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[libc][math] Refactor exp2f implementation to header-only in src/__support/math folder. (#161992)

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Part of #147386

in preparation for: https://discourse.llvm.org/t/rfc-make-clang-builtin-math-functions-constexpr-with-llvm-libc-to-support-c-23-constexpr-math-functions/86450
This commit is contained in:
Muhammad Bassiouni
2025-10-06 21:23:44 +03:00
committed by GitHub
parent bf8c2f2f4f
commit 596ff855d0
10 changed files with 80 additions and 53 deletions
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1
libc/shared/math.h
View File

@@ -48,6 +48,7 @@
#include "math/exp10m1f.h"
#include "math/exp10m1f16.h"
#include "math/exp2.h"
#include "math/exp2f.h"
#include "math/expf.h"
#include "math/expf16.h"
#include "math/frexpf.h"

23
libc/shared/math/exp2f.h Normal file
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@@ -0,0 +1,23 @@
//===-- Shared exp2f function -----------------------------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_LIBC_SHARED_MATH_EXP2F_H
#define LLVM_LIBC_SHARED_MATH_EXP2F_H
#include "shared/libc_common.h"
#include "src/__support/math/exp2f.h"
namespace LIBC_NAMESPACE_DECL {
namespace shared {
using math::exp2f;
} // namespace shared
} // namespace LIBC_NAMESPACE_DECL
#endif // LLVM_LIBC_SHARED_MATH_EXP2F_H

18
libc/src/__support/math/CMakeLists.txt
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@@ -735,6 +735,24 @@ add_header_library(
libc.src.errno.errno
)
add_header_library(
exp2f
HDRS
exp2f.h
DEPENDS
.exp10f_utils
libc.src.__support.FPUtil.except_value_utils
libc.src.__support.FPUtil.fenv_impl
libc.src.__support.FPUtil.fp_bits
libc.src.__support.FPUtil.multiply_add
libc.src.__support.FPUtil.nearest_integer
libc.src.__support.FPUtil.polyeval
libc.src.__support.FPUtil.rounding_mode
libc.src.__support.macros.optimization
libc.src.__support.common
libc.src.errno.errno
)
add_header_library(
exp10
HDRS

22
libc/src/math/generic/exp2f_impl.h → libc/src/__support/math/exp2f.h
View File

@@ -1,4 +1,4 @@
//===-- Single-precision 2^x function -------------------------------------===//
//===-- Implementation header for exp2f -------------------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
@@ -6,9 +6,10 @@
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_LIBC_SRC_MATH_GENERIC_EXP2F_IMPL_H
#define LLVM_LIBC_SRC_MATH_GENERIC_EXP2F_IMPL_H
#ifndef LLVM_LIBC_SRC___SUPPORT_MATH_EXP2F_H
#define LLVM_LIBC_SRC___SUPPORT_MATH_EXP2F_H
#include "exp10f_utils.h"
#include "src/__support/FPUtil/FEnvImpl.h"
#include "src/__support/FPUtil/FPBits.h"
#include "src/__support/FPUtil/PolyEval.h"
@@ -20,12 +21,12 @@
#include "src/__support/macros/config.h"
#include "src/__support/macros/optimization.h" // LIBC_UNLIKELY
#include "src/__support/macros/properties/cpu_features.h"
#include "src/__support/math/exp10f_utils.h"
namespace LIBC_NAMESPACE_DECL {
namespace generic {
LIBC_INLINE float exp2f(float x) {
namespace math {
LIBC_INLINE static constexpr float exp2f(float x) {
using FPBits = typename fputil::FPBits<float>;
FPBits xbits(x);
@@ -120,8 +121,8 @@ LIBC_INLINE float exp2f(float x) {
// of 2^mid.
// kf = (hi + mid) * 2^5 = round(x * 2^5)
float kf;
int k;
float kf = 0;
int k = 0;
#ifdef LIBC_TARGET_CPU_HAS_NEAREST_INT
kf = fputil::nearest_integer(x * 32.0f);
k = static_cast<int>(kf);
@@ -161,7 +162,8 @@ LIBC_INLINE float exp2f(float x) {
return static_cast<float>(fputil::multiply_add(p, dx_sq * mh, c1 * mh));
}
} // namespace generic
} // namespace math
} // namespace LIBC_NAMESPACE_DECL
#endif // LLVM_LIBC_SRC_MATH_GENERIC_EXP2F_IMPL_H
#endif // LLVM_LIBC_SRC___SUPPORT_MATH_EXP2F_H

22
libc/src/math/generic/CMakeLists.txt
View File

@@ -1451,24 +1451,6 @@ add_entrypoint_object(
libc.src.__support.math.exp2
)
add_header_library(
exp2f_impl
HDRS
exp2f_impl.h
DEPENDS
libc.src.__support.FPUtil.except_value_utils
libc.src.__support.FPUtil.fenv_impl
libc.src.__support.FPUtil.fp_bits
libc.src.__support.FPUtil.multiply_add
libc.src.__support.FPUtil.nearest_integer
libc.src.__support.FPUtil.polyeval
libc.src.__support.FPUtil.rounding_mode
libc.src.__support.macros.optimization
libc.src.__support.math.exp10f_utils
libc.src.__support.common
libc.src.errno.errno
)
add_entrypoint_object(
exp2f
SRCS
@@ -1476,7 +1458,7 @@ add_entrypoint_object(
HDRS
../exp2f.h
DEPENDS
.exp2f_impl
libc.src.__support.math.exp2f
)
add_entrypoint_object(
@@ -1659,8 +1641,8 @@ add_entrypoint_object(
HDRS
../powf.h
DEPENDS
.exp2f_impl
libc.src.__support.math.exp10f
libc.src.__support.math.exp2f
libc.src.__support.CPP.bit
libc.src.__support.FPUtil.fenv_impl
libc.src.__support.FPUtil.fp_bits

4
libc/src/math/generic/exp2f.cpp
View File

@@ -9,10 +9,10 @@
#include "src/math/exp2f.h"
#include "src/__support/common.h" // for LLVM_LIBC_FUNCTION
#include "src/__support/macros/config.h"
#include "src/math/generic/exp2f_impl.h"
#include "src/__support/math/exp2f.h"
namespace LIBC_NAMESPACE_DECL {
LLVM_LIBC_FUNCTION(float, exp2f, (float x)) { return generic::exp2f(x); }
LLVM_LIBC_FUNCTION(float, exp2f, (float x)) { return math::exp2f(x); }
} // namespace LIBC_NAMESPACE_DECL

5
libc/src/math/generic/powf.cpp
View File

@@ -20,10 +20,9 @@
#include "src/__support/macros/optimization.h" // LIBC_UNLIKELY
#include "src/__support/math/common_constants.h" // Lookup tables EXP_M1 and EXP_M2.
#include "src/__support/math/exp10f.h" // Speedup for powf(10, y) = exp10f(y)
#include "src/__support/math/exp2f.h" // Speedup for powf(2, y) = exp2f(y)
#include "src/__support/math/exp_constants.h"
#include "exp2f_impl.h" // Speedup for powf(2, y) = exp2f(y)
namespace LIBC_NAMESPACE_DECL {
using fputil::DoubleDouble;
@@ -779,7 +778,7 @@ LLVM_LIBC_FUNCTION(float, powf, (float x, float y)) {
#ifndef LIBC_MATH_HAS_SKIP_ACCURATE_PASS
case 0x4000'0000: // x = 2.0f
// pow(2, y) = exp2(y)
return generic::exp2f(y);
return math::exp2f(y);
case 0x4120'0000: // x = 10.0f
// pow(10, y) = exp10(y)
return math::exp10f(y);

1
libc/test/shared/CMakeLists.txt
View File

@@ -41,6 +41,7 @@ add_fp_unittest(
libc.src.__support.math.erff
libc.src.__support.math.exp
libc.src.__support.math.exp2
libc.src.__support.math.exp2f
libc.src.__support.math.exp10
libc.src.__support.math.exp10f
libc.src.__support.math.exp10f16

1
libc/test/shared/shared_math_test.cpp
View File

@@ -62,6 +62,7 @@ TEST(LlvmLibcSharedMathTest, AllFloat) {
EXPECT_FP_EQ(0x0p+0f, LIBC_NAMESPACE::shared::erff(0.0f));
EXPECT_FP_EQ(0x1p+0f, LIBC_NAMESPACE::shared::exp10f(0.0f));
EXPECT_FP_EQ(0x1p+0f, LIBC_NAMESPACE::shared::expf(0.0f));
EXPECT_FP_EQ(0x1p+0f, LIBC_NAMESPACE::shared::exp2f(0.0f));
EXPECT_FP_EQ_ALL_ROUNDING(0.75f,
LIBC_NAMESPACE::shared::frexpf(24.0f, &exponent));

36
utils/bazel/llvm-project-overlay/libc/BUILD.bazel
View File

@@ -2167,22 +2167,6 @@ libc_support_library(
],
)
libc_support_library(
name = "exp2f_impl",
hdrs = ["src/math/generic/exp2f_impl.h"],
deps = [
":__support_fputil_except_value_utils",
":__support_fputil_fma",
":__support_fputil_multiply_add",
":__support_fputil_nearest_integer",
":__support_fputil_polyeval",
":__support_fputil_rounding_mode",
":__support_macros_optimization",
":__support_math_common_constants",
":__support_math_exp10f_utils",
],
)
libc_support_library(
name = "__support_math_acos",
hdrs = ["src/__support/math/acos.h"],
@@ -2895,6 +2879,22 @@ libc_support_library(
],
)
libc_support_library(
name = "__support_math_exp2f",
hdrs = ["src/__support/math/exp2f.h"],
deps = [
":__support_fputil_except_value_utils",
":__support_fputil_fma",
":__support_fputil_multiply_add",
":__support_fputil_nearest_integer",
":__support_fputil_polyeval",
":__support_fputil_rounding_mode",
":__support_macros_optimization",
":__support_math_common_constants",
":__support_math_exp10f_utils",
],
)
libc_support_library(
name = "__support_math_exp10",
hdrs = ["src/__support/math/exp10.h"],
@@ -3676,7 +3676,7 @@ libc_math_function(
libc_math_function(
name = "exp2f",
additional_deps = [
":exp2f_impl",
":__support_math_exp2f",
],
)
@@ -4511,7 +4511,7 @@ libc_math_function(
":__support_macros_optimization",
":__support_math_exp10f",
":__support_math_common_constants",
":exp2f_impl",
":__support_math_exp2f",
],
)