changed

+250
-167
lines changed

‎libc/shared/math.h‎

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@@ -51,6 +51,7 @@
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#include "math/exp2f.h"
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#include "math/exp2f16.h"
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#include "math/exp2m1f.h"
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#include "math/exp2m1f16.h"
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#include "math/expf.h"
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#include "math/expf16.h"
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#include "math/frexpf.h"

‎libc/shared/math/exp2m1f16.h‎

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//===-- Shared exp2m1f16 function -------------------------------*- C++ -*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_LIBC_SHARED_MATH_EXP2M1F16_H
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#define LLVM_LIBC_SHARED_MATH_EXP2M1F16_H
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#include "include/llvm-libc-macros/float16-macros.h"
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#include "shared/libc_common.h"
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#ifdef LIBC_TYPES_HAS_FLOAT16
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#include "src/__support/math/exp2m1f16.h"
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namespace LIBC_NAMESPACE_DECL {
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namespace shared {
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using math::exp2m1f16;
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} // namespace shared
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} // namespace LIBC_NAMESPACE_DECL
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#endif // LIBC_TYPES_HAS_FLOAT16
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#endif // LLVM_LIBC_SHARED_MATH_EXP2M1F16_H

‎libc/src/__support/math/CMakeLists.txt‎

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@@ -785,6 +785,24 @@ add_header_library(
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libc.src.__support.macros.properties.cpu_features
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)
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add_header_library(
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exp2m1f16
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HDRS
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exp2m1f16.h
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DEPENDS
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.expxf16_utils
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libc.src.__support.common
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libc.src.__support.FPUtil.cast
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libc.src.__support.FPUtil.except_value_utils
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libc.src.__support.FPUtil.fenv_impl
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libc.src.__support.FPUtil.fp_bits
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libc.src.__support.FPUtil.multiply_add
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libc.src.__support.FPUtil.polyeval
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libc.src.__support.FPUtil.rounding_mode
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libc.src.__support.macros.optimization
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libc.src.__support.macros.properties.cpu_features
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)
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add_header_library(
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exp10
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HDRS

‎libc/src/__support/math/exp2m1f16.h‎

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//===-- Implementation header for exp2m1f16 ----------------------*- C++-*-===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_LIBC_SRC___SUPPORT_MATH_EXP2M1F16_H
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#define LLVM_LIBC_SRC___SUPPORT_MATH_EXP2M1F16_H
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#include "include/llvm-libc-macros/float16-macros.h"
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#ifdef LIBC_TYPES_HAS_FLOAT16
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#include "src/__support/FPUtil/FEnvImpl.h"
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#include "src/__support/FPUtil/FPBits.h"
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#include "src/__support/FPUtil/PolyEval.h"
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#include "src/__support/FPUtil/cast.h"
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#include "src/__support/FPUtil/except_value_utils.h"
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#include "src/__support/FPUtil/multiply_add.h"
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#include "src/__support/FPUtil/rounding_mode.h"
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#include "src/__support/macros/config.h"
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#include "src/__support/macros/optimization.h"
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#include "src/__support/macros/properties/cpu_features.h"
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#include "src/__support/math/expxf16_utils.h"
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namespace LIBC_NAMESPACE_DECL {
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namespace math {
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LIBC_INLINE static constexpr float16 exp2m1f16(float16 x) {
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#ifndef LIBC_MATH_HAS_SKIP_ACCURATE_PASS
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constexpr fputil::ExceptValues<float16, 6> EXP2M1F16_EXCEPTS_LO = {{
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// (input, RZ output, RU offset, RD offset, RN offset)
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// x = 0x1.cf4p-13, exp2m1f16(x) = 0x1.41p-13 (RZ)
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{0x0b3dU, 0x0904U, 1U, 0U, 1U},
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// x = 0x1.4fcp-12, exp2m1f16(x) = 0x1.d14p-13 (RZ)
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{0x0d3fU, 0x0b45U, 1U, 0U, 1U},
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// x = 0x1.63p-11, exp2m1f16(x) = 0x1.ec4p-12 (RZ)
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{0x118cU, 0x0fb1U, 1U, 0U, 0U},
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// x = 0x1.6fp-7, exp2m1f16(x) = 0x1.fe8p-8 (RZ)
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{0x21bcU, 0x1ffaU, 1U, 0U, 1U},
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// x = -0x1.c6p-10, exp2m1f16(x) = -0x1.3a8p-10 (RZ)
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{0x9718U, 0x94eaU, 0U, 1U, 0U},
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// x = -0x1.cfcp-10, exp2m1f16(x) = -0x1.414p-10 (RZ)
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{0x973fU, 0x9505U, 0U, 1U, 0U},
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}};
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#ifdef LIBC_TARGET_CPU_HAS_FMA_FLOAT
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constexpr size_t N_EXP2M1F16_EXCEPTS_HI = 6;
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#else
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constexpr size_t N_EXP2M1F16_EXCEPTS_HI = 7;
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#endif
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constexpr fputil::ExceptValues<float16, N_EXP2M1F16_EXCEPTS_HI>
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EXP2M1F16_EXCEPTS_HI = {{
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// (input, RZ output, RU offset, RD offset, RN offset)
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// x = 0x1.e58p-3, exp2m1f16(x) = 0x1.6dcp-3 (RZ)
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{0x3396U, 0x31b7U, 1U, 0U, 0U},
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#ifndef LIBC_TARGET_CPU_HAS_FMA_FLOAT
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// x = 0x1.2e8p-2, exp2m1f16(x) = 0x1.d14p-3 (RZ)
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{0x34baU, 0x3345U, 1U, 0U, 0U},
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#endif
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// x = 0x1.ad8p-2, exp2m1f16(x) = 0x1.598p-2 (RZ)
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{0x36b6U, 0x3566U, 1U, 0U, 0U},
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#ifdef LIBC_TARGET_CPU_HAS_FMA_FLOAT
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// x = 0x1.edcp-2, exp2m1f16(x) = 0x1.964p-2 (RZ)
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{0x37b7U, 0x3659U, 1U, 0U, 1U},
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#endif
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// x = -0x1.804p-3, exp2m1f16(x) = -0x1.f34p-4 (RZ)
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{0xb201U, 0xafcdU, 0U, 1U, 1U},
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// x = -0x1.f3p-3, exp2m1f16(x) = -0x1.3e4p-3 (RZ)
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{0xb3ccU, 0xb0f9U, 0U, 1U, 0U},
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// x = -0x1.294p-1, exp2m1f16(x) = -0x1.53p-2 (RZ)
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{0xb8a5U, 0xb54cU, 0U, 1U, 1U},
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#ifndef LIBC_TARGET_CPU_HAS_FMA_FLOAT
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// x = -0x1.a34p-1, exp2m1f16(x) = -0x1.bb4p-2 (RZ)
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{0xba8dU, 0xb6edU, 0U, 1U, 1U},
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#endif
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}};
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#endif // !LIBC_MATH_HAS_SKIP_ACCURATE_PASS
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using namespace math::expxf16_internal;
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using FPBits = fputil::FPBits<float16>;
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FPBits x_bits(x);
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uint16_t x_u = x_bits.uintval();
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uint16_t x_abs = x_u & 0x7fffU;
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// When |x| <= 2^(-3), or |x| >= 11, or x is NaN.
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if (LIBC_UNLIKELY(x_abs <= 0x3000U || x_abs >= 0x4980U)) {
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// exp2m1(NaN) = NaN
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if (x_bits.is_nan()) {
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if (x_bits.is_signaling_nan()) {
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fputil::raise_except_if_required(FE_INVALID);
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return FPBits::quiet_nan().get_val();
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}
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return x;
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}
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// When x >= 16.
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if (x_u >= 0x4c00 && x_bits.is_pos()) {
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// exp2m1(+inf) = +inf
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if (x_bits.is_inf())
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return FPBits::inf().get_val();
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switch (fputil::quick_get_round()) {
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case FE_TONEAREST:
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case FE_UPWARD:
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fputil::set_errno_if_required(ERANGE);
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fputil::raise_except_if_required(FE_OVERFLOW | FE_INEXACT);
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return FPBits::inf().get_val();
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default:
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return FPBits::max_normal().get_val();
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}
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}
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// When x < -11.
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if (x_u > 0xc980U) {
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// exp2m1(-inf) = -1
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if (x_bits.is_inf())
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return FPBits::one(Sign::NEG).get_val();
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// When -12 < x < -11, round(2^x - 1, HP, RN) = -0x1.ffcp-1.
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if (x_u < 0xca00U)
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return fputil::round_result_slightly_down(
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fputil::cast<float16>(-0x1.ffcp-1));
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// When x <= -12, round(2^x - 1, HP, RN) = -1.
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switch (fputil::quick_get_round()) {
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case FE_TONEAREST:
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case FE_DOWNWARD:
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return FPBits::one(Sign::NEG).get_val();
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default:
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return fputil::cast<float16>(-0x1.ffcp-1);
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}
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}
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// When |x| <= 2^(-3).
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if (x_abs <= 0x3000U) {
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#ifndef LIBC_MATH_HAS_SKIP_ACCURATE_PASS
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if (auto r = EXP2M1F16_EXCEPTS_LO.lookup(x_u);
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LIBC_UNLIKELY(r.has_value()))
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return r.value();
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#endif // !LIBC_MATH_HAS_SKIP_ACCURATE_PASS
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float xf = x;
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// Degree-5 minimax polynomial generated by Sollya with the following
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// commands:
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// > display = hexadecimal;
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// > P = fpminimax((2^x - 1)/x, 4, [|SG...|], [-2^-3, 2^-3]);
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// > x * P;
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return fputil::cast<float16>(
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xf * fputil::polyeval(xf, 0x1.62e43p-1f, 0x1.ebfbdep-3f,
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0x1.c6af88p-5f, 0x1.3b45d6p-7f,
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0x1.641e7cp-10f));
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}
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}
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#ifndef LIBC_MATH_HAS_SKIP_ACCURATE_PASS
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if (auto r = EXP2M1F16_EXCEPTS_HI.lookup(x_u); LIBC_UNLIKELY(r.has_value()))
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return r.value();
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#endif // !LIBC_MATH_HAS_SKIP_ACCURATE_PASS
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// exp2(x) = exp2(hi + mid) * exp2(lo)
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auto [exp2_hi_mid, exp2_lo] = exp2_range_reduction(x);
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// exp2m1(x) = exp2(hi + mid) * exp2(lo) - 1
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return fputil::cast<float16>(
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fputil::multiply_add(exp2_hi_mid, exp2_lo, -1.0f));
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}
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} // namespace math
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} // namespace LIBC_NAMESPACE_DECL
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#endif // LIBC_TYPES_HAS_FLOAT16
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#endif // LLVM_LIBC_SRC___SUPPORT_MATH_EXP2M1F16_H

‎libc/src/math/generic/CMakeLists.txt‎

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@@ -1488,19 +1488,7 @@ add_entrypoint_object(
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HDRS
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../exp2m1f16.h
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DEPENDS
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libc.hdr.errno_macros
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libc.hdr.fenv_macros
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libc.src.__support.common
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libc.src.__support.FPUtil.cast
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libc.src.__support.FPUtil.except_value_utils
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libc.src.__support.FPUtil.fenv_impl
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libc.src.__support.FPUtil.fp_bits
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libc.src.__support.FPUtil.multiply_add
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libc.src.__support.FPUtil.polyeval
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libc.src.__support.FPUtil.rounding_mode
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libc.src.__support.macros.optimization
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libc.src.__support.macros.properties.cpu_features
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libc.src.__support.math.expxf16_utils
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libc.src.__support.math.exp2m1f16
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)
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add_entrypoint_object(

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