[libc][math][c23] Add tanpif16 function (#115183)

wldfngrs · web-flow · commit f7bb12901e29 · 2024-11-08T09:56:31.000-05:00
- Implementation of `tan` for 16-bit floating point inputs scaled by pi.
i.e,. `tanpif16()`
- Implementation of Tanpi in MPFRWrapper for MPFR versions &lt; 4.2
- Exhaustive tests for `tanpif16()`
diff --git a/libc/config/linux/x86_64/entrypoints.txt b/libc/config/linux/x86_64/entrypoints.txt
@@ -702,6 +702,7 @@ if(LIBC_TYPES_HAS_FLOAT16)
     libc.src.math.sinpif16
     libc.src.math.sqrtf16
     libc.src.math.tanhf16
+    libc.src.math.tanpif16
     libc.src.math.totalorderf16
     libc.src.math.totalordermagf16
     libc.src.math.truncf16
diff --git a/libc/docs/math/index.rst b/libc/docs/math/index.rst
@@ -350,7 +350,7 @@ Higher Math Functions
 +-----------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+
 | tanh      | |check|          |                 |                        | |check|              |                        | 7.12.5.6               | F.10.2.6                   |
 +-----------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+
-| tanpi     |                  |                 |                        |                      |                        | 7.12.4.14              | F.10.1.14                  |
+| tanpi     |                  |                 |                        | |check|              |                        | 7.12.4.14              | F.10.1.14                  |
 +-----------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+
 | tgamma    |                  |                 |                        |                      |                        | 7.12.8.4               | F.10.5.4                   |
 +-----------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+
diff --git a/libc/newhdrgen/yaml/math.yaml b/libc/newhdrgen/yaml/math.yaml
@@ -2416,6 +2416,13 @@ functions:
     arguments:
       - type: _Float16
     guard: LIBC_TYPES_HAS_FLOAT16
+  - name: tanpif16
+    standards:
+      - stdc
+    return_type: _Float16
+    arguments:
+      - type: _Float16
+    guard: LIBC_TYPES_HAS_FLOAT16
   - name: totalorder
     standards:
       - stdc
diff --git a/libc/src/math/CMakeLists.txt b/libc/src/math/CMakeLists.txt
@@ -503,6 +503,7 @@ add_math_entrypoint_object(tanf)
 add_math_entrypoint_object(tanh)
 add_math_entrypoint_object(tanhf)
 add_math_entrypoint_object(tanhf16)
+add_math_entrypoint_object(tanpif16)
 
 add_math_entrypoint_object(tgamma)
 add_math_entrypoint_object(tgammaf)
diff --git a/libc/src/math/cospif16.h b/libc/src/math/cospif16.h
@@ -18,4 +18,4 @@ float16 cospif16(float16 x);
 
 } // namespace LIBC_NAMESPACE_DECL
 
-#endif // LLVM_LIBC_SRC_MATH_SINPIF16_H
+#endif // LLVM_LIBC_SRC_MATH_COSPIF16_H
diff --git a/libc/src/math/generic/CMakeLists.txt b/libc/src/math/generic/CMakeLists.txt
@@ -620,6 +620,26 @@ add_entrypoint_object(
     -O3
 )
 
+add_entrypoint_object(
+  tanpif16
+  SRCS
+    tanpif16.cpp
+  HDRS
+    ../tanpif16.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
+  COMPILE_OPTIONS
+    -O3
+)
+
 add_entrypoint_object(
   fabs
   SRCS
diff --git a/libc/src/math/generic/cospif16.cpp b/libc/src/math/generic/cospif16.cpp
@@ -37,7 +37,7 @@ LLVM_LIBC_FUNCTION(float16, cospif16, (float16 x)) {
   //   k = round(x * 32)
   //   y = x * 32 - k
   //
-  // Once k and y are computed, we then deduce the answer by the sine of sum
+  // Once k and y are computed, we then deduce the answer by the cosine of sum
   // formula:
   //   cos(x * pi) = cos((k + y) * pi/32)
   //               = cos(k * pi/32) * cos(y * pi/32) +
diff --git a/libc/src/math/generic/tanpif16.cpp b/libc/src/math/generic/tanpif16.cpp
@@ -0,0 +1,103 @@
+//===-- Half-precision tanpif 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/tanpif16.h"
+#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 {
+
+constexpr size_t N_EXCEPTS = 21;
+
+constexpr fputil::ExceptValues<float16, N_EXCEPTS> TANF16_EXCEPTS{{
+    // (input, RZ output, RU offset, RD offset, RN offset)
+    {0x07f2, 0x0e3d, 1, 0, 0}, {0x086a, 0x0eee, 1, 0, 1},
+    {0x08db, 0x0fa0, 1, 0, 0}, {0x094c, 0x1029, 1, 0, 0},
+    {0x0b10, 0x118c, 1, 0, 0}, {0x1ce0, 0x23a8, 1, 0, 1},
+    {0x1235, 0x18e0, 1, 0, 0}, {0x2579, 0x2c4e, 1, 0, 0},
+    {0x28b2, 0x2f68, 1, 0, 1}, {0x2a43, 0x30f4, 1, 0, 1},
+    {0x31b7, 0x3907, 1, 0, 0}, {0x329d, 0x3a12, 1, 0, 1},
+    {0x34f1, 0x3dd7, 1, 0, 0}, {0x3658, 0x41ee, 1, 0, 0},
+    {0x38d4, 0xc1ee, 0, 1, 0}, {0x3d96, 0x41ee, 1, 0, 0},
+    {0x3e6a, 0xc1ee, 0, 1, 0}, {0x40cb, 0x41ee, 1, 0, 0},
+    {0x4135, 0xc1ee, 0, 1, 0}, {0x42cb, 0x41ee, 1, 0, 0},
+    {0x4335, 0xc1ee, 0, 1, 0},
+}};
+
+LLVM_LIBC_FUNCTION(float16, tanpif16, (float16 x)) {
+  using FPBits = typename fputil::FPBits<float16>;
+  FPBits xbits(x);
+
+  uint16_t x_u = xbits.uintval();
+  uint16_t x_abs = x_u & 0x7fff;
+
+  // Handle exceptional values
+  if (LIBC_UNLIKELY(x_abs <= 0x4335)) {
+    if (LIBC_UNLIKELY(x_abs == 0U))
+      return x;
+
+    bool x_sign = x_u >> 15;
+    if (auto r = TANF16_EXCEPTS.lookup_odd(x_abs, x_sign);
+        LIBC_UNLIKELY(r.has_value()))
+      return r.value();
+  }
+
+  // Numbers greater or equal to 2^10 are integers, or infinity, or NaN
+  if (LIBC_UNLIKELY(x_abs >= 0x6400)) {
+    // Check for NaN or infinity values
+    if (LIBC_UNLIKELY(x_abs >= 0x7c00)) {
+      if (x_abs == 0x7c00) {
+        fputil::set_errno_if_required(EDOM);
+        fputil::raise_except_if_required(FE_INVALID);
+      }
+
+      return x + FPBits::quiet_nan().get_val();
+    }
+
+    return FPBits::zero(xbits.sign()).get_val();
+  }
+  // Range reduction:
+  // For |x| > 1/32, we perform range reduction as follows:
+  // Find k and y such that:
+  //   x = (k + y) * 1/32
+  //   k is an integer
+  //   |y| < 0.5
+  //
+  // This is done by performing:
+  //   k = round(x * 32)
+  //   y = x * 32 - k
+  //
+  // Once k and y are computed, we then deduce the answer by tthe formula:
+  // tan(x) = sin(x) / cos(x)
+  //        = (sin_y * cos_k + cos_y * sin_k) / (cos_y * cos_k - sin_y * sin_k)
+  float xf = x;
+  float sin_k, cos_k, sin_y, cosm1_y;
+  sincospif16_eval(xf, sin_k, cos_k, sin_y, cosm1_y);
+
+  if (LIBC_UNLIKELY(sin_y == 0 && cos_k == 0)) {
+    fputil::set_errno_if_required(EDOM);
+    fputil::raise_except_if_required(FE_DIVBYZERO);
+
+    int16_t x_mp5_u = static_cast<int16_t>(x - 0.5);
+    return ((x_mp5_u & 0x1) ? -1 : 1) * FPBits::inf().get_val();
+  }
+
+  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 LIBC_NAMESPACE_DECL
diff --git a/libc/src/math/tanpif16.h b/libc/src/math/tanpif16.h
@@ -0,0 +1,21 @@
+//===-- Implementation header for tanpif16 ----------------------*- 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_TANPIF16_H
+#define LLVM_LIBC_SRC_MATH_TANPIF16_H
+
+#include "src/__support/macros/config.h"
+#include "src/__support/macros/properties/types.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+float16 tanpif16(float16 x);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_MATH_TANPIF16_H
diff --git a/libc/test/src/math/CMakeLists.txt b/libc/test/src/math/CMakeLists.txt
@@ -168,6 +168,17 @@ add_fp_unittest(
     libc.src.__support.FPUtil.fp_bits
 )
 
+add_fp_unittest(
+  tanpif16_test
+  NEED_MPFR
+  SUITE
+    libc-math-unittests
+  SRCS
+    tanpif16_test.cpp
+  DEPENDS
+    libc.src.math.tanpif16
+)
+
 add_fp_unittest(
   fabs_test
   NEED_MPFR
diff --git a/libc/test/src/math/smoke/CMakeLists.txt b/libc/test/src/math/smoke/CMakeLists.txt
@@ -99,6 +99,17 @@ add_fp_unittest(
     libc.src.__support.FPUtil.fp_bits
 )
 
+add_fp_unittest(
+  tanpif16_test
+  SUITE
+    libc-math-smoke-tests
+  SRCS
+    tanpif16_test.cpp
+  DEPENDS
+    libc.src.errno.errno
+    libc.src.math.tanpif16
+)
+
 add_fp_unittest(
   fabs_test
   SUITE
diff --git a/libc/test/src/math/smoke/tanpif16_test.cpp b/libc/test/src/math/smoke/tanpif16_test.cpp
@@ -0,0 +1,33 @@
+//===-- Unittests for tanpif16 --------------------------------------------===//
+//
+// 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/tanpif16.h"
+#include "test/UnitTest/FPMatcher.h"
+#include "test/UnitTest/Test.h"
+
+using LlvmLibcTanpif16Test = LIBC_NAMESPACE::testing::FPTest<float16>;
+
+TEST_F(LlvmLibcTanpif16Test, SpecialNumbers) {
+  LIBC_NAMESPACE::libc_errno = 0;
+
+  EXPECT_FP_EQ(aNaN, LIBC_NAMESPACE::tanpif16(aNaN));
+  EXPECT_MATH_ERRNO(0);
+
+  EXPECT_FP_EQ(zero, LIBC_NAMESPACE::tanpif16(zero));
+  EXPECT_MATH_ERRNO(0);
+
+  EXPECT_FP_EQ(neg_zero, LIBC_NAMESPACE::tanpif16(neg_zero));
+  EXPECT_MATH_ERRNO(0);
+
+  EXPECT_FP_EQ(aNaN, LIBC_NAMESPACE::tanpif16(inf));
+  EXPECT_MATH_ERRNO(EDOM);
+
+  EXPECT_FP_EQ(aNaN, LIBC_NAMESPACE::tanpif16(neg_inf));
+  EXPECT_MATH_ERRNO(EDOM);
+}
diff --git a/libc/test/src/math/tanpif16_test.cpp b/libc/test/src/math/tanpif16_test.cpp
@@ -0,0 +1,40 @@
+//===-- Exhaustive test for cospif16 --------------------------------------===//
+//
+// 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/tanpif16.h"
+#include "test/UnitTest/FPMatcher.h"
+#include "test/UnitTest/Test.h"
+#include "utils/MPFRWrapper/MPFRUtils.h"
+
+using LlvmLibcTanpif16Test = 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(LlvmLibcTanpif16Test, PositiveRange) {
+  for (uint16_t v = POS_START; v <= POS_STOP; ++v) {
+    float16 x = FPBits(v).get_val();
+    EXPECT_MPFR_MATCH_ALL_ROUNDING(mpfr::Operation::Tanpi, x,
+                                   LIBC_NAMESPACE::tanpif16(x), 0.5);
+  }
+}
+
+TEST_F(LlvmLibcTanpif16Test, NegativeRange) {
+  for (uint16_t v = NEG_START; v <= NEG_STOP; ++v) {
+    float16 x = FPBits(v).get_val();
+    EXPECT_MPFR_MATCH_ALL_ROUNDING(mpfr::Operation::Tanpi, x,
+                                   LIBC_NAMESPACE::tanpif16(x), 0.5);
+  }
+}
diff --git a/libc/utils/MPFRWrapper/MPFRUtils.cpp b/libc/utils/MPFRWrapper/MPFRUtils.cpp
@@ -560,6 +560,56 @@ class MPFRNumber {
     return result;
   }
 
+  MPFRNumber tanpi() const {
+    MPFRNumber result(*this);
+
+#if MPFR_VERSION_MAJOR > 4 ||                                                  \
+    (MPFR_VERSION_MAJOR == 4 && MPFR_VERSION_MINOR >= 2)
+
+    mpfr_tanpi(result.value, value, mpfr_rounding);
+    return result;
+#else
+    MPFRNumber value_ret_exact(*this);
+    MPFRNumber value_one(*this);
+    mpfr_set_si(value_one.value, 1, MPFR_RNDN);
+    mpfr_fmod(value_ret_exact.value, value, value_one.value, mpfr_rounding);
+    mpfr_mul_si(value_ret_exact.value, value_ret_exact.value, 4, MPFR_RNDN);
+
+    if (mpfr_integer_p(value_ret_exact.value)) {
+      int mod = mpfr_get_si(value_ret_exact.value, MPFR_RNDN);
+      mod = (mod < 0 ? -1 * mod : mod);
+
+      switch (mod) {
+      case 0:
+        mpfr_set_si(result.value, 0, mpfr_rounding);
+        break;
+      case 1:
+        mpfr_set_si(result.value, (mpfr_signbit(value) ? -1 : 1),
+                    mpfr_rounding);
+        break;
+      case 2: {
+        auto d = mpfr_get_si(value, MPFR_RNDZ);
+        d += mpfr_sgn(value) > 0 ? 0 : 1;
+        mpfr_set_inf(result.value, (d & 1) ? -1 : 1);
+        break;
+      }
+      case 3:
+        mpfr_set_si(result.value, (mpfr_signbit(value) ? 1 : -1),
+                    mpfr_rounding);
+        break;
+      }
+
+      return result;
+    }
+
+    MPFRNumber value_pi(0.0, 1280);
+    mpfr_const_pi(value_pi.value, MPFR_RNDN);
+    mpfr_mul(value_pi.value, value_pi.value, value, MPFR_RNDN);
+    mpfr_tan(result.value, value_pi.value, mpfr_rounding);
+    return result;
+#endif
+  }
+
   MPFRNumber trunc() const {
     MPFRNumber result(*this);
     mpfr_trunc(result.value, value);
@@ -798,6 +848,8 @@ unary_operation(Operation op, InputType input, unsigned int precision,
     return mpfrInput.tan();
   case Operation::Tanh:
     return mpfrInput.tanh();
+  case Operation::Tanpi:
+    return mpfrInput.tanpi();
   case Operation::Trunc:
     return mpfrInput.trunc();
   default:
diff --git a/libc/utils/MPFRWrapper/MPFRUtils.h b/libc/utils/MPFRWrapper/MPFRUtils.h
@@ -60,6 +60,7 @@ enum class Operation : int {
   Sqrt,
   Tan,
   Tanh,
+  Tanpi,
   Trunc,
   EndUnaryOperationsSingleOutput,
 

Original file line number	Diff line number	Diff line change
`@@ -18,4 +18,4 @@ float16 cospif16(float16 x);`
`18`	`18`
`19`	`19`	`} // namespace LIBC_NAMESPACE_DECL`
`20`	`20`
`21`		`-#endif // LLVM_LIBC_SRC_MATH_SINPIF16_H`
	`21`	`+#endif // LLVM_LIBC_SRC_MATH_COSPIF16_H`
-Original file line number
+Diff line change
   Sqrt,
   Tan,
   Tanh,
 +  Tanpi,
   Trunc,
   EndUnaryOperationsSingleOutput,