[libc-commits] [libc] 851f7c7 - [libc][math][c23] Add acospif16() function (#134664)
via libc-commits
libc-commits at lists.llvm.org
Thu Apr 24 15:03:28 PDT 2025
Author: Anton
Date: 2025-04-24T18:03:24-04:00
New Revision: 851f7c74213e8497afb2b2a3b7facb9faedf9f5f
URL: https://github.com/llvm/llvm-project/commit/851f7c74213e8497afb2b2a3b7facb9faedf9f5f
DIFF: https://github.com/llvm/llvm-project/commit/851f7c74213e8497afb2b2a3b7facb9faedf9f5f.diff
LOG: [libc][math][c23] Add acospif16() function (#134664)
Addresses #132211 #132754
Part of #95250
Added:
libc/src/math/acospif16.h
libc/src/math/generic/acospif16.cpp
libc/test/src/math/acospif16_test.cpp
libc/test/src/math/smoke/acospif16_test.cpp
Modified:
libc/config/linux/x86_64/entrypoints.txt
libc/docs/headers/math/index.rst
libc/include/math.yaml
libc/src/math/CMakeLists.txt
libc/src/math/generic/CMakeLists.txt
libc/test/src/math/CMakeLists.txt
libc/test/src/math/smoke/CMakeLists.txt
libc/utils/MPFRWrapper/MPCommon.cpp
libc/utils/MPFRWrapper/MPCommon.h
libc/utils/MPFRWrapper/MPFRUtils.cpp
libc/utils/MPFRWrapper/MPFRUtils.h
Removed:
################################################################################
diff --git a/libc/config/linux/x86_64/entrypoints.txt b/libc/config/linux/x86_64/entrypoints.txt
index 73dfeae1a2c94..0e4fbdd2f2f57 100644
--- a/libc/config/linux/x86_64/entrypoints.txt
+++ b/libc/config/linux/x86_64/entrypoints.txt
@@ -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
diff --git a/libc/docs/headers/math/index.rst b/libc/docs/headers/math/index.rst
index 947bd4b60b391..cf88e6237d1e3 100644
--- a/libc/docs/headers/math/index.rst
+++ b/libc/docs/headers/math/index.rst
@@ -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 |
+-----------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+
diff --git a/libc/include/math.yaml b/libc/include/math.yaml
index fef829422244d..b725c33c0bb06 100644
--- a/libc/include/math.yaml
+++ b/libc/include/math.yaml
@@ -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
diff --git a/libc/src/math/CMakeLists.txt b/libc/src/math/CMakeLists.txt
index d177ff79141c0..5161b2b61aa94 100644
--- a/libc/src/math/CMakeLists.txt
+++ b/libc/src/math/CMakeLists.txt
@@ -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)
diff --git a/libc/src/math/acospif16.h b/libc/src/math/acospif16.h
new file mode 100644
index 0000000000000..e94a35bdf6fb7
--- /dev/null
+++ b/libc/src/math/acospif16.h
@@ -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
diff --git a/libc/src/math/generic/CMakeLists.txt b/libc/src/math/generic/CMakeLists.txt
index adbed5b2de48c..25f583035fbc2 100644
--- a/libc/src/math/generic/CMakeLists.txt
+++ b/libc/src/math/generic/CMakeLists.txt
@@ -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
diff --git a/libc/src/math/generic/acospif16.cpp b/libc/src/math/generic/acospif16.cpp
new file mode 100644
index 0000000000000..bfdf1694e3ba6
--- /dev/null
+++ b/libc/src/math/generic/acospif16.cpp
@@ -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
diff --git a/libc/test/src/math/CMakeLists.txt b/libc/test/src/math/CMakeLists.txt
index 7ee8b86135557..ebf9f1c86cf15 100644
--- a/libc/test/src/math/CMakeLists.txt
+++ b/libc/test/src/math/CMakeLists.txt
@@ -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
diff --git a/libc/test/src/math/acospif16_test.cpp b/libc/test/src/math/acospif16_test.cpp
new file mode 100644
index 0000000000000..1dd951f602c90
--- /dev/null
+++ b/libc/test/src/math/acospif16_test.cpp
@@ -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);
+ }
+}
diff --git a/libc/test/src/math/smoke/CMakeLists.txt b/libc/test/src/math/smoke/CMakeLists.txt
index 223d1933bca38..79b189159e9d8 100644
--- a/libc/test/src/math/smoke/CMakeLists.txt
+++ b/libc/test/src/math/smoke/CMakeLists.txt
@@ -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
diff --git a/libc/test/src/math/smoke/acospif16_test.cpp b/libc/test/src/math/smoke/acospif16_test.cpp
new file mode 100644
index 0000000000000..66b94706eab94
--- /dev/null
+++ b/libc/test/src/math/smoke/acospif16_test.cpp
@@ -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);
+}
diff --git a/libc/utils/MPFRWrapper/MPCommon.cpp b/libc/utils/MPFRWrapper/MPCommon.cpp
index ac8cde2f97221..ccd4d2d01a4e2 100644
--- a/libc/utils/MPFRWrapper/MPCommon.cpp
+++ b/libc/utils/MPFRWrapper/MPCommon.cpp
@@ -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);
diff --git a/libc/utils/MPFRWrapper/MPCommon.h b/libc/utils/MPFRWrapper/MPCommon.h
index eaa512e30bc86..99cb7ec66a2ca 100644
--- a/libc/utils/MPFRWrapper/MPCommon.h
+++ b/libc/utils/MPFRWrapper/MPCommon.h
@@ -181,6 +181,7 @@ class MPFRNumber {
MPFRNumber abs() const;
MPFRNumber acos() const;
MPFRNumber acosh() const;
+ MPFRNumber acospi() const;
MPFRNumber add(const MPFRNumber &b) const;
MPFRNumber asin() const;
MPFRNumber asinh() const;
diff --git a/libc/utils/MPFRWrapper/MPFRUtils.cpp b/libc/utils/MPFRWrapper/MPFRUtils.cpp
index 4a033dbc2049b..8853f96ef8f92 100644
--- a/libc/utils/MPFRWrapper/MPFRUtils.cpp
+++ b/libc/utils/MPFRWrapper/MPFRUtils.cpp
@@ -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:
diff --git a/libc/utils/MPFRWrapper/MPFRUtils.h b/libc/utils/MPFRWrapper/MPFRUtils.h
index bc65f87c6b5ab..c77a6aa3adeae 100644
--- a/libc/utils/MPFRWrapper/MPFRUtils.h
+++ b/libc/utils/MPFRWrapper/MPFRUtils.h
@@ -28,6 +28,7 @@ enum class Operation : int {
Abs,
Acos,
Acosh,
+ Acospi,
Asin,
Asinh,
Atan,
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