[libc] Add sinpif16 function

libc/config/linux/aarch64/entrypoints.txt

@@ -570,6 +570,7 @@ set(TARGET_LIBM_ENTRYPOINTS
     libc.src.math.sinf
     libc.src.math.sinhf
     libc.src.math.sinpif
+    libc.src.math.sinpif16
     libc.src.math.sqrt
     libc.src.math.sqrtf
     libc.src.math.sqrtl

libc/config/linux/arm/entrypoints.txt

@@ -390,6 +390,7 @@ set(TARGET_LIBM_ENTRYPOINTS
     libc.src.math.sincosf
     libc.src.math.sinf
     libc.src.math.sinhf
+    libc.src.math.sinpif16
     libc.src.math.sqrt
     libc.src.math.sqrtf
     libc.src.math.sqrtl

libc/config/linux/riscv/entrypoints.txt

@@ -573,6 +573,7 @@ set(TARGET_LIBM_ENTRYPOINTS
     libc.src.math.sinf
     libc.src.math.sinhf
     libc.src.math.sinpif
+    libc.src.math.sinpif16
     libc.src.math.sqrt
     libc.src.math.sqrtf
     libc.src.math.sqrtl

libc/config/linux/x86_64/entrypoints.txt

@@ -573,6 +573,7 @@ set(TARGET_LIBM_ENTRYPOINTS
     libc.src.math.sinf
     libc.src.math.sinhf
     libc.src.math.sinpif
+    libc.src.math.sinpif16
     libc.src.math.sqrt
     libc.src.math.sqrtf
     libc.src.math.sqrtl

libc/config/windows/entrypoints.txt

@@ -275,7 +275,8 @@ set(TARGET_LIBM_ENTRYPOINTS
     libc.src.math.sincosf
     libc.src.math.sincosf
     libc.src.math.sinf
-    libc.src.math.sinhf
+    libc.src.math.sinhfi
+    libc.src.math.sinpif16
     libc.src.math.sqrt
     libc.src.math.sqrtf
     libc.src.math.sqrtl

libc/newhdrgen/yaml/math.yaml

@@ -2290,6 +2290,12 @@ functions:
     return_type: float
     arguments:
       - type: float
+  - name: sinpif16
+    standards:
+      - stdc
+    return_type: _Float16
+    arguments:
+      - type: _Float16
   - name: sqrt
     standards:
       - stdc

libc/src/math/CMakeLists.txt

@@ -474,6 +474,7 @@ add_math_entrypoint_object(sincosf)
 add_math_entrypoint_object(sin)
 add_math_entrypoint_object(sinf)
 add_math_entrypoint_object(sinpif)
+add_math_entrypoint_object(sinpif16)
 
 add_math_entrypoint_object(sinh)
 add_math_entrypoint_object(sinhf)

libc/src/math/generic/CMakeLists.txt

@@ -528,6 +528,22 @@ add_entrypoint_object(
     -O3
 )
 
+add_entrypoint_object(
+  sinpif16
+  SRCS
+    sinpif16.cpp
+  HDRS
+    ../sinpif16.h
+  DEPENDS
+    libc.src.__support.macros.properties.types
+    libc.src.__support.FPUtil.fp_bits
+    libc.src.__support.FPUtil.multiply_add
+    libc.src.__support.common
+    libc.src.__support.macros.config
+  COMPILE_OPTIONS
+    -O3
+)
+
 add_entrypoint_object(
   tan
   SRCS

libc/src/math/generic/sinpif16.cpp

@@ -0,0 +1,197 @@
+//===-- Half-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/sinpif16.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/FPUtil/nearest_integer.h"
+#include "src/__support/common.h"
+#include "src/__support/macros/config.h"
+
+// TODO: Should probably create a new file; sincospif16_utils.h
+// To store the following helper functions and constants.
+// I'd defer to @lntue for suggestions regarding that
+
+// HELPER_START
+namespace LIBC_NAMESPACE_DECL {
+
+constexpr float PI_OVER_32 = 0x1.921fb6p-4f;
+
+// In Sollya generate 10 coeffecients for a degree-9 chebyshev polynomial
+// approximating the sine function in [-pi / 32, pi / 32] with the following
+// commands:
+// > prec=24;
+// > TL = chebyshevform(sin(x), 9, [-pi / 32, pi / 32]);
+// > TL[0];
+const float SIN_COEFF[10] = {
+    0x1.d333p-26, 0x1.000048p0, -0x1.a5d2p-14, -0x1.628588p-3, 0x1.c1eep-5,
+    0x1.4455p1,   -0x1.317a8p3, -0x1.6bb9p8,   0x1.00ef8p9,    0x1.0edcp14};
+// In Sollya generate 10 coefficients for a degree-9 chebyshev polynomial
+// approximating the sine function in [-pi/32, pi/32] with the following
+// commands:
+// > prec = 24;
+// > TL = chebyshevform(cos(x), 9, [-pi / 32, pi / 32]);
+// > TL[0];
+const float COS_COEFF[10] = {
+    0x1.000006p0, 0x1.e1eap-15, -0x1.0071p-1, -0x1.3b56p-4, 0x1.f3dfp-2,
+    0x1.ccbap4,   -0x1.3034p6,  -0x1.f817p11, 0x1.fc59p11,  0x1.7079p17};
+// Lookup table for sin(k * pi / 32) with k = 0, ..., 63.
+// Table is generated with Sollya as follows:
+// > display = hexadecimmal;
+// > prec = 24;
+// > for k from 0 to 63 do {sin(k * pi/32);};
+
+const float SIN_K_PI_OVER_32[64] = {0,
+                                    0x1.917a6cp-4,
+                                    0x1.8f8b84p-3,
+                                    0x1.294062p-2,
+                                    0x1.87de2ap-2,
+                                    0x1.e2b5d4p-2,
+                                    0x1.1c73b4p-1,
+                                    0x1.44cf32p-1,
+                                    0x1.6a09e6p-1,
+                                    0x1.8bc806p-1,
+                                    0x1.a9b662p-1,
+                                    0x1.c38b3p-1,
+                                    0x1.d906bcp-1,
+                                    0x1.e9f416p-1,
+                                    0x1.f6297cp-1,
+                                    0x1.fd88dap-1,
+                                    0x1p0,
+                                    0x1.fd88dap-1,
+                                    0x1.f6297cp-1,
+                                    0x1.e9f416p-1,
+                                    0x1.d906bcp-1,
+                                    0x1.c38b3p-1,
+                                    0x1.a9b662p-1,
+                                    0x1.8bc806p-1,
+                                    0x1.6a09e6p-1,
+                                    0x1.44cf32p-1,
+                                    0x1.1c73b4p-1,
+                                    0x1.e2b5d4p-2,
+                                    0x1.87de2ap-2,
+                                    0x1.294062p-2,
+                                    0x1.8f8b84p-3,
+                                    0x1.917a6cp-4,
+                                    0,
+                                    -0x1.917a6cp-4,
+                                    -0x1.8f8b84p-3,
+                                    -0x1.294062p-2,
+                                    -0x1.87de2ap-2,
+                                    -0x1.e2b5d4p-2,
+                                    -0x1.1c73b4p-1,
+                                    -0x1.44cf32p-1,
+                                    -0x1.6a09e6p-1,
+                                    -0x1.8bc806p-1,
+                                    -0x1.a9b662p-1,
+                                    -0x1.c38b3p-1,
+                                    -0x1.d906bcp-1,
+                                    -0x1.e9f416p-1,
+                                    -0x1.f6297ep-1,
+                                    -0x1.fd88dap-1,
+                                    -0x1p0,
+                                    -0x1.fd88dap-1,
+                                    -0x1.f6297cp-1,
+                                    -0x1.e9f416p-1,
+                                    -0x1.d906bcp-1,
+                                    -0x1.c38b3p-1,
+                                    -0x1.a9b662p-1,
+                                    -0x1.8bc806p-1,
+                                    -0x1.6a09e6p-1,
+                                    -0x1.44cf32p-1,
+                                    -0x1.1c73b4p-1,
+                                    -0x1.e2b5d4p-2,
+                                    -0x1.87de2ap-2,
+                                    -0x1.294062p-2,
+                                    -0x1.8f8b84p-3,
+                                    -0x1.917a6cp-4};
+
+int32_t range_reduction(float x, float &y) {
+  float kf = fputil::nearest_integer(x * 32);
+  y = fputil::multiply_add<float>(x, 32.0, -kf);
+
+  return static_cast<int32_t>(kf);
+}
+// HELPER_END
+
+LLVM_LIBC_FUNCTION(float16, sinpif16, (float16 x)) {
+  using FPBits = typename fputil::FPBits<float16>;
+  FPBits xbits(x);
+
+  uint16_t x_u = xbits.uintval();
+  uint16_t x_abs = x_u & 0x7fff;
+
+  // 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 sine of sum
+  // formula:
+  //   sin(x * pi) = sin((k + y) * pi/32)
+  //           = sin(k * pi/32) * cos(y * pi/32) + sin (y * pi/32) * cos (k *
+  //           pi/32)
+  // The values of sin(k * pi/32) and cos (k * pi/32) for k = 0...63 are
+  // precomputed and stored using a vector of 64 single precision floats. sin(y
+  // * pi/32) and cos(y * pi/32) are computed using degree-9 chebyshev
+  // polynomials generated by Sollya.
+
+  if (LIBC_UNLIKELY(x_abs == 0U)) {
+    // For signed zeros
+    return x;
+  }
+
+  // Numbers greater or equal to 2^10 are integers or NaN
+  if (LIBC_UNLIKELY(x_abs >= 0x6400)) {
+    // Check for NaN or infinity values
+    if (LIBC_UNLIKELY(x_abs >= 0x7c00)) {
+      // If value is equal to infinity
+      if (x_abs == 0x7c00) {
+        fputil::set_errno_if_required(EDOM);
+        fputil::raise_except_if_required(FE_INVALID);
+      }
+
+      // If value is NaN
+      return x + FPBits::quiet_nan().get_val();
+    }
+    return FPBits::zero(xbits.sign()).get_val();
+  }
+
+  float f32 = static_cast<float>(x);
+  float y;
+  int32_t k = range_reduction(f32, y);
+
+  float sin_k = SIN_K_PI_OVER_32[k & 63];
+  float cos_k = SIN_K_PI_OVER_32[(k + 16) & 63];
+
+  float cos_y, sin_y;
+  if (y == 0) {
+    cos_y = 1;
+    sin_y = 0;
+  } else {
+    cos_y = fputil::polyeval(y * PI_OVER_32, COS_COEFF[0], COS_COEFF[1],
+                             COS_COEFF[2], COS_COEFF[3], COS_COEFF[4],
+                             COS_COEFF[5], COS_COEFF[6], COS_COEFF[7],
+                             COS_COEFF[8], COS_COEFF[9]);
+    sin_y = fputil::polyeval(y * PI_OVER_32, SIN_COEFF[0], SIN_COEFF[1],
+                             SIN_COEFF[2], SIN_COEFF[3], SIN_COEFF[4],
+                             SIN_COEFF[5], SIN_COEFF[6], SIN_COEFF[7],
+                             SIN_COEFF[8], SIN_COEFF[9]);
+  }
+
+  return static_cast<float16>(fputil::multiply_add(
+      sin_k, cos_y, fputil::multiply_add(sin_y, cos_k, 0.0f)));
+}
+} // namespace LIBC_NAMESPACE_DECL

libc/src/math/sinpif16.h

@@ -0,0 +1,22 @@
+//===-- Implementation header for sinpif16 ---------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache Licese 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_SINPIF16_H
+#define LLVM_LIBC_SRC_MATH_SINPIF16_H
+
+#include "include/llvm-libc-macros/float16-macros.h"
+#include "src/__support/macros/config.h"
+#include "src/__support/macros/properties/types.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+float16 sinpif16(float16 x);
+
+} // namespace LIBC_NAMESPACE_DECL
+
+#endif // LLVM_LIBC_SRC_MATH_SINPIF16_H

libc/test/src/math/smoke/CMakeLists.txt

@@ -51,6 +51,19 @@ add_fp_unittest(
     libc.src.__support.FPUtil.fp_bits
 )
 
+add_fp_unittest(
+  sinpif16_test
+  SUITE
+    libc-math-smoke-tests
+  SRCS
+    sinpif16_test.cpp
+  DEPENDS
+    libc.src.math.sinpif16
+    libc.src.errno.errno
+    libc.src.__support.CPP.array
+    libc.src.__support.FPUtil.fp_bits  
+)
+
 add_fp_unittest(
   sincosf_test
   SUITE

libc/test/src/math/smoke/sinpif16_test.cpp

@@ -0,0 +1,44 @@
+//===-- Unittests for sinpif16 --------------------------------------------===//
+//
+// 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/sinpif16.h"
+#include "test/UnitTest/FPMatcher.h"
+
+#include <stdint.h>
+
+using LlvmLibcSinpif16Test = LIBC_NAMESPACE::testing::FPTest<float16>;
+
+TEST_F(LlvmLibcSinpif16Test, SpecialNumbers) {
+  LIBC_NAMESPACE::libc_errno = 0;
+
+  EXPECT_FP_EQ(aNaN, LIBC_NAMESPACE::sinpif16(aNaN));
+  EXPECT_MATH_ERRNO(0);
+
+  EXPECT_FP_EQ(0.0f, LIBC_NAMESPACE::sinpif16(0.0f));
+  EXPECT_MATH_ERRNO(0);
+
+  EXPECT_FP_EQ(-0.0f, LIBC_NAMESPACE::sinpif16(-0.0f));
+  EXPECT_MATH_ERRNO(0);
+
+  EXPECT_FP_EQ(aNaN, LIBC_NAMESPACE::sinpif16(inf));
+  EXPECT_MATH_ERRNO(EDOM);
+
+  EXPECT_FP_EQ(aNaN, LIBC_NAMESPACE::sinpif16(neg_inf));
+  EXPECT_MATH_ERRNO(EDOM);
+}
+
+TEST_F(LlvmLibcSinpif16Test, Integers) {
+  EXPECT_FP_EQ(-0.0, LIBC_NAMESPACE::sinpif16(-0x420));
+  EXPECT_FP_EQ(-0.0, LIBC_NAMESPACE::sinpif16(-0x1p+10));
+  EXPECT_FP_EQ(-0.0, LIBC_NAMESPACE::sinpif16(-0x1.4p+14));
+  EXPECT_FP_EQ(0.0, LIBC_NAMESPACE::sinpif16(0x420));
+  EXPECT_FP_EQ(0.0, LIBC_NAMESPACE::sinpif16(0x1.cp+15));
+  EXPECT_FP_EQ(0.0, LIBC_NAMESPACE::sinpif16(0x1.cp+7));
+}