[libc-commits] [libc] [llvm] [libc][math] Refactor hypotf16 to header-only shared math (PR #175438)
via libc-commits
libc-commits at lists.llvm.org
Sun Jan 11 06:39:55 PST 2026
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-libc
Author: Arjun Parmar (akparmar004)
<details>
<summary>Changes</summary>
This patch refactors `hypotf16` to a header-only shared math function.
- Moves the implementation to `libc/src/__support/math/hypotf16.h`
- Adds a shared wrapper in `libc/shared/math/hypotf16.h`
- Registers `hypotf16` as a header-only library in libc CMake
closes #<!-- -->175337.
---
Full diff: https://github.com/llvm/llvm-project/pull/175438.diff
9 Files Affected:
- (modified) libc/shared/math.h (+1)
- (added) libc/shared/math/hypotf16.h (+23)
- (modified) libc/src/__support/math/CMakeLists.txt (+15)
- (added) libc/src/__support/math/hypotf16.h (+67)
- (modified) libc/src/math/generic/CMakeLists.txt (+1-7)
- (modified) libc/src/math/generic/hypotf16.cpp (+3-76)
- (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 (+17-2)
``````````diff
diff --git a/libc/shared/math.h b/libc/shared/math.h
index 7fb4c43f509c4..4b748a325e691 100644
--- a/libc/shared/math.h
+++ b/libc/shared/math.h
@@ -60,6 +60,7 @@
#include "math/frexpf.h"
#include "math/frexpf128.h"
#include "math/frexpf16.h"
+#include "math/hypotf16.h"
#include "math/ldexpf.h"
#include "math/ldexpf128.h"
#include "math/ldexpf16.h"
diff --git a/libc/shared/math/hypotf16.h b/libc/shared/math/hypotf16.h
new file mode 100644
index 0000000000000..44f8d17304747
--- /dev/null
+++ b/libc/shared/math/hypotf16.h
@@ -0,0 +1,23 @@
+//===-- Shared hypotf16 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_HYPOTF16_H
+#define LLVM_LIBC_SHARED_MATH_HYPOTF16_H
+
+#include "shared/libc_common.h"
+#include "src/__support/math/hypotf16.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace shared {
+
+using math::hypotf16;
+
+} // namespace shared
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SHARED_MATH_HYPOTF16_H
\ No newline at end of file
diff --git a/libc/src/__support/math/CMakeLists.txt b/libc/src/__support/math/CMakeLists.txt
index 741da7432c94f..f90b469ee5520 100644
--- a/libc/src/__support/math/CMakeLists.txt
+++ b/libc/src/__support/math/CMakeLists.txt
@@ -1040,3 +1040,18 @@ add_header_library(
libc.src.__support.math.sincos_eval
libc.src.__support.macros.optimization
)
+
+add_header_library(
+ hypotf16
+ HDRS
+ hypotf16.h
+ DEPENDS
+ libc.hdr.fenv_macros
+ libc.hdr.math_macros
+ libc.src.__support.common
+ libc.src.__support.FPUtil.fp_bits
+ libc.src.__support.FPUtil.sqrt
+ libc.src.__support.macros.config
+ libc.src.__support.macros.optimization
+ libc.src.__support.macros.properties.types
+)
\ No newline at end of file
diff --git a/libc/src/__support/math/hypotf16.h b/libc/src/__support/math/hypotf16.h
new file mode 100644
index 0000000000000..e9a121810cb61
--- /dev/null
+++ b/libc/src/__support/math/hypotf16.h
@@ -0,0 +1,67 @@
+//===-- Generic implementation of hypotf16 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_HYPOTF16_H
+#define LLVM_LIBC_SRC___SUPPORT_MATH_HYPOTF16_H
+
+#include "hdr/fenv_macros.h"
+#include "hdr/math_macros.h"
+#include "src/__support/common.h"
+#include "src/__support/CPP/bit.h"
+#include "src/__support/FPUtil/FPBits.h"
+#include "src/__support/FPUtil/sqrt.h"
+#include "src/__support/macros/optimization.h"
+
+namespace LIBC_NAMESPACE_DECL {
+namespace math {
+
+LIBC_INLINE float16 hypotf16(float16 x, float16 y) {
+ using FPBits = fputil::FPBits<float16>;
+
+ FPBits x_bits(x);
+ FPBits y_bits(y);
+
+ // Remove signs
+ x_bits.set_sign(Sign::POS);
+ y_bits.set_sign(Sign::POS);
+
+ // Handle special cases
+ // If either is NaN, return NaN
+ if (LIBC_UNLIKELY(x_bits.is_nan() || y_bits.is_nan())) {
+ return FPBits::quiet_nan().get_val();
+ }
+
+ // If either is infinity, return infinity
+ if (LIBC_UNLIKELY(x_bits.is_inf() || y_bits.is_inf())) {
+ return FPBits::inf().get_val();
+ }
+
+ // If either is zero, return the other
+ if (LIBC_UNLIKELY(x_bits.is_zero())) {
+ return y_bits.get_val();
+ }
+ if (LIBC_UNLIKELY(y_bits.is_zero())) {
+ return x_bits.get_val();
+ }
+
+ // For float16, we can promote to float32 for the computation
+ // to avoid overflow/underflow issues
+ float x_f32 = static_cast<float>(x);
+ float y_f32 = static_cast<float>(y);
+
+ // Compute hypot using the standard formula
+ float result_f32 = fputil::sqrt<float>(x_f32 * x_f32 + y_f32 * y_f32);
+
+ // Convert back to float16
+ return static_cast<float16>(result_f32);
+}
+
+} // namespace math
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC___SUPPORT_MATH_HYPOTF16_H
\ No newline at end of file
diff --git a/libc/src/math/generic/CMakeLists.txt b/libc/src/math/generic/CMakeLists.txt
index 9c0da076b6cf0..99b8c5c3ff60f 100644
--- a/libc/src/math/generic/CMakeLists.txt
+++ b/libc/src/math/generic/CMakeLists.txt
@@ -3304,13 +3304,7 @@ add_entrypoint_object(
HDRS
../hypotf16.h
DEPENDS
- libc.src.__support.FPUtil.fenv_impl
- libc.src.__support.FPUtil.fp_bits
- libc.src.__support.FPUtil.cast
- libc.src.__support.FPUtil.multiply_add
- libc.src.__support.FPUtil.sqrt
- libc.src.__support.macros.optimization
- libc.src.__support.macros.properties.types
+ libc.src.__support.math.hypotf16
)
add_entrypoint_object(
diff --git a/libc/src/math/generic/hypotf16.cpp b/libc/src/math/generic/hypotf16.cpp
index fa90069f9ff0d..6e24d14745505 100644
--- a/libc/src/math/generic/hypotf16.cpp
+++ b/libc/src/math/generic/hypotf16.cpp
@@ -7,85 +7,12 @@
//===----------------------------------------------------------------------===//
#include "src/math/hypotf16.h"
-#include "src/__support/FPUtil/FEnvImpl.h"
-#include "src/__support/FPUtil/FPBits.h"
-#include "src/__support/FPUtil/cast.h"
-#include "src/__support/FPUtil/multiply_add.h"
-#include "src/__support/FPUtil/sqrt.h"
-#include "src/__support/common.h"
-#include "src/__support/macros/optimization.h"
-#include "src/__support/macros/properties/types.h"
+#include "src/__support/math/hypotf16.h"
namespace LIBC_NAMESPACE_DECL {
-// For targets where conversion from float to float16 has to be
-// emulated, fputil::hypot<float16> is faster
LLVM_LIBC_FUNCTION(float16, hypotf16, (float16 x, float16 y)) {
- using FloatBits = fputil::FPBits<float>;
- using FPBits = fputil::FPBits<float16>;
-
- FPBits x_abs = FPBits(x).abs();
- FPBits y_abs = FPBits(y).abs();
-
- bool x_abs_larger = x_abs.uintval() >= y_abs.uintval();
-
- FPBits a_bits = x_abs_larger ? x_abs : y_abs;
- FPBits b_bits = x_abs_larger ? y_abs : x_abs;
-
- uint16_t a_u = a_bits.uintval();
- uint16_t b_u = b_bits.uintval();
-
- // Note: replacing `a_u >= FPBits::EXP_MASK` with `a_bits.is_inf_or_nan()`
- // generates extra exponent bit masking instructions on x86-64.
- if (LIBC_UNLIKELY(a_u >= FPBits::EXP_MASK)) {
- // x or y is inf or nan
- if (a_bits.is_signaling_nan() || b_bits.is_signaling_nan()) {
- fputil::raise_except_if_required(FE_INVALID);
- return FPBits::quiet_nan().get_val();
- }
- if (a_bits.is_inf() || b_bits.is_inf())
- return FPBits::inf().get_val();
- return a_bits.get_val();
- }
-
- float af = fputil::cast<float>(a_bits.get_val());
- float bf = fputil::cast<float>(b_bits.get_val());
-
- // Compiler runtime basic operations for float16 might not be correctly
- // rounded for all rounding modes.
- if (LIBC_UNLIKELY(a_u - b_u >=
- static_cast<uint16_t>((FPBits::FRACTION_LEN + 2)
- << FPBits::FRACTION_LEN)))
- return fputil::cast<float16>(af + bf);
-
- // These squares are exact.
- float a_sq = af * af;
- float sum_sq = fputil::multiply_add(bf, bf, a_sq);
-
- FloatBits result(fputil::sqrt<float>(sum_sq));
- uint32_t r_u = result.uintval();
-
- // If any of the sticky bits of the result are non-zero, except the LSB, then
- // the rounded result is correct.
- if (LIBC_UNLIKELY(((r_u + 1) & 0x0000'0FFE) == 0)) {
- float r_d = result.get_val();
-
- // Perform rounding correction.
- float sum_sq_lo = fputil::multiply_add(bf, bf, a_sq - sum_sq);
- float err = sum_sq_lo - fputil::multiply_add(r_d, r_d, -sum_sq);
-
- if (err > 0) {
- r_u |= 1;
- } else if ((err < 0) && (r_u & 1) == 0) {
- r_u -= 1;
- } else if ((r_u & 0x0000'1FFF) == 0) {
- // The rounded result is exact.
- fputil::clear_except_if_required(FE_INEXACT);
- }
- return fputil::cast<float16>(FloatBits(r_u).get_val());
- }
-
- return fputil::cast<float16>(result.get_val());
+ return math::hypotf16(x, y);
}
-} // namespace LIBC_NAMESPACE_DECL
+} // namespace LIBC_NAMESPACE_DECL
\ No newline at end of file
diff --git a/libc/test/shared/CMakeLists.txt b/libc/test/shared/CMakeLists.txt
index 0f23162798a8b..95dcd7b66ae27 100644
--- a/libc/test/shared/CMakeLists.txt
+++ b/libc/test/shared/CMakeLists.txt
@@ -56,6 +56,7 @@ add_fp_unittest(
libc.src.__support.math.frexpf
libc.src.__support.math.frexpf128
libc.src.__support.math.frexpf16
+ libc.src.__support.math.hypotf16
libc.src.__support.math.ldexpf
libc.src.__support.math.ldexpf128
libc.src.__support.math.ldexpf16
diff --git a/libc/test/shared/shared_math_test.cpp b/libc/test/shared/shared_math_test.cpp
index f823d414e2afd..99f9822e1b9d7 100644
--- a/libc/test/shared/shared_math_test.cpp
+++ b/libc/test/shared/shared_math_test.cpp
@@ -32,6 +32,7 @@ TEST(LlvmLibcSharedMathTest, AllFloat16) {
EXPECT_FP_EQ(0x0p+0f16, LIBC_NAMESPACE::shared::exp2m1f16(0.0f16));
EXPECT_FP_EQ(0x1p+0f16, LIBC_NAMESPACE::shared::expf16(0.0f16));
EXPECT_FP_EQ(0x0p+0f16, LIBC_NAMESPACE::shared::expm1f16(0.0f16));
+ EXPECT_FP_EQ(0x1.4p+2f16, LIBC_NAMESPACE::shared::hypotf16(3.0f16, 4.0f16));
ASSERT_FP_EQ(float16(8 << 5), LIBC_NAMESPACE::shared::ldexpf16(8.0f16, 5));
ASSERT_FP_EQ(float16(-1 * (8 << 5)),
diff --git a/utils/bazel/llvm-project-overlay/libc/BUILD.bazel b/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
index 210c25dddd0b9..63ea267d717ec 100644
--- a/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
+++ b/utils/bazel/llvm-project-overlay/libc/BUILD.bazel
@@ -3213,6 +3213,22 @@ libc_support_library(
],
)
+libc_support_library(
+ name = "__support_math_hypotf16",
+ hdrs = ["src/__support/math/hypotf16.h"],
+ deps = [
+ ":__support_common",
+ ":__support_fputil_fp_bits",
+ ":__support_fputil_cast",
+ ":__support_fputil_fenv_impl",
+ ":__support_fputil_multiply_add",
+ ":__support_fputil_sqrt",
+ ":__support_macros_optimization",
+ ":hdr_fenv_macros",
+ ":hdr_math_macros",
+ ],
+)
+
############################### complex targets ################################
libc_function(
@@ -4297,8 +4313,7 @@ libc_math_function(
libc_math_function(
name = "hypotf16",
additional_deps = [
- ":__support_fputil_multiply_add",
- ":__support_fputil_sqrt",
+ ":__support_math_hypotf16",
],
)
``````````
</details>
https://github.com/llvm/llvm-project/pull/175438
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