[libc-commits] [libc] [llvm] [libc][math] Refactor exp10f16 implementation to header-only in src/__support/math folder. (PR #148408)
Muhammad Bassiouni via libc-commits
libc-commits at lists.llvm.org
Thu Jul 17 22:46:33 PDT 2025
https://github.com/bassiounix updated https://github.com/llvm/llvm-project/pull/148408
>From d27b9713135e189b3ee5792bb8e0b760ba50211e Mon Sep 17 00:00:00 2001
From: bassiounix <muhammad.m.bassiouni at gmail.com>
Date: Thu, 17 Jul 2025 20:50:40 +0300
Subject: [PATCH 1/2] [libc][math] Refactor exp10f16 implementation to
header-only in src/__support/math folder.
---
libc/shared/math.h | 1 +
libc/shared/math/exp10f16.h | 29 ++++
libc/src/__support/math/CMakeLists.txt | 34 +++++
.../__support/math/exp10_float16_constants.h | 43 ++++++
libc/src/__support/math/exp10f16.h | 141 ++++++++++++++++++
libc/src/__support/math/exp10f16_utils.h | 64 ++++++++
libc/src/math/generic/CMakeLists.txt | 21 +--
libc/src/math/generic/exp10f16.cpp | 122 +--------------
libc/src/math/generic/exp10m1f16.cpp | 2 +-
libc/src/math/generic/expxf16.h | 56 +------
.../llvm-project-overlay/libc/BUILD.bazel | 38 ++++-
11 files changed, 357 insertions(+), 194 deletions(-)
create mode 100644 libc/shared/math/exp10f16.h
create mode 100644 libc/src/__support/math/exp10_float16_constants.h
create mode 100644 libc/src/__support/math/exp10f16.h
create mode 100644 libc/src/__support/math/exp10f16_utils.h
diff --git a/libc/shared/math.h b/libc/shared/math.h
index 2ae7c1d58ae10..26f69d6fa43ea 100644
--- a/libc/shared/math.h
+++ b/libc/shared/math.h
@@ -14,6 +14,7 @@
#include "math/exp.h"
#include "math/exp10.h"
#include "math/exp10f.h"
+#include "math/exp10f16.h"
#include "math/expf.h"
#include "math/expf16.h"
#include "math/frexpf.h"
diff --git a/libc/shared/math/exp10f16.h b/libc/shared/math/exp10f16.h
new file mode 100644
index 0000000000000..8acdbdb7c70a1
--- /dev/null
+++ b/libc/shared/math/exp10f16.h
@@ -0,0 +1,29 @@
+//===-- Shared exp10f16 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_EXP10F_H
+#define LLVM_LIBC_SHARED_MATH_EXP10F_H
+
+#include "include/llvm-libc-macros/float16-macros.h"
+
+#ifdef LIBC_TYPES_HAS_FLOAT16
+
+#include "shared/libc_common.h"
+#include "src/__support/math/exp10f16.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace shared {
+
+using math::exp10f16;
+
+} // namespace shared
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LIBC_TYPES_HAS_FLOAT16
+
+#endif // LLVM_LIBC_SHARED_MATH_EXP10F_H
diff --git a/libc/src/__support/math/CMakeLists.txt b/libc/src/__support/math/CMakeLists.txt
index ad36679409f89..77a47c65489dd 100644
--- a/libc/src/__support/math/CMakeLists.txt
+++ b/libc/src/__support/math/CMakeLists.txt
@@ -198,3 +198,37 @@ add_header_library(
libc.src.__support.FPUtil.rounding_mode
libc.src.__support.macros.optimization
)
+
+add_header_library(
+ exp10_float16_constants
+ HDRS
+ exp10_float16_constants.h
+ DEPENDS
+ libc.src.__support.CPP.array
+)
+
+add_header_library(
+ exp10f16_utils
+ HDRS
+ exp10f16_utils.h
+ DEPENDS
+ .expf16_utils
+ .exp10_float16_constants
+ libc.src.__support.FPUtil.fp_bits
+)
+
+add_header_library(
+ exp10f16
+ HDRS
+ exp10f16.h
+ DEPENDS
+ .exp10f16_utils
+ libc.src.__support.FPUtil.fp_bits
+ src.__support.FPUtil.FEnvImpl
+ src.__support.FPUtil.FPBits
+ src.__support.FPUtil.cast
+ src.__support.FPUtil.rounding_mode
+ src.__support.FPUtil.except_value_utils
+ src.__support.macros.optimization
+ src.__support.macros.properties.cpu_features
+)
diff --git a/libc/src/__support/math/exp10_float16_constants.h b/libc/src/__support/math/exp10_float16_constants.h
new file mode 100644
index 0000000000000..f5928db740ee4
--- /dev/null
+++ b/libc/src/__support/math/exp10_float16_constants.h
@@ -0,0 +1,43 @@
+//===-- Constants for exp10f16 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_SRC___SUPPORT_MATH_EXP10_FLOAT16_CONSTANTS_H
+#define LLVM_LIBC_SRC___SUPPORT_MATH_EXP10_FLOAT16_CONSTANTS_H
+
+#include "include/llvm-libc-macros/float16-macros.h"
+#include <stdint.h>
+
+#ifdef LIBC_TYPES_HAS_FLOAT16
+
+#include "src/__support/CPP/array.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+// Generated by Sollya with the following commands:
+// > display = hexadecimal;
+// > for i from 0 to 7 do printsingle(round(2^(i * 2^-3), SG, RN));
+static constexpr cpp::array<uint32_t, 8> EXP2_MID_BITS = {
+ 0x3f80'0000U, 0x3f8b'95c2U, 0x3f98'37f0U, 0x3fa5'fed7U,
+ 0x3fb5'04f3U, 0x3fc5'672aU, 0x3fd7'44fdU, 0x3fea'c0c7U,
+};
+
+// Generated by Sollya with the following commands:
+// > display = hexadecimal;
+// > round(log2(10), SG, RN);
+static constexpr float LOG2F_10 = 0x1.a934fp+1f;
+
+// Generated by Sollya with the following commands:
+// > display = hexadecimal;
+// > round(log10(2), SG, RN);
+static constexpr float LOG10F_2 = 0x1.344136p-2f;
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LIBC_TYPES_HAS_FLOAT16
+
+#endif // LLVM_LIBC_SRC___SUPPORT_MATH_EXP10F16_H
diff --git a/libc/src/__support/math/exp10f16.h b/libc/src/__support/math/exp10f16.h
new file mode 100644
index 0000000000000..0d8b125348844
--- /dev/null
+++ b/libc/src/__support/math/exp10f16.h
@@ -0,0 +1,141 @@
+//===-- Implementation header for exp10f16 ----------------------*- 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_EXP10F16_H
+#define LLVM_LIBC_SRC___SUPPORT_MATH_EXP10F16_H
+
+#include "include/llvm-libc-macros/float16-macros.h"
+
+#ifdef LIBC_TYPES_HAS_FLOAT16
+
+#include "exp10f16_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/macros/config.h"
+#include "src/__support/macros/optimization.h"
+#include "src/__support/macros/properties/cpu_features.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+namespace math {
+
+#ifndef LIBC_MATH_HAS_SKIP_ACCURATE_PASS
+#ifdef LIBC_TARGET_CPU_HAS_FMA_FLOAT
+static constexpr size_t N_EXP10F16_EXCEPTS = 5;
+#else
+static constexpr size_t N_EXP10F16_EXCEPTS = 8;
+#endif
+
+static constexpr fputil::ExceptValues<float16, N_EXP10F16_EXCEPTS>
+ EXP10F16_EXCEPTS = {{
+ // x = 0x1.8f4p-2, exp10f16(x) = 0x1.3ap+1 (RZ)
+ {0x363dU, 0x40e8U, 1U, 0U, 1U},
+ // x = 0x1.95cp-2, exp10f16(x) = 0x1.3ecp+1 (RZ)
+ {0x3657U, 0x40fbU, 1U, 0U, 0U},
+ // x = -0x1.018p-4, exp10f16(x) = 0x1.bbp-1 (RZ)
+ {0xac06U, 0x3aecU, 1U, 0U, 0U},
+ // x = -0x1.c28p+0, exp10f16(x) = 0x1.1ccp-6 (RZ)
+ {0xbf0aU, 0x2473U, 1U, 0U, 0U},
+ // x = -0x1.e1cp+1, exp10f16(x) = 0x1.694p-13 (RZ)
+ {0xc387U, 0x09a5U, 1U, 0U, 0U},
+#ifndef LIBC_TARGET_CPU_HAS_FMA_FLOAT
+ // x = 0x1.0cp+1, exp10f16(x) = 0x1.f04p+6 (RZ)
+ {0x4030U, 0x57c1U, 1U, 0U, 1U},
+ // x = 0x1.1b8p+1, exp10f16(x) = 0x1.47cp+7 (RZ)
+ {0x406eU, 0x591fU, 1U, 0U, 1U},
+ // x = 0x1.1b8p+2, exp10f16(x) = 0x1.a4p+14 (RZ)
+ {0x446eU, 0x7690U, 1U, 0U, 1U},
+#endif
+ }};
+#endif // !LIBC_MATH_HAS_SKIP_ACCURATE_PASS
+
+static constexpr float16 exp10f16(float16 x) {
+ 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| >= 5, or x is NaN.
+ if (LIBC_UNLIKELY(x_abs >= 0x4500U)) {
+ // exp10(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 >= 5.
+ if (x_bits.is_pos()) {
+ // exp10(+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 <= -8.
+ if (x_u >= 0xc800U) {
+ // exp10(-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();
+ }
+ }
+
+ // When x is 1, 2, 3, or 4. These are hard-to-round cases with exact results.
+ if (LIBC_UNLIKELY((x_u & ~(0x3c00U | 0x4000U | 0x4200U | 0x4400U)) == 0)) {
+ switch (x_u) {
+ case 0x3c00U: // x = 1.0f16
+ return fputil::cast<float16>(10.0);
+ case 0x4000U: // x = 2.0f16
+ return fputil::cast<float16>(100.0);
+ case 0x4200U: // x = 3.0f16
+ return fputil::cast<float16>(1'000.0);
+ case 0x4400U: // x = 4.0f16
+ return fputil::cast<float16>(10'000.0);
+ }
+ }
+
+#ifndef LIBC_MATH_HAS_SKIP_ACCURATE_PASS
+ if (auto r = EXP10F16_EXCEPTS.lookup(x_u); LIBC_UNLIKELY(r.has_value()))
+ return r.value();
+#endif // !LIBC_MATH_HAS_SKIP_ACCURATE_PASS
+
+ // 10^x = 2^((hi + mid) * log2(10)) * 10^lo
+ auto [exp2_hi_mid, exp10_lo] = exp10_range_reduction(x);
+ return fputil::cast<float16>(exp2_hi_mid * exp10_lo);
+}
+
+} // namespace math
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LIBC_TYPES_HAS_FLOAT16
+
+#endif // LLVM_LIBC_SRC___SUPPORT_MATH_EXP10F16_H
diff --git a/libc/src/__support/math/exp10f16_utils.h b/libc/src/__support/math/exp10f16_utils.h
new file mode 100644
index 0000000000000..ae251fc7ce800
--- /dev/null
+++ b/libc/src/__support/math/exp10f16_utils.h
@@ -0,0 +1,64 @@
+//===-- Common utils for exp10f16 -------------------------------*- 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_EXP_FLOAT_CONSTANTS_H
+#define LLVM_LIBC_SRC___SUPPORT_MATH_EXP_FLOAT_CONSTANTS_H
+
+#include "include/llvm-libc-macros/float16-macros.h"
+
+#ifdef LIBC_TYPES_HAS_FLOAT16
+
+#include "exp10_float16_constants.h"
+#include "expf16_utils.h"
+#include "src/__support/FPUtil/FPBits.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+LIBC_INLINE static constexpr ExpRangeReduction
+exp10_range_reduction(float16 x) {
+ // For -8 < x < 5, to compute 10^x, we perform the following range reduction:
+ // find hi, mid, lo, such that:
+ // x = (hi + mid) * log2(10) + lo, in which
+ // hi is an integer,
+ // mid * 2^3 is an integer,
+ // -2^(-4) <= lo < 2^(-4).
+ // In particular,
+ // hi + mid = round(x * 2^3) * 2^(-3).
+ // Then,
+ // 10^x = 10^(hi + mid + lo) = 2^((hi + mid) * log2(10)) + 10^lo
+ // We store 2^mid in the lookup table EXP2_MID_BITS, and compute 2^hi * 2^mid
+ // by adding hi to the exponent field of 2^mid. 10^lo is computed using a
+ // degree-4 minimax polynomial generated by Sollya.
+
+ float xf = x;
+ float kf = fputil::nearest_integer(xf * (LOG2F_10 * 0x1.0p+3f));
+ int x_hi_mid = static_cast<int>(kf);
+ unsigned x_hi = static_cast<unsigned>(x_hi_mid) >> 3;
+ unsigned x_mid = static_cast<unsigned>(x_hi_mid) & 0x7;
+ // lo = x - (hi + mid) = round(x * 2^3 * log2(10)) * log10(2) * (-2^(-3)) + x
+ float lo = fputil::multiply_add(kf, LOG10F_2 * -0x1.0p-3f, xf);
+
+ uint32_t exp2_hi_mid_bits =
+ EXP2_MID_BITS[x_mid] +
+ static_cast<uint32_t>(x_hi << fputil::FPBits<float>::FRACTION_LEN);
+ float exp2_hi_mid = fputil::FPBits<float>(exp2_hi_mid_bits).get_val();
+ // Degree-4 minimax polynomial generated by Sollya with the following
+ // commands:
+ // > display = hexadecimal;
+ // > P = fpminimax((10^x - 1)/x, 3, [|SG...|], [-2^-4, 2^-4]);
+ // > 1 + x * P;
+ float exp10_lo = fputil::polyeval(lo, 0x1p+0f, 0x1.26bb14p+1f, 0x1.53526p+1f,
+ 0x1.04b434p+1f, 0x1.2bcf9ep+0f);
+ return {exp2_hi_mid, exp10_lo};
+}
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LIBC_TYPES_HAS_FLOAT16
+
+#endif // LLVM_LIBC_SRC___SUPPORT_MATH_EXP10F16_H
diff --git a/libc/src/math/generic/CMakeLists.txt b/libc/src/math/generic/CMakeLists.txt
index 99db743315d43..fb253a4502700 100644
--- a/libc/src/math/generic/CMakeLists.txt
+++ b/libc/src/math/generic/CMakeLists.txt
@@ -1477,20 +1477,8 @@ add_entrypoint_object(
HDRS
../exp10f16.h
DEPENDS
- .expxf16
- libc.hdr.errno_macros
- libc.hdr.fenv_macros
- libc.src.__support.CPP.array
- 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.nearest_integer
- libc.src.__support.FPUtil.polyeval
- libc.src.__support.FPUtil.rounding_mode
- libc.src.__support.macros.optimization
- libc.src.__support.macros.properties.cpu_features
+ libc.src.__support.math.exp10f16
+ libc.src.errno.errno
)
add_entrypoint_object(
@@ -1519,7 +1507,6 @@ add_entrypoint_object(
HDRS
../exp10m1f16.h
DEPENDS
- .expxf16
libc.hdr.errno_macros
libc.hdr.fenv_macros
libc.src.__support.FPUtil.cast
@@ -1531,6 +1518,7 @@ add_entrypoint_object(
libc.src.__support.FPUtil.rounding_mode
libc.src.__support.macros.optimization
libc.src.__support.macros.properties.cpu_features
+ libc.src.__support.math.exp10f16_utils
)
add_entrypoint_object(
@@ -5023,10 +5011,11 @@ add_header_library(
HDRS
expxf16.h
DEPENDS
- libc.src.__support.FPUtil.cast
libc.src.__support.FPUtil.fp_bits
+ libc.src.__support.FPUtil.cast
libc.src.__support.FPUtil.multiply_add
libc.src.__support.FPUtil.nearest_integer
libc.src.__support.macros.attributes
libc.src.__support.math.expf16_utils
+ libc.src.__support.math.exp10_float16_constants
)
diff --git a/libc/src/math/generic/exp10f16.cpp b/libc/src/math/generic/exp10f16.cpp
index 31abf3b4f89b2..cb3c8599c9231 100644
--- a/libc/src/math/generic/exp10f16.cpp
+++ b/libc/src/math/generic/exp10f16.cpp
@@ -7,128 +7,10 @@
//===----------------------------------------------------------------------===//
#include "src/math/exp10f16.h"
-#include "expxf16.h"
-#include "hdr/errno_macros.h"
-#include "hdr/fenv_macros.h"
-#include "src/__support/CPP/array.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/nearest_integer.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/macros/properties/cpu_features.h"
+#include "src/__support/math/exp10f16.h"
namespace LIBC_NAMESPACE_DECL {
-#ifndef LIBC_MATH_HAS_SKIP_ACCURATE_PASS
-#ifdef LIBC_TARGET_CPU_HAS_FMA_FLOAT
-static constexpr size_t N_EXP10F16_EXCEPTS = 5;
-#else
-static constexpr size_t N_EXP10F16_EXCEPTS = 8;
-#endif
-
-static constexpr fputil::ExceptValues<float16, N_EXP10F16_EXCEPTS>
- EXP10F16_EXCEPTS = {{
- // x = 0x1.8f4p-2, exp10f16(x) = 0x1.3ap+1 (RZ)
- {0x363dU, 0x40e8U, 1U, 0U, 1U},
- // x = 0x1.95cp-2, exp10f16(x) = 0x1.3ecp+1 (RZ)
- {0x3657U, 0x40fbU, 1U, 0U, 0U},
- // x = -0x1.018p-4, exp10f16(x) = 0x1.bbp-1 (RZ)
- {0xac06U, 0x3aecU, 1U, 0U, 0U},
- // x = -0x1.c28p+0, exp10f16(x) = 0x1.1ccp-6 (RZ)
- {0xbf0aU, 0x2473U, 1U, 0U, 0U},
- // x = -0x1.e1cp+1, exp10f16(x) = 0x1.694p-13 (RZ)
- {0xc387U, 0x09a5U, 1U, 0U, 0U},
-#ifndef LIBC_TARGET_CPU_HAS_FMA_FLOAT
- // x = 0x1.0cp+1, exp10f16(x) = 0x1.f04p+6 (RZ)
- {0x4030U, 0x57c1U, 1U, 0U, 1U},
- // x = 0x1.1b8p+1, exp10f16(x) = 0x1.47cp+7 (RZ)
- {0x406eU, 0x591fU, 1U, 0U, 1U},
- // x = 0x1.1b8p+2, exp10f16(x) = 0x1.a4p+14 (RZ)
- {0x446eU, 0x7690U, 1U, 0U, 1U},
-#endif
- }};
-#endif // !LIBC_MATH_HAS_SKIP_ACCURATE_PASS
-
-LLVM_LIBC_FUNCTION(float16, exp10f16, (float16 x)) {
- 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| >= 5, or x is NaN.
- if (LIBC_UNLIKELY(x_abs >= 0x4500U)) {
- // exp10(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 >= 5.
- if (x_bits.is_pos()) {
- // exp10(+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 <= -8.
- if (x_u >= 0xc800U) {
- // exp10(-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();
- }
- }
-
- // When x is 1, 2, 3, or 4. These are hard-to-round cases with exact results.
- if (LIBC_UNLIKELY((x_u & ~(0x3c00U | 0x4000U | 0x4200U | 0x4400U)) == 0)) {
- switch (x_u) {
- case 0x3c00U: // x = 1.0f16
- return fputil::cast<float16>(10.0);
- case 0x4000U: // x = 2.0f16
- return fputil::cast<float16>(100.0);
- case 0x4200U: // x = 3.0f16
- return fputil::cast<float16>(1'000.0);
- case 0x4400U: // x = 4.0f16
- return fputil::cast<float16>(10'000.0);
- }
- }
-
-#ifndef LIBC_MATH_HAS_SKIP_ACCURATE_PASS
- if (auto r = EXP10F16_EXCEPTS.lookup(x_u); LIBC_UNLIKELY(r.has_value()))
- return r.value();
-#endif // !LIBC_MATH_HAS_SKIP_ACCURATE_PASS
-
- // 10^x = 2^((hi + mid) * log2(10)) * 10^lo
- auto [exp2_hi_mid, exp10_lo] = exp10_range_reduction(x);
- return fputil::cast<float16>(exp2_hi_mid * exp10_lo);
-}
+LLVM_LIBC_FUNCTION(float16, exp10f16, (float16 x)) { return math::exp10f16(x); }
} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/src/math/generic/exp10m1f16.cpp b/libc/src/math/generic/exp10m1f16.cpp
index 545c479694811..6c2fdbea418df 100644
--- a/libc/src/math/generic/exp10m1f16.cpp
+++ b/libc/src/math/generic/exp10m1f16.cpp
@@ -7,7 +7,6 @@
//===----------------------------------------------------------------------===//
#include "src/math/exp10m1f16.h"
-#include "expxf16.h"
#include "hdr/errno_macros.h"
#include "hdr/fenv_macros.h"
#include "src/__support/FPUtil/FEnvImpl.h"
@@ -21,6 +20,7 @@
#include "src/__support/macros/config.h"
#include "src/__support/macros/optimization.h"
#include "src/__support/macros/properties/cpu_features.h"
+#include "src/__support/math/exp10f16_utils.h"
namespace LIBC_NAMESPACE_DECL {
diff --git a/libc/src/math/generic/expxf16.h b/libc/src/math/generic/expxf16.h
index 05ac95d586823..b17b14fa2d756 100644
--- a/libc/src/math/generic/expxf16.h
+++ b/libc/src/math/generic/expxf16.h
@@ -17,18 +17,11 @@
#include "src/__support/macros/config.h"
#include <stdint.h>
+#include "src/__support/math/exp10_float16_constants.h"
#include "src/__support/math/expf16_utils.h"
namespace LIBC_NAMESPACE_DECL {
-// Generated by Sollya with the following commands:
-// > display = hexadecimal;
-// > for i from 0 to 7 do printsingle(round(2^(i * 2^-3), SG, RN));
-constexpr cpp::array<uint32_t, 8> EXP2_MID_BITS = {
- 0x3f80'0000U, 0x3f8b'95c2U, 0x3f98'37f0U, 0x3fa5'fed7U,
- 0x3fb5'04f3U, 0x3fc5'672aU, 0x3fd7'44fdU, 0x3fea'c0c7U,
-};
-
LIBC_INLINE ExpRangeReduction exp2_range_reduction(float16 x) {
// For -25 < x < 16, to compute 2^x, we perform the following range reduction:
// find hi, mid, lo, such that:
@@ -66,53 +59,6 @@ LIBC_INLINE ExpRangeReduction exp2_range_reduction(float16 x) {
return {exp2_hi_mid, exp2_lo};
}
-// Generated by Sollya with the following commands:
-// > display = hexadecimal;
-// > round(log2(10), SG, RN);
-static constexpr float LOG2F_10 = 0x1.a934fp+1f;
-
-// Generated by Sollya with the following commands:
-// > display = hexadecimal;
-// > round(log10(2), SG, RN);
-static constexpr float LOG10F_2 = 0x1.344136p-2f;
-
-LIBC_INLINE ExpRangeReduction exp10_range_reduction(float16 x) {
- // For -8 < x < 5, to compute 10^x, we perform the following range reduction:
- // find hi, mid, lo, such that:
- // x = (hi + mid) * log2(10) + lo, in which
- // hi is an integer,
- // mid * 2^3 is an integer,
- // -2^(-4) <= lo < 2^(-4).
- // In particular,
- // hi + mid = round(x * 2^3) * 2^(-3).
- // Then,
- // 10^x = 10^(hi + mid + lo) = 2^((hi + mid) * log2(10)) + 10^lo
- // We store 2^mid in the lookup table EXP2_MID_BITS, and compute 2^hi * 2^mid
- // by adding hi to the exponent field of 2^mid. 10^lo is computed using a
- // degree-4 minimax polynomial generated by Sollya.
-
- float xf = x;
- float kf = fputil::nearest_integer(xf * (LOG2F_10 * 0x1.0p+3f));
- int x_hi_mid = static_cast<int>(kf);
- unsigned x_hi = static_cast<unsigned>(x_hi_mid) >> 3;
- unsigned x_mid = static_cast<unsigned>(x_hi_mid) & 0x7;
- // lo = x - (hi + mid) = round(x * 2^3 * log2(10)) * log10(2) * (-2^(-3)) + x
- float lo = fputil::multiply_add(kf, LOG10F_2 * -0x1.0p-3f, xf);
-
- uint32_t exp2_hi_mid_bits =
- EXP2_MID_BITS[x_mid] +
- static_cast<uint32_t>(x_hi << fputil::FPBits<float>::FRACTION_LEN);
- float exp2_hi_mid = fputil::FPBits<float>(exp2_hi_mid_bits).get_val();
- // Degree-4 minimax polynomial generated by Sollya with the following
- // commands:
- // > display = hexadecimal;
- // > P = fpminimax((10^x - 1)/x, 3, [|SG...|], [-2^-4, 2^-4]);
- // > 1 + x * P;
- float exp10_lo = fputil::polyeval(lo, 0x1p+0f, 0x1.26bb14p+1f, 0x1.53526p+1f,
- 0x1.04b434p+1f, 0x1.2bcf9ep+0f);
- return {exp2_hi_mid, exp10_lo};
-}
-
// Generated by Sollya with the following commands:
// > display = hexadecimal;
// > round(log2(exp(1)), SG, RN);
diff --git a/utils/bazel/llvm-project-overlay/libc/BUILD.bazel b/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
index e3d807a46fe6a..f0b45a99aae40 100644
--- a/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
+++ b/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
@@ -2073,6 +2073,7 @@ libc_support_library(
":__support_fputil_fp_bits",
":__support_fputil_nearest_integer",
":__support_math_expf16_utils",
+ ":__support_math_exp10_float16_constants",
],
)
@@ -2276,6 +2277,38 @@ libc_support_library(
],
)
+libc_support_library(
+ name = "__support_math_exp10_float16_constants",
+ hdrs = ["src/__support/math/exp10_float16_constants.h"],
+ deps = [
+ ":__support_cpp_array",
+ ],
+)
+
+libc_support_library(
+ name = "__support_math_exp10f16_utils",
+ hdrs = ["src/__support/math/exp10f16_utils.h"],
+ deps = [
+ ":__support_math_exp10_float16_constants",
+ ":__support_math_expf16_utils",
+ ":__support_fputil_fp_bits",
+ ],
+)
+
+libc_support_library(
+ name = "__support_math_exp10f16",
+ hdrs = ["src/__support/math/exp10f16.h"],
+ deps = [
+ ":__support_math_exp10f16_utils",
+ ":__support_fputil_fp_bits",
+ ":__support_fputil_cast",
+ ":__support_fputil_rounding_mode",
+ ":__support_fputil_except_value_utils",
+ ":__support_macros_optimization",
+ ":__support_macros_properties_cpu_features",
+ ],
+)
+
############################### complex targets ################################
libc_function(
@@ -2896,14 +2929,15 @@ libc_math_function(
libc_math_function(
name = "exp10f16",
additional_deps = [
- ":expxf16",
+ ":__support_math_exp10f16",
+ ":errno",
],
)
libc_math_function(
name = "exp10m1f16",
additional_deps = [
- ":expxf16",
+ ":__support_math_exp10f16_utils",
],
)
>From a099be5a67899e8980c206e6d4dc8c53b7fca8b6 Mon Sep 17 00:00:00 2001
From: bassiounix <muhammad.m.bassiouni at gmail.com>
Date: Fri, 18 Jul 2025 08:46:20 +0300
Subject: [PATCH 2/2] apply temp diff (remove later before merge)
---
libc/cmake/modules/LLVMLibCTestRules.cmake | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/libc/cmake/modules/LLVMLibCTestRules.cmake b/libc/cmake/modules/LLVMLibCTestRules.cmake
index e210992c5111a..e128b4500fc2a 100644
--- a/libc/cmake/modules/LLVMLibCTestRules.cmake
+++ b/libc/cmake/modules/LLVMLibCTestRules.cmake
@@ -571,6 +571,8 @@ function(add_integration_test test_name)
target_compile_options(${fq_build_target_name} PRIVATE
${compile_options} ${INTEGRATION_TEST_COMPILE_OPTIONS})
+ set(link_libraries "")
+
if(LIBC_TARGET_ARCHITECTURE_IS_AMDGPU)
target_link_options(${fq_build_target_name} PRIVATE
${LIBC_COMPILE_OPTIONS_DEFAULT} ${INTEGRATION_TEST_COMPILE_OPTIONS}
@@ -599,17 +601,19 @@ function(add_integration_test test_name)
set(link_options
-nolibc
-nostartfiles
- -static
+ -nostdlib
${LIBC_LINK_OPTIONS_DEFAULT}
${LIBC_TEST_LINK_OPTIONS_DEFAULT}
)
target_link_options(${fq_build_target_name} PRIVATE ${link_options})
+ list(APPEND link_libraries ${LIBGCC_S_LOCATION})
endif()
target_link_libraries(
${fq_build_target_name}
${fq_target_name}.__libc__
libc.startup.${LIBC_TARGET_OS}.crt1
libc.test.IntegrationTest.test
+ ${link_libraries}
)
add_dependencies(${fq_build_target_name}
libc.test.IntegrationTest.test
@@ -807,7 +811,7 @@ function(add_libc_hermetic test_name)
set(link_options
-nolibc
-nostartfiles
- -static
+ -nostdlib
${LIBC_LINK_OPTIONS_DEFAULT}
${LIBC_TEST_LINK_OPTIONS_DEFAULT}
)
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