[libc][math] Refactor atanf16 implementation to header-only in src/__support/math folder. #150868
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This was referenced Jul 28, 2025
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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/150868.diff 9 Files Affected:
diff --git a/libc/shared/math.h b/libc/shared/math.h
index 21536647948f4..bcbe0de56170a 100644
--- a/libc/shared/math.h
+++ b/libc/shared/math.h
@@ -24,6 +24,7 @@
#include "math/asinhf16.h"
#include "math/atan.h"
#include "math/atanf.h"
+#include "math/atanf16.h"
#include "math/erff.h"
#include "math/exp.h"
#include "math/exp10.h"
diff --git a/libc/shared/math/atanf16.h b/libc/shared/math/atanf16.h
new file mode 100644
index 0000000000000..f196907059e01
--- /dev/null
+++ b/libc/shared/math/atanf16.h
@@ -0,0 +1,28 @@
+//===-- Shared atanf16 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_ATANF16_H
+#define LLVM_LIBC_SHARED_MATH_ATANF16_H
+
+#include "shared/libc_common.h"
+
+#ifdef LIBC_TYPES_HAS_FLOAT16
+
+#include "src/__support/math/atanf16.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace shared {
+
+using math::atanf16;
+
+} // namespace shared
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LIBC_TYPES_HAS_FLOAT16
+
+#endif // LLVM_LIBC_SHARED_MATH_ATANF16_H
diff --git a/libc/src/__support/math/CMakeLists.txt b/libc/src/__support/math/CMakeLists.txt
index 95acc962cc885..04cbd3fd1cc01 100644
--- a/libc/src/__support/math/CMakeLists.txt
+++ b/libc/src/__support/math/CMakeLists.txt
@@ -214,6 +214,21 @@ add_header_library(
libc.src.__support.macros.optimization
)
+add_header_library(
+ atanf16
+ HDRS
+ atanf16.h
+ DEPENDS
+ 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.sqrt
+ libc.src.__support.macros.optimization
+)
+
add_header_library(
asinf
HDRS
diff --git a/libc/src/__support/math/atanf16.h b/libc/src/__support/math/atanf16.h
new file mode 100644
index 0000000000000..f75d145f36852
--- /dev/null
+++ b/libc/src/__support/math/atanf16.h
@@ -0,0 +1,119 @@
+//===-- Implementation header for atanf16 -----------------------*- 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_ATANF16_H
+#define LLVM_LIBC_SRC___SUPPORT_MATH_ATANF16_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/sqrt.h"
+#include "src/__support/macros/optimization.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+namespace math {
+
+LIBC_INLINE static constexpr float16 atanf16(float16 x) {
+ // Generated by Solly using the following command:
+ // > round(pi/2, SG, RN);
+ constexpr float PI_2 = 0x1.921fb6p0;
+
+#ifndef LIBC_MATH_HAS_SKIP_ACCURATE_PASS
+ constexpr size_t N_EXCEPTS = 6;
+
+ constexpr fputil::ExceptValues<float16, N_EXCEPTS> ATANF16_EXCEPTS{{
+ // (input, RZ output, RU offset, RD offset, RN offset)
+ {0x2745, 0x2744, 1, 0, 1},
+ {0x3099, 0x3090, 1, 0, 1},
+ {0x3c6c, 0x3aae, 1, 0, 1},
+ {0x466e, 0x3daa, 1, 0, 1},
+ {0x48ae, 0x3ddb, 1, 0, 0},
+ {0x5619, 0x3e3d, 1, 0, 1},
+ }};
+#endif // !LIBC_MATH_HAS_SKIP_ACCURATE_PASS
+
+ using FPBits = fputil::FPBits<float16>;
+ FPBits xbits(x);
+
+ uint16_t x_u = xbits.uintval();
+ uint16_t x_abs = x_u & 0x7fff;
+ bool x_sign = x_u >> 15;
+ float sign = (x_sign ? -1.0 : 1.0);
+
+ // |x| >= +/-inf
+ if (LIBC_UNLIKELY(x_abs >= 0x7c00)) {
+ if (xbits.is_nan()) {
+ if (xbits.is_signaling_nan()) {
+ fputil::raise_except_if_required(FE_INVALID);
+ return FPBits::quiet_nan().get_val();
+ }
+ return x;
+ }
+
+ // atanf16(+/-inf) = +/-pi/2
+ return fputil::cast<float16>(sign * PI_2);
+ }
+
+ float xf = x;
+ float xsq = xf * xf;
+#ifndef LIBC_MATH_HAS_SKIP_ACCURATE_PASS
+ // Handle exceptional values
+ if (auto r = ATANF16_EXCEPTS.lookup_odd(x_abs, x_sign);
+ LIBC_UNLIKELY(r.has_value()))
+ return r.value();
+#endif
+
+ // |x| <= 0x1p0, |x| <= 1
+ if (x_abs <= 0x3c00) {
+ // atanf16(+/-0) = +/-0
+ if (LIBC_UNLIKELY(x_abs == 0))
+ return x;
+
+ // Degree-14 minimax odd polynomial of atan(x) generated by Sollya with:
+ // > P = fpminimax(atan(x)/x, [|0, 2, 4, 6, 8, 10, 12, 14|], [|SG...|],
+ // [0, 1]);
+ float result = fputil::polyeval(
+ xsq, 0x1.fffffcp-1f, -0x1.55519ep-2f, 0x1.98f6a8p-3f, -0x1.1f0a92p-3f,
+ 0x1.95b654p-4f, -0x1.e65492p-5f, 0x1.8c0c36p-6f, -0x1.32316ep-8f);
+ return fputil::cast<float16>(xf * result);
+ }
+
+ // If |x| > 1
+ // y = atan(x) = sign(x) * atan(|x|)
+ // atan(|x|) = pi/2 - atan(1/|x|)
+ // Recall, 1/|x| < 1
+ float x_inv_sq = 1.0f / xsq;
+ float x_inv = fputil::sqrt<float>(x_inv_sq);
+
+ // Degree-14 minimax odd polynomial of atan(x) generated by Sollya with:
+ // > P = fpminimax(atan(x)/x, [|0, 2, 4, 6, 8, 10, 12, 14|], [|SG...|],
+ // [0, 1]);
+ float interm =
+ fputil::polyeval(x_inv_sq, 0x1.fffffcp-1f, -0x1.55519ep-2f,
+ 0x1.98f6a8p-3f, -0x1.1f0a92p-3f, 0x1.95b654p-4f,
+ -0x1.e65492p-5f, 0x1.8c0c36p-6f, -0x1.32316ep-8f);
+
+ return fputil::cast<float16>(sign *
+ fputil::multiply_add(x_inv, -interm, PI_2));
+}
+
+} // namespace math
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LIBC_TYPES_HAS_FLOAT16
+
+#endif // LLVM_LIBC_SRC___SUPPORT_MATH_ATANF16_H
diff --git a/libc/src/math/generic/CMakeLists.txt b/libc/src/math/generic/CMakeLists.txt
index 196e00841f2d1..007e5701b7538 100644
--- a/libc/src/math/generic/CMakeLists.txt
+++ b/libc/src/math/generic/CMakeLists.txt
@@ -4024,17 +4024,7 @@ add_entrypoint_object(
HDRS
../atanf16.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.sqrt
- libc.src.__support.macros.optimization
- libc.src.__support.macros.properties.types
+ libc.src.__support.math.atanf16
)
add_entrypoint_object(
diff --git a/libc/src/math/generic/atanf16.cpp b/libc/src/math/generic/atanf16.cpp
index 9b6ec657417a5..7191c4242160a 100644
--- a/libc/src/math/generic/atanf16.cpp
+++ b/libc/src/math/generic/atanf16.cpp
@@ -7,101 +7,10 @@
//===----------------------------------------------------------------------===//
#include "src/math/atanf16.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/sqrt.h"
-#include "src/__support/macros/optimization.h"
+#include "src/__support/math/atanf16.h"
namespace LIBC_NAMESPACE_DECL {
-// Generated by Solly using the following command:
-// > round(pi/2, SG, RN);
-static constexpr float PI_2 = 0x1.921fb6p0;
-
-#ifndef LIBC_MATH_HAS_SKIP_ACCURATE_PASS
-static constexpr size_t N_EXCEPTS = 6;
-
-static constexpr fputil::ExceptValues<float16, N_EXCEPTS> ATANF16_EXCEPTS{{
- // (input, RZ output, RU offset, RD offset, RN offset)
- {0x2745, 0x2744, 1, 0, 1},
- {0x3099, 0x3090, 1, 0, 1},
- {0x3c6c, 0x3aae, 1, 0, 1},
- {0x466e, 0x3daa, 1, 0, 1},
- {0x48ae, 0x3ddb, 1, 0, 0},
- {0x5619, 0x3e3d, 1, 0, 1},
-}};
-#endif // !LIBC_MATH_HAS_SKIP_ACCURATE_PASS
-
-LLVM_LIBC_FUNCTION(float16, atanf16, (float16 x)) {
- using FPBits = fputil::FPBits<float16>;
- FPBits xbits(x);
-
- uint16_t x_u = xbits.uintval();
- uint16_t x_abs = x_u & 0x7fff;
- bool x_sign = x_u >> 15;
- float sign = (x_sign ? -1.0 : 1.0);
-
- // |x| >= +/-inf
- if (LIBC_UNLIKELY(x_abs >= 0x7c00)) {
- if (xbits.is_nan()) {
- if (xbits.is_signaling_nan()) {
- fputil::raise_except_if_required(FE_INVALID);
- return FPBits::quiet_nan().get_val();
- }
- return x;
- }
-
- // atanf16(+/-inf) = +/-pi/2
- return fputil::cast<float16>(sign * PI_2);
- }
-
- float xf = x;
- float xsq = xf * xf;
-#ifndef LIBC_MATH_HAS_SKIP_ACCURATE_PASS
- // Handle exceptional values
- if (auto r = ATANF16_EXCEPTS.lookup_odd(x_abs, x_sign);
- LIBC_UNLIKELY(r.has_value()))
- return r.value();
-#endif
-
- // |x| <= 0x1p0, |x| <= 1
- if (x_abs <= 0x3c00) {
- // atanf16(+/-0) = +/-0
- if (LIBC_UNLIKELY(x_abs == 0))
- return x;
-
- // Degree-14 minimax odd polynomial of atan(x) generated by Sollya with:
- // > P = fpminimax(atan(x)/x, [|0, 2, 4, 6, 8, 10, 12, 14|], [|SG...|],
- // [0, 1]);
- float result = fputil::polyeval(
- xsq, 0x1.fffffcp-1f, -0x1.55519ep-2f, 0x1.98f6a8p-3f, -0x1.1f0a92p-3f,
- 0x1.95b654p-4f, -0x1.e65492p-5f, 0x1.8c0c36p-6f, -0x1.32316ep-8f);
- return fputil::cast<float16>(xf * result);
- }
-
- // If |x| > 1
- // y = atan(x) = sign(x) * atan(|x|)
- // atan(|x|) = pi/2 - atan(1/|x|)
- // Recall, 1/|x| < 1
- float x_inv_sq = 1.0f / xsq;
- float x_inv = fputil::sqrt<float>(x_inv_sq);
-
- // Degree-14 minimax odd polynomial of atan(x) generated by Sollya with:
- // > P = fpminimax(atan(x)/x, [|0, 2, 4, 6, 8, 10, 12, 14|], [|SG...|],
- // [0, 1]);
- float interm =
- fputil::polyeval(x_inv_sq, 0x1.fffffcp-1f, -0x1.55519ep-2f,
- 0x1.98f6a8p-3f, -0x1.1f0a92p-3f, 0x1.95b654p-4f,
- -0x1.e65492p-5f, 0x1.8c0c36p-6f, -0x1.32316ep-8f);
-
- return fputil::cast<float16>(sign *
- fputil::multiply_add(x_inv, -interm, PI_2));
-}
+LLVM_LIBC_FUNCTION(float16, atanf16, (float16 x)) { return math::atanf16(x); }
} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/test/shared/CMakeLists.txt b/libc/test/shared/CMakeLists.txt
index 6d0601feda138..2dd5bdafe24f6 100644
--- a/libc/test/shared/CMakeLists.txt
+++ b/libc/test/shared/CMakeLists.txt
@@ -20,6 +20,7 @@ add_fp_unittest(
libc.src.__support.math.asinhf16
libc.src.__support.math.atan
libc.src.__support.math.atanf
+ libc.src.__support.math.atanf16
libc.src.__support.math.erff
libc.src.__support.math.exp
libc.src.__support.math.exp10
diff --git a/libc/test/shared/shared_math_test.cpp b/libc/test/shared/shared_math_test.cpp
index 228fa42ec834e..2b80068f991be 100644
--- a/libc/test/shared/shared_math_test.cpp
+++ b/libc/test/shared/shared_math_test.cpp
@@ -19,6 +19,7 @@ TEST(LlvmLibcSharedMathTest, AllFloat16) {
EXPECT_FP_EQ(0x0p+0f16, LIBC_NAMESPACE::shared::acospif16(1.0f16));
EXPECT_FP_EQ(0x0p+0f16, LIBC_NAMESPACE::shared::asinf16(0.0f16));
EXPECT_FP_EQ(0x0p+0f16, LIBC_NAMESPACE::shared::asinhf16(0.0f16));
+ EXPECT_FP_EQ(0x0p+0f16, LIBC_NAMESPACE::shared::atanf16(0.0f16));
EXPECT_FP_EQ(0x1p+0f16, LIBC_NAMESPACE::shared::exp10f16(0.0f16));
diff --git a/utils/bazel/llvm-project-overlay/libc/BUILD.bazel b/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
index e8c59fa87d4c3..77e4829f44758 100644
--- a/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
+++ b/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
@@ -2288,6 +2288,21 @@ libc_support_library(
],
)
+libc_support_library(
+ name = "__support_math_atanf16",
+ hdrs = ["src/__support/math/atanf16.h"],
+ deps = [
+ ":__support_fputil_cast",
+ ":__support_fputil_except_value_utils",
+ ":__support_fputil_fenv_impl",
+ ":__support_fputil_fp_bits",
+ ":__support_fputil_polyeval",
+ ":__support_fputil_multiply_add",
+ ":__support_fputil_sqrt",
+ ":__support_macros_optimization",
+ ],
+)
+
libc_support_library(
name = "__support_math_asinf",
hdrs = ["src/__support/math/asinf.h"],
@@ -2904,6 +2919,13 @@ libc_math_function(
],
)
+libc_math_function(
+ name = "atanf16",
+ additional_deps = [
+ ":__support_math_atanf16"
+ ],
+)
+
libc_math_function(
name = "atan",
additional_deps = [
|
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[libc][math] Refactor exp10m1f16 implementation to header-only in src/__support/math folder.
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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