[libc-commits] [libc] [llvm] [libc][math] Refactor log10f16 to Header Only. (PR #176523)
via libc-commits
libc-commits at lists.llvm.org
Fri Jan 16 18:12:49 PST 2026
https://github.com/AnonMiraj updated https://github.com/llvm/llvm-project/pull/176523
>From bf93ee74d43c0aa6b1dd8d90952e05a24b13e0da Mon Sep 17 00:00:00 2001
From: anonmiraj <nabilmalek48 at gmail.com>
Date: Sat, 17 Jan 2026 03:09:03 +0200
Subject: [PATCH] [libc][math] Refactor log10f16 to Header Only.
---
libc/shared/math.h | 1 +
libc/shared/math/log10f16.h | 28 +++
libc/src/__support/math/CMakeLists.txt | 18 ++
libc/src/__support/math/log10f16.h | 182 ++++++++++++++++++
libc/src/math/generic/CMakeLists.txt | 13 +-
libc/src/math/generic/log10f16.cpp | 157 +--------------
libc/test/shared/CMakeLists.txt | 1 +
libc/test/shared/shared_math_test.cpp | 1 +
.../llvm-project-overlay/libc/BUILD.bazel | 18 +-
9 files changed, 252 insertions(+), 167 deletions(-)
create mode 100644 libc/shared/math/log10f16.h
create mode 100644 libc/src/__support/math/log10f16.h
diff --git a/libc/shared/math.h b/libc/shared/math.h
index 017c94f8ad54a..0cf0380c7049b 100644
--- a/libc/shared/math.h
+++ b/libc/shared/math.h
@@ -71,6 +71,7 @@
#include "math/ldexpf16.h"
#include "math/llogbf.h"
#include "math/log.h"
+#include "math/log10f16.h"
#include "math/logbf.h"
#include "math/logbf128.h"
#include "math/logbf16.h"
diff --git a/libc/shared/math/log10f16.h b/libc/shared/math/log10f16.h
new file mode 100644
index 0000000000000..883191c1385e2
--- /dev/null
+++ b/libc/shared/math/log10f16.h
@@ -0,0 +1,28 @@
+//===-- Shared log10f16 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_LOG10F16_H
+#define LLVM_LIBC_SHARED_MATH_LOG10F16_H
+
+#include "include/llvm-libc-macros/float16-macros.h"
+#include "shared/libc_common.h"
+#ifdef LIBC_TYPES_HAS_FLOAT16
+
+#include "src/__support/math/log10f16.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace shared {
+
+using math::log10f16;
+
+} // namespace shared
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LIBC_TYPES_HAS_FLOAT16
+
+#endif // LLVM_LIBC_SHARED_MATH_LOG10F16_H
diff --git a/libc/src/__support/math/CMakeLists.txt b/libc/src/__support/math/CMakeLists.txt
index cb03b18678145..14917b6542495 100644
--- a/libc/src/__support/math/CMakeLists.txt
+++ b/libc/src/__support/math/CMakeLists.txt
@@ -1103,6 +1103,24 @@ add_header_library(
libc.src.__support.macros.optimization
)
+add_header_library(
+ log10f16
+ HDRS
+ log10f16.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.macros.optimization
+ libc.src.__support.macros.properties.cpu_features
+ libc.src.__support.math.expxf16_utils
+)
+
add_header_library(
logbf128
HDRS
diff --git a/libc/src/__support/math/log10f16.h b/libc/src/__support/math/log10f16.h
new file mode 100644
index 0000000000000..fc9505e413c39
--- /dev/null
+++ b/libc/src/__support/math/log10f16.h
@@ -0,0 +1,182 @@
+//===-- Implementation header for log10f16 ----------------------*- 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_LOG10F16_H
+#define LLVM_LIBC_SRC___SUPPORT_MATH_LOG10F16_H
+
+#include "include/llvm-libc-macros/float16-macros.h"
+
+#ifdef LIBC_TYPES_HAS_FLOAT16
+
+#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/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/expxf16_utils.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_LOG10F16_EXCEPTS = 11;
+#else
+static constexpr size_t N_LOG10F16_EXCEPTS = 17;
+#endif
+
+static constexpr fputil::ExceptValues<float16, N_LOG10F16_EXCEPTS>
+ LOG10F16_EXCEPTS = {{
+ // (input, RZ output, RU offset, RD offset, RN offset)
+ // x = 0x1.e3cp-3, log10f16(x) = -0x1.40cp-1 (RZ)
+ {0x338fU, 0xb903U, 0U, 1U, 0U},
+ // x = 0x1.fep-3, log10f16(x) = -0x1.35p-1 (RZ)
+ {0x33f8U, 0xb8d4U, 0U, 1U, 1U},
+#ifndef LIBC_TARGET_CPU_HAS_FMA_FLOAT
+ // x = 0x1.394p-1, log10f16(x) = -0x1.b4cp-3 (RZ)
+ {0x38e5U, 0xb2d3U, 0U, 1U, 1U},
+#endif
+ // x = 0x1.ea8p-1, log10f16(x) = -0x1.31p-6 (RZ)
+ {0x3baaU, 0xa4c4U, 0U, 1U, 1U},
+ // x = 0x1.ebp-1, log10f16(x) = -0x1.29cp-6 (RZ)
+ {0x3bacU, 0xa4a7U, 0U, 1U, 1U},
+ // x = 0x1.f3p-1, log10f16(x) = -0x1.6dcp-7 (RZ)
+ {0x3bccU, 0xa1b7U, 0U, 1U, 1U},
+// x = 0x1.f38p-1, log10f16(x) = -0x1.5f8p-7 (RZ)
+#ifndef LIBC_TARGET_CPU_HAS_FMA_FLOAT
+ {0x3bceU, 0xa17eU, 0U, 1U, 1U},
+ // x = 0x1.fd8p-1, log10f16(x) = -0x1.168p-9 (RZ)
+ {0x3bf6U, 0x985aU, 0U, 1U, 1U},
+ // x = 0x1.ff8p-1, log10f16(x) = -0x1.bccp-12 (RZ)
+ {0x3bfeU, 0x8ef3U, 0U, 1U, 1U},
+ // x = 0x1.374p+0, log10f16(x) = 0x1.5b8p-4 (RZ)
+ {0x3cddU, 0x2d6eU, 1U, 0U, 1U},
+ // x = 0x1.3ecp+1, log10f16(x) = 0x1.958p-2 (RZ)
+ {0x40fbU, 0x3656U, 1U, 0U, 1U},
+#endif
+ // x = 0x1.4p+3, log10f16(x) = 0x1p+0 (RZ)
+ {0x4900U, 0x3c00U, 0U, 0U, 0U},
+ // x = 0x1.9p+6, log10f16(x) = 0x1p+1 (RZ)
+ {0x5640U, 0x4000U, 0U, 0U, 0U},
+ // x = 0x1.f84p+6, log10f16(x) = 0x1.0ccp+1 (RZ)
+ {0x57e1U, 0x4033U, 1U, 0U, 0U},
+ // x = 0x1.f4p+9, log10f16(x) = 0x1.8p+1 (RZ)
+ {0x63d0U, 0x4200U, 0U, 0U, 0U},
+ // x = 0x1.388p+13, log10f16(x) = 0x1p+2 (RZ)
+ {0x70e2U, 0x4400U, 0U, 0U, 0U},
+ // x = 0x1.674p+13, log10f16(x) = 0x1.03cp+2 (RZ)
+ {0x719dU, 0x440fU, 1U, 0U, 0U},
+ }};
+#endif // !LIBC_MATH_HAS_SKIP_ACCURATE_PASS
+
+LIBC_INLINE static constexpr float16 log10f16(float16 x) {
+ using namespace math::expxf16_internal;
+ using FPBits = fputil::FPBits<float16>;
+ FPBits x_bits(x);
+
+ uint16_t x_u = x_bits.uintval();
+
+ // If x <= 0, or x is 1, or x is +inf, or x is NaN.
+ if (LIBC_UNLIKELY(x_u == 0U || x_u == 0x3c00U || x_u >= 0x7c00U)) {
+ // log10(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;
+ }
+
+ // log10(+/-0) = −inf
+ if ((x_u & 0x7fffU) == 0U) {
+ fputil::raise_except_if_required(FE_DIVBYZERO);
+ return FPBits::inf(Sign::NEG).get_val();
+ }
+
+ if (x_u == 0x3c00U)
+ return FPBits::zero().get_val();
+
+ // When x < 0.
+ if (x_u > 0x8000U) {
+ fputil::set_errno_if_required(EDOM);
+ fputil::raise_except_if_required(FE_INVALID);
+ return FPBits::quiet_nan().get_val();
+ }
+
+ // log10(+inf) = +inf
+ return FPBits::inf().get_val();
+ }
+
+#ifndef LIBC_MATH_HAS_SKIP_ACCURATE_PASS
+ if (auto r = LOG10F16_EXCEPTS.lookup(x_u); LIBC_UNLIKELY(r.has_value()))
+ return r.value();
+#endif // !LIBC_MATH_HAS_SKIP_ACCURATE_PASS
+
+ // To compute log10(x), we perform the following range reduction:
+ // x = 2^m * 1.mant,
+ // log10(x) = m * log10(2) + log10(1.mant).
+ // To compute log10(1.mant), let f be the highest 6 bits including the hidden
+ // bit, and d be the difference (1.mant - f), i.e., the remaining 5 bits of
+ // the mantissa, then:
+ // log10(1.mant) = log10(f) + log10(1.mant / f)
+ // = log10(f) + log10(1 + d/f)
+ // since d/f is sufficiently small.
+ // We store log10(f) and 1/f in the lookup tables LOG10F_F and ONE_OVER_F_F
+ // respectively.
+
+ int m = -FPBits::EXP_BIAS;
+
+ // When x is subnormal, normalize it.
+ if ((x_u & FPBits::EXP_MASK) == 0U) {
+ // Can't pass an integer to fputil::cast directly.
+ constexpr float NORMALIZE_EXP = 1U << FPBits::FRACTION_LEN;
+ x_bits = FPBits(x_bits.get_val() * fputil::cast<float16>(NORMALIZE_EXP));
+ x_u = x_bits.uintval();
+ m -= FPBits::FRACTION_LEN;
+ }
+
+ uint16_t mant = x_bits.get_mantissa();
+ // Leading 10 - 5 = 5 bits of the mantissa.
+ int f = mant >> 5;
+ // Unbiased exponent.
+ m += x_u >> FPBits::FRACTION_LEN;
+
+ // Set bits to 1.mant instead of 2^m * 1.mant.
+ x_bits.set_biased_exponent(FPBits::EXP_BIAS);
+ float mant_f = x_bits.get_val();
+ // v = 1.mant * 1/f - 1 = d/f
+ float v = fputil::multiply_add(mant_f, ONE_OVER_F_F[f], -1.0f);
+
+ // Degree-3 minimax polynomial generated by Sollya with the following
+ // commands:
+ // > display = hexadecimal;
+ // > P = fpminimax(log10(1 + x)/x, 2, [|SG...|], [-2^-5, 2^-5]);
+ // > x * P;
+ float log10p1_d_over_f =
+ v * fputil::polyeval(v, 0x1.bcb7bp-2f, -0x1.bce168p-3f, 0x1.28acb8p-3f);
+ // log10(1.mant) = log10(f) + log10(1 + d/f)
+ float log10_1_mant = LOG10F_F[f] + log10p1_d_over_f;
+ return fputil::cast<float16>(
+ fputil::multiply_add(static_cast<float>(m), LOG10F_2, log10_1_mant));
+}
+
+} // namespace math
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LIBC_TYPES_HAS_FLOAT16
+
+#endif // LLVM_LIBC_SRC___SUPPORT_MATH_LOG10F16_H
diff --git a/libc/src/math/generic/CMakeLists.txt b/libc/src/math/generic/CMakeLists.txt
index e4ad6fcafeaf0..c5f0ad73640a9 100644
--- a/libc/src/math/generic/CMakeLists.txt
+++ b/libc/src/math/generic/CMakeLists.txt
@@ -1993,17 +1993,8 @@ add_entrypoint_object(
HDRS
../log10f16.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.macros.optimization
- libc.src.__support.macros.properties.cpu_features
- libc.src.__support.math.expxf16_utils
+ libc.src.__support.math.log10f16
+ libc.src.errno.errno
)
add_entrypoint_object(
diff --git a/libc/src/math/generic/log10f16.cpp b/libc/src/math/generic/log10f16.cpp
index 4bb684a2206cc..57f8e57e31b27 100644
--- a/libc/src/math/generic/log10f16.cpp
+++ b/libc/src/math/generic/log10f16.cpp
@@ -7,163 +7,10 @@
//===----------------------------------------------------------------------===//
#include "src/math/log10f16.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/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/expxf16_utils.h"
+#include "src/__support/math/log10f16.h"
namespace LIBC_NAMESPACE_DECL {
-#ifndef LIBC_MATH_HAS_SKIP_ACCURATE_PASS
-#ifdef LIBC_TARGET_CPU_HAS_FMA_FLOAT
-static constexpr size_t N_LOG10F16_EXCEPTS = 11;
-#else
-static constexpr size_t N_LOG10F16_EXCEPTS = 17;
-#endif
-
-static constexpr fputil::ExceptValues<float16, N_LOG10F16_EXCEPTS>
- LOG10F16_EXCEPTS = {{
- // (input, RZ output, RU offset, RD offset, RN offset)
- // x = 0x1.e3cp-3, log10f16(x) = -0x1.40cp-1 (RZ)
- {0x338fU, 0xb903U, 0U, 1U, 0U},
- // x = 0x1.fep-3, log10f16(x) = -0x1.35p-1 (RZ)
- {0x33f8U, 0xb8d4U, 0U, 1U, 1U},
-#ifndef LIBC_TARGET_CPU_HAS_FMA_FLOAT
- // x = 0x1.394p-1, log10f16(x) = -0x1.b4cp-3 (RZ)
- {0x38e5U, 0xb2d3U, 0U, 1U, 1U},
-#endif
- // x = 0x1.ea8p-1, log10f16(x) = -0x1.31p-6 (RZ)
- {0x3baaU, 0xa4c4U, 0U, 1U, 1U},
- // x = 0x1.ebp-1, log10f16(x) = -0x1.29cp-6 (RZ)
- {0x3bacU, 0xa4a7U, 0U, 1U, 1U},
- // x = 0x1.f3p-1, log10f16(x) = -0x1.6dcp-7 (RZ)
- {0x3bccU, 0xa1b7U, 0U, 1U, 1U},
-// x = 0x1.f38p-1, log10f16(x) = -0x1.5f8p-7 (RZ)
-#ifndef LIBC_TARGET_CPU_HAS_FMA_FLOAT
- {0x3bceU, 0xa17eU, 0U, 1U, 1U},
- // x = 0x1.fd8p-1, log10f16(x) = -0x1.168p-9 (RZ)
- {0x3bf6U, 0x985aU, 0U, 1U, 1U},
- // x = 0x1.ff8p-1, log10f16(x) = -0x1.bccp-12 (RZ)
- {0x3bfeU, 0x8ef3U, 0U, 1U, 1U},
- // x = 0x1.374p+0, log10f16(x) = 0x1.5b8p-4 (RZ)
- {0x3cddU, 0x2d6eU, 1U, 0U, 1U},
- // x = 0x1.3ecp+1, log10f16(x) = 0x1.958p-2 (RZ)
- {0x40fbU, 0x3656U, 1U, 0U, 1U},
-#endif
- // x = 0x1.4p+3, log10f16(x) = 0x1p+0 (RZ)
- {0x4900U, 0x3c00U, 0U, 0U, 0U},
- // x = 0x1.9p+6, log10f16(x) = 0x1p+1 (RZ)
- {0x5640U, 0x4000U, 0U, 0U, 0U},
- // x = 0x1.f84p+6, log10f16(x) = 0x1.0ccp+1 (RZ)
- {0x57e1U, 0x4033U, 1U, 0U, 0U},
- // x = 0x1.f4p+9, log10f16(x) = 0x1.8p+1 (RZ)
- {0x63d0U, 0x4200U, 0U, 0U, 0U},
- // x = 0x1.388p+13, log10f16(x) = 0x1p+2 (RZ)
- {0x70e2U, 0x4400U, 0U, 0U, 0U},
- // x = 0x1.674p+13, log10f16(x) = 0x1.03cp+2 (RZ)
- {0x719dU, 0x440fU, 1U, 0U, 0U},
- }};
-#endif // !LIBC_MATH_HAS_SKIP_ACCURATE_PASS
-
-LLVM_LIBC_FUNCTION(float16, log10f16, (float16 x)) {
- using namespace math::expxf16_internal;
- using FPBits = fputil::FPBits<float16>;
- FPBits x_bits(x);
-
- uint16_t x_u = x_bits.uintval();
-
- // If x <= 0, or x is 1, or x is +inf, or x is NaN.
- if (LIBC_UNLIKELY(x_u == 0U || x_u == 0x3c00U || x_u >= 0x7c00U)) {
- // log10(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;
- }
-
- // log10(+/-0) = −inf
- if ((x_u & 0x7fffU) == 0U) {
- fputil::raise_except_if_required(FE_DIVBYZERO);
- return FPBits::inf(Sign::NEG).get_val();
- }
-
- if (x_u == 0x3c00U)
- return FPBits::zero().get_val();
-
- // When x < 0.
- if (x_u > 0x8000U) {
- fputil::set_errno_if_required(EDOM);
- fputil::raise_except_if_required(FE_INVALID);
- return FPBits::quiet_nan().get_val();
- }
-
- // log10(+inf) = +inf
- return FPBits::inf().get_val();
- }
-
-#ifndef LIBC_MATH_HAS_SKIP_ACCURATE_PASS
- if (auto r = LOG10F16_EXCEPTS.lookup(x_u); LIBC_UNLIKELY(r.has_value()))
- return r.value();
-#endif // !LIBC_MATH_HAS_SKIP_ACCURATE_PASS
-
- // To compute log10(x), we perform the following range reduction:
- // x = 2^m * 1.mant,
- // log10(x) = m * log10(2) + log10(1.mant).
- // To compute log10(1.mant), let f be the highest 6 bits including the hidden
- // bit, and d be the difference (1.mant - f), i.e., the remaining 5 bits of
- // the mantissa, then:
- // log10(1.mant) = log10(f) + log10(1.mant / f)
- // = log10(f) + log10(1 + d/f)
- // since d/f is sufficiently small.
- // We store log10(f) and 1/f in the lookup tables LOG10F_F and ONE_OVER_F_F
- // respectively.
-
- int m = -FPBits::EXP_BIAS;
-
- // When x is subnormal, normalize it.
- if ((x_u & FPBits::EXP_MASK) == 0U) {
- // Can't pass an integer to fputil::cast directly.
- constexpr float NORMALIZE_EXP = 1U << FPBits::FRACTION_LEN;
- x_bits = FPBits(x_bits.get_val() * fputil::cast<float16>(NORMALIZE_EXP));
- x_u = x_bits.uintval();
- m -= FPBits::FRACTION_LEN;
- }
-
- uint16_t mant = x_bits.get_mantissa();
- // Leading 10 - 5 = 5 bits of the mantissa.
- int f = mant >> 5;
- // Unbiased exponent.
- m += x_u >> FPBits::FRACTION_LEN;
-
- // Set bits to 1.mant instead of 2^m * 1.mant.
- x_bits.set_biased_exponent(FPBits::EXP_BIAS);
- float mant_f = x_bits.get_val();
- // v = 1.mant * 1/f - 1 = d/f
- float v = fputil::multiply_add(mant_f, ONE_OVER_F_F[f], -1.0f);
-
- // Degree-3 minimax polynomial generated by Sollya with the following
- // commands:
- // > display = hexadecimal;
- // > P = fpminimax(log10(1 + x)/x, 2, [|SG...|], [-2^-5, 2^-5]);
- // > x * P;
- float log10p1_d_over_f =
- v * fputil::polyeval(v, 0x1.bcb7bp-2f, -0x1.bce168p-3f, 0x1.28acb8p-3f);
- // log10(1.mant) = log10(f) + log10(1 + d/f)
- float log10_1_mant = LOG10F_F[f] + log10p1_d_over_f;
- return fputil::cast<float16>(
- fputil::multiply_add(static_cast<float>(m), LOG10F_2, log10_1_mant));
-}
+LLVM_LIBC_FUNCTION(float16, log10f16, (float16 x)) { return math::log10f16(x); }
} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/test/shared/CMakeLists.txt b/libc/test/shared/CMakeLists.txt
index 61625c0bc0444..0ac62775a8cdf 100644
--- a/libc/test/shared/CMakeLists.txt
+++ b/libc/test/shared/CMakeLists.txt
@@ -63,6 +63,7 @@ add_fp_unittest(
libc.src.__support.math.ilogbf16
libc.src.__support.math.ilogbl
libc.src.__support.math.log
+ libc.src.__support.math.log10f16
libc.src.__support.math.logbf
libc.src.__support.math.logbf128
libc.src.__support.math.logbf16
diff --git a/libc/test/shared/shared_math_test.cpp b/libc/test/shared/shared_math_test.cpp
index 49047631fb227..4134eb77b5337 100644
--- a/libc/test/shared/shared_math_test.cpp
+++ b/libc/test/shared/shared_math_test.cpp
@@ -42,6 +42,7 @@ TEST(LlvmLibcSharedMathTest, AllFloat16) {
EXPECT_EQ(exponent, 5);
EXPECT_EQ(0, LIBC_NAMESPACE::shared::ilogbf16(1.0f16));
+ EXPECT_FP_EQ(0x1p+0f16, LIBC_NAMESPACE::shared::log10f16(10.0f16));
EXPECT_FP_EQ(0x0p+0f16, LIBC_NAMESPACE::shared::logbf16(1.0f16));
EXPECT_FP_EQ(0x1.921fb6p+0f16, LIBC_NAMESPACE::shared::acosf16(0.0f16));
diff --git a/utils/bazel/llvm-project-overlay/libc/BUILD.bazel b/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
index 3d9491e8baa0c..34c9265529e78 100644
--- a/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
+++ b/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
@@ -2932,6 +2932,21 @@ libc_support_library(
],
)
+libc_support_library(
+ name = "__support_math_log10f16",
+ hdrs = ["src/__support/math/log10f16.h"],
+ deps = [
+ ":__support_fputil_cast",
+ ":__support_fputil_except_value_utils",
+ ":__support_fputil_fenv_impl",
+ ":__support_fputil_fp_bits",
+ ":__support_fputil_multiply_add",
+ ":__support_fputil_polyeval",
+ ":__support_macros_optimization",
+ ":__support_math_expxf16_utils",
+ ],
+)
+
libc_support_library(
name = "__support_math_logbf",
hdrs = ["src/__support/math/logbf.h"],
@@ -4548,7 +4563,8 @@ libc_math_function(
libc_math_function(
name = "log10f16",
additional_deps = [
- ":__support_math_expxf16_utils",
+ ":__support_math_log10f16",
+ ":errno",
],
)
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