[libc][math][c23] implement C23 math function tanpif (#147192)

c8ef · web-flow · commit c3abe3ff2263 · 2025-07-12T12:39:33.000+08:00
The smoke test and exhaustive test pass on x86_64 Linux. Closes #94895.
diff --git a/libc/config/darwin/aarch64/entrypoints.txt b/libc/config/darwin/aarch64/entrypoints.txt
@@ -363,6 +363,7 @@ set(TARGET_LIBM_ENTRYPOINTS
     libc.src.math.tan
     libc.src.math.tanf
     libc.src.math.tanhf
+    libc.src.math.tanpif
     libc.src.math.totalorder
     libc.src.math.totalorderf
     libc.src.math.totalorderl
diff --git a/libc/config/linux/aarch64/entrypoints.txt b/libc/config/linux/aarch64/entrypoints.txt
@@ -625,6 +625,7 @@ set(TARGET_LIBM_ENTRYPOINTS
     libc.src.math.tan
     libc.src.math.tanf
     libc.src.math.tanhf
+    libc.src.math.tanpif
     libc.src.math.totalorder
     libc.src.math.totalorderf
     libc.src.math.totalorderl
diff --git a/libc/config/linux/arm/entrypoints.txt b/libc/config/linux/arm/entrypoints.txt
@@ -437,6 +437,7 @@ set(TARGET_LIBM_ENTRYPOINTS
     libc.src.math.tan
     libc.src.math.tanf
     libc.src.math.tanhf
+    libc.src.math.tanpif
     libc.src.math.totalorder
     libc.src.math.totalorderf
     libc.src.math.totalorderl
diff --git a/libc/config/linux/riscv/entrypoints.txt b/libc/config/linux/riscv/entrypoints.txt
@@ -635,6 +635,7 @@ set(TARGET_LIBM_ENTRYPOINTS
     libc.src.math.tan
     libc.src.math.tanf
     libc.src.math.tanhf
+    libc.src.math.tanpif
     libc.src.math.totalorder
     libc.src.math.totalorderf
     libc.src.math.totalorderl
diff --git a/libc/config/linux/x86_64/entrypoints.txt b/libc/config/linux/x86_64/entrypoints.txt
@@ -659,6 +659,7 @@ set(TARGET_LIBM_ENTRYPOINTS
     libc.src.math.tan
     libc.src.math.tanf
     libc.src.math.tanhf
+    libc.src.math.tanpif
     libc.src.math.totalorder
     libc.src.math.totalorderf
     libc.src.math.totalorderl
diff --git a/libc/config/windows/entrypoints.txt b/libc/config/windows/entrypoints.txt
@@ -295,6 +295,7 @@ set(TARGET_LIBM_ENTRYPOINTS
     libc.src.math.tan
     libc.src.math.tanf
     libc.src.math.tanhf
+    libc.src.math.tanpif
     libc.src.math.trunc
     libc.src.math.truncf
     libc.src.math.truncl
diff --git a/libc/docs/headers/math/index.rst b/libc/docs/headers/math/index.rst
@@ -349,7 +349,7 @@ Higher Math Functions
 +-----------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+
 | tanh      | |check|          |                 |                        | |check|              |                        | 7.12.5.6               | F.10.2.6                   |
 +-----------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+
-| tanpi     |                  |                 |                        | |check|              |                        | 7.12.4.14              | F.10.1.14                  |
+| tanpi     | |check|          |                 |                        | |check|              |                        | 7.12.4.14              | F.10.1.14                  |
 +-----------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+
 | tgamma    |                  |                 |                        |                      |                        | 7.12.8.4               | F.10.5.4                   |
 +-----------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+
diff --git a/libc/include/math.yaml b/libc/include/math.yaml
@@ -2524,6 +2524,12 @@ functions:
     arguments:
       - type: _Float16
     guard: LIBC_TYPES_HAS_FLOAT16
+  - name: tanpif
+    standards:
+      - stdc
+    return_type: float
+    arguments:
+      - type: float
   - name: tanpif16
     standards:
       - stdc
diff --git a/libc/src/math/CMakeLists.txt b/libc/src/math/CMakeLists.txt
@@ -519,6 +519,8 @@ add_math_entrypoint_object(tanf16)
 add_math_entrypoint_object(tanh)
 add_math_entrypoint_object(tanhf)
 add_math_entrypoint_object(tanhf16)
+
+add_math_entrypoint_object(tanpif)
 add_math_entrypoint_object(tanpif16)
 
 add_math_entrypoint_object(tgamma)
diff --git a/libc/src/math/generic/CMakeLists.txt b/libc/src/math/generic/CMakeLists.txt
@@ -606,6 +606,21 @@ add_entrypoint_object(
     libc.src.__support.macros.properties.types
 )
 
+add_entrypoint_object(
+  tanpif
+  SRCS
+    tanpif.cpp
+  HDRS
+    ../tanpif.h
+  DEPENDS
+    .sincosf_utils
+    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.macros.optimization
+)
+
 add_entrypoint_object(
   tanpif16
   SRCS
diff --git a/libc/src/math/generic/tanpif.cpp b/libc/src/math/generic/tanpif.cpp
@@ -0,0 +1,106 @@
+//===-- Single-precision tanpi 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/tanpif.h"
+#include "sincosf_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/common.h"
+#include "src/__support/macros/config.h"
+#include "src/__support/macros/optimization.h" // LIBC_UNLIKELY
+
+namespace LIBC_NAMESPACE_DECL {
+
+#ifndef LIBC_MATH_HAS_SKIP_ACCURATE_PASS
+constexpr size_t N_EXCEPTS = 3;
+
+constexpr fputil::ExceptValues<float, N_EXCEPTS> TANPIF_EXCEPTS{{
+    // (input, RZ output, RU offset, RD offset, RN offset)
+    {0x38F26685, 0x39BE6182, 1, 0, 0},
+    {0x3E933802, 0x3FA267DD, 1, 0, 0},
+    {0x3F3663FF, 0xBFA267DD, 0, 1, 0},
+}};
+#endif // !LIBC_MATH_HAS_SKIP_ACCURATE_PASS
+
+LLVM_LIBC_FUNCTION(float, tanpif, (float x)) {
+  using FPBits = typename fputil::FPBits<float>;
+  FPBits xbits(x);
+
+  uint32_t x_u = xbits.uintval();
+  uint32_t x_abs = x_u & 0x7fff'ffffU;
+  double xd = static_cast<double>(xbits.get_val());
+
+  // Handle exceptional values
+  if (LIBC_UNLIKELY(x_abs <= 0x3F3663FF)) {
+    if (LIBC_UNLIKELY(x_abs == 0U))
+      return x;
+
+#ifndef LIBC_MATH_HAS_SKIP_ACCURATE_PASS
+    bool x_sign = x_u >> 31;
+
+    if (auto r = TANPIF_EXCEPTS.lookup_odd(x_abs, x_sign);
+        LIBC_UNLIKELY(r.has_value()))
+      return r.value();
+#endif // !LIBC_MATH_HAS_SKIP_ACCURATE_PASS
+  }
+
+  // Numbers greater or equal to 2^23 are always integers, or infinity, or NaN
+  if (LIBC_UNLIKELY(x_abs >= 0x4B00'0000)) {
+    // x is inf or NaN.
+    if (LIBC_UNLIKELY(x_abs >= 0x7f80'0000U)) {
+      if (xbits.is_signaling_nan()) {
+        fputil::raise_except_if_required(FE_INVALID);
+        return FPBits::quiet_nan().get_val();
+      }
+
+      if (x_abs == 0x7f80'0000U) {
+        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 the formula:
+  // tan(x) = sin(x) / cos(x)
+  //        = (sin_y * cos_k + cos_y * sin_k) / (cos_y * cos_k - sin_y * sin_k)
+  double sin_k, cos_k, sin_y, cosm1_y;
+  sincospif_eval(xd, 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);
+
+    int32_t x_mp5_i = static_cast<int32_t>(xd - 0.5);
+    return FPBits::inf((x_mp5_i & 0x1) ? Sign::NEG : Sign::POS).get_val();
+  }
+
+  using fputil::multiply_add;
+  return fputil::cast<float>(
+      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/tanpif.h b/libc/src/math/tanpif.h
@@ -0,0 +1,20 @@
+//===-- Implementation header for tanpif ------------------------*- 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_TANPIF_H
+#define LLVM_LIBC_SRC_MATH_TANPIF_H
+
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+float tanpif(float x);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_MATH_TANPIF_H
diff --git a/libc/test/src/math/CMakeLists.txt b/libc/test/src/math/CMakeLists.txt
@@ -201,6 +201,21 @@ add_fp_unittest(
     libc.src.math.tanf16
 )
 
+add_fp_unittest(
+  tanpif_test
+  NEED_MPFR
+  SUITE
+    libc-math-unittests
+  SRCS
+    tanpif_test.cpp
+  HDRS
+    sdcomp26094.h
+  DEPENDS
+    libc.src.math.tanpif
+    libc.src.__support.CPP.array
+    libc.src.__support.FPUtil.fp_bits
+)
+
 add_fp_unittest(
   tanpif16_test
   NEED_MPFR
diff --git a/libc/test/src/math/exhaustive/CMakeLists.txt b/libc/test/src/math/exhaustive/CMakeLists.txt
@@ -122,6 +122,22 @@ add_fp_unittest(
     -lpthread
 )
 
+add_fp_unittest(
+  tanpif_test
+  NO_RUN_POSTBUILD
+  NEED_MPFR
+  SUITE
+    libc_math_exhaustive_tests
+  SRCS
+    tanpif_test.cpp
+  DEPENDS
+    .exhaustive_test
+    libc.src.math.tanpif
+    libc.src.__support.FPUtil.fp_bits
+  LINK_LIBRARIES
+    -lpthread
+)
+
 add_fp_unittest(
   erff_test
   NO_RUN_POSTBUILD
diff --git a/libc/test/src/math/exhaustive/tanpif_test.cpp b/libc/test/src/math/exhaustive/tanpif_test.cpp
@@ -0,0 +1,33 @@
+//===-- Exhaustive test for tanpif ----------------------------------------===//
+//
+// 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 "exhaustive_test.h"
+#include "src/math/tanpif.h"
+#include "utils/MPFRWrapper/MPFRUtils.h"
+
+namespace mpfr = LIBC_NAMESPACE::testing::mpfr;
+
+using LlvmLibcTanpifExhaustiveTest =
+    LlvmLibcUnaryOpExhaustiveMathTest<float, mpfr::Operation::Tanpi,
+                                      LIBC_NAMESPACE::tanpif>;
+
+// Range: [0, Inf];
+static constexpr uint32_t POS_START = 0x0000'0000U;
+static constexpr uint32_t POS_STOP = 0x7f80'0000U;
+
+TEST_F(LlvmLibcTanpifExhaustiveTest, PostiveRange) {
+  test_full_range_all_roundings(POS_START, POS_STOP);
+}
+
+// Range: [-Inf, 0];
+static constexpr uint32_t NEG_START = 0xb000'0000U;
+static constexpr uint32_t NEG_STOP = 0xff80'0000U;
+
+TEST_F(LlvmLibcTanpifExhaustiveTest, NegativeRange) {
+  test_full_range_all_roundings(NEG_START, NEG_STOP);
+}
diff --git a/libc/test/src/math/smoke/CMakeLists.txt b/libc/test/src/math/smoke/CMakeLists.txt
@@ -134,6 +134,17 @@ add_fp_unittest(
     libc.src.math.tanf16
 )
 
+add_fp_unittest(
+  tanpif_test
+  SUITE
+    libc-math-smoke-tests
+  SRCS
+    tanpif_test.cpp
+  DEPENDS
+    libc.src.errno.errno
+    libc.src.math.tanpif
+)
+
 add_fp_unittest(
   tanpif16_test
   SUITE
diff --git a/libc/test/src/math/smoke/tanpif_test.cpp b/libc/test/src/math/smoke/tanpif_test.cpp
@@ -0,0 +1,36 @@
+//===-- Unittests for tanpif ----------------------------------------------===//
+//
+// 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/__support/libc_errno.h"
+#include "src/math/tanpif.h"
+#include "test/UnitTest/FPMatcher.h"
+#include "test/UnitTest/Test.h"
+
+using LlvmLibcTanpifTest = LIBC_NAMESPACE::testing::FPTest<float>;
+
+TEST_F(LlvmLibcTanpifTest, SpecialNumbers) {
+  libc_errno = 0;
+
+  EXPECT_FP_EQ_WITH_EXCEPTION(aNaN, LIBC_NAMESPACE::tanpif(sNaN), FE_INVALID);
+  EXPECT_MATH_ERRNO(0);
+
+  EXPECT_FP_EQ(aNaN, LIBC_NAMESPACE::tanpif(aNaN));
+  EXPECT_MATH_ERRNO(0);
+
+  EXPECT_FP_EQ(zero, LIBC_NAMESPACE::tanpif(zero));
+  EXPECT_MATH_ERRNO(0);
+
+  EXPECT_FP_EQ(neg_zero, LIBC_NAMESPACE::tanpif(neg_zero));
+  EXPECT_MATH_ERRNO(0);
+
+  EXPECT_FP_EQ(aNaN, LIBC_NAMESPACE::tanpif(inf));
+  EXPECT_MATH_ERRNO(EDOM);
+
+  EXPECT_FP_EQ(aNaN, LIBC_NAMESPACE::tanpif(neg_inf));
+  EXPECT_MATH_ERRNO(EDOM);
+}
diff --git a/libc/test/src/math/tanpif_test.cpp b/libc/test/src/math/tanpif_test.cpp
