[libc-commits] [libc] ea93c53 - [libc][math][c23] Implemented sinpif function correctly rounded for all rounding modes. (#97149)

via libc-commits libc-commits at lists.llvm.org
Mon Jul 1 13:38:08 PDT 2024


Author: Hendrik Hübner
Date: 2024-07-01T16:38:03-04:00
New Revision: ea93c538c78ed191f83026d372bd71dd4a135cbc

URL: https://github.com/llvm/llvm-project/commit/ea93c538c78ed191f83026d372bd71dd4a135cbc
DIFF: https://github.com/llvm/llvm-project/commit/ea93c538c78ed191f83026d372bd71dd4a135cbc.diff

LOG: [libc][math][c23] Implemented sinpif function correctly rounded for all rounding modes. (#97149)

This implements the sinpif function. An exhaustive test shows it's
correct for all rounding modes.

Issue:  #94895

Added: 
    libc/src/math/generic/sinpif.cpp
    libc/src/math/sinpif.h
    libc/test/src/math/exhaustive/sinpif_test.cpp
    libc/test/src/math/sinpif_test.cpp
    libc/test/src/math/smoke/sinpif_test.cpp

Modified: 
    libc/config/darwin/arm/entrypoints.txt
    libc/config/linux/aarch64/entrypoints.txt
    libc/config/linux/riscv/entrypoints.txt
    libc/config/linux/x86_64/entrypoints.txt
    libc/docs/math/index.rst
    libc/src/math/CMakeLists.txt
    libc/src/math/generic/CMakeLists.txt
    libc/src/math/generic/range_reduction_fma.h
    libc/src/math/generic/sincosf_utils.h
    libc/test/src/math/CMakeLists.txt
    libc/test/src/math/exhaustive/CMakeLists.txt
    libc/test/src/math/smoke/CMakeLists.txt
    libc/utils/MPFRWrapper/MPFRUtils.cpp
    libc/utils/MPFRWrapper/MPFRUtils.h

Removed: 
    


################################################################################
diff  --git a/libc/config/darwin/arm/entrypoints.txt b/libc/config/darwin/arm/entrypoints.txt
index 4d5536318724d..cb4603c79c79c 100644
--- a/libc/config/darwin/arm/entrypoints.txt
+++ b/libc/config/darwin/arm/entrypoints.txt
@@ -230,6 +230,7 @@ set(TARGET_LIBM_ENTRYPOINTS
     libc.src.math.sinhf
     libc.src.math.sin
     libc.src.math.sinf
+    libc.src.math.sinpif
     libc.src.math.sqrt
     libc.src.math.sqrtf
     libc.src.math.sqrtl

diff  --git a/libc/config/linux/aarch64/entrypoints.txt b/libc/config/linux/aarch64/entrypoints.txt
index ea89f8bd138d6..07fdbfdbcd7c9 100644
--- a/libc/config/linux/aarch64/entrypoints.txt
+++ b/libc/config/linux/aarch64/entrypoints.txt
@@ -485,6 +485,7 @@ set(TARGET_LIBM_ENTRYPOINTS
     libc.src.math.sincosf
     libc.src.math.sinf
     libc.src.math.sinhf
+    libc.src.math.sinpif
     libc.src.math.sqrt
     libc.src.math.sqrtf
     libc.src.math.sqrtl

diff  --git a/libc/config/linux/riscv/entrypoints.txt b/libc/config/linux/riscv/entrypoints.txt
index ee8b3d531637e..51d85eed9ff16 100644
--- a/libc/config/linux/riscv/entrypoints.txt
+++ b/libc/config/linux/riscv/entrypoints.txt
@@ -493,6 +493,7 @@ set(TARGET_LIBM_ENTRYPOINTS
     libc.src.math.sincosf
     libc.src.math.sinf
     libc.src.math.sinhf
+    libc.src.math.sinpif
     libc.src.math.sqrt
     libc.src.math.sqrtf
     libc.src.math.sqrtl

diff  --git a/libc/config/linux/x86_64/entrypoints.txt b/libc/config/linux/x86_64/entrypoints.txt
index 9f67dea006699..89f9011a52b64 100644
--- a/libc/config/linux/x86_64/entrypoints.txt
+++ b/libc/config/linux/x86_64/entrypoints.txt
@@ -514,6 +514,7 @@ set(TARGET_LIBM_ENTRYPOINTS
     libc.src.math.sincosf
     libc.src.math.sinf
     libc.src.math.sinhf
+    libc.src.math.sinpif
     libc.src.math.sqrt
     libc.src.math.sqrtf
     libc.src.math.sqrtl

diff  --git a/libc/docs/math/index.rst b/libc/docs/math/index.rst
index 3ca7bf9fdb283..ccafb1f9c73fc 100644
--- a/libc/docs/math/index.rst
+++ b/libc/docs/math/index.rst
@@ -330,7 +330,7 @@ Higher Math Functions
 +-----------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+
 | sinh      | |check|          |                 |                        |                      |                        | 7.12.5.5               | F.10.2.5                   |
 +-----------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+
-| sinpi     |                  |                 |                        |                      |                        | 7.12.4.13              | F.10.1.13                  |
+| sinpi     | |check|          |                 |                        |                      |                        | 7.12.4.13              | F.10.1.13                  |
 +-----------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+
 | sqrt      | |check|          | |check|         | |check|                |                      | |check|                | 7.12.7.10              | F.10.4.10                  |
 +-----------+------------------+-----------------+------------------------+----------------------+------------------------+------------------------+----------------------------+

diff  --git a/libc/src/math/CMakeLists.txt b/libc/src/math/CMakeLists.txt
index 4777f669f0cb5..607051a6ad78d 100644
--- a/libc/src/math/CMakeLists.txt
+++ b/libc/src/math/CMakeLists.txt
@@ -376,6 +376,7 @@ add_math_entrypoint_object(sincosf)
 
 add_math_entrypoint_object(sin)
 add_math_entrypoint_object(sinf)
+add_math_entrypoint_object(sinpif)
 
 add_math_entrypoint_object(sinh)
 add_math_entrypoint_object(sinhf)

diff  --git a/libc/src/math/generic/CMakeLists.txt b/libc/src/math/generic/CMakeLists.txt
index 7dd6c4812fa15..395d4f8cc9270 100644
--- a/libc/src/math/generic/CMakeLists.txt
+++ b/libc/src/math/generic/CMakeLists.txt
@@ -283,6 +283,25 @@ add_entrypoint_object(
     -O3
 )
 
+add_entrypoint_object(
+  sinpif
+  SRCS
+    sinpif.cpp
+  HDRS
+    ../sinpif.h
+  DEPENDS
+    .sincosf_utils
+    libc.src.__support.FPUtil.fenv_impl
+    libc.src.__support.FPUtil.fp_bits
+    libc.src.__support.FPUtil.fma
+    libc.src.__support.FPUtil.multiply_add
+    libc.src.__support.FPUtil.polyeval
+    libc.src.__support.common
+    libc.src.__support.macros.optimization
+  COMPILE_OPTIONS
+    -O3
+)
+
 add_entrypoint_object(
   sincosf
   SRCS

diff  --git a/libc/src/math/generic/range_reduction_fma.h b/libc/src/math/generic/range_reduction_fma.h
index 82b4ae1c705e1..97b9e3d0f89db 100644
--- a/libc/src/math/generic/range_reduction_fma.h
+++ b/libc/src/math/generic/range_reduction_fma.h
@@ -12,7 +12,6 @@
 #include "src/__support/FPUtil/FMA.h"
 #include "src/__support/FPUtil/FPBits.h"
 #include "src/__support/FPUtil/nearest_integer.h"
-#include "src/__support/common.h"
 
 namespace LIBC_NAMESPACE {
 

diff  --git a/libc/src/math/generic/sincosf_utils.h b/libc/src/math/generic/sincosf_utils.h
index 904df4f4ed08e..f20fb6a05a324 100644
--- a/libc/src/math/generic/sincosf_utils.h
+++ b/libc/src/math/generic/sincosf_utils.h
@@ -19,6 +19,7 @@
 using LIBC_NAMESPACE::fma::FAST_PASS_BOUND;
 using LIBC_NAMESPACE::fma::large_range_reduction;
 using LIBC_NAMESPACE::fma::small_range_reduction;
+
 #else
 #include "range_reduction.h"
 // using namespace LIBC_NAMESPACE::generic;
@@ -58,18 +59,9 @@ const double SIN_K_PI_OVER_32[64] = {
     -0x1.917a6bc29b42cp-4,
 };
 
-LIBC_INLINE void sincosf_eval(double xd, uint32_t x_abs, double &sin_k,
-                              double &cos_k, double &sin_y, double &cosm1_y) {
-  int64_t k;
-  double y;
-
-  if (LIBC_LIKELY(x_abs < FAST_PASS_BOUND)) {
-    k = small_range_reduction(xd, y);
-  } else {
-    fputil::FPBits<float> x_bits(x_abs);
-    k = large_range_reduction(xd, x_bits.get_exponent(), y);
-  }
-
+static LIBC_INLINE void sincosf_poly_eval(int64_t k, double y, double &sin_k,
+                                          double &cos_k, double &sin_y,
+                                          double &cosm1_y) {
   // After range reduction, k = round(x * 32 / pi) and y = (x * 32 / pi) - k.
   // So k is an integer and -0.5 <= y <= 0.5.
   // Then sin(x) = sin((k + y)*pi/32)
@@ -95,6 +87,38 @@ LIBC_INLINE void sincosf_eval(double xd, uint32_t x_abs, double &sin_k,
                                    0x1.03c1f070c2e27p-18, -0x1.55cc84bd942p-30);
 }
 
+LIBC_INLINE void sincosf_eval(double xd, uint32_t x_abs, double &sin_k,
+                              double &cos_k, double &sin_y, double &cosm1_y) {
+  int64_t k;
+  double y;
+
+  if (LIBC_LIKELY(x_abs < FAST_PASS_BOUND)) {
+    k = small_range_reduction(xd, y);
+  } else {
+    fputil::FPBits<float> x_bits(x_abs);
+    k = large_range_reduction(xd, x_bits.get_exponent(), y);
+  }
+
+  sincosf_poly_eval(k, y, sin_k, cos_k, sin_y, cosm1_y);
+}
+
+// Return k and y, where
+//   k = round(x * 32) and y = (x * 32) - k.
+//   => pi * x = (k + y) * pi / 32
+static LIBC_INLINE int64_t range_reduction_sincospi(double x, double &y) {
+  double kd = fputil::nearest_integer(x * 32);
+  y = fputil::multiply_add<double>(x, 32.0, -kd);
+
+  return static_cast<int64_t>(kd);
+}
+
+LIBC_INLINE void sincospif_eval(double xd, double &sin_k, double &cos_k,
+                                double &sin_y, double &cosm1_y) {
+  double y;
+  int64_t k = range_reduction_sincospi(xd, y);
+  sincosf_poly_eval(k, y, sin_k, cos_k, sin_y, cosm1_y);
+}
+
 } // namespace LIBC_NAMESPACE
 
 #endif // LLVM_LIBC_SRC_MATH_GENERIC_SINCOSF_UTILS_H

diff  --git a/libc/src/math/generic/sinpif.cpp b/libc/src/math/generic/sinpif.cpp
new file mode 100644
index 0000000000000..662263c9fc43e
--- /dev/null
+++ b/libc/src/math/generic/sinpif.cpp
@@ -0,0 +1,111 @@
+//===-- Single-precision sinpif 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/sinpif.h"
+#include "sincosf_utils.h"
+#include "src/__support/FPUtil/FEnvImpl.h"
+#include "src/__support/FPUtil/FPBits.h"
+#include "src/__support/FPUtil/PolyEval.h"
+#include "src/__support/FPUtil/multiply_add.h"
+#include "src/__support/common.h"
+#include "src/__support/macros/optimization.h" // LIBC_UNLIKELY
+
+namespace LIBC_NAMESPACE {
+
+LLVM_LIBC_FUNCTION(float, sinpif, (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>(x);
+
+  // Range reduction:
+  // For |x| > pi/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
+  // For small range (|x| < 2^45 when FMA instructions are available, 2^22
+  // otherwise), 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 sine of sum
+  // formula:
+  //   sin(x * pi) = sin((k + y)*pi/32)
+  //          = sin(y*pi/32) * cos(k*pi/32) + cos(y*pi/32) * sin(k*pi/32)
+  // The values of sin(k*pi/32) and cos(k*pi/32) for k = 0..31 are precomputed
+  // and stored using a vector of 32 doubles. Sin(y*pi/32) and cos(y*pi/32) are
+  // computed using degree-7 and degree-6 minimax polynomials generated by
+  // Sollya respectively.
+
+  // |x| <= 1/16
+  if (LIBC_UNLIKELY(x_abs <= 0x3d80'0000U)) {
+
+    if (LIBC_UNLIKELY(x_abs < 0x33CD'01D7U)) {
+      if (LIBC_UNLIKELY(x_abs == 0U)) {
+        // For signed zeros.
+        return x;
+      }
+
+      // For very small values we can approximate sinpi(x) with x * pi
+      // An exhaustive test shows that this is accurate for |x| < 9.546391 ×
+      // 10-8
+      double xdpi = xd * 0x1.921fb54442d18p1;
+      return static_cast<float>(xdpi);
+    }
+
+    // |x| < 1/16.
+    double xsq = xd * xd;
+
+    // Degree-9 polynomial approximation:
+    //   sinpi(x) ~ x + a_3 x^3 + a_5 x^5 + a_7 x^7 + a_9 x^9
+    //          = x (1 + a_3 x^2 + ... + a_9 x^8)
+    //          = x * P(x^2)
+    // generated by Sollya with the following commands:
+    // > display = hexadecimal;
+    // > Q = fpminimax(sin(pi * x)/x, [|0, 2, 4, 6, 8|], [|D...|], [0, 1/16]);
+    double result = fputil::polyeval(
+        xsq, 0x1.921fb54442d18p1, -0x1.4abbce625bbf2p2, 0x1.466bc675e116ap1,
+        -0x1.32d2c0b62d41cp-1, 0x1.501ec4497cb7dp-4);
+    return static_cast<float>(xd * result);
+  }
+
+  // Numbers greater or equal to 2^23 are always integers or NaN
+  if (LIBC_UNLIKELY(x_abs >= 0x4B00'0000)) {
+
+    // check for NaN values
+    if (LIBC_UNLIKELY(x_abs >= 0x7f80'0000U)) {
+      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();
+  }
+
+  // Combine the results with the sine of sum formula:
+  //   sin(x * pi) = sin((k + y)*pi/32)
+  //          = sin(y*pi/32) * cos(k*pi/32) + cos(y*pi/32) * sin(k*pi/32)
+  //          = sin_y * cos_k + (1 + cosm1_y) * sin_k
+  //          = sin_y * cos_k + (cosm1_y * sin_k + 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 && sin_k == 0))
+    return FPBits::zero(xbits.sign()).get_val();
+
+  return static_cast<float>(fputil::multiply_add(
+      sin_y, cos_k, fputil::multiply_add(cosm1_y, sin_k, sin_k)));
+}
+
+} // namespace LIBC_NAMESPACE

diff  --git a/libc/src/math/sinpif.h b/libc/src/math/sinpif.h
new file mode 100644
index 0000000000000..63d481945f470
--- /dev/null
+++ b/libc/src/math/sinpif.h
@@ -0,0 +1,18 @@
+//===-- Implementation header for sinpif ------------------------*- 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_SINPIF_H
+#define LLVM_LIBC_SRC_MATH_SINPIF_H
+
+namespace LIBC_NAMESPACE {
+
+float sinpif(float x);
+
+} // namespace LIBC_NAMESPACE
+
+#endif // LLVM_LIBC_SRC_MATH_SINPIF_H

diff  --git a/libc/test/src/math/CMakeLists.txt b/libc/test/src/math/CMakeLists.txt
index 263bee65315f1..c07c6d77fa233 100644
--- a/libc/test/src/math/CMakeLists.txt
+++ b/libc/test/src/math/CMakeLists.txt
@@ -44,6 +44,22 @@ add_fp_unittest(
     libc.src.__support.FPUtil.fp_bits
 )
 
+add_fp_unittest(
+  sinpif_test
+  NEED_MPFR
+  SUITE
+    libc-math-unittests
+  SRCS
+    sinpif_test.cpp
+  HDRS
+    sdcomp26094.h
+  DEPENDS
+    libc.src.errno.errno
+    libc.src.math.sinpif
+    libc.src.__support.CPP.array
+    libc.src.__support.FPUtil.fp_bits
+)
+
 add_fp_unittest(
   sin_test
   NEED_MPFR

diff  --git a/libc/test/src/math/exhaustive/CMakeLists.txt b/libc/test/src/math/exhaustive/CMakeLists.txt
index fb3596c3378ff..412ca031d0e99 100644
--- a/libc/test/src/math/exhaustive/CMakeLists.txt
+++ b/libc/test/src/math/exhaustive/CMakeLists.txt
@@ -42,6 +42,22 @@ add_fp_unittest(
     -lpthread
 )
 
+add_fp_unittest(
+  sinpif_test
+  NO_RUN_POSTBUILD
+  NEED_MPFR
+  SUITE
+    libc_math_exhaustive_tests
+  SRCS
+    sinpif_test.cpp
+  DEPENDS
+    .exhaustive_test
+    libc.src.math.sinpif
+    libc.src.__support.FPUtil.fp_bits
+  LINK_LIBRARIES
+    -lpthread
+)
+
 add_fp_unittest(
   cosf_test
   NO_RUN_POSTBUILD

diff  --git a/libc/test/src/math/exhaustive/sinpif_test.cpp b/libc/test/src/math/exhaustive/sinpif_test.cpp
new file mode 100644
index 0000000000000..8bc1d81eb7e3d
--- /dev/null
+++ b/libc/test/src/math/exhaustive/sinpif_test.cpp
@@ -0,0 +1,35 @@
+//===-- Exhaustive test for sinpif ----------------------------------------===//
+//
+// 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 "mpfr.h"
+#include "src/math/sinpif.h"
+#include "utils/MPFRWrapper/MPFRUtils.h"
+#include <sys/types.h>
+
+namespace mpfr = LIBC_NAMESPACE::testing::mpfr;
+
+using LlvmLibcSinpifExhaustiveTest =
+    LlvmLibcUnaryOpExhaustiveMathTest<float, mpfr::Operation::Sinpi,
+                                      LIBC_NAMESPACE::sinpif>;
+
+static constexpr uint32_t POS_START = 0x0000'0000U;
+static constexpr uint32_t POS_STOP = 0x7f80'0000U;
+
+// Range: [0, Inf]
+TEST_F(LlvmLibcSinpifExhaustiveTest, 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(LlvmLibcSinpifExhaustiveTest, NegativeRange) {
+  test_full_range_all_roundings(NEG_START, NEG_STOP);
+}

diff  --git a/libc/test/src/math/sinpif_test.cpp b/libc/test/src/math/sinpif_test.cpp
new file mode 100644
index 0000000000000..d00fd77d288c6
--- /dev/null
+++ b/libc/test/src/math/sinpif_test.cpp
@@ -0,0 +1,126 @@
+//===-- Unittests for sinpif ----------------------------------------------===//
+//
+// 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/sinpif.h"
+#include "test/UnitTest/FPMatcher.h"
+#include "test/src/math/sdcomp26094.h"
+#include "utils/MPFRWrapper/MPFRUtils.h"
+
+#include <stdint.h>
+
+using LlvmLibcSinpifTest = LIBC_NAMESPACE::testing::FPTest<float>;
+
+using LIBC_NAMESPACE::testing::SDCOMP26094_VALUES;
+
+namespace mpfr = LIBC_NAMESPACE::testing::mpfr;
+
+TEST_F(LlvmLibcSinpifTest, SpecialNumbers) {
+  LIBC_NAMESPACE::libc_errno = 0;
+
+  EXPECT_FP_EQ(aNaN, LIBC_NAMESPACE::sinpif(aNaN));
+  EXPECT_MATH_ERRNO(0);
+
+  EXPECT_FP_EQ(0.0f, LIBC_NAMESPACE::sinpif(0.0f));
+  EXPECT_MATH_ERRNO(0);
+
+  EXPECT_FP_EQ(-0.0f, LIBC_NAMESPACE::sinpif(-0.0f));
+  EXPECT_MATH_ERRNO(0);
+
+  EXPECT_FP_EQ(aNaN, LIBC_NAMESPACE::sinpif(inf));
+  EXPECT_MATH_ERRNO(EDOM);
+
+  EXPECT_FP_EQ(aNaN, LIBC_NAMESPACE::sinpif(neg_inf));
+  EXPECT_MATH_ERRNO(EDOM);
+}
+
+TEST_F(LlvmLibcSinpifTest, SpecificBitPatterns) {
+  constexpr int N = 36;
+  constexpr uint32_t INPUTS[N] = {
+      0x3f06'0a92U, // x = pi/6
+      0x3f3a'dc51U, // x = 0x1.75b8a2p-1f
+      0x3f49'0fdbU, // x = pi/4
+      0x3f86'0a92U, // x = pi/3
+      0x3fa7'832aU, // x = 0x1.4f0654p+0f
+      0x3fc9'0fdbU, // x = pi/2
+      0x4017'1973U, // x = 0x1.2e32e6p+1f
+      0x4049'0fdbU, // x = pi
+      0x4096'cbe4U, // x = 0x1.2d97c8p+2f
+      0x40c9'0fdbU, // x = 2*pi
+      0x433b'7490U, // x = 0x1.76e92p+7f
+      0x437c'e5f1U, // x = 0x1.f9cbe2p+7f
+      0x4619'9998U, // x = 0x1.33333p+13f
+      0x474d'246fU, // x = 0x1.9a48dep+15f
+      0x4afd'ece4U, // x = 0x1.fbd9c8p+22f
+      0x4c23'32e9U, // x = 0x1.4665d2p+25f
+      0x50a3'e87fU, // x = 0x1.47d0fep+34f
+      0x5239'47f6U, // x = 0x1.728fecp+37f
+      0x53b1'46a6U, // x = 0x1.628d4cp+40f
+      0x55ca'fb2aU, // x = 0x1.95f654p+44f
+      0x588e'f060U, // x = 0x1.1de0cp+50f
+      0x5c07'bcd0U, // x = 0x1.0f79ap+57f
+      0x5ebc'fddeU, // x = 0x1.79fbbcp+62f
+      0x5fa6'eba7U, // x = 0x1.4dd74ep+64f
+      0x61a4'0b40U, // x = 0x1.48168p+68f
+      0x6386'134eU, // x = 0x1.0c269cp+72f
+      0x6589'8498U, // x = 0x1.13093p+76f
+      0x6600'0001U, // x = 0x1.000002p+77f
+      0x664e'46e4U, // x = 0x1.9c8dc8p+77f
+      0x66b0'14aaU, // x = 0x1.602954p+78f
+      0x67a9'242bU, // x = 0x1.524856p+80f
+      0x6a19'76f1U, // x = 0x1.32ede2p+85f
+      0x6c55'da58U, // x = 0x1.abb4bp+89f
+      0x6f79'be45U, // x = 0x1.f37c8ap+95f
+      0x7276'69d4U, // x = 0x1.ecd3a8p+101f
+      0x7758'4625U, // x = 0x1.b08c4ap+111f
+  };
+
+  for (int i = 0; i < N; ++i) {
+    float x = FPBits(INPUTS[i]).get_val();
+    EXPECT_MPFR_MATCH_ALL_ROUNDING(mpfr::Operation::Sinpi, x,
+                                   LIBC_NAMESPACE::sinpif(x), 0.5);
+    EXPECT_MPFR_MATCH_ALL_ROUNDING(mpfr::Operation::Sinpi, -x,
+                                   LIBC_NAMESPACE::sinpif(-x), 0.5);
+  }
+}
+
+// For small values, sinpi(x) is pi * x.
+TEST_F(LlvmLibcSinpifTest, SmallValues) {
+  float x = FPBits(0x1780'0000U).get_val();
+  EXPECT_MPFR_MATCH_ALL_ROUNDING(mpfr::Operation::Sinpi, x,
+                                 LIBC_NAMESPACE::sinpif(x), 0.5);
+
+  x = FPBits(0x0040'0000U).get_val();
+  EXPECT_MPFR_MATCH_ALL_ROUNDING(mpfr::Operation::Sinpi, x,
+                                 LIBC_NAMESPACE::sinpif(x), 0.5);
+}
+
+// SDCOMP-26094: check sinfpi in the cases for which the range reducer
+// returns values furthest beyond its nominal upper bound of pi/4.
+TEST_F(LlvmLibcSinpifTest, SDCOMP_26094) {
+  for (uint32_t v : SDCOMP26094_VALUES) {
+    float x = FPBits((v)).get_val();
+    EXPECT_MPFR_MATCH_ALL_ROUNDING(mpfr::Operation::Sinpi, x,
+                                   LIBC_NAMESPACE::sinpif(x), 0.5);
+  }
+}
+
+// sinpi(-n) = -0.0
+// sinpi(+n) = +0.0
+TEST_F(LlvmLibcSinpifTest, SignedZeros) {
+  EXPECT_FP_EQ(-0.0, LIBC_NAMESPACE::sinpif(-0x99));
+  EXPECT_FP_EQ(-0.0, LIBC_NAMESPACE::sinpif(-0x1p+43));
+  EXPECT_FP_EQ(-0.0, LIBC_NAMESPACE::sinpif(-0x1.4p+64));
+  EXPECT_FP_EQ(-0.0, LIBC_NAMESPACE::sinpif(-0x1.cp+106));
+  EXPECT_FP_EQ(-0.0, LIBC_NAMESPACE::sinpif(-0x1.cp+21));
+  EXPECT_FP_EQ(-0.0, LIBC_NAMESPACE::sinpif(-0x9999));
+  EXPECT_FP_EQ(0.0, LIBC_NAMESPACE::sinpif(0x1p+43));
+  EXPECT_FP_EQ(0.0, LIBC_NAMESPACE::sinpif(0x1.4p+64));
+  EXPECT_FP_EQ(0.0, LIBC_NAMESPACE::sinpif(0x1.cp+106));
+  EXPECT_FP_EQ(0.0, LIBC_NAMESPACE::sinpif(0x1.cp+21));
+}

diff  --git a/libc/test/src/math/smoke/CMakeLists.txt b/libc/test/src/math/smoke/CMakeLists.txt
index a1b4a03eb2e85..a363644e6fa83 100644
--- a/libc/test/src/math/smoke/CMakeLists.txt
+++ b/libc/test/src/math/smoke/CMakeLists.txt
@@ -27,6 +27,19 @@ add_fp_unittest(
     libc.src.__support.FPUtil.fp_bits
 )
 
+add_fp_unittest(
+  sinpif_test
+  SUITE
+    libc-math-smoke-tests
+  SRCS
+    sinpif_test.cpp
+  DEPENDS
+    libc.src.errno.errno
+    libc.src.math.sinpif
+    libc.src.__support.CPP.array
+    libc.src.__support.FPUtil.fp_bits
+)
+
 add_fp_unittest(
   sincosf_test
   SUITE

diff  --git a/libc/test/src/math/smoke/sinpif_test.cpp b/libc/test/src/math/smoke/sinpif_test.cpp
new file mode 100644
index 0000000000000..0918294ab3611
--- /dev/null
+++ b/libc/test/src/math/smoke/sinpif_test.cpp
@@ -0,0 +1,43 @@
+//===-- Unittests for sinpif ----------------------------------------------===//
+//
+// 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/sinpif.h"
+#include "test/UnitTest/FPMatcher.h"
+
+#include <stdint.h>
+
+using LlvmLibcSinpifTest = LIBC_NAMESPACE::testing::FPTest<float>;
+
+TEST_F(LlvmLibcSinpifTest, SpecialNumbers) {
+  LIBC_NAMESPACE::libc_errno = 0;
+
+  EXPECT_FP_EQ(aNaN, LIBC_NAMESPACE::sinpif(aNaN));
+  EXPECT_MATH_ERRNO(0);
+
+  EXPECT_FP_EQ(0.0f, LIBC_NAMESPACE::sinpif(0.0f));
+  EXPECT_MATH_ERRNO(0);
+
+  EXPECT_FP_EQ(-0.0f, LIBC_NAMESPACE::sinpif(-0.0f));
+  EXPECT_MATH_ERRNO(0);
+
+  EXPECT_FP_EQ(aNaN, LIBC_NAMESPACE::sinpif(inf));
+  EXPECT_MATH_ERRNO(EDOM);
+
+  EXPECT_FP_EQ(aNaN, LIBC_NAMESPACE::sinpif(neg_inf));
+  EXPECT_MATH_ERRNO(EDOM);
+}
+
+TEST_F(LlvmLibcSinpifTest, Integers) {
+  EXPECT_FP_EQ(-0.0, LIBC_NAMESPACE::sinpif(-0x420));
+  EXPECT_FP_EQ(-0.0, LIBC_NAMESPACE::sinpif(-0x1p+43));
+  EXPECT_FP_EQ(-0.0, LIBC_NAMESPACE::sinpif(-0x1.4p+64));
+  EXPECT_FP_EQ(0.0, LIBC_NAMESPACE::sinpif(0x420));
+  EXPECT_FP_EQ(0.0, LIBC_NAMESPACE::sinpif(0x1.cp+106));
+  EXPECT_FP_EQ(0.0, LIBC_NAMESPACE::sinpif(0x1.cp+21));
+}

diff  --git a/libc/utils/MPFRWrapper/MPFRUtils.cpp b/libc/utils/MPFRWrapper/MPFRUtils.cpp
index 9a0e498708c03..379a631a356a3 100644
--- a/libc/utils/MPFRWrapper/MPFRUtils.cpp
+++ b/libc/utils/MPFRWrapper/MPFRUtils.cpp
@@ -15,10 +15,7 @@
 #include "src/__support/FPUtil/FPBits.h"
 #include "src/__support/FPUtil/fpbits_str.h"
 #include "src/__support/macros/properties/types.h"
-#include "test/UnitTest/FPMatcher.h"
 
-#include "hdr/math_macros.h"
-#include <memory>
 #include <stdint.h>
 
 #include "mpfr_inc.h"
@@ -437,6 +434,23 @@ class MPFRNumber {
     return result;
   }
 
+  MPFRNumber sinpi() const {
+    MPFRNumber result(*this);
+
+#if MPFR_VERSION_MAJOR > 4 ||                                                  \
+    (MPFR_VERSION_MAJOR == 4 && MPFR_VERSION_MINOR >= 2)
+
+    mpfr_sinpi(result.value, value, mpfr_rounding);
+#else
+    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_sin(result.value, value_pi.value, mpfr_rounding);
+#endif
+
+    return result;
+  }
+
   MPFRNumber sinh() const {
     MPFRNumber result(*this);
     mpfr_sinh(result.value, value, mpfr_rounding);
@@ -677,6 +691,8 @@ unary_operation(Operation op, InputType input, unsigned int precision,
     return mpfrInput.roundeven();
   case Operation::Sin:
     return mpfrInput.sin();
+  case Operation::Sinpi:
+    return mpfrInput.sinpi();
   case Operation::Sinh:
     return mpfrInput.sinh();
   case Operation::Sqrt:

diff  --git a/libc/utils/MPFRWrapper/MPFRUtils.h b/libc/utils/MPFRWrapper/MPFRUtils.h
index 46f3375fd4b7e..11e323bf6881d 100644
--- a/libc/utils/MPFRWrapper/MPFRUtils.h
+++ b/libc/utils/MPFRWrapper/MPFRUtils.h
@@ -51,6 +51,7 @@ enum class Operation : int {
   Round,
   RoundEven,
   Sin,
+  Sinpi,
   Sinh,
   Sqrt,
   Tan,


        


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