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[libc][math] Refactor exp2f16 implementation to header-only in src/__support/math folder. #161993

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[libc][math] Refactor exp2f16 implementation to header-only in src/__support/math folder. #161993

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1 change: 1 addition & 0 deletions libc/shared/math.h
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Original file line number Diff line number Diff line change
Expand Up @@ -49,6 +49,7 @@
#include "math/exp10m1f16.h"
#include "math/exp2.h"
#include "math/exp2f.h"
#include "math/exp2f16.h"
#include "math/expf.h"
#include "math/expf16.h"
#include "math/frexpf.h"
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29 changes: 29 additions & 0 deletions libc/shared/math/exp2f16.h
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@@ -0,0 +1,29 @@
//===-- Shared exp2f16 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_EXP2F16_H
#define LLVM_LIBC_SHARED_MATH_EXP2F16_H

#include "include/llvm-libc-macros/float16-macros.h"
#include "shared/libc_common.h"

#ifdef LIBC_TYPES_HAS_FLOAT16

#include "src/__support/math/exp2f16.h"

namespace LIBC_NAMESPACE_DECL {
namespace shared {

using math::exp2f16;

} // namespace shared
} // namespace LIBC_NAMESPACE_DECL

#endif // LIBC_TYPES_HAS_FLOAT16

#endif // LLVM_LIBC_SHARED_MATH_EXP2F16_H
14 changes: 14 additions & 0 deletions libc/src/__support/math/CMakeLists.txt
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Expand Up @@ -753,6 +753,20 @@ add_header_library(
libc.src.errno.errno
)

add_header_library(
exp2f16
HDRS
exp2f16.h
DEPENDS
.expxf16_utils
libc.src.__support.FPUtil.cast
libc.src.__support.FPUtil.except_value_utils
libc.src.__support.FPUtil.fenv_impl
libc.src.__support.FPUtil.fp_bits
libc.src.__support.FPUtil.rounding_mode
libc.src.__support.macros.optimization
)

add_header_library(
exp10
HDRS
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111 changes: 111 additions & 0 deletions libc/src/__support/math/exp2f16.h
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@@ -0,0 +1,111 @@
//===-- Implementation header for exp2f16 -----------------------*- 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_EXP2F16_H
#define LLVM_LIBC_SRC___SUPPORT_MATH_EXP2F16_H

#include "include/llvm-libc-macros/float16-macros.h"

#ifdef LIBC_TYPES_HAS_FLOAT16

#include "expxf16_utils.h"
#include "src/__support/FPUtil/FEnvImpl.h"
#include "src/__support/FPUtil/FPBits.h"
#include "src/__support/FPUtil/cast.h"
#include "src/__support/FPUtil/except_value_utils.h"
#include "src/__support/FPUtil/rounding_mode.h"
#include "src/__support/common.h"
#include "src/__support/macros/config.h"
#include "src/__support/macros/optimization.h"

namespace LIBC_NAMESPACE_DECL {

namespace math {

LIBC_INLINE static constexpr float16 exp2f16(float16 x) {

#ifndef LIBC_MATH_HAS_SKIP_ACCURATE_PASS
constexpr fputil::ExceptValues<float16, 3> EXP2F16_EXCEPTS = {{
// (input, RZ output, RU offset, RD offset, RN offset)
// x = 0x1.714p-11, exp2f16(x) = 0x1p+0 (RZ)
{0x11c5U, 0x3c00U, 1U, 0U, 1U},
// x = -0x1.558p-4, exp2f16(x) = 0x1.e34p-1 (RZ)
{0xad56U, 0x3b8dU, 1U, 0U, 0U},
// x = -0x1.d5cp-4, exp2f16(x) = 0x1.d8cp-1 (RZ)
{0xaf57U, 0x3b63U, 1U, 0U, 0U},
}};
#endif // !LIBC_MATH_HAS_SKIP_ACCURATE_PASS

using namespace math::expxf16_internal;
using FPBits = fputil::FPBits<float16>;
FPBits x_bits(x);

uint16_t x_u = x_bits.uintval();
uint16_t x_abs = x_u & 0x7fffU;

// When |x| >= 16, or x is NaN.
if (LIBC_UNLIKELY(x_abs >= 0x4c00U)) {
// exp2(NaN) = NaN
if (x_bits.is_nan()) {
if (x_bits.is_signaling_nan()) {
fputil::raise_except_if_required(FE_INVALID);
return FPBits::quiet_nan().get_val();
}

return x;
}

// When x >= 16.
if (x_bits.is_pos()) {
// exp2(+inf) = +inf
if (x_bits.is_inf())
return FPBits::inf().get_val();

switch (fputil::quick_get_round()) {
case FE_TONEAREST:
case FE_UPWARD:
fputil::set_errno_if_required(ERANGE);
fputil::raise_except_if_required(FE_OVERFLOW);
return FPBits::inf().get_val();
default:
return FPBits::max_normal().get_val();
}
}

// When x <= -25.
if (x_u >= 0xce40U) {
// exp2(-inf) = +0
if (x_bits.is_inf())
return FPBits::zero().get_val();

fputil::set_errno_if_required(ERANGE);
fputil::raise_except_if_required(FE_UNDERFLOW | FE_INEXACT);

if (fputil::fenv_is_round_up())
return FPBits::min_subnormal().get_val();
return FPBits::zero().get_val();
}
}

#ifndef LIBC_MATH_HAS_SKIP_ACCURATE_PASS
if (auto r = EXP2F16_EXCEPTS.lookup(x_u); LIBC_UNLIKELY(r.has_value()))
return r.value();
#endif // !LIBC_MATH_HAS_SKIP_ACCURATE_PASS

// exp2(x) = exp2(hi + mid) * exp2(lo)
auto [exp2_hi_mid, exp2_lo] = exp2_range_reduction(x);
return fputil::cast<float16>(exp2_hi_mid * exp2_lo);
}

} // namespace math

} // namespace LIBC_NAMESPACE_DECL

#endif // LIBC_TYPES_HAS_FLOAT16

#endif // LLVM_LIBC_SRC___SUPPORT_MATH_EXP2F16_H
10 changes: 1 addition & 9 deletions libc/src/math/generic/CMakeLists.txt
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Expand Up @@ -1468,15 +1468,7 @@ add_entrypoint_object(
HDRS
../exp2f16.h
DEPENDS
libc.hdr.errno_macros
libc.hdr.fenv_macros
libc.src.__support.FPUtil.cast
libc.src.__support.FPUtil.except_value_utils
libc.src.__support.FPUtil.fenv_impl
libc.src.__support.FPUtil.fp_bits
libc.src.__support.FPUtil.rounding_mode
libc.src.__support.macros.optimization
libc.src.__support.math.expxf16_utils
libc.src.__support.math.exp2f16
)

add_entrypoint_object(
Expand Down
86 changes: 2 additions & 84 deletions libc/src/math/generic/exp2f16.cpp
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Expand Up @@ -7,92 +7,10 @@
//===----------------------------------------------------------------------===//

#include "src/math/exp2f16.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/except_value_utils.h"
#include "src/__support/FPUtil/rounding_mode.h"
#include "src/__support/common.h"
#include "src/__support/macros/config.h"
#include "src/__support/macros/optimization.h"
#include "src/__support/math/expxf16_utils.h"
#include "src/__support/math/exp2f16.h"

namespace LIBC_NAMESPACE_DECL {

#ifndef LIBC_MATH_HAS_SKIP_ACCURATE_PASS
static constexpr fputil::ExceptValues<float16, 3> EXP2F16_EXCEPTS = {{
// (input, RZ output, RU offset, RD offset, RN offset)
// x = 0x1.714p-11, exp2f16(x) = 0x1p+0 (RZ)
{0x11c5U, 0x3c00U, 1U, 0U, 1U},
// x = -0x1.558p-4, exp2f16(x) = 0x1.e34p-1 (RZ)
{0xad56U, 0x3b8dU, 1U, 0U, 0U},
// x = -0x1.d5cp-4, exp2f16(x) = 0x1.d8cp-1 (RZ)
{0xaf57U, 0x3b63U, 1U, 0U, 0U},
}};
#endif // !LIBC_MATH_HAS_SKIP_ACCURATE_PASS

LLVM_LIBC_FUNCTION(float16, exp2f16, (float16 x)) {
using namespace math::expxf16_internal;
using FPBits = fputil::FPBits<float16>;
FPBits x_bits(x);

uint16_t x_u = x_bits.uintval();
uint16_t x_abs = x_u & 0x7fffU;

// When |x| >= 16, or x is NaN.
if (LIBC_UNLIKELY(x_abs >= 0x4c00U)) {
// exp2(NaN) = NaN
if (x_bits.is_nan()) {
if (x_bits.is_signaling_nan()) {
fputil::raise_except_if_required(FE_INVALID);
return FPBits::quiet_nan().get_val();
}

return x;
}

// When x >= 16.
if (x_bits.is_pos()) {
// exp2(+inf) = +inf
if (x_bits.is_inf())
return FPBits::inf().get_val();

switch (fputil::quick_get_round()) {
case FE_TONEAREST:
case FE_UPWARD:
fputil::set_errno_if_required(ERANGE);
fputil::raise_except_if_required(FE_OVERFLOW);
return FPBits::inf().get_val();
default:
return FPBits::max_normal().get_val();
}
}

// When x <= -25.
if (x_u >= 0xce40U) {
// exp2(-inf) = +0
if (x_bits.is_inf())
return FPBits::zero().get_val();

fputil::set_errno_if_required(ERANGE);
fputil::raise_except_if_required(FE_UNDERFLOW | FE_INEXACT);

if (fputil::fenv_is_round_up())
return FPBits::min_subnormal().get_val();
return FPBits::zero().get_val();
}
}

#ifndef LIBC_MATH_HAS_SKIP_ACCURATE_PASS
if (auto r = EXP2F16_EXCEPTS.lookup(x_u); LIBC_UNLIKELY(r.has_value()))
return r.value();
#endif // !LIBC_MATH_HAS_SKIP_ACCURATE_PASS

// exp2(x) = exp2(hi + mid) * exp2(lo)
auto [exp2_hi_mid, exp2_lo] = exp2_range_reduction(x);
return fputil::cast<float16>(exp2_hi_mid * exp2_lo);
}
LLVM_LIBC_FUNCTION(float16, exp2f16, (float16 x)) { return math::exp2f16(x); }

} // namespace LIBC_NAMESPACE_DECL
1 change: 1 addition & 0 deletions libc/test/shared/CMakeLists.txt
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Expand Up @@ -42,6 +42,7 @@ add_fp_unittest(
libc.src.__support.math.exp
libc.src.__support.math.exp2
libc.src.__support.math.exp2f
libc.src.__support.math.exp2f16
libc.src.__support.math.exp10
libc.src.__support.math.exp10f
libc.src.__support.math.exp10f16
Expand Down
2 changes: 1 addition & 1 deletion libc/test/shared/shared_math_test.cpp
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Expand Up @@ -28,7 +28,7 @@ TEST(LlvmLibcSharedMathTest, AllFloat16) {
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(0x0p+0f16, LIBC_NAMESPACE::shared::exp10m1f16(0.0f16));

EXPECT_FP_EQ(0x1p+0f16, LIBC_NAMESPACE::shared::exp2f16(0.0f16));
EXPECT_FP_EQ(0x1p+0f16, LIBC_NAMESPACE::shared::expf16(0.0f16));

ASSERT_FP_EQ(float16(8 << 5), LIBC_NAMESPACE::shared::ldexpf16(8.0f16, 5));
Expand Down
18 changes: 17 additions & 1 deletion utils/bazel/llvm-project-overlay/libc/BUILD.bazel
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Expand Up @@ -2895,6 +2895,22 @@ libc_support_library(
],
)

libc_support_library(
name = "__support_math_exp2f16",
hdrs = ["src/__support/math/exp2f16.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_expxf16_utils",
],
)

libc_support_library(
name = "__support_math_exp10",
hdrs = ["src/__support/math/exp10.h"],
Expand Down Expand Up @@ -3683,7 +3699,7 @@ libc_math_function(
libc_math_function(
name = "exp2f16",
additional_deps = [
":__support_math_expxf16_utils",
":__support_math_exp2f16",
],
)

Expand Down
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