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[libc][math][c23] Add acospif16() function (#134664)

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Addresses #132211  #132754
Part of #95250
This commit is contained in:
Anton
2025-04-24 18:03:24 -04:00
committed by GitHub
parent 67cbfb9d8c
commit 851f7c7421
15 changed files with 308 additions and 1 deletions
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1
libc/config/linux/x86_64/entrypoints.txt
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@@ -662,6 +662,7 @@ if(LIBC_TYPES_HAS_FLOAT16)
# math.h C23 _Float16 entrypoints
libc.src.math.acosf16
libc.src.math.acoshf16
libc.src.math.acospif16
libc.src.math.asinf16
libc.src.math.asinhf16
libc.src.math.canonicalizef16

2
libc/docs/headers/math/index.rst
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@@ -253,7 +253,7 @@ Higher Math Functions
+-----------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+
| acosh | |check| | | | |check| | | 7.12.5.1 | F.10.2.1 |
+-----------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+
| acospi | | | | | | 7.12.4.8 | F.10.1.8 |
| acospi | | | | |check| | | 7.12.4.8 | F.10.1.8 |
+-----------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+
| asin | |check| | | | |check| | | 7.12.4.2 | F.10.1.2 |
+-----------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+

7
libc/include/math.yaml
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@@ -34,6 +34,13 @@ functions:
arguments:
- type: _Float16
guard: LIBC_TYPES_HAS_FLOAT16
name: acospif16
standards:
- stdc
return_type: _Float16
arguments:
- type: _Float16
guard: LIBC_TYPES_HAS_FLOAT16
- name: asin
standards:
- stdc

2
libc/src/math/CMakeLists.txt
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@@ -48,6 +48,8 @@ add_math_entrypoint_object(acosh)
add_math_entrypoint_object(acoshf)
add_math_entrypoint_object(acoshf16)
add_math_entrypoint_object(acospif16)
add_math_entrypoint_object(asin)
add_math_entrypoint_object(asinf)
add_math_entrypoint_object(asinf16)

21
libc/src/math/acospif16.h Normal file
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@@ -0,0 +1,21 @@
//===-- Implementation header for acospif16 ---------------------*- 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_MATH_ACOSPIF16_H
#define LLVM_LIBC_SRC_MATH_ACOSPIF16_H
#include "src/__support/macros/config.h"
#include "src/__support/macros/properties/types.h"
namespace LIBC_NAMESPACE_DECL {
float16 acospif16(float16 x);
} // namespace LIBC_NAMESPACE_DECL
#endif // LLVM_LIBC_SRC_MATH_ACOSPIF16_H

19
libc/src/math/generic/CMakeLists.txt
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@@ -4112,6 +4112,25 @@ add_entrypoint_object(
libc.src.__support.macros.properties.types
)
add_entrypoint_object(
acospif16
SRCS
acospif16.cpp
HDRS
../acospif16.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.FPUtil.polyeval
libc.src.__support.FPUtil.sqrt
libc.src.__support.macros.optimization
libc.src.__support.macros.properties.types
)
add_header_library(
atan_utils
HDRS

134
libc/src/math/generic/acospif16.cpp Normal file
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@@ -0,0 +1,134 @@
//===-- Half-precision acospi function ------------------------------------===//
//
// 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.
//
//===----------------------------------------------------------------------===//
#include "src/math/acospif16.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/PolyEval.h"
#include "src/__support/FPUtil/cast.h"
#include "src/__support/FPUtil/multiply_add.h"
#include "src/__support/FPUtil/sqrt.h"
#include "src/__support/macros/optimization.h"
namespace LIBC_NAMESPACE_DECL {
LLVM_LIBC_FUNCTION(float16, acospif16, (float16 x)) {
using FPBits = fputil::FPBits<float16>;
FPBits xbits(x);
uint16_t x_u = xbits.uintval();
uint16_t x_abs = x_u & 0x7fff;
uint16_t x_sign = x_u >> 15;
// |x| > 0x1p0, |x| > 1, or x is NaN.
if (LIBC_UNLIKELY(x_abs > 0x3c00)) {
// acospif16(NaN) = NaN
if (xbits.is_nan()) {
if (xbits.is_signaling_nan()) {
fputil::raise_except_if_required(FE_INVALID);
return FPBits::quiet_nan().get_val();
}
return x;
}
// 1 < |x| <= +inf
fputil::raise_except_if_required(FE_INVALID);
fputil::set_errno_if_required(EDOM);
return FPBits::quiet_nan().get_val();
}
// |x| == 0x1p0, x is 1 or -1
// if x is (-)1, return 1
// if x is (+)1, return 0
if (LIBC_UNLIKELY(x_abs == 0x3c00))
return fputil::cast<float16>(x_sign ? 1.0f : 0.0f);
float xf = x;
float xsq = xf * xf;
// Degree-6 minimax polynomial coefficients of asin(x) generated by Sollya
// with: > P = fpminimax(asin(x)/(pi * x), [|0, 2, 4, 6, 8|], [|SG...|], [0,
// 0.5]);
constexpr float POLY_COEFFS[5] = {0x1.45f308p-2f, 0x1.b2900cp-5f,
0x1.897e36p-6f, 0x1.9efafcp-7f,
0x1.06d884p-6f};
// |x| <= 0x1p-1, |x| <= 0.5
if (x_abs <= 0x3800) {
// if x is 0, return 0.5
if (LIBC_UNLIKELY(x_abs == 0))
return fputil::cast<float16>(0.5f);
// Note that: acos(x) = pi/2 + asin(-x) = pi/2 - asin(x), then
// acospi(x) = 0.5 - asin(x)/pi
float interm =
fputil::polyeval(xsq, POLY_COEFFS[0], POLY_COEFFS[1], POLY_COEFFS[2],
POLY_COEFFS[3], POLY_COEFFS[4]);
return fputil::cast<float16>(fputil::multiply_add(-xf, interm, 0.5f));
}
// When |x| > 0.5, assume that 0.5 < |x| <= 1
//
// Step-by-step range-reduction proof:
// 1: Let y = asin(x), such that, x = sin(y)
// 2: From complimentary angle identity:
// x = sin(y) = cos(pi/2 - y)
// 3: Let z = pi/2 - y, such that x = cos(z)
// 4: From double angle formula; cos(2A) = 1 - 2 * sin^2(A):
// z = 2A, z/2 = A
// cos(z) = 1 - 2 * sin^2(z/2)
// 5: Make sin(z/2) subject of the formula:
// sin(z/2) = sqrt((1 - cos(z))/2)
// 6: Recall [3]; x = cos(z). Therefore:
// sin(z/2) = sqrt((1 - x)/2)
// 7: Let u = (1 - x)/2
// 8: Therefore:
// asin(sqrt(u)) = z/2
// 2 * asin(sqrt(u)) = z
// 9: Recall [3]; z = pi/2 - y. Therefore:
// y = pi/2 - z
// y = pi/2 - 2 * asin(sqrt(u))
// 10: Recall [1], y = asin(x). Therefore:
// asin(x) = pi/2 - 2 * asin(sqrt(u))
// 11: Recall that: acos(x) = pi/2 + asin(-x) = pi/2 - asin(x)
// Therefore:
// acos(x) = pi/2 - (pi/2 - 2 * asin(sqrt(u)))
// acos(x) = 2 * asin(sqrt(u))
// acospi(x) = 2 * (asin(sqrt(u)) / pi)
//
// THE RANGE REDUCTION, HOW?
// 12: Recall [7], u = (1 - x)/2
// 13: Since 0.5 < x <= 1, therefore:
// 0 <= u <= 0.25 and 0 <= sqrt(u) <= 0.5
//
// Hence, we can reuse the same [0, 0.5] domain polynomial approximation for
// Step [11] as `sqrt(u)` is in range.
// When -1 < x <= -0.5, the identity:
// acos(x) = pi - acos(-x)
// acospi(x) = 1 - acos(-x)/pi
// allows us to compute for the negative x value (lhs)
// with a positive x value instead (rhs).
float xf_abs = (xf < 0 ? -xf : xf);
float u = fputil::multiply_add(-0.5f, xf_abs, 0.5f);
float sqrt_u = fputil::sqrt<float>(u);
float asin_sqrt_u =
sqrt_u * fputil::polyeval(u, POLY_COEFFS[0], POLY_COEFFS[1],
POLY_COEFFS[2], POLY_COEFFS[3], POLY_COEFFS[4]);
// Same as acos(x), but devided the expression with pi
return fputil::cast<float16>(
x_sign ? fputil::multiply_add(-2.0f, asin_sqrt_u, 1.0f)
: 2.0f * asin_sqrt_u);
}
} // namespace LIBC_NAMESPACE_DECL

11
libc/test/src/math/CMakeLists.txt
View File

@@ -2269,6 +2269,17 @@ add_fp_unittest(
libc.src.math.acosf16
)
add_fp_unittest(
acospif16_test
NEED_MPFR
SUITE
libc-math-unittests
SRCS
acospif16_test.cpp
DEPENDS
libc.src.math.acospif16
)
add_fp_unittest(
atanf_test
NEED_MPFR

42
libc/test/src/math/acospif16_test.cpp Normal file
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@@ -0,0 +1,42 @@
//===-- Exhaustive test for acospif16 -------------------------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
#include "src/math/acospif16.h"
#include "test/UnitTest/FPMatcher.h"
#include "test/UnitTest/Test.h"
#include "utils/MPFRWrapper/MPFRUtils.h"
using LlvmLibcAcospif16Test = LIBC_NAMESPACE::testing::FPTest<float16>;
namespace mpfr = LIBC_NAMESPACE::testing::mpfr;
// Range: [0, Inf]
static constexpr uint16_t POS_START = 0x0000U;
static constexpr uint16_t POS_STOP = 0x7c00U;
// Range: [-Inf, 0]
static constexpr uint16_t NEG_START = 0x8000U;
static constexpr uint16_t NEG_STOP = 0xfc00U;
TEST_F(LlvmLibcAcospif16Test, PositiveRange) {
for (uint16_t v = POS_START; v <= POS_STOP; ++v) {
float16 x = FPBits(v).get_val();
EXPECT_MPFR_MATCH_ALL_ROUNDING(mpfr::Operation::Acospi, x,
LIBC_NAMESPACE::acospif16(x), 0.5);
}
}
TEST_F(LlvmLibcAcospif16Test, NegativeRange) {
for (uint16_t v = NEG_START; v <= NEG_STOP; ++v) {
float16 x = FPBits(v).get_val();
EXPECT_MPFR_MATCH_ALL_ROUNDING(mpfr::Operation::Acospi, x,
LIBC_NAMESPACE::acospif16(x), 0.5);
}
}

11
libc/test/src/math/smoke/CMakeLists.txt
View File

@@ -4040,6 +4040,17 @@ add_fp_unittest(
libc.src.math.acosf16
)
add_fp_unittest(
acospif16_test
SUITE
libc-math-smoke-tests
SRCS
acospif16_test.cpp
DEPENDS
libc.src.errno.errno
libc.src.math.acospif16
)
add_fp_unittest(
atanf_test
SUITE

38
libc/test/src/math/smoke/acospif16_test.cpp Normal file
View File

@@ -0,0 +1,38 @@
//===-- Unittests for acospif16 -------------------------------------------===//
//
// 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.
//
//===----------------------------------------------------------------------===//
#include "src/errno/libc_errno.h"
#include "src/math/acospif16.h"
#include "test/UnitTest/FPMatcher.h"
#include "test/UnitTest/Test.h"
using LlvmLibcAcospif16Test = LIBC_NAMESPACE::testing::FPTest<float16>;
TEST_F(LlvmLibcAcospif16Test, SpecialNumbers) {
LIBC_NAMESPACE::libc_errno = 0;
EXPECT_FP_EQ(aNaN, LIBC_NAMESPACE::acospif16(aNaN));
EXPECT_MATH_ERRNO(0);
EXPECT_FP_EQ_WITH_EXCEPTION(aNaN, LIBC_NAMESPACE::acospif16(sNaN),
FE_INVALID);
EXPECT_MATH_ERRNO(0);
EXPECT_FP_EQ(zero, LIBC_NAMESPACE::acospif16(1.0f));
EXPECT_MATH_ERRNO(0);
EXPECT_FP_EQ(aNaN, LIBC_NAMESPACE::acospif16(inf));
EXPECT_MATH_ERRNO(EDOM);
EXPECT_FP_EQ(aNaN, LIBC_NAMESPACE::acospif16(neg_inf));
EXPECT_MATH_ERRNO(EDOM);
EXPECT_FP_EQ(aNaN, LIBC_NAMESPACE::acospif16(2.0f));
EXPECT_MATH_ERRNO(EDOM);
EXPECT_FP_EQ(aNaN, LIBC_NAMESPACE::acospif16(-2.0f));
EXPECT_MATH_ERRNO(EDOM);
}

17
libc/utils/MPFRWrapper/MPCommon.cpp
View File

@@ -70,6 +70,23 @@ MPFRNumber MPFRNumber::acosh() const {
return result;
}
MPFRNumber MPFRNumber::acospi() const {
MPFRNumber result(*this);
#if MPFR_VERSION_MAJOR > 4 || \
(MPFR_VERSION_MAJOR == 4 && MPFR_VERSION_MINOR >= 2)
mpfr_acospi(result.value, value, mpfr_rounding);
return result;
#else
MPFRNumber value_acos(0.0, 1280);
mpfr_acos(value_acos.value, value, MPFR_RNDN);
MPFRNumber value_pi(0.0, 1280);
mpfr_const_pi(value_pi.value, MPFR_RNDN);
mpfr_div(result.value, value_acos.value, value_pi.value, mpfr_rounding);
return result;
#endif
}
MPFRNumber MPFRNumber::add(const MPFRNumber &b) const {
MPFRNumber result(*this);
mpfr_add(result.value, value, b.value, mpfr_rounding);

1
libc/utils/MPFRWrapper/MPCommon.h
View File

@@ -181,6 +181,7 @@ public:
MPFRNumber abs() const;
MPFRNumber acos() const;
MPFRNumber acosh() const;
MPFRNumber acospi() const;
MPFRNumber add(const MPFRNumber &b) const;
MPFRNumber asin() const;
MPFRNumber asinh() const;

2
libc/utils/MPFRWrapper/MPFRUtils.cpp
View File

@@ -32,6 +32,8 @@ unary_operation(Operation op, InputType input, unsigned int precision,
return mpfrInput.acos();
case Operation::Acosh:
return mpfrInput.acosh();
case Operation::Acospi:
return mpfrInput.acospi();
case Operation::Asin:
return mpfrInput.asin();
case Operation::Asinh:

1
libc/utils/MPFRWrapper/MPFRUtils.h
View File

@@ -28,6 +28,7 @@ enum class Operation : int {
Abs,
Acos,
Acosh,
Acospi,
Asin,
Asinh,
Atan,