[libc-commits] [libc] [llvm] [libc][math] Refactor tanf16 to header only (PR #181523)
via libc-commits
libc-commits at lists.llvm.org
Sat Feb 14 20:17:06 PST 2026
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-libc
Author: Xinlong Chen (Xinlong-Chen)
<details>
<summary>Changes</summary>
Part of https://github.com/llvm/llvm-project/issues/147386
---
Full diff: https://github.com/llvm/llvm-project/pull/181523.diff
9 Files Affected:
- (modified) libc/shared/math.h (+1)
- (added) libc/shared/math/tanf16.h (+29)
- (modified) libc/src/__support/math/CMakeLists.txt (+17)
- (added) libc/src/__support/math/tanf16.h (+142)
- (modified) libc/src/math/generic/CMakeLists.txt (+1-10)
- (modified) libc/src/math/generic/tanf16.cpp (+2-110)
- (modified) libc/test/shared/CMakeLists.txt (+1)
- (modified) libc/test/shared/shared_math_test.cpp (+1)
- (modified) utils/bazel/llvm-project-overlay/libc/BUILD.bazel (+18-3)
``````````diff
diff --git a/libc/shared/math.h b/libc/shared/math.h
index e4487d7305e4b..80c38e26238d0 100644
--- a/libc/shared/math.h
+++ b/libc/shared/math.h
@@ -122,6 +122,7 @@
#include "math/sqrtf16.h"
#include "math/tan.h"
#include "math/tanf.h"
+#include "math/tanf16.h"
#include "math/tanhf.h"
#include "math/tanhf16.h"
diff --git a/libc/shared/math/tanf16.h b/libc/shared/math/tanf16.h
new file mode 100644
index 0000000000000..b8ca2b87335e5
--- /dev/null
+++ b/libc/shared/math/tanf16.h
@@ -0,0 +1,29 @@
+//===-- Shared tanf16 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_TANF16_H
+#define LLVM_LIBC_SHARED_MATH_TANF16_H
+
+#include "include/llvm-libc-macros/float16-macros.h"
+
+#ifdef LIBC_TYPES_HAS_FLOAT16
+
+#include "shared/libc_common.h"
+#include "src/__support/math/tanf16.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace shared {
+
+using math::tanf16;
+
+} // namespace shared
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LIBC_TYPES_HAS_FLOAT16
+
+#endif // LLVM_LIBC_SHARED_MATH_TANF16_H
diff --git a/libc/src/__support/math/CMakeLists.txt b/libc/src/__support/math/CMakeLists.txt
index 8027180e2cf08..81902e047c06d 100644
--- a/libc/src/__support/math/CMakeLists.txt
+++ b/libc/src/__support/math/CMakeLists.txt
@@ -1750,6 +1750,23 @@ add_header_library(
libc.src.__support.macros.optimization
)
+add_header_library(
+ tanf16
+ HDRS
+ tanf16.h
+ DEPENDS
+ .sincosf16_utils
+ libc.hdr.errno_macros
+ libc.hdr.fenv_macros
+ libc.src.__support.FPUtil.cast
+ libc.src.__support.FPUtil.fenv_impl
+ libc.src.__support.FPUtil.fp_bits
+ libc.src.__support.FPUtil.except_value_utils
+ libc.src.__support.FPUtil.multiply_add
+ libc.src.__support.macros.optimization
+ libc.src.__support.macros.properties.types
+)
+
add_header_library(
tanhf
HDRS
diff --git a/libc/src/__support/math/tanf16.h b/libc/src/__support/math/tanf16.h
new file mode 100644
index 0000000000000..4a7b0ddabc668
--- /dev/null
+++ b/libc/src/__support/math/tanf16.h
@@ -0,0 +1,142 @@
+//===-- Single-precision tanf16 function ----------------------------------===//
+//
+// 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_TANF16_H
+#define LLVM_LIBC_SRC___SUPPORT_MATH_TANF16_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 "sincosf16_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/multiply_add.h"
+#include "src/__support/macros/optimization.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+namespace math {
+
+namespace tanf16_internal {
+#ifndef LIBC_MATH_HAS_SKIP_ACCURATE_PASS
+LIBC_INLINE_VAR constexpr size_t N_EXCEPTS = 9;
+
+LIBC_INLINE_VAR constexpr fputil::ExceptValues<float16, N_EXCEPTS>
+ TANF16_EXCEPTS{{
+ // (input, RZ output, RU offset, RD offset, RN offset)
+ {0x2894, 0x2894, 1, 0, 1},
+ {0x3091, 0x3099, 1, 0, 0},
+ {0x3098, 0x30a0, 1, 0, 0},
+ {0x55ed, 0x3911, 1, 0, 0},
+ {0x607b, 0xc638, 0, 1, 1},
+ {0x674e, 0x3b7d, 1, 0, 0},
+ {0x6807, 0x4014, 1, 0, 1},
+ {0x6f4d, 0xbe19, 0, 1, 1},
+ {0x7330, 0xcb62, 0, 1, 0},
+ }};
+#endif // !LIBC_MATH_HAS_SKIP_ACCURATE_PASS
+} // namespace tanf16_internal
+
+LIBC_INLINE float16 tanf16(float16 x) {
+ using namespace sincosf16_internal;
+ using namespace tanf16_internal;
+ using FPBits = fputil::FPBits<float16>;
+ FPBits xbits(x);
+
+ uint16_t x_u = xbits.uintval();
+ uint16_t x_abs = x_u & 0x7fff;
+ float xf = x;
+
+#ifndef LIBC_MATH_HAS_SKIP_ACCURATE_PASS
+ bool x_sign = x_u >> 15;
+ // Handle exceptional values
+ if (auto r = TANF16_EXCEPTS.lookup_odd(x_abs, x_sign);
+ LIBC_UNLIKELY(r.has_value()))
+ return r.value();
+#endif // !LIBC_MATH_HAS_SKIP_ACCURATE_PASS
+
+ // |x| <= 0x1.d1p-5
+ if (LIBC_UNLIKELY(x_abs <= 0x2b44)) {
+ // |x| <= 0x1.398p-11
+ if (LIBC_UNLIKELY(x_abs <= 0x10e6)) {
+ // tan(+/-0) = +/-0
+ if (LIBC_UNLIKELY(x_abs == 0))
+ return x;
+
+ int rounding = fputil::quick_get_round();
+
+ // Exhaustive tests show that, when:
+ // x > 0, and rounding upward or
+ // x < 0, and rounding downward then,
+ // tan(x) = x * 2^-11 + x
+ if ((xbits.is_pos() && rounding == FE_UPWARD) ||
+ (xbits.is_neg() && rounding == FE_DOWNWARD))
+ return fputil::cast<float16>(fputil::multiply_add(xf, 0x1.0p-11f, xf));
+ return x;
+ }
+
+ float xsq = xf * xf;
+
+ // Degree-6 minimax odd polynomial of tan(x) generated by Sollya with:
+ // > P = fpminimax(tan(x)/x, [|0, 2, 4, 6|], [|1, SG...|], [0, pi/32]);
+ float result = fputil::polyeval(xsq, 0x1p0f, 0x1.555556p-2f, 0x1.110ee4p-3f,
+ 0x1.be80f6p-5f);
+
+ return fputil::cast<float16>(xf * result);
+ }
+
+ // tan(+/-inf) = NaN, and tan(NaN) = NaN
+ if (LIBC_UNLIKELY(x_abs >= 0x7c00)) {
+ if (xbits.is_signaling_nan()) {
+ fputil::raise_except_if_required(FE_INVALID);
+ return FPBits::quiet_nan().get_val();
+ }
+ // x = +/-inf
+ if (x_abs == 0x7c00) {
+ fputil::set_errno_if_required(EDOM);
+ fputil::raise_except_if_required(FE_INVALID);
+ }
+
+ return x + FPBits::quiet_nan().get_val();
+ }
+
+ // Range reduction:
+ // For |x| > pi/32, we perform range reduction as follows:
+ // Find k and y such that:
+ // x = (k + y) * pi/32;
+ // k is an integer, |y| < 0.5
+ //
+ // This is done by performing:
+ // k = round(x * 32/pi)
+ // y = x * 32/pi - k
+ //
+ // Once k and y are computed, we then deduce the answer by the formula:
+ // tan(x) = sin(x) / cos(x)
+ // = (sin_y * cos_k + cos_y * sin_k) / (cos_y * cos_k - sin_y * sin_k)
+ float sin_k, cos_k, sin_y, cosm1_y;
+ sincosf16_eval(xf, sin_k, cos_k, sin_y, cosm1_y);
+
+ // Note that, cosm1_y = cos_y - 1:
+ using fputil::multiply_add;
+ return fputil::cast<float16>(
+ multiply_add(sin_y, cos_k, multiply_add(cosm1_y, sin_k, sin_k)) /
+ multiply_add(sin_y, -sin_k, multiply_add(cosm1_y, cos_k, cos_k)));
+}
+
+} // namespace math
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LIBC_TYPES_HAS_FLOAT16
+
+#endif // LLVM_LIBC_SRC___SUPPORT_MATH_TANF16_H
diff --git a/libc/src/math/generic/CMakeLists.txt b/libc/src/math/generic/CMakeLists.txt
index b7c1f5a911831..62d916144209a 100644
--- a/libc/src/math/generic/CMakeLists.txt
+++ b/libc/src/math/generic/CMakeLists.txt
@@ -475,16 +475,7 @@ add_entrypoint_object(
HDRS
../tanf16.h
DEPENDS
- libc.hdr.errno_macros
- libc.hdr.fenv_macros
- libc.src.__support.FPUtil.cast
- libc.src.__support.FPUtil.fenv_impl
- libc.src.__support.FPUtil.fp_bits
- libc.src.__support.FPUtil.except_value_utils
- libc.src.__support.FPUtil.multiply_add
- libc.src.__support.macros.optimization
- libc.src.__support.macros.properties.types
- libc.src.__support.math.sincosf16_utils
+ libc.src.__support.math.tanf16
)
add_entrypoint_object(
diff --git a/libc/src/math/generic/tanf16.cpp b/libc/src/math/generic/tanf16.cpp
index 880ba0101a96e..8126a06cbaba9 100644
--- a/libc/src/math/generic/tanf16.cpp
+++ b/libc/src/math/generic/tanf16.cpp
@@ -7,118 +7,10 @@
//===----------------------------------------------------------------------===//
#include "src/math/tanf16.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/multiply_add.h"
-#include "src/__support/macros/optimization.h"
-#include "src/__support/math/sincosf16_utils.h"
+#include "src/__support/math/tanf16.h"
namespace LIBC_NAMESPACE_DECL {
-#ifndef LIBC_MATH_HAS_SKIP_ACCURATE_PASS
-constexpr size_t N_EXCEPTS = 9;
-
-constexpr fputil::ExceptValues<float16, N_EXCEPTS> TANF16_EXCEPTS{{
- // (input, RZ output, RU offset, RD offset, RN offset)
- {0x2894, 0x2894, 1, 0, 1},
- {0x3091, 0x3099, 1, 0, 0},
- {0x3098, 0x30a0, 1, 0, 0},
- {0x55ed, 0x3911, 1, 0, 0},
- {0x607b, 0xc638, 0, 1, 1},
- {0x674e, 0x3b7d, 1, 0, 0},
- {0x6807, 0x4014, 1, 0, 1},
- {0x6f4d, 0xbe19, 0, 1, 1},
- {0x7330, 0xcb62, 0, 1, 0},
-}};
-#endif // !LIBC_MATH_HAS_SKIP_ACCURATE_PASS
-
-LLVM_LIBC_FUNCTION(float16, tanf16, (float16 x)) {
- using namespace math::sincosf16_internal;
- using FPBits = fputil::FPBits<float16>;
- FPBits xbits(x);
-
- uint16_t x_u = xbits.uintval();
- uint16_t x_abs = x_u & 0x7fff;
- float xf = x;
-
-#ifndef LIBC_MATH_HAS_SKIP_ACCURATE_PASS
- bool x_sign = x_u >> 15;
- // Handle exceptional values
- if (auto r = TANF16_EXCEPTS.lookup_odd(x_abs, x_sign);
- LIBC_UNLIKELY(r.has_value()))
- return r.value();
-#endif // !LIBC_MATH_HAS_SKIP_ACCURATE_PASS
-
- // |x| <= 0x1.d1p-5
- if (LIBC_UNLIKELY(x_abs <= 0x2b44)) {
- // |x| <= 0x1.398p-11
- if (LIBC_UNLIKELY(x_abs <= 0x10e6)) {
- // tan(+/-0) = +/-0
- if (LIBC_UNLIKELY(x_abs == 0))
- return x;
-
- int rounding = fputil::quick_get_round();
-
- // Exhaustive tests show that, when:
- // x > 0, and rounding upward or
- // x < 0, and rounding downward then,
- // tan(x) = x * 2^-11 + x
- if ((xbits.is_pos() && rounding == FE_UPWARD) ||
- (xbits.is_neg() && rounding == FE_DOWNWARD))
- return fputil::cast<float16>(fputil::multiply_add(xf, 0x1.0p-11f, xf));
- return x;
- }
-
- float xsq = xf * xf;
-
- // Degree-6 minimax odd polynomial of tan(x) generated by Sollya with:
- // > P = fpminimax(tan(x)/x, [|0, 2, 4, 6|], [|1, SG...|], [0, pi/32]);
- float result = fputil::polyeval(xsq, 0x1p0f, 0x1.555556p-2f, 0x1.110ee4p-3f,
- 0x1.be80f6p-5f);
-
- return fputil::cast<float16>(xf * result);
- }
-
- // tan(+/-inf) = NaN, and tan(NaN) = NaN
- if (LIBC_UNLIKELY(x_abs >= 0x7c00)) {
- if (xbits.is_signaling_nan()) {
- fputil::raise_except_if_required(FE_INVALID);
- return FPBits::quiet_nan().get_val();
- }
- // x = +/-inf
- if (x_abs == 0x7c00) {
- fputil::set_errno_if_required(EDOM);
- fputil::raise_except_if_required(FE_INVALID);
- }
-
- return x + FPBits::quiet_nan().get_val();
- }
-
- // Range reduction:
- // For |x| > pi/32, we perform range reduction as follows:
- // Find k and y such that:
- // x = (k + y) * pi/32;
- // k is an integer, |y| < 0.5
- //
- // This is done by performing:
- // k = round(x * 32/pi)
- // y = x * 32/pi - k
- //
- // Once k and y are computed, we then deduce the answer by the formula:
- // tan(x) = sin(x) / cos(x)
- // = (sin_y * cos_k + cos_y * sin_k) / (cos_y * cos_k - sin_y * sin_k)
- float sin_k, cos_k, sin_y, cosm1_y;
- sincosf16_eval(xf, sin_k, cos_k, sin_y, cosm1_y);
-
- // Note that, cosm1_y = cos_y - 1:
- using fputil::multiply_add;
- return fputil::cast<float16>(
- multiply_add(sin_y, cos_k, multiply_add(cosm1_y, sin_k, sin_k)) /
- multiply_add(sin_y, -sin_k, multiply_add(cosm1_y, cos_k, cos_k)));
-}
+LLVM_LIBC_FUNCTION(float16, tanf16, (float16 x)) { return math::tanf16(x); }
} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/test/shared/CMakeLists.txt b/libc/test/shared/CMakeLists.txt
index 1a0559af51acd..a68bf9b07341c 100644
--- a/libc/test/shared/CMakeLists.txt
+++ b/libc/test/shared/CMakeLists.txt
@@ -119,6 +119,7 @@ add_fp_unittest(
libc.src.__support.math.sqrtf
libc.src.__support.math.tan
libc.src.__support.math.tanf
+ libc.src.__support.math.tanf16
libc.src.__support.math.tanhf
libc.src.__support.math.tanhf16
)
diff --git a/libc/test/shared/shared_math_test.cpp b/libc/test/shared/shared_math_test.cpp
index fc6e6c74b3720..37f9875155f4a 100644
--- a/libc/test/shared/shared_math_test.cpp
+++ b/libc/test/shared/shared_math_test.cpp
@@ -73,6 +73,7 @@ TEST(LlvmLibcSharedMathTest, AllFloat16) {
EXPECT_FP_EQ(0x1.921fb6p+0f16, LIBC_NAMESPACE::shared::acosf16(0.0f16));
EXPECT_FP_EQ(0x1p+0f16, LIBC_NAMESPACE::shared::f16sqrtl(1.0L));
EXPECT_FP_EQ(0.0f16, LIBC_NAMESPACE::shared::sinf16(0.0f16));
+ EXPECT_FP_EQ(0.0f16, LIBC_NAMESPACE::shared::tanf16(0.0f16));
EXPECT_FP_EQ(0.0f16, LIBC_NAMESPACE::shared::tanhf16(0.0f16));
}
diff --git a/utils/bazel/llvm-project-overlay/libc/BUILD.bazel b/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
index 0eaff89f04215..73b0ff925ae43 100644
--- a/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
+++ b/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
@@ -3950,6 +3950,23 @@ libc_support_library(
],
)
+libc_support_library(
+ name = "__support_math_tanf16",
+ hdrs = ["src/__support/math/tanf16.h"],
+ deps = [
+ ":__support_fputil_cast",
+ ":__support_fputil_except_value_utils",
+ ":__support_fputil_fenv_impl",
+ ":__support_fputil_fp_bits",
+ ":__support_fputil_multiply_add",
+ ":__support_macros_optimization",
+ ":__support_macros_properties_types",
+ ":__support_math_sincosf16_utils",
+ ":hdr_errno_macros",
+ ":hdr_fenv_macros",
+ ],
+)
+
libc_support_library(
name = "__support_math_tanhf",
hdrs = ["src/__support/math/tanhf.h"],
@@ -5472,9 +5489,7 @@ libc_math_function(
libc_math_function(
name = "tanf16",
additional_deps = [
- ":__support_fputil_nearest_integer",
- ":__support_fputil_polyeval",
- ":__support_math_sincosf16_utils",
+ ":__support_math_tanf16",
],
)
``````````
</details>
https://github.com/llvm/llvm-project/pull/181523
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