[libc][math][c23] Add asinhf16 function (#131351)

meltq · web-flow · commit d22e35be1768 · 2025-03-29T13:54:52.000+01:00
Implement asinh for Float16 along with tests. Closes #131001
diff --git a/libc/config/linux/x86_64/entrypoints.txt b/libc/config/linux/x86_64/entrypoints.txt
@@ -653,9 +653,10 @@ endif()
 if(LIBC_TYPES_HAS_FLOAT16)
   list(APPEND TARGET_LIBM_ENTRYPOINTS
     # math.h C23 _Float16 entrypoints
-    libc.src.math.asinf16
     libc.src.math.acosf16
     libc.src.math.acoshf16
+    libc.src.math.asinf16
+    libc.src.math.asinhf16
     libc.src.math.canonicalizef16
     libc.src.math.ceilf16
     libc.src.math.copysignf16
diff --git a/libc/docs/headers/math/index.rst b/libc/docs/headers/math/index.rst
@@ -257,7 +257,7 @@ Higher Math Functions
 +-----------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+
 | asin      | |check|          |                 |                        | |check|              |                        | 7.12.4.2               | F.10.1.2                   |
 +-----------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+
-| asinh     | |check|          |                 |                        |                      |                        | 7.12.5.2               | F.10.2.2                   |
+| asinh     | |check|          |                 |                        | |check|              |                        | 7.12.5.2               | F.10.2.2                   |
 +-----------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+
 | asinpi    |                  |                 |                        |                      |                        | 7.12.4.9               | F.10.1.9                   |
 +-----------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+
diff --git a/libc/include/math.yaml b/libc/include/math.yaml
@@ -59,6 +59,13 @@ functions:
     return_type: float
     arguments:
       - type: float
+  - name: asinhf16
+    standards:
+      - stdc
+    return_type: _Float16
+    arguments:
+      - type: _Float16
+    guard: LIBC_TYPES_HAS_FLOAT16
   - name: atan
     standards:
       - stdc
diff --git a/libc/src/math/CMakeLists.txt b/libc/src/math/CMakeLists.txt
@@ -54,6 +54,7 @@ add_math_entrypoint_object(asinf16)
 
 add_math_entrypoint_object(asinh)
 add_math_entrypoint_object(asinhf)
+add_math_entrypoint_object(asinhf16)
 
 add_math_entrypoint_object(atan)
 add_math_entrypoint_object(atanf)
diff --git a/libc/src/math/asinhf16.h b/libc/src/math/asinhf16.h
@@ -0,0 +1,21 @@
+//===-- Implementation header for asinhf16 ----------------------*- 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_MATH_ASINHF16_H
+#define LLVM_LIBC_SRC_MATH_ASINHF16_H
+
+#include "src/__support/macros/config.h"
+#include "src/__support/macros/properties/types.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+float16 asinhf16(float16 x);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_MATH_ASINHF16_H
diff --git a/libc/src/math/generic/CMakeLists.txt b/libc/src/math/generic/CMakeLists.txt
@@ -3980,6 +3980,27 @@ add_entrypoint_object(
     libc.src.__support.macros.optimization
 )
 
+add_entrypoint_object(
+  asinhf16
+  SRCS
+    asinhf16.cpp
+  HDRS
+    ../asinhf16.h
+  DEPENDS
+    .explogxf
+    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.rounding_mode
+    libc.src.__support.FPUtil.sqrt
+    libc.src.__support.macros.optimization
+    libc.src.__support.macros.properties.types
+)
+
 add_entrypoint_object(
   atanhf
   SRCS
diff --git a/libc/src/math/generic/asinhf16.cpp b/libc/src/math/generic/asinhf16.cpp
@@ -0,0 +1,107 @@
+//===-- Half-precision asinh(x) 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.
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/math/asinhf16.h"
+#include "explogxf.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/rounding_mode.h"
+#include "src/__support/FPUtil/sqrt.h"
+#include "src/__support/common.h"
+#include "src/__support/macros/config.h"
+#include "src/__support/macros/optimization.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+#ifndef LIBC_MATH_HAS_SKIP_ACCURATE_PASS
+static constexpr size_t N_EXCEPTS = 8;
+
+static constexpr fputil::ExceptValues<float16, N_EXCEPTS> ASINHF16_EXCEPTS{{
+    // (input, RZ output, RU offset, RD offset, RN offset)
+
+    // x = 0x1.da4p-2, asinhf16(x) = 0x1.ca8p-2 (RZ)
+    {0x3769, 0x372a, 1, 0, 1},
+    // x = 0x1.d6cp-1, asinhf16(x) = 0x1.a58p-1 (RZ)
+    {0x3b5b, 0x3a96, 1, 0, 0},
+    // x = 0x1.c7cp+3, asinhf16(x) = 0x1.accp+1 (RZ)
+    {0x4b1f, 0x42b3, 1, 0, 0},
+    // x = 0x1.26cp+4, asinhf16(x) = 0x1.cd8p+1 (RZ)
+    {0x4c9b, 0x4336, 1, 0, 1},
+    // x = -0x1.da4p-2, asinhf16(x) = -0x1.ca8p-2 (RZ)
+    {0xb769, 0xb72a, 0, 1, 1},
+    // x = -0x1.d6cp-1, asinhf16(x) = -0x1.a58p-1 (RZ)
+    {0xbb5b, 0xba96, 0, 1, 0},
+    // x = -0x1.c7cp+3, asinhf16(x) = -0x1.accp+1 (RZ)
+    {0xcb1f, 0xc2b3, 0, 1, 0},
+    // x = -0x1.26cp+4, asinhf16(x) = -0x1.cd8p+1 (RZ)
+    {0xcc9b, 0xc336, 0, 1, 1},
+}};
+#endif // !LIBC_MATH_HAS_SKIP_ACCURATE_PASS
+
+LLVM_LIBC_FUNCTION(float16, asinhf16, (float16 x)) {
+  using FPBits = fputil::FPBits<float16>;
+  FPBits xbits(x);
+
+  uint16_t x_u = xbits.uintval();
+  uint16_t x_abs = x_u & 0x7fff;
+
+  if (LIBC_UNLIKELY(xbits.is_inf_or_nan())) {
+    if (xbits.is_signaling_nan()) {
+      fputil::raise_except_if_required(FE_INVALID);
+      return FPBits::quiet_nan().get_val();
+    }
+
+    return x;
+  }
+
+#ifndef LIBC_MATH_HAS_SKIP_ACCURATE_PASS
+  // Handle exceptional values
+  if (auto r = ASINHF16_EXCEPTS.lookup(x_u); LIBC_UNLIKELY(r.has_value()))
+    return r.value();
+#endif // !LIBC_MATH_HAS_SKIP_ACCURATE_PASS
+
+  float xf = x;
+  const float SIGN[2] = {1.0f, -1.0f};
+  float x_sign = SIGN[x_u >> 15];
+
+  // |x| <= 0.25
+  if (LIBC_UNLIKELY(x_abs <= 0x3400)) {
+    // when |x| < 0x1.718p-5, asinhf16(x) = x. Adjust by 1 ULP for certain
+    // rounding types.
+    if (LIBC_UNLIKELY(x_abs < 0x29c6)) {
+      int rounding = fputil::quick_get_round();
+      if ((rounding == FE_UPWARD || rounding == FE_TOWARDZERO) && xf < 0)
+        return fputil::cast<float16>(xf + 0x1p-24f);
+      if ((rounding == FE_DOWNWARD || rounding == FE_TOWARDZERO) && xf > 0)
+        return fputil::cast<float16>(xf - 0x1p-24f);
+      return fputil::cast<float16>(xf);
+    }
+
+    float x_sq = xf * xf;
+    // Generated by Sollya with:
+    // > P = fpminimax(asinh(x)/x, [|0, 2, 4, 6, 8|], [|SG...|], [0, 2^-2]);
+    // The last coefficient 0x1.bd114ep-6f has been changed to 0x1.bd114ep-5f
+    // for better accuracy.
+    float p = fputil::polyeval(x_sq, 1.0f, -0x1.555552p-3f, 0x1.332f6ap-4f,
+                               -0x1.6c53dep-5f, 0x1.bd114ep-5f);
+
+    return fputil::cast<float16>(xf * p);
+  }
+
+  // General case: asinh(x) = ln(x + sqrt(x^2 + 1))
+  float sqrt_term = fputil::sqrt<float>(fputil::multiply_add(xf, xf, 1.0f));
+  return fputil::cast<float16>(
+      x_sign * log_eval(fputil::multiply_add(xf, x_sign, sqrt_term)));
+}
+
+} // namespace LIBC_NAMESPACE_DECL
diff --git a/libc/test/src/math/CMakeLists.txt b/libc/test/src/math/CMakeLists.txt
@@ -2175,6 +2175,17 @@ add_fp_unittest(
     libc.src.__support.FPUtil.fp_bits
 )
 
+add_fp_unittest(
+  asinhf16_test
+  NEED_MPFR
+  SUITE
+    libc-math-unittests
+  SRCS
+    asinhf16_test.cpp
+  DEPENDS
+    libc.src.math.asinhf16
+)
+
 add_fp_unittest(
   acoshf_test
   NEED_MPFR
diff --git a/libc/test/src/math/asinhf16_test.cpp b/libc/test/src/math/asinhf16_test.cpp
@@ -0,0 +1,42 @@
+//===-- Exhaustive test for asinhf16 --------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/math/asinhf16.h"
+#include "test/UnitTest/FPMatcher.h"
+#include "test/UnitTest/Test.h"
+#include "utils/MPFRWrapper/MPFRUtils.h"
+
+using LlvmLibcAsinhf16Test = LIBC_NAMESPACE::testing::FPTest<float16>;
+
+namespace mpfr = LIBC_NAMESPACE::testing::mpfr;
+
+// Range: [0, Inf]
+static constexpr uint16_t POS_START = 0x0000U;
+static constexpr uint16_t POS_STOP = 0x7c00U;
+
+// Range: [-Inf, 0]
+static constexpr uint16_t NEG_START = 0x8000U;
+static constexpr uint16_t NEG_STOP = 0xfc00U;
+
+TEST_F(LlvmLibcAsinhf16Test, PositiveRange) {
+  for (uint16_t v = POS_START; v <= POS_STOP; ++v) {
+    float16 x = FPBits(v).get_val();
+
+    EXPECT_MPFR_MATCH_ALL_ROUNDING(mpfr::Operation::Asinh, x,
+                                   LIBC_NAMESPACE::asinhf16(x), 0.5);
+  }
+}
+
+TEST_F(LlvmLibcAsinhf16Test, NegativeRange) {
+  for (uint16_t v = NEG_START; v <= NEG_STOP; ++v) {
+    float16 x = FPBits(v).get_val();
+
+    EXPECT_MPFR_MATCH_ALL_ROUNDING(mpfr::Operation::Asinh, x,
+                                   LIBC_NAMESPACE::asinhf16(x), 0.5);
+  }
+}
diff --git a/libc/test/src/math/smoke/CMakeLists.txt b/libc/test/src/math/smoke/CMakeLists.txt
@@ -3946,6 +3946,17 @@ add_fp_unittest(
     libc.src.__support.FPUtil.fp_bits
 )
 
+add_fp_unittest(
+  asinhf16_test
+  SUITE
+    libc-math-smoke-tests
+  SRCS
+    asinhf16_test.cpp
+  DEPENDS
+    libc.src.errno.errno
+    libc.src.math.asinhf16
+)
+
 add_fp_unittest(
   acoshf_test
   SUITE
diff --git a/libc/test/src/math/smoke/asinhf16_test.cpp b/libc/test/src/math/smoke/asinhf16_test.cpp
@@ -0,0 +1,35 @@
+//===-- Unittests for asinhf16 --------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/errno/libc_errno.h"
+#include "src/math/asinhf16.h"
+#include "test/UnitTest/FPMatcher.h"
+#include "test/UnitTest/Test.h"
+
+using LlvmLibcAsinhf16Test = LIBC_NAMESPACE::testing::FPTest<float16>;
+
+TEST_F(LlvmLibcAsinhf16Test, SpecialNumbers) {
+  LIBC_NAMESPACE::libc_errno = 0;
+  EXPECT_FP_EQ(aNaN, LIBC_NAMESPACE::asinhf16(aNaN));
+  EXPECT_MATH_ERRNO(0);
+
+  EXPECT_FP_EQ_WITH_EXCEPTION(aNaN, LIBC_NAMESPACE::asinhf16(sNaN), FE_INVALID);
+  EXPECT_MATH_ERRNO(0);
+
+  EXPECT_FP_EQ(zero, LIBC_NAMESPACE::asinhf16(zero));
+  EXPECT_MATH_ERRNO(0);
+
+  EXPECT_FP_EQ(neg_zero, LIBC_NAMESPACE::asinhf16(neg_zero));
+  EXPECT_MATH_ERRNO(0);
+
+  EXPECT_FP_EQ(inf, LIBC_NAMESPACE::asinhf16(inf));
+  EXPECT_MATH_ERRNO(0);
+
+  EXPECT_FP_EQ(neg_inf, LIBC_NAMESPACE::asinhf16(neg_inf));
+  EXPECT_MATH_ERRNO(0);
+}
