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add atanf16() function
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+245
-2
lines changed

11 files changed

+245
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‎libc/config/linux/x86_64/entrypoints.txt‎

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@@ -667,6 +667,7 @@ if(LIBC_TYPES_HAS_FLOAT16)
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libc.src.math.acospif16
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libc.src.math.asinf16
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libc.src.math.asinhf16
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libc.src.math.atanf16
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libc.src.math.atanhf16
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libc.src.math.canonicalizef16
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libc.src.math.ceilf16

‎libc/docs/headers/math/index.rst‎

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@@ -255,13 +255,13 @@ Higher Math Functions
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+-----------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+
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| acospi | | | | |check| | | 7.12.4.8 | F.10.1.8 |
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+-----------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+
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| asin | |check| | |check| | | | | 7.12.4.2 | F.10.1.2 |
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| asin | |check| | |check| | | |check| | | 7.12.4.2 | F.10.1.2 |
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+-----------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+
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| asinh | |check| | | | |check| | | 7.12.5.2 | F.10.2.2 |
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+-----------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+
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| asinpi | | | | | | 7.12.4.9 | F.10.1.9 |
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+-----------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+
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| atan | |check| | 1 ULP | | | | 7.12.4.3 | F.10.1.3 |
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| atan | |check| | 1 ULP | | |check| | | 7.12.4.3 | F.10.1.3 |
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+-----------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+
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| atan2 | |check| | 1 ULP | | | 1 ULP | 7.12.4.4 | F.10.1.4 |
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+-----------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+

‎libc/include/math.yaml‎

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@@ -120,6 +120,13 @@ functions:
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return_type: float
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arguments:
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- type: float
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- name: atanf16
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standards:
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- stdc
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return_type: _Float16
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arguments:
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- type: _Float16
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guard: LIBC_TYPES_HAS_FLOAT16
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- name: atanhf
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standards:
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- stdc

‎libc/src/math/CMakeLists.txt‎

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@@ -60,6 +60,7 @@ add_math_entrypoint_object(asinhf16)
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add_math_entrypoint_object(atan)
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add_math_entrypoint_object(atanf)
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add_math_entrypoint_object(atanf16)
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add_math_entrypoint_object(atan2)
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add_math_entrypoint_object(atan2f)

‎libc/src/math/atanf16.h‎

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@@ -0,0 +1,20 @@
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//===-- Implementation header for atanf16 -----------------------*- 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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#ifndef LLVM_LIBC_SRC_MATH_ATANF16_H
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#define LLVM_LIBC_SRC_MATH_ATANF16_H
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#include "src/__support/macros/config.h"
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#include "src/__support/macros/properties/types.h"
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namespace LIBC_NAMESPACE_DECL {
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float16 atanf16(float16 x);
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} // namespace LIBC_NAMESPACE_DECL
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#endif // LLVM_LIBC_SRC_MATH_ATANF16_H

‎libc/src/math/generic/CMakeLists.txt‎

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@@ -4234,6 +4234,26 @@ add_entrypoint_object(
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libc.src.__support.macros.optimization
42354235
)
42364236

4237+
add_entrypoint_object(
4238+
atanf16
4239+
SRCS
4240+
atanf16.cpp
4241+
HDRS
4242+
../atanf16.h
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DEPENDS
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libc.hdr.errno_macros
4245+
libc.hdr.fenv_macros
4246+
libc.src.__support.FPUtil.cast
4247+
libc.src.__support.FPUtil.except_value_utils
4248+
libc.src.__support.FPUtil.fenv_impl
4249+
libc.src.__support.FPUtil.fp_bits
4250+
libc.src.__support.FPUtil.multiply_add
4251+
libc.src.__support.FPUtil.polyeval
4252+
libc.src.__support.FPUtil.sqrt
4253+
libc.src.__support.macros.optimization
4254+
libc.src.__support.macros.properties.types
4255+
)
4256+
42374257
add_entrypoint_object(
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atan
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SRCS

‎libc/src/math/generic/atanf16.cpp‎

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@@ -0,0 +1,104 @@
1+
//===-- Half-precision atanf16(x) function --------------------------------===//
2+
//
3+
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4+
// See https://llvm.org/LICENSE.txt for license information.
5+
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception.
6+
//
7+
//===----------------------------------------------------------------------===//
8+
9+
#include "src/math/atanf16.h"
10+
#include "hdr/errno_macros.h"
11+
#include "hdr/fenv_macros.h"
12+
#include "src/__support/FPUtil/FEnvImpl.h"
13+
#include "src/__support/FPUtil/FPBits.h"
14+
#include "src/__support/FPUtil/PolyEval.h"
15+
#include "src/__support/FPUtil/cast.h"
16+
#include "src/__support/FPUtil/except_value_utils.h"
17+
#include "src/__support/FPUtil/multiply_add.h"
18+
#include "src/__support/FPUtil/sqrt.h"
19+
#include "src/__support/macros/optimization.h"
20+
21+
namespace LIBC_NAMESPACE_DECL {
22+
23+
// Generated by Solly using the following command:
24+
// > round(pi/2, D, RN);
25+
static constexpr float PI_2 = 0x1.921fb54442d18p0f;
26+
27+
#ifndef LIBC_MATH_HAS_SKIP_ACCURATE_PASS
28+
static constexpr size_t N_EXCEPTS = 6;
29+
30+
static constexpr fputil::ExceptValues<float16, N_EXCEPTS> ATANF16_EXCEPTS{{
31+
// (input, RZ output, RU offset, RD offset, RN offset)
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{0x2745, 0x2744, 1, 0, 1},
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{0x3099, 0x3090, 1, 0, 1},
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{0x3c6c, 0x3aae, 1, 0, 1},
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{0x466e, 0x3daa, 1, 0, 1},
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{0x48ae, 0x3ddb, 1, 0, 0},
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{0x5619, 0x3e3d, 1, 0, 1},
38+
}};
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#endif // !LIBC_MATH_HAS_SKIP_ACCURATE_PASS
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LLVM_LIBC_FUNCTION(float16, atanf16, (float16 x)) {
42+
using FPBits = fputil::FPBits<float16>;
43+
FPBits xbits(x);
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45+
uint16_t x_u = xbits.uintval();
46+
uint16_t x_abs = x_u & 0x7fff;
47+
bool x_sign = x_u >> 15;
48+
float sign = (x_sign ? -1.0 : 1.0);
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// |x| >= +/-inf
51+
if (LIBC_UNLIKELY(x_abs >= 0x7c00U)) {
52+
if (xbits.is_nan()) {
53+
if (xbits.is_signaling_nan()) {
54+
fputil::raise_except_if_required(FE_INVALID);
55+
return FPBits::quiet_nan().get_val();
56+
}
57+
return x;
58+
}
59+
60+
// atanf16(+/-inf) = +/-pi/2
61+
return fputil::cast<float16>(sign * PI_2);
62+
}
63+
64+
float xf = x;
65+
float xsq = xf * xf;
66+
#ifndef LIBC_MATH_HAS_SKIP_ACCURATE_PASS
67+
// Handle exceptional values
68+
if (auto r = ATANF16_EXCEPTS.lookup_odd(x_abs, x_sign);
69+
LIBC_UNLIKELY(r.has_value()))
70+
return r.value();
71+
#endif
72+
73+
// |x| <= 0x1p0, |x| <= 1
74+
if (x_abs <= 0x3C00) {
75+
// atanf16(+/-0) = +/-0
76+
if (LIBC_UNLIKELY(x_abs == 0)) {
77+
return x;
78+
}
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80+
// Degree-14 minimax odd polynomial of atan(x) generated by Sollya with:
81+
// > P = fpminimax(atan(x)/x, [|0, 2, 4, 6, 8, 10, 12, 14|], [|SG...|], [0,
82+
// 1]);
83+
float result = fputil::polyeval(
84+
xsq, 0x1.fffffcp-1f, -0x1.55519ep-2f, 0x1.98f6a8p-3f, -0x1.1f0a92p-3f,
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0x1.95b654p-4f, -0x1.e65492p-5f, 0x1.8c0c36p-6f, -0x1.32316ep-8f);
86+
return fputil::cast<float16>(xf * result);
87+
}
88+
89+
// If |x| > 1
90+
// y = atan(x)
91+
// y = atan(|x|) = pi/2 - atan(1/|x|)
92+
// Recall, 1/|x| < 1
93+
float x_inv_sq = 1 / xsq;
94+
float x_inv = fputil::sqrt<float>(x_inv_sq);
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float interm =
96+
fputil::polyeval(x_inv_sq, 0x1.fffffcp-1f, -0x1.55519ep-2f,
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0x1.98f6a8p-3f, -0x1.1f0a92p-3f, 0x1.95b654p-4f,
98+
-0x1.e65492p-5f, 0x1.8c0c36p-6f, -0x1.32316ep-8f);
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100+
return fputil::cast<float16>(sign *
101+
fputil::multiply_add(x_inv, -interm, PI_2));
102+
}
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104+
} // namespace LIBC_NAMESPACE_DECL

‎libc/test/src/math/CMakeLists.txt‎

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@@ -2338,6 +2338,17 @@ add_fp_unittest(
23382338
libc.src.__support.FPUtil.fp_bits
23392339
)
23402340

2341+
add_fp_unittest(
2342+
atanf16_test
2343+
NEED_MPFR
2344+
SUITE
2345+
libc-math-unittests
2346+
SRCS
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atanf16_test.cpp
2348+
DEPENDS
2349+
libc.src.math.atanf16
2350+
)
2351+
23412352
add_fp_unittest(
23422353
scalbn_test
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NEED_MPFR

‎libc/test/src/math/atanf16_test.cpp‎

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@@ -0,0 +1,32 @@
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#include "src/math/atanf16.h"
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#include "test/UnitTest/FPMatcher.h"
3+
#include "test/UnitTest/Test.h"
4+
#include "utils/MPFRWrapper/MPFRUtils.h"
5+
6+
using LlvmLibcAtanf16Test = LIBC_NAMESPACE::testing::FPTest<float16>;
7+
8+
namespace mpfr = LIBC_NAMESPACE::testing::mpfr;
9+
10+
// Range: [0, Inf]
11+
static constexpr uint16_t POS_START = 0x0000U;
12+
static constexpr uint16_t POS_STOP = 0x7c00U;
13+
14+
// Range: [-Inf, 0]
15+
static constexpr uint16_t NEG_START = 0x8000U;
16+
static constexpr uint16_t NEG_STOP = 0xfc00U;
17+
18+
TEST_F(LlvmLibcAtanf16Test, PositiveRange) {
19+
for (uint16_t v = POS_START; v <= POS_STOP; ++v) {
20+
float16 x = FPBits(v).get_val();
21+
EXPECT_MPFR_MATCH_ALL_ROUNDING(mpfr::Operation::Atan, x,
22+
LIBC_NAMESPACE::atanf16(x), 0.5);
23+
}
24+
}
25+
26+
TEST_F(LlvmLibcAtanf16Test, NegativeRange) {
27+
for (uint16_t v = NEG_START; v <= NEG_STOP; ++v) {
28+
float16 x = FPBits(v).get_val();
29+
EXPECT_MPFR_MATCH_ALL_ROUNDING(mpfr::Operation::Atan, x,
30+
LIBC_NAMESPACE::atanf16(x), 0.5);
31+
}
32+
}

‎libc/test/src/math/smoke/CMakeLists.txt‎

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@@ -4107,6 +4107,17 @@ add_fp_unittest(
41074107
libc.src.math.atan
41084108
)
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4110+
add_fp_unittest(
4111+
atanf16_test
4112+
SUITE
4113+
libc-math-smoke-tests
4114+
SRCS
4115+
atanf16_test.cpp
4116+
DEPENDS
4117+
libc.src.errno.errno
4118+
libc.src.math.atanf16
4119+
)
4120+
41104121
add_fp_unittest(
41114122
atan2f_test
41124123
SUITE

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