[libc][math] Refactor expm1f16 implementation to header-only in src/__support/math folder. #162132
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@llvm/pr-subscribers-libc Author: Muhammad Bassiouni (bassiounix) ChangesPart 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 Full diff: https://github.com/llvm/llvm-project/pull/162132.diff 9 Files Affected:
diff --git a/libc/shared/math.h b/libc/shared/math.h
index 663900b1d3519..1c3b46e439c1d 100644
--- a/libc/shared/math.h
+++ b/libc/shared/math.h
@@ -56,6 +56,7 @@
#include "math/expf16.h"
#include "math/expm1.h"
#include "math/expm1f.h"
+#include "math/expm1f16.h"
#include "math/frexpf.h"
#include "math/frexpf128.h"
#include "math/frexpf16.h"
diff --git a/libc/shared/math/expm1f16.h b/libc/shared/math/expm1f16.h
new file mode 100644
index 0000000000000..5698400d7066a
--- /dev/null
+++ b/libc/shared/math/expm1f16.h
@@ -0,0 +1,29 @@
+//===-- Shared expm1f16 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_EXPM1F16_H
+#define LLVM_LIBC_SHARED_MATH_EXPM1F16_H
+
+#include "include/llvm-libc-macros/float16-macros.h"
+#include "shared/libc_common.h"
+
+#ifdef LIBC_TYPES_HAS_FLOAT16
+
+#include "src/__support/math/expm1f16.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace shared {
+
+using math::expm1f16;
+
+} // namespace shared
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LIBC_TYPES_HAS_FLOAT16
+
+#endif // LLVM_LIBC_SHARED_MATH_EXPM1F16_H
diff --git a/libc/src/__support/math/CMakeLists.txt b/libc/src/__support/math/CMakeLists.txt
index 00b44c5725565..7fe029ddcfb65 100644
--- a/libc/src/__support/math/CMakeLists.txt
+++ b/libc/src/__support/math/CMakeLists.txt
@@ -923,6 +923,22 @@ add_header_library(
libc.src.errno.errno
)
+add_header_library(
+ expm1f16
+ HDRS
+ expm1f16.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.multiply_add
+ libc.src.__support.FPUtil.polyeval
+ libc.src.__support.FPUtil.rounding_mode
+ libc.src.__support.macros.optimization
+)
+
add_header_library(
range_reduction_double
HDRS
diff --git a/libc/src/__support/math/expm1f16.h b/libc/src/__support/math/expm1f16.h
new file mode 100644
index 0000000000000..79547b62b0892
--- /dev/null
+++ b/libc/src/__support/math/expm1f16.h
@@ -0,0 +1,153 @@
+//===-- Implementation header for expm1f16 ----------------------*- 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_EXPM1F16_H
+#define LLVM_LIBC_SRC___SUPPORT_MATH_EXPM1F16_H
+
+#include "include/llvm-libc-macros/float16-macros.h"
+
+#ifdef LIBC_TYPES_HAS_FLOAT16
+
+#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/except_value_utils.h"
+#include "src/__support/FPUtil/multiply_add.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"
+
+namespace LIBC_NAMESPACE_DECL {
+
+namespace math {
+
+LIBC_INLINE static constexpr float16 expm1f16(float16 x) {
+#ifndef LIBC_MATH_HAS_SKIP_ACCURATE_PASS
+ constexpr fputil::ExceptValues<float16, 1> EXPM1F16_EXCEPTS_LO = {{
+ // (input, RZ output, RU offset, RD offset, RN offset)
+ // x = 0x1.564p-5, expm1f16(x) = 0x1.5d4p-5 (RZ)
+ {0x2959U, 0x2975U, 1U, 0U, 1U},
+ }};
+
+#ifdef LIBC_TARGET_CPU_HAS_FMA_FLOAT
+ constexpr size_t N_EXPM1F16_EXCEPTS_HI = 2;
+#else
+ constexpr size_t N_EXPM1F16_EXCEPTS_HI = 3;
+#endif
+
+ constexpr fputil::ExceptValues<float16, N_EXPM1F16_EXCEPTS_HI>
+ EXPM1F16_EXCEPTS_HI = {{
+ // (input, RZ output, RU offset, RD offset, RN offset)
+ // x = 0x1.c34p+0, expm1f16(x) = 0x1.34cp+2 (RZ)
+ {0x3f0dU, 0x44d3U, 1U, 0U, 1U},
+ // x = -0x1.e28p-3, expm1f16(x) = -0x1.adcp-3 (RZ)
+ {0xb38aU, 0xb2b7U, 0U, 1U, 1U},
+#ifndef LIBC_TARGET_CPU_HAS_FMA_FLOAT
+ // x = 0x1.a08p-3, exp10m1f(x) = 0x1.cdcp-3 (RZ)
+ {0x3282U, 0x3337U, 1U, 0U, 0U},
+#endif
+ }};
+#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| <= 2^(-3), or |x| >= -11 * log(2), or x is NaN.
+ if (LIBC_UNLIKELY(x_abs <= 0x3000U || x_abs >= 0x47a0U)) {
+ // expm1(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;
+ }
+
+ // expm1(+/-0) = +/-0
+ if (x_abs == 0)
+ return x;
+
+ // When x >= 16 * log(2).
+ if (x_bits.is_pos() && x_abs >= 0x498cU) {
+ // expm1(+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 | FE_INEXACT);
+ return FPBits::inf().get_val();
+ default:
+ return FPBits::max_normal().get_val();
+ }
+ }
+
+ // When x <= -11 * log(2).
+ if (x_u >= 0xc7a0U) {
+ // expm1(-inf) = -1
+ if (x_bits.is_inf())
+ return FPBits::one(Sign::NEG).get_val();
+
+ // When x > -0x1.0ap+3, round(expm1(x), HP, RN) = -1.
+ if (x_u > 0xc828U)
+ return fputil::round_result_slightly_up(
+ FPBits::one(Sign::NEG).get_val());
+ // When x <= -0x1.0ap+3, round(expm1(x), HP, RN) = -0x1.ffcp-1.
+ return fputil::round_result_slightly_down(
+ fputil::cast<float16>(-0x1.ffcp-1));
+ }
+
+ // When 0 < |x| <= 2^(-3).
+ if (x_abs <= 0x3000U && !x_bits.is_zero()) {
+
+#ifndef LIBC_MATH_HAS_SKIP_ACCURATE_PASS
+ if (auto r = EXPM1F16_EXCEPTS_LO.lookup(x_u);
+ LIBC_UNLIKELY(r.has_value()))
+ return r.value();
+#endif // !LIBC_MATH_HAS_SKIP_ACCURATE_PASS
+
+ float xf = x;
+ // Degree-5 minimax polynomial generated by Sollya with the following
+ // commands:
+ // > display = hexadecimal;
+ // > P = fpminimax(expm1(x)/x, 4, [|SG...|], [-2^-3, 2^-3]);
+ // > x * P;
+ return fputil::cast<float16>(
+ xf * fputil::polyeval(xf, 0x1p+0f, 0x1.fffff8p-2f, 0x1.555556p-3f,
+ 0x1.55905ep-5f, 0x1.1124c2p-7f));
+ }
+ }
+
+#ifndef LIBC_MATH_HAS_SKIP_ACCURATE_PASS
+ if (auto r = EXPM1F16_EXCEPTS_HI.lookup(x_u); LIBC_UNLIKELY(r.has_value()))
+ return r.value();
+#endif // !LIBC_MATH_HAS_SKIP_ACCURATE_PASS
+
+ // exp(x) = exp(hi + mid) * exp(lo)
+ auto [exp_hi_mid, exp_lo] = exp_range_reduction(x);
+ // expm1(x) = exp(hi + mid) * exp(lo) - 1
+ return fputil::cast<float16>(fputil::multiply_add(exp_hi_mid, exp_lo, -1.0f));
+}
+
+} // namespace math
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LIBC_TYPES_HAS_FLOAT16
+
+#endif // LLVM_LIBC_SRC___SUPPORT_MATH_EXPM1F16_H
diff --git a/libc/src/math/generic/CMakeLists.txt b/libc/src/math/generic/CMakeLists.txt
index 2a2f4e7567c71..c14f356b39476 100644
--- a/libc/src/math/generic/CMakeLists.txt
+++ b/libc/src/math/generic/CMakeLists.txt
@@ -1571,17 +1571,7 @@ add_entrypoint_object(
HDRS
../expm1f16.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.multiply_add
- libc.src.__support.FPUtil.polyeval
- libc.src.__support.FPUtil.rounding_mode
- libc.src.__support.macros.optimization
- libc.src.__support.math.expxf16_utils
+ libc.src.__support.math.expm1f16
)
add_entrypoint_object(
diff --git a/libc/src/math/generic/expm1f16.cpp b/libc/src/math/generic/expm1f16.cpp
index c2231f0aca715..68bf21df1721e 100644
--- a/libc/src/math/generic/expm1f16.cpp
+++ b/libc/src/math/generic/expm1f16.cpp
@@ -7,135 +7,9 @@
//===----------------------------------------------------------------------===//
#include "src/math/expm1f16.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/except_value_utils.h"
-#include "src/__support/FPUtil/multiply_add.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/expm1f16.h"
namespace LIBC_NAMESPACE_DECL {
-
-#ifndef LIBC_MATH_HAS_SKIP_ACCURATE_PASS
-static constexpr fputil::ExceptValues<float16, 1> EXPM1F16_EXCEPTS_LO = {{
- // (input, RZ output, RU offset, RD offset, RN offset)
- // x = 0x1.564p-5, expm1f16(x) = 0x1.5d4p-5 (RZ)
- {0x2959U, 0x2975U, 1U, 0U, 1U},
-}};
-
-#ifdef LIBC_TARGET_CPU_HAS_FMA_FLOAT
-static constexpr size_t N_EXPM1F16_EXCEPTS_HI = 2;
-#else
-static constexpr size_t N_EXPM1F16_EXCEPTS_HI = 3;
-#endif
-
-static constexpr fputil::ExceptValues<float16, N_EXPM1F16_EXCEPTS_HI>
- EXPM1F16_EXCEPTS_HI = {{
- // (input, RZ output, RU offset, RD offset, RN offset)
- // x = 0x1.c34p+0, expm1f16(x) = 0x1.34cp+2 (RZ)
- {0x3f0dU, 0x44d3U, 1U, 0U, 1U},
- // x = -0x1.e28p-3, expm1f16(x) = -0x1.adcp-3 (RZ)
- {0xb38aU, 0xb2b7U, 0U, 1U, 1U},
-#ifndef LIBC_TARGET_CPU_HAS_FMA_FLOAT
- // x = 0x1.a08p-3, exp10m1f(x) = 0x1.cdcp-3 (RZ)
- {0x3282U, 0x3337U, 1U, 0U, 0U},
-#endif
- }};
-#endif // !LIBC_MATH_HAS_SKIP_ACCURATE_PASS
-
-LLVM_LIBC_FUNCTION(float16, expm1f16, (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| <= 2^(-3), or |x| >= -11 * log(2), or x is NaN.
- if (LIBC_UNLIKELY(x_abs <= 0x3000U || x_abs >= 0x47a0U)) {
- // expm1(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;
- }
-
- // expm1(+/-0) = +/-0
- if (x_abs == 0)
- return x;
-
- // When x >= 16 * log(2).
- if (x_bits.is_pos() && x_abs >= 0x498cU) {
- // expm1(+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 | FE_INEXACT);
- return FPBits::inf().get_val();
- default:
- return FPBits::max_normal().get_val();
- }
- }
-
- // When x <= -11 * log(2).
- if (x_u >= 0xc7a0U) {
- // expm1(-inf) = -1
- if (x_bits.is_inf())
- return FPBits::one(Sign::NEG).get_val();
-
- // When x > -0x1.0ap+3, round(expm1(x), HP, RN) = -1.
- if (x_u > 0xc828U)
- return fputil::round_result_slightly_up(
- FPBits::one(Sign::NEG).get_val());
- // When x <= -0x1.0ap+3, round(expm1(x), HP, RN) = -0x1.ffcp-1.
- return fputil::round_result_slightly_down(
- fputil::cast<float16>(-0x1.ffcp-1));
- }
-
- // When 0 < |x| <= 2^(-3).
- if (x_abs <= 0x3000U && !x_bits.is_zero()) {
-
-#ifndef LIBC_MATH_HAS_SKIP_ACCURATE_PASS
- if (auto r = EXPM1F16_EXCEPTS_LO.lookup(x_u);
- LIBC_UNLIKELY(r.has_value()))
- return r.value();
-#endif // !LIBC_MATH_HAS_SKIP_ACCURATE_PASS
-
- float xf = x;
- // Degree-5 minimax polynomial generated by Sollya with the following
- // commands:
- // > display = hexadecimal;
- // > P = fpminimax(expm1(x)/x, 4, [|SG...|], [-2^-3, 2^-3]);
- // > x * P;
- return fputil::cast<float16>(
- xf * fputil::polyeval(xf, 0x1p+0f, 0x1.fffff8p-2f, 0x1.555556p-3f,
- 0x1.55905ep-5f, 0x1.1124c2p-7f));
- }
- }
-
-#ifndef LIBC_MATH_HAS_SKIP_ACCURATE_PASS
- if (auto r = EXPM1F16_EXCEPTS_HI.lookup(x_u); LIBC_UNLIKELY(r.has_value()))
- return r.value();
-#endif // !LIBC_MATH_HAS_SKIP_ACCURATE_PASS
-
- // exp(x) = exp(hi + mid) * exp(lo)
- auto [exp_hi_mid, exp_lo] = exp_range_reduction(x);
- // expm1(x) = exp(hi + mid) * exp(lo) - 1
- return fputil::cast<float16>(fputil::multiply_add(exp_hi_mid, exp_lo, -1.0f));
-}
+LLVM_LIBC_FUNCTION(float16, expm1f16, (float16 x)) { return math::expm1f16(x); }
} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/test/shared/CMakeLists.txt b/libc/test/shared/CMakeLists.txt
index 64d000d6fc445..aadbd4ad980f0 100644
--- a/libc/test/shared/CMakeLists.txt
+++ b/libc/test/shared/CMakeLists.txt
@@ -47,6 +47,7 @@ add_fp_unittest(
libc.src.__support.math.exp2m1f16
libc.src.__support.math.expm1
libc.src.__support.math.expm1f
+ libc.src.__support.math.expm1f16
libc.src.__support.math.exp10
libc.src.__support.math.exp10f
libc.src.__support.math.exp10f16
diff --git a/libc/test/shared/shared_math_test.cpp b/libc/test/shared/shared_math_test.cpp
index bbe1fde87592b..cf75672774105 100644
--- a/libc/test/shared/shared_math_test.cpp
+++ b/libc/test/shared/shared_math_test.cpp
@@ -31,6 +31,7 @@ TEST(LlvmLibcSharedMathTest, AllFloat16) {
EXPECT_FP_EQ(0x1p+0f16, LIBC_NAMESPACE::shared::exp2f16(0.0f16));
EXPECT_FP_EQ(0x0p+0f16, LIBC_NAMESPACE::shared::exp2m1f16(0.0f16));
EXPECT_FP_EQ(0x1p+0f16, LIBC_NAMESPACE::shared::expf16(0.0f16));
+ EXPECT_FP_EQ(0x0p+0f16, LIBC_NAMESPACE::shared::expm1f16(0.0f16));
ASSERT_FP_EQ(float16(8 << 5), LIBC_NAMESPACE::shared::ldexpf16(8.0f16, 5));
ASSERT_FP_EQ(float16(-1 * (8 << 5)),
diff --git a/utils/bazel/llvm-project-overlay/libc/BUILD.bazel b/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
index 7c563ff109fb8..3ccddbacf833d 100644
--- a/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
+++ b/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
@@ -3053,6 +3053,22 @@ libc_support_library(
],
)
+libc_support_library(
+ name = "__support_math_expm1f16",
+ hdrs = ["src/__support/math/expm1f16.h"],
+ deps = [
+ ":__support_fputil_fma",
+ ":__support_fputil_multiply_add",
+ ":__support_fputil_nearest_integer",
+ ":__support_fputil_polyeval",
+ ":__support_fputil_rounding_mode",
+ ":__support_fputil_except_value_utils",
+ ":__support_macros_optimization",
+ ":__support_macros_properties_cpu_features",
+ ":__support_math_expxf16_utils"
+ ],
+)
+
libc_support_library(
name = "__support_range_reduction_double",
hdrs = [
@@ -3799,7 +3815,7 @@ libc_math_function(
libc_math_function(
name = "expm1f16",
additional_deps = [
- ":__support_math_expxf16_utils",
+ ":__support_math_expm1f16",
],
)
|
This was referenced Oct 6, 2025
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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