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[libc][math] Refactor cospif16 implementation to header-only in src/__support/math folder. (#154222)

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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 2025-08-22 05:04:13 +03:00 committed by GitHub
parent 3ce25abd4a
commit 4d323206ed
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GPG Key ID: B5690EEEBB952194
9 changed files with 159 additions and 83 deletions
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1
libc/shared/math.h
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@ -38,6 +38,7 @@
#include "math/coshf.h"
#include "math/coshf16.h"
#include "math/cospif.h"
#include "math/cospif16.h"
#include "math/erff.h"
#include "math/exp.h"
#include "math/exp10.h"

28
libc/shared/math/cospif16.h Normal file
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@ -0,0 +1,28 @@
//===-- Shared cospif16 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_COSPIF16_H
#define LLVM_LIBC_SHARED_MATH_COSPIF16_H
#include "shared/libc_common.h"
#ifdef LIBC_TYPES_HAS_FLOAT16
#include "src/__support/math/cospif16.h"
namespace LIBC_NAMESPACE_DECL {
namespace shared {
using math::cospif16;
} // namespace shared
} // namespace LIBC_NAMESPACE_DECL
#endif // LIBC_TYPES_HAS_FLOAT16
#endif // LLVM_LIBC_SHARED_MATH_COSPIF_H

13
libc/src/__support/math/CMakeLists.txt
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@ -444,6 +444,19 @@ add_header_library(
libc.src.__support.macros.optimization
)
add_header_library(
cospif16
HDRS
cospif16.h
DEPENDS
.sincosf16_utils
libc.src.__support.FPUtil.cast
libc.src.__support.FPUtil.fenv_impl
libc.src.__support.FPUtil.fp_bits
libc.src.__support.FPUtil.multiply_add
libc.src.__support.macros.optimization
)
add_header_library(
erff
HDRS

99
libc/src/__support/math/cospif16.h Normal file
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@ -0,0 +1,99 @@
//===-- Implementation header for cospif16 ----------------------*- 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_SRC___SUPPORT_MATH_COSPIF16_H
#define LLVM_LIBC_SRC___SUPPORT_MATH_COSPIF16_H
#include "include/llvm-libc-macros/float16-macros.h"
#ifdef LIBC_TYPES_HAS_FLOAT16
#include "sincosf16_utils.h"
#include "src/__support/FPUtil/FEnvImpl.h"
#include "src/__support/FPUtil/FPBits.h"
#include "src/__support/FPUtil/cast.h"
#include "src/__support/FPUtil/multiply_add.h"
#include "src/__support/macros/optimization.h"
namespace LIBC_NAMESPACE_DECL {
namespace math {
LIBC_INLINE static constexpr float16 cospif16(float16 x) {
using namespace sincosf16_internal;
using FPBits = typename fputil::FPBits<float16>;
FPBits xbits(x);
uint16_t x_u = xbits.uintval();
uint16_t x_abs = x_u & 0x7fff;
float xf = x;
// Range reduction:
// For |x| > 1/32, we perform range reduction as follows:
// Find k and y such that:
// x = (k + y) * 1/32
// k is an integer
// |y| < 0.5
//
// This is done by performing:
// k = round(x * 32)
// y = x * 32 - k
//
// Once k and y are computed, we then deduce the answer by the cosine of sum
// formula:
// cos(x * pi) = cos((k + y) * pi/32)
// = cos(k * pi/32) * cos(y * pi/32) +
// sin(y * pi/32) * sin(k * pi/32)
// For signed zeros
if (LIBC_UNLIKELY(x_abs == 0U))
return fputil::cast<float16>(1.0f);
// Numbers greater or equal to 2^10 are integers, or infinity, or NaN
if (LIBC_UNLIKELY(x_abs >= 0x6400)) {
if (LIBC_UNLIKELY(x_abs <= 0x67FF))
return fputil::cast<float16>((x_abs & 0x1) ? -1.0f : 1.0f);
// Check for NaN or infintiy values
if (LIBC_UNLIKELY(x_abs >= 0x7c00)) {
if (xbits.is_signaling_nan()) {
fputil::raise_except_if_required(FE_INVALID);
return FPBits::quiet_nan().get_val();
}
// If value is equal to infinity
if (x_abs == 0x7c00) {
fputil::set_errno_if_required(EDOM);
fputil::raise_except_if_required(FE_INVALID);
}
return x + FPBits::quiet_nan().get_val();
}
return fputil::cast<float16>(1.0f);
}
float sin_k = 0, cos_k = 0, sin_y = 0, cosm1_y = 0;
sincospif16_eval(xf, sin_k, cos_k, sin_y, cosm1_y);
if (LIBC_UNLIKELY(sin_y == 0 && cos_k == 0))
return fputil::cast<float16>(0.0f);
// Since, cosm1_y = cos_y - 1, therefore:
// cos(x * pi) = cos_k(cosm1_y) + cos_k - sin_k * sin_y
return fputil::cast<float16>(fputil::multiply_add(
cos_k, cosm1_y, fputil::multiply_add(-sin_k, sin_y, cos_k)));
}
} // namespace math
} // namespace LIBC_NAMESPACE_DECL
#endif // LIBC_TYPES_HAS_FLOAT16
#endif // LLVM_LIBC_SRC___SUPPORT_MATH_COSHF16_H

9
libc/src/math/generic/CMakeLists.txt
View File

@ -325,14 +325,7 @@ add_entrypoint_object(
HDRS
../cospif16.h
DEPENDS
libc.hdr.errno_macros
libc.hdr.fenv_macros
libc.src.__support.FPUtil.cast
libc.src.__support.FPUtil.fenv_impl
libc.src.__support.FPUtil.fp_bits
libc.src.__support.FPUtil.multiply_add
libc.src.__support.macros.optimization
libc.src.__support.math.sincosf16_utils
libc.src.__support.math.cospif16
)
add_entrypoint_object(

74
libc/src/math/generic/cospif16.cpp
View File

@ -7,80 +7,10 @@
//===----------------------------------------------------------------------===//
#include "src/math/cospif16.h"
#include "hdr/errno_macros.h"
#include "hdr/fenv_macros.h"
#include "src/__support/FPUtil/FEnvImpl.h"
#include "src/__support/FPUtil/FPBits.h"
#include "src/__support/FPUtil/cast.h"
#include "src/__support/FPUtil/multiply_add.h"
#include "src/__support/macros/optimization.h"
#include "src/__support/math/sincosf16_utils.h"
#include "src/__support/math/cospif16.h"
namespace LIBC_NAMESPACE_DECL {
LLVM_LIBC_FUNCTION(float16, cospif16, (float16 x)) {
using namespace sincosf16_internal;
using FPBits = typename fputil::FPBits<float16>;
FPBits xbits(x);
uint16_t x_u = xbits.uintval();
uint16_t x_abs = x_u & 0x7fff;
float xf = x;
// Range reduction:
// For |x| > 1/32, we perform range reduction as follows:
// Find k and y such that:
// x = (k + y) * 1/32
// k is an integer
// |y| < 0.5
//
// This is done by performing:
// k = round(x * 32)
// y = x * 32 - k
//
// Once k and y are computed, we then deduce the answer by the cosine of sum
// formula:
// cos(x * pi) = cos((k + y) * pi/32)
// = cos(k * pi/32) * cos(y * pi/32) +
// sin(y * pi/32) * sin(k * pi/32)
// For signed zeros
if (LIBC_UNLIKELY(x_abs == 0U))
return fputil::cast<float16>(1.0f);
// Numbers greater or equal to 2^10 are integers, or infinity, or NaN
if (LIBC_UNLIKELY(x_abs >= 0x6400)) {
if (LIBC_UNLIKELY(x_abs <= 0x67FF))
return fputil::cast<float16>((x_abs & 0x1) ? -1.0f : 1.0f);
// Check for NaN or infintiy values
if (LIBC_UNLIKELY(x_abs >= 0x7c00)) {
if (xbits.is_signaling_nan()) {
fputil::raise_except_if_required(FE_INVALID);
return FPBits::quiet_nan().get_val();
}
// If value is equal to infinity
if (x_abs == 0x7c00) {
fputil::set_errno_if_required(EDOM);
fputil::raise_except_if_required(FE_INVALID);
}
return x + FPBits::quiet_nan().get_val();
}
return fputil::cast<float16>(1.0f);
}
float sin_k, cos_k, sin_y, cosm1_y;
sincospif16_eval(xf, sin_k, cos_k, sin_y, cosm1_y);
if (LIBC_UNLIKELY(sin_y == 0 && cos_k == 0))
return fputil::cast<float16>(0.0f);
// Since, cosm1_y = cos_y - 1, therefore:
// cos(x * pi) = cos_k(cosm1_y) + cos_k - sin_k * sin_y
return fputil::cast<float16>(fputil::multiply_add(
cos_k, cosm1_y, fputil::multiply_add(-sin_k, sin_y, cos_k)));
}
LLVM_LIBC_FUNCTION(float16, cospif16, (float16 x)) { return math::cospif16(x); }
} // namespace LIBC_NAMESPACE_DECL

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

@ -34,6 +34,7 @@ add_fp_unittest(
libc.src.__support.math.coshf
libc.src.__support.math.coshf16
libc.src.__support.math.cospif
libc.src.__support.math.cospif16
libc.src.__support.math.erff
libc.src.__support.math.exp
libc.src.__support.math.exp10

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

@ -23,6 +23,7 @@ TEST(LlvmLibcSharedMathTest, AllFloat16) {
EXPECT_FP_EQ(0x0p+0f16, LIBC_NAMESPACE::shared::atanhf16(0.0f16));
EXPECT_FP_EQ(0x1p+0f16, LIBC_NAMESPACE::shared::cosf16(0.0f16));
EXPECT_FP_EQ(0x1p+0f16, LIBC_NAMESPACE::shared::coshf16(0.0f16));
EXPECT_FP_EQ(0x1p+0f16, LIBC_NAMESPACE::shared::cospif16(0.0f16));
EXPECT_FP_EQ(0x1p+0f16, LIBC_NAMESPACE::shared::exp10f16(0.0f16));
EXPECT_FP_EQ(0x1p+0f16, LIBC_NAMESPACE::shared::expf16(0.0f16));

16
utils/bazel/llvm-project-overlay/libc/BUILD.bazel
View File

@ -2407,6 +2407,18 @@ libc_support_library(
],
)
libc_support_library(
name = "__support_math_cospif16",
hdrs = ["src/__support/math/cospif16.h"],
deps = [
":__support_fputil_cast",
":__support_fputil_fenv_impl",
":__support_fputil_multiply_add",
":__support_macros_optimization",
":__support_math_sincosf16_utils",
],
)
libc_support_library(
name = "__support_math_erff",
hdrs = ["src/__support/math/erff.h"],
@ -3242,9 +3254,7 @@ libc_math_function(
libc_math_function(
name = "cospif16",
additional_deps = [
":__support_fputil_multiply_add",
":__support_macros_optimization",
":__support_math_sincosf16_utils",
":__support_math_cospif16",
],
)