[libc-commits] [libc] [llvm] [libc][math] Refactor log10f to Header Only. (PR #176520)
via libc-commits
libc-commits at lists.llvm.org
Fri Jan 16 16:59:20 PST 2026
https://github.com/AnonMiraj created https://github.com/llvm/llvm-project/pull/176520
@bassiounix
closes : #176511
>From a159cc786f8f1797ea07e03aaae4ac65eda52a20 Mon Sep 17 00:00:00 2001
From: anonmiraj <nabilmalek48 at gmail.com>
Date: Sat, 17 Jan 2026 02:57:24 +0200
Subject: [PATCH] [libc][math] Refactor log10f to Header Only.
---
libc/shared/math.h | 1 +
libc/shared/math/log10f.h | 22 ++
libc/src/__support/math/CMakeLists.txt | 13 +
libc/src/__support/math/log10f.h | 229 ++++++++++++++++++
libc/src/math/generic/CMakeLists.txt | 8 +-
libc/src/math/generic/log10f.cpp | 208 +---------------
libc/test/shared/CMakeLists.txt | 1 +
libc/test/shared/shared_math_test.cpp | 1 +
.../llvm-project-overlay/libc/BUILD.bazel | 21 +-
9 files changed, 286 insertions(+), 218 deletions(-)
create mode 100644 libc/shared/math/log10f.h
create mode 100644 libc/src/__support/math/log10f.h
diff --git a/libc/shared/math.h b/libc/shared/math.h
index 6a8860eedfc27..eb862ee2e4488 100644
--- a/libc/shared/math.h
+++ b/libc/shared/math.h
@@ -69,6 +69,7 @@
#include "math/ldexpf16.h"
#include "math/llogbf.h"
#include "math/log.h"
+#include "math/log10f.h"
#include "math/logbf.h"
#include "math/logbf128.h"
#include "math/logbf16.h"
diff --git a/libc/shared/math/log10f.h b/libc/shared/math/log10f.h
new file mode 100644
index 0000000000000..dec434f66351e
--- /dev/null
+++ b/libc/shared/math/log10f.h
@@ -0,0 +1,22 @@
+//===-- Shared log10f 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_LOG10F_H
+#define LLVM_LIBC_SHARED_MATH_LOG10F_H
+#include "shared/libc_common.h"
+#include "src/__support/math/log10f.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace shared {
+
+using math::log10f;
+
+} // namespace shared
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SHARED_MATH_LOG10F_H
diff --git a/libc/src/__support/math/CMakeLists.txt b/libc/src/__support/math/CMakeLists.txt
index cf0c8412c1c97..321b554f6f30b 100644
--- a/libc/src/__support/math/CMakeLists.txt
+++ b/libc/src/__support/math/CMakeLists.txt
@@ -1146,3 +1146,16 @@ add_header_library(
libc.src.__support.macros.config
)
+
+add_header_library(
+ log10f
+ HDRS
+ log10f.h
+ DEPENDS
+ libc.src.__support.FPUtil.except_value_utils
+ libc.src.__support.FPUtil.fenv_impl
+ libc.src.__support.FPUtil.fma
+ libc.src.__support.FPUtil.fp_bits
+ libc.src.__support.FPUtil.polyeval
+ libc.src.__support.math.common_constants
+)
diff --git a/libc/src/__support/math/log10f.h b/libc/src/__support/math/log10f.h
new file mode 100644
index 0000000000000..41f7eb711c034
--- /dev/null
+++ b/libc/src/__support/math/log10f.h
@@ -0,0 +1,229 @@
+//===-- Implementation header for log10f ------------------------*- 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_LOG10F_H
+#define LLVM_LIBC_SRC___SUPPORT_MATH_LOG10F_H
+
+#include "src/__support/FPUtil/FEnvImpl.h"
+#include "src/__support/FPUtil/FMA.h"
+#include "src/__support/FPUtil/FPBits.h"
+#include "src/__support/FPUtil/PolyEval.h"
+#include "src/__support/FPUtil/except_value_utils.h"
+#include "src/__support/FPUtil/multiply_add.h"
+#include "src/__support/common.h"
+#include "src/__support/macros/config.h"
+#include "src/__support/macros/optimization.h" // LIBC_UNLIKELY
+#include "src/__support/macros/properties/cpu_features.h"
+#include "src/__support/math/common_constants.h" // Lookup table for (1/f)
+
+// This is an algorithm for log10(x) in single precision which is
+// correctly rounded for all rounding modes, based on the implementation of
+// log10(x) from the RLIBM project at:
+// https://people.cs.rutgers.edu/~sn349/rlibm
+
+// Step 1 - Range reduction:
+// For x = 2^m * 1.mant, log(x) = m * log10(2) + log10(1.m)
+// If x is denormal, we normalize it by multiplying x by 2^23 and subtracting
+// m by 23.
+
+// Step 2 - Another range reduction:
+// To compute log(1.mant), let f be the highest 8 bits including the hidden
+// bit, and d be the difference (1.mant - f), i.e. the remaining 16 bits of the
+// mantissa. Then we have the following approximation formula:
+// log10(1.mant) = log10(f) + log10(1.mant / f)
+// = log10(f) + log10(1 + d/f)
+// ~ log10(f) + P(d/f)
+// since d/f is sufficiently small.
+// log10(f) and 1/f are then stored in two 2^7 = 128 entries look-up tables.
+
+// Step 3 - Polynomial approximation:
+// To compute P(d/f), we use a single degree-5 polynomial in double precision
+// which provides correct rounding for all but few exception values.
+// For more detail about how this polynomial is obtained, please refer to the
+// papers:
+// Lim, J. and Nagarakatte, S., "One Polynomial Approximation to Produce
+// Correctly Rounded Results of an Elementary Function for Multiple
+// Representations and Rounding Modes", Proceedings of the 49th ACM SIGPLAN
+// Symposium on Principles of Programming Languages (POPL-2022), Philadelphia,
+// USA, Jan. 16-22, 2022.
+// https://people.cs.rutgers.edu/~sn349/papers/rlibmall-popl-2022.pdf
+// Aanjaneya, M., Lim, J., and Nagarakatte, S., "RLibm-Prog: Progressive
+// Polynomial Approximations for Fast Correctly Rounded Math Libraries",
+// Dept. of Comp. Sci., Rutgets U., Technical Report DCS-TR-758, Nov. 2021.
+// https://arxiv.org/pdf/2111.12852.pdf.
+
+namespace LIBC_NAMESPACE_DECL {
+
+namespace math {
+
+// Lookup table for -log10(r) where r is defined in common_constants.cpp.
+static constexpr double LOG10_R[128] = {
+ 0x0.0000000000000p+0, 0x1.be76bd77b4fc3p-9, 0x1.c03a80ae5e054p-8,
+ 0x1.51824c7587ebp-7, 0x1.c3d0837784c41p-7, 0x1.1b85d6044e9aep-6,
+ 0x1.559bd2406c3bap-6, 0x1.902c31d62a843p-6, 0x1.cb38fccd8bfdbp-6,
+ 0x1.e8eeb09f2f6cbp-6, 0x1.125d0432ea20ep-5, 0x1.30838cdc2fbfdp-5,
+ 0x1.3faf7c663060ep-5, 0x1.5e3966b7e9295p-5, 0x1.7d070145f4fd7p-5,
+ 0x1.8c878eeb05074p-5, 0x1.abbcebd84fcap-5, 0x1.bb7209d1e24e5p-5,
+ 0x1.db11ed766abf4p-5, 0x1.eafd05035bd3bp-5, 0x1.0585283764178p-4,
+ 0x1.0d966cc6500fap-4, 0x1.1dd5460c8b16fp-4, 0x1.2603072a25f82p-4,
+ 0x1.367ba3aaa1883p-4, 0x1.3ec6ad5407868p-4, 0x1.4f7aad9bbcbafp-4,
+ 0x1.57e3d47c3af7bp-4, 0x1.605735ee985f1p-4, 0x1.715d0ce367afcp-4,
+ 0x1.79efb57b0f803p-4, 0x1.828cfed29a215p-4, 0x1.93e7de0fc3e8p-4,
+ 0x1.9ca5aa1729f45p-4, 0x1.a56e8325f5c87p-4, 0x1.ae4285509950bp-4,
+ 0x1.b721cd17157e3p-4, 0x1.c902a19e65111p-4, 0x1.d204698cb42bdp-4,
+ 0x1.db11ed766abf4p-4, 0x1.e42b4c16caaf3p-4, 0x1.ed50a4a26eafcp-4,
+ 0x1.ffbfc2bbc7803p-4, 0x1.0484e4942aa43p-3, 0x1.093025a19976cp-3,
+ 0x1.0de1b56356b04p-3, 0x1.1299a4fb3e306p-3, 0x1.175805d1587c1p-3,
+ 0x1.1c1ce9955c0c6p-3, 0x1.20e8624038fedp-3, 0x1.25ba8215af7fcp-3,
+ 0x1.2a935ba5f1479p-3, 0x1.2f7301cf4e87bp-3, 0x1.345987bfeea91p-3,
+ 0x1.394700f7953fdp-3, 0x1.3e3b8149739d4p-3, 0x1.43371cde076c2p-3,
+ 0x1.4839e83506c87p-3, 0x1.4d43f8275a483p-3, 0x1.525561e9256eep-3,
+ 0x1.576e3b0bde0a7p-3, 0x1.5c8e998072fe2p-3, 0x1.61b6939983048p-3,
+ 0x1.66e6400da3f77p-3, 0x1.6c1db5f9bb336p-3, 0x1.6c1db5f9bb336p-3,
+ 0x1.715d0ce367afcp-3, 0x1.76a45cbb7e6ffp-3, 0x1.7bf3bde099f3p-3,
+ 0x1.814b4921bd52bp-3, 0x1.86ab17c10bc7fp-3, 0x1.86ab17c10bc7fp-3,
+ 0x1.8c13437695532p-3, 0x1.9183e673394fap-3, 0x1.96fd1b639fc09p-3,
+ 0x1.9c7efd734a2f9p-3, 0x1.a209a84fbcff8p-3, 0x1.a209a84fbcff8p-3,
+ 0x1.a79d382bc21d9p-3, 0x1.ad39c9c2c608p-3, 0x1.b2df7a5c50299p-3,
+ 0x1.b2df7a5c50299p-3, 0x1.b88e67cf9798p-3, 0x1.be46b087354bcp-3,
+ 0x1.c4087384f4f8p-3, 0x1.c4087384f4f8p-3, 0x1.c9d3d065c5b42p-3,
+ 0x1.cfa8e765cbb72p-3, 0x1.cfa8e765cbb72p-3, 0x1.d587d96494759p-3,
+ 0x1.db70c7e96e7f3p-3, 0x1.db70c7e96e7f3p-3, 0x1.e163d527e68cfp-3,
+ 0x1.e76124046b3f3p-3, 0x1.e76124046b3f3p-3, 0x1.ed68d819191fcp-3,
+ 0x1.f37b15bab08d1p-3, 0x1.f37b15bab08d1p-3, 0x1.f99801fdb749dp-3,
+ 0x1.ffbfc2bbc7803p-3, 0x1.ffbfc2bbc7803p-3, 0x1.02f93f4c87101p-2,
+ 0x1.06182e84fd4acp-2, 0x1.06182e84fd4acp-2, 0x1.093cc32c90f84p-2,
+ 0x1.093cc32c90f84p-2, 0x1.0c6711d6abd7ap-2, 0x1.0f972f87ff3d6p-2,
+ 0x1.0f972f87ff3d6p-2, 0x1.12cd31b9c99ffp-2, 0x1.12cd31b9c99ffp-2,
+ 0x1.16092e5d3a9a6p-2, 0x1.194b3bdef6b9ep-2, 0x1.194b3bdef6b9ep-2,
+ 0x1.1c93712abc7ffp-2, 0x1.1c93712abc7ffp-2, 0x1.1fe1e5af2c141p-2,
+ 0x1.1fe1e5af2c141p-2, 0x1.2336b161b3337p-2, 0x1.2336b161b3337p-2,
+ 0x1.2691ecc29f042p-2, 0x1.2691ecc29f042p-2, 0x1.29f3b0e15584bp-2,
+ 0x1.29f3b0e15584bp-2, 0x1.2d5c1760b86bbp-2, 0x1.2d5c1760b86bbp-2,
+ 0x1.30cb3a7bb3625p-2, 0x1.34413509f79ffp-2};
+
+LIBC_INLINE static constexpr float log10f(float x) {
+ using namespace common_constants_internal;
+ constexpr double LOG10_2 = 0x1.34413509f79ffp-2;
+
+ using FPBits = typename fputil::FPBits<float>;
+
+ FPBits xbits(x);
+ uint32_t x_u = xbits.uintval();
+
+ // Exact powers of 10 and other hard-to-round cases.
+ if (LIBC_UNLIKELY((x_u & 0x3FF) == 0)) {
+ switch (x_u) {
+ case 0x3f80'0000U: // x = 1
+ return 0.0f;
+ case 0x4120'0000U: // x = 10
+ return 1.0f;
+ case 0x42c8'0000U: // x = 100
+ return 2.0f;
+ case 0x447a'0000U: // x = 1,000
+ return 3.0f;
+ case 0x461c'4000U: // x = 10,000
+ return 4.0f;
+ case 0x47c3'5000U: // x = 100,000
+ return 5.0f;
+ case 0x4974'2400U: // x = 1,000,000
+ return 6.0f;
+ }
+ } else {
+ switch (x_u) {
+ case 0x4b18'9680U: // x = 10,000,000
+ return 7.0f;
+ case 0x4cbe'bc20U: // x = 100,000,000
+ return 8.0f;
+ case 0x4e6e'6b28U: // x = 1,000,000,000
+ return 9.0f;
+ case 0x5015'02f9U: // x = 10,000,000,000
+ return 10.0f;
+#ifndef LIBC_MATH_HAS_SKIP_ACCURATE_PASS
+ case 0x0efe'ee7aU: // x = 0x1.fddcf4p-98f
+ return fputil::round_result_slightly_up(-0x1.d33a46p+4f);
+ case 0x3f5f'de1bU: // x = 0x1.bfbc36p-1f
+ return fputil::round_result_slightly_up(-0x1.dd2c6ep-5f);
+ case 0x3f80'70d8U: // x = 0x1.00e1bp0f
+ return fputil::round_result_slightly_up(0x1.8762c4p-10f);
+#ifndef LIBC_TARGET_CPU_HAS_FMA_DOUBLE
+ case 0x08ae'a356U: // x = 0x1.5d46acp-110f
+ return fputil::round_result_slightly_up(-0x1.07d3b4p+5f);
+ case 0x120b'93dcU: // x = 0x1.1727b8p-91f
+ return fputil::round_result_slightly_down(-0x1.b5b2aep+4f);
+ case 0x13ae'78d3U: // x = 0x1.5cf1a6p-88f
+ return fputil::round_result_slightly_down(-0x1.a5b2aep+4f);
+ case 0x4f13'4f83U: // x = 2471461632.0
+ return fputil::round_result_slightly_down(0x1.2c9314p+3f);
+ case 0x7956'ba5eU: // x = 69683218960000541503257137270226944.0
+ return fputil::round_result_slightly_up(0x1.16bebap+5f);
+#endif // LIBC_TARGET_CPU_HAS_FMA_DOUBLE
+#endif // !LIBC_MATH_HAS_SKIP_ACCURATE_PASS
+ }
+ }
+
+ int m = -FPBits::EXP_BIAS;
+
+ if (LIBC_UNLIKELY(x_u < FPBits::min_normal().uintval() ||
+ x_u > FPBits::max_normal().uintval())) {
+ if (x == 0.0f) {
+ // Return -inf and raise FE_DIVBYZERO
+ fputil::set_errno_if_required(ERANGE);
+ fputil::raise_except_if_required(FE_DIVBYZERO);
+ return FPBits::inf(Sign::NEG).get_val();
+ }
+ if (xbits.is_neg() && !xbits.is_nan()) {
+ // Return NaN and raise FE_INVALID
+ fputil::set_errno_if_required(EDOM);
+ fputil::raise_except_if_required(FE_INVALID);
+ return FPBits::quiet_nan().get_val();
+ }
+ if (xbits.is_inf_or_nan()) {
+ return x;
+ }
+ // Normalize denormal inputs.
+ xbits = FPBits(xbits.get_val() * 0x1.0p23f);
+ m -= 23;
+ x_u = xbits.uintval();
+ }
+
+ // Add unbiased exponent.
+ m += static_cast<int>(x_u >> 23);
+ // Extract 7 leading fractional bits of the mantissa
+ int index = (x_u >> 16) & 0x7F;
+ // Set bits to 1.m
+ xbits.set_biased_exponent(0x7F);
+
+ float u = xbits.get_val();
+#ifdef LIBC_TARGET_CPU_HAS_FMA_FLOAT
+ double v =
+ static_cast<double>(fputil::multiply_add(u, R[index], -1.0f)); // Exact.
+#else
+ double v = fputil::multiply_add(static_cast<double>(u),
+ static_cast<double>(R[index]), -1.0); // Exact
+#endif // LIBC_TARGET_CPU_HAS_FMA_FLOAT
+
+ // Degree-5 polynomial approximation of log10 generated by:
+ // > P = fpminimax(log10(1 + x)/x, 4, [|D...|], [-2^-8, 2^-7]);
+ constexpr double COEFFS[5] = {0x1.bcb7b1526e2e5p-2, -0x1.bcb7b1528d43dp-3,
+ 0x1.287a77eb4ca0dp-3, -0x1.bcb8110a181b5p-4,
+ 0x1.60e7e3e747129p-4};
+ double v2 = v * v; // Exact
+ double p2 = fputil::multiply_add(v, COEFFS[4], COEFFS[3]);
+ double p1 = fputil::multiply_add(v, COEFFS[2], COEFFS[1]);
+ double p0 = fputil::multiply_add(v, COEFFS[0], LOG10_R[index]);
+ double r = fputil::multiply_add(static_cast<double>(m), LOG10_2,
+ fputil::polyeval(v2, p0, p1, p2));
+
+ return static_cast<float>(r);
+}
+
+} // namespace math
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC___SUPPORT_MATH_LOG10F_H
diff --git a/libc/src/math/generic/CMakeLists.txt b/libc/src/math/generic/CMakeLists.txt
index bc2abbc8e4588..f116bd487c539 100644
--- a/libc/src/math/generic/CMakeLists.txt
+++ b/libc/src/math/generic/CMakeLists.txt
@@ -1977,12 +1977,8 @@ add_entrypoint_object(
HDRS
../log10f.h
DEPENDS
- libc.src.__support.FPUtil.except_value_utils
- libc.src.__support.FPUtil.fenv_impl
- libc.src.__support.FPUtil.fp_bits
- libc.src.__support.FPUtil.fma
- libc.src.__support.FPUtil.polyeval
- libc.src.__support.math.common_constants
+ libc.src.__support.math.log10f
+ libc.src.errno.errno
)
add_entrypoint_object(
diff --git a/libc/src/math/generic/log10f.cpp b/libc/src/math/generic/log10f.cpp
index 6b9cc5d3e0dbf..9010591d62095 100644
--- a/libc/src/math/generic/log10f.cpp
+++ b/libc/src/math/generic/log10f.cpp
@@ -7,216 +7,12 @@
//===----------------------------------------------------------------------===//
#include "src/math/log10f.h"
-#include "src/__support/FPUtil/FEnvImpl.h"
-#include "src/__support/FPUtil/FMA.h"
-#include "src/__support/FPUtil/FPBits.h"
-#include "src/__support/FPUtil/PolyEval.h"
-#include "src/__support/FPUtil/except_value_utils.h"
-#include "src/__support/FPUtil/multiply_add.h"
-#include "src/__support/common.h"
-#include "src/__support/macros/config.h"
-#include "src/__support/macros/optimization.h" // LIBC_UNLIKELY
-#include "src/__support/macros/properties/cpu_features.h"
-#include "src/__support/math/common_constants.h" // Lookup table for (1/f)
-
-// This is an algorithm for log10(x) in single precision which is
-// correctly rounded for all rounding modes, based on the implementation of
-// log10(x) from the RLIBM project at:
-// https://people.cs.rutgers.edu/~sn349/rlibm
-
-// Step 1 - Range reduction:
-// For x = 2^m * 1.mant, log(x) = m * log10(2) + log10(1.m)
-// If x is denormal, we normalize it by multiplying x by 2^23 and subtracting
-// m by 23.
-
-// Step 2 - Another range reduction:
-// To compute log(1.mant), let f be the highest 8 bits including the hidden
-// bit, and d be the difference (1.mant - f), i.e. the remaining 16 bits of the
-// mantissa. Then we have the following approximation formula:
-// log10(1.mant) = log10(f) + log10(1.mant / f)
-// = log10(f) + log10(1 + d/f)
-// ~ log10(f) + P(d/f)
-// since d/f is sufficiently small.
-// log10(f) and 1/f are then stored in two 2^7 = 128 entries look-up tables.
-
-// Step 3 - Polynomial approximation:
-// To compute P(d/f), we use a single degree-5 polynomial in double precision
-// which provides correct rounding for all but few exception values.
-// For more detail about how this polynomial is obtained, please refer to the
-// papers:
-// Lim, J. and Nagarakatte, S., "One Polynomial Approximation to Produce
-// Correctly Rounded Results of an Elementary Function for Multiple
-// Representations and Rounding Modes", Proceedings of the 49th ACM SIGPLAN
-// Symposium on Principles of Programming Languages (POPL-2022), Philadelphia,
-// USA, Jan. 16-22, 2022.
-// https://people.cs.rutgers.edu/~sn349/papers/rlibmall-popl-2022.pdf
-// Aanjaneya, M., Lim, J., and Nagarakatte, S., "RLibm-Prog: Progressive
-// Polynomial Approximations for Fast Correctly Rounded Math Libraries",
-// Dept. of Comp. Sci., Rutgets U., Technical Report DCS-TR-758, Nov. 2021.
-// https://arxiv.org/pdf/2111.12852.pdf.
+#include "src/__support/math/log10f.h"
namespace LIBC_NAMESPACE_DECL {
-// Lookup table for -log10(r) where r is defined in common_constants.cpp.
-static constexpr double LOG10_R[128] = {
- 0x0.0000000000000p+0, 0x1.be76bd77b4fc3p-9, 0x1.c03a80ae5e054p-8,
- 0x1.51824c7587ebp-7, 0x1.c3d0837784c41p-7, 0x1.1b85d6044e9aep-6,
- 0x1.559bd2406c3bap-6, 0x1.902c31d62a843p-6, 0x1.cb38fccd8bfdbp-6,
- 0x1.e8eeb09f2f6cbp-6, 0x1.125d0432ea20ep-5, 0x1.30838cdc2fbfdp-5,
- 0x1.3faf7c663060ep-5, 0x1.5e3966b7e9295p-5, 0x1.7d070145f4fd7p-5,
- 0x1.8c878eeb05074p-5, 0x1.abbcebd84fcap-5, 0x1.bb7209d1e24e5p-5,
- 0x1.db11ed766abf4p-5, 0x1.eafd05035bd3bp-5, 0x1.0585283764178p-4,
- 0x1.0d966cc6500fap-4, 0x1.1dd5460c8b16fp-4, 0x1.2603072a25f82p-4,
- 0x1.367ba3aaa1883p-4, 0x1.3ec6ad5407868p-4, 0x1.4f7aad9bbcbafp-4,
- 0x1.57e3d47c3af7bp-4, 0x1.605735ee985f1p-4, 0x1.715d0ce367afcp-4,
- 0x1.79efb57b0f803p-4, 0x1.828cfed29a215p-4, 0x1.93e7de0fc3e8p-4,
- 0x1.9ca5aa1729f45p-4, 0x1.a56e8325f5c87p-4, 0x1.ae4285509950bp-4,
- 0x1.b721cd17157e3p-4, 0x1.c902a19e65111p-4, 0x1.d204698cb42bdp-4,
- 0x1.db11ed766abf4p-4, 0x1.e42b4c16caaf3p-4, 0x1.ed50a4a26eafcp-4,
- 0x1.ffbfc2bbc7803p-4, 0x1.0484e4942aa43p-3, 0x1.093025a19976cp-3,
- 0x1.0de1b56356b04p-3, 0x1.1299a4fb3e306p-3, 0x1.175805d1587c1p-3,
- 0x1.1c1ce9955c0c6p-3, 0x1.20e8624038fedp-3, 0x1.25ba8215af7fcp-3,
- 0x1.2a935ba5f1479p-3, 0x1.2f7301cf4e87bp-3, 0x1.345987bfeea91p-3,
- 0x1.394700f7953fdp-3, 0x1.3e3b8149739d4p-3, 0x1.43371cde076c2p-3,
- 0x1.4839e83506c87p-3, 0x1.4d43f8275a483p-3, 0x1.525561e9256eep-3,
- 0x1.576e3b0bde0a7p-3, 0x1.5c8e998072fe2p-3, 0x1.61b6939983048p-3,
- 0x1.66e6400da3f77p-3, 0x1.6c1db5f9bb336p-3, 0x1.6c1db5f9bb336p-3,
- 0x1.715d0ce367afcp-3, 0x1.76a45cbb7e6ffp-3, 0x1.7bf3bde099f3p-3,
- 0x1.814b4921bd52bp-3, 0x1.86ab17c10bc7fp-3, 0x1.86ab17c10bc7fp-3,
- 0x1.8c13437695532p-3, 0x1.9183e673394fap-3, 0x1.96fd1b639fc09p-3,
- 0x1.9c7efd734a2f9p-3, 0x1.a209a84fbcff8p-3, 0x1.a209a84fbcff8p-3,
- 0x1.a79d382bc21d9p-3, 0x1.ad39c9c2c608p-3, 0x1.b2df7a5c50299p-3,
- 0x1.b2df7a5c50299p-3, 0x1.b88e67cf9798p-3, 0x1.be46b087354bcp-3,
- 0x1.c4087384f4f8p-3, 0x1.c4087384f4f8p-3, 0x1.c9d3d065c5b42p-3,
- 0x1.cfa8e765cbb72p-3, 0x1.cfa8e765cbb72p-3, 0x1.d587d96494759p-3,
- 0x1.db70c7e96e7f3p-3, 0x1.db70c7e96e7f3p-3, 0x1.e163d527e68cfp-3,
- 0x1.e76124046b3f3p-3, 0x1.e76124046b3f3p-3, 0x1.ed68d819191fcp-3,
- 0x1.f37b15bab08d1p-3, 0x1.f37b15bab08d1p-3, 0x1.f99801fdb749dp-3,
- 0x1.ffbfc2bbc7803p-3, 0x1.ffbfc2bbc7803p-3, 0x1.02f93f4c87101p-2,
- 0x1.06182e84fd4acp-2, 0x1.06182e84fd4acp-2, 0x1.093cc32c90f84p-2,
- 0x1.093cc32c90f84p-2, 0x1.0c6711d6abd7ap-2, 0x1.0f972f87ff3d6p-2,
- 0x1.0f972f87ff3d6p-2, 0x1.12cd31b9c99ffp-2, 0x1.12cd31b9c99ffp-2,
- 0x1.16092e5d3a9a6p-2, 0x1.194b3bdef6b9ep-2, 0x1.194b3bdef6b9ep-2,
- 0x1.1c93712abc7ffp-2, 0x1.1c93712abc7ffp-2, 0x1.1fe1e5af2c141p-2,
- 0x1.1fe1e5af2c141p-2, 0x1.2336b161b3337p-2, 0x1.2336b161b3337p-2,
- 0x1.2691ecc29f042p-2, 0x1.2691ecc29f042p-2, 0x1.29f3b0e15584bp-2,
- 0x1.29f3b0e15584bp-2, 0x1.2d5c1760b86bbp-2, 0x1.2d5c1760b86bbp-2,
- 0x1.30cb3a7bb3625p-2, 0x1.34413509f79ffp-2};
-
LLVM_LIBC_FUNCTION(float, log10f, (float x)) {
- using namespace common_constants_internal;
- constexpr double LOG10_2 = 0x1.34413509f79ffp-2;
-
- using FPBits = typename fputil::FPBits<float>;
-
- FPBits xbits(x);
- uint32_t x_u = xbits.uintval();
-
- // Exact powers of 10 and other hard-to-round cases.
- if (LIBC_UNLIKELY((x_u & 0x3FF) == 0)) {
- switch (x_u) {
- case 0x3f80'0000U: // x = 1
- return 0.0f;
- case 0x4120'0000U: // x = 10
- return 1.0f;
- case 0x42c8'0000U: // x = 100
- return 2.0f;
- case 0x447a'0000U: // x = 1,000
- return 3.0f;
- case 0x461c'4000U: // x = 10,000
- return 4.0f;
- case 0x47c3'5000U: // x = 100,000
- return 5.0f;
- case 0x4974'2400U: // x = 1,000,000
- return 6.0f;
- }
- } else {
- switch (x_u) {
- case 0x4b18'9680U: // x = 10,000,000
- return 7.0f;
- case 0x4cbe'bc20U: // x = 100,000,000
- return 8.0f;
- case 0x4e6e'6b28U: // x = 1,000,000,000
- return 9.0f;
- case 0x5015'02f9U: // x = 10,000,000,000
- return 10.0f;
-#ifndef LIBC_MATH_HAS_SKIP_ACCURATE_PASS
- case 0x0efe'ee7aU: // x = 0x1.fddcf4p-98f
- return fputil::round_result_slightly_up(-0x1.d33a46p+4f);
- case 0x3f5f'de1bU: // x = 0x1.bfbc36p-1f
- return fputil::round_result_slightly_up(-0x1.dd2c6ep-5f);
- case 0x3f80'70d8U: // x = 0x1.00e1bp0f
- return fputil::round_result_slightly_up(0x1.8762c4p-10f);
-#ifndef LIBC_TARGET_CPU_HAS_FMA_DOUBLE
- case 0x08ae'a356U: // x = 0x1.5d46acp-110f
- return fputil::round_result_slightly_up(-0x1.07d3b4p+5f);
- case 0x120b'93dcU: // x = 0x1.1727b8p-91f
- return fputil::round_result_slightly_down(-0x1.b5b2aep+4f);
- case 0x13ae'78d3U: // x = 0x1.5cf1a6p-88f
- return fputil::round_result_slightly_down(-0x1.a5b2aep+4f);
- case 0x4f13'4f83U: // x = 2471461632.0
- return fputil::round_result_slightly_down(0x1.2c9314p+3f);
- case 0x7956'ba5eU: // x = 69683218960000541503257137270226944.0
- return fputil::round_result_slightly_up(0x1.16bebap+5f);
-#endif // LIBC_TARGET_CPU_HAS_FMA_DOUBLE
-#endif // !LIBC_MATH_HAS_SKIP_ACCURATE_PASS
- }
- }
-
- int m = -FPBits::EXP_BIAS;
-
- if (LIBC_UNLIKELY(x_u < FPBits::min_normal().uintval() ||
- x_u > FPBits::max_normal().uintval())) {
- if (x == 0.0f) {
- // Return -inf and raise FE_DIVBYZERO
- fputil::set_errno_if_required(ERANGE);
- fputil::raise_except_if_required(FE_DIVBYZERO);
- return FPBits::inf(Sign::NEG).get_val();
- }
- if (xbits.is_neg() && !xbits.is_nan()) {
- // Return NaN and raise FE_INVALID
- fputil::set_errno_if_required(EDOM);
- fputil::raise_except_if_required(FE_INVALID);
- return FPBits::quiet_nan().get_val();
- }
- if (xbits.is_inf_or_nan()) {
- return x;
- }
- // Normalize denormal inputs.
- xbits = FPBits(xbits.get_val() * 0x1.0p23f);
- m -= 23;
- x_u = xbits.uintval();
- }
-
- // Add unbiased exponent.
- m += static_cast<int>(x_u >> 23);
- // Extract 7 leading fractional bits of the mantissa
- int index = (x_u >> 16) & 0x7F;
- // Set bits to 1.m
- xbits.set_biased_exponent(0x7F);
-
- float u = xbits.get_val();
- double v;
-#ifdef LIBC_TARGET_CPU_HAS_FMA_FLOAT
- v = static_cast<double>(fputil::multiply_add(u, R[index], -1.0f)); // Exact.
-#else
- v = fputil::multiply_add(static_cast<double>(u),
- static_cast<double>(R[index]), -1.0); // Exact
-#endif // LIBC_TARGET_CPU_HAS_FMA_FLOAT
-
- // Degree-5 polynomial approximation of log10 generated by:
- // > P = fpminimax(log10(1 + x)/x, 4, [|D...|], [-2^-8, 2^-7]);
- constexpr double COEFFS[5] = {0x1.bcb7b1526e2e5p-2, -0x1.bcb7b1528d43dp-3,
- 0x1.287a77eb4ca0dp-3, -0x1.bcb8110a181b5p-4,
- 0x1.60e7e3e747129p-4};
- double v2 = v * v; // Exact
- double p2 = fputil::multiply_add(v, COEFFS[4], COEFFS[3]);
- double p1 = fputil::multiply_add(v, COEFFS[2], COEFFS[1]);
- double p0 = fputil::multiply_add(v, COEFFS[0], LOG10_R[index]);
- double r = fputil::multiply_add(static_cast<double>(m), LOG10_2,
- fputil::polyeval(v2, p0, p1, p2));
-
- return static_cast<float>(r);
+ return math::log10f(x);
}
} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/test/shared/CMakeLists.txt b/libc/test/shared/CMakeLists.txt
index 5e89d96595db1..e469e6be8f08d 100644
--- a/libc/test/shared/CMakeLists.txt
+++ b/libc/test/shared/CMakeLists.txt
@@ -71,4 +71,5 @@ add_fp_unittest(
libc.src.__support.math.rsqrtf
libc.src.__support.math.rsqrtf16
libc.src.__support.math.sin
+ libc.src.__support.math.log10f
)
diff --git a/libc/test/shared/shared_math_test.cpp b/libc/test/shared/shared_math_test.cpp
index 3d0fbf350daaa..693f689419f6d 100644
--- a/libc/test/shared/shared_math_test.cpp
+++ b/libc/test/shared/shared_math_test.cpp
@@ -80,6 +80,7 @@ TEST(LlvmLibcSharedMathTest, AllFloat) {
ASSERT_FP_EQ(float(-1 * (8 << 5)), LIBC_NAMESPACE::shared::ldexpf(-8.0f, 5));
EXPECT_EQ(long(0), LIBC_NAMESPACE::shared::llogbf(1.0f));
+ EXPECT_FP_EQ(0x0p+0f, LIBC_NAMESPACE::shared::log10f(0.0f));
EXPECT_FP_EQ(0x0p+0f, LIBC_NAMESPACE::shared::logbf(1.0f));
EXPECT_FP_EQ(0x1p+0f, LIBC_NAMESPACE::shared::rsqrtf(1.0f));
}
diff --git a/utils/bazel/llvm-project-overlay/libc/BUILD.bazel b/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
index 26fcbdb9075f9..8018e4c5b9f35 100644
--- a/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
+++ b/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
@@ -4514,12 +4514,8 @@ libc_math_function(
libc_math_function(
name = "log10f",
additional_deps = [
- ":__support_fputil_fma",
- ":__support_fputil_multiply_add",
- ":__support_fputil_polyeval",
- ":__support_macros_optimization",
- ":__support_macros_properties_cpu_features",
- ":__support_math_common_constants",
+ ":__support_math_log10f",
+ ":errno",
],
)
@@ -7942,3 +7938,16 @@ libc_function(
":types_wchar_t",
],
)
+
+libc_support_library(
+ name = "__support_math_log10f",
+ hdrs = ["src/__support/math/log10f.h"],
+ deps = [
+ ":__support_fputil_except_value_utils",
+ ":__support_fputil_fenv_impl",
+ ":__support_fputil_fma",
+ ":__support_fputil_fp_bits",
+ ":__support_fputil_polyeval",
+ ":__support_math_common_constants",
+ ],
+)
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