[libc][math] Implement double precision sincos correctly rounded to all rounding modes. (#96719)

Sharing the same algorithm as double precision sin:
https://github.com/llvm/llvm-project/pull/95736 and cos:
https://github.com/llvm/llvm-project/pull/96591

4 files changed, 183 insertions, 0 deletions

diff --git a/libc/test/src/math/CMakeLists.txt b/libc/test/src/math/CMakeLists.txt
index ba58866..1ddb5c7 100644
--- a/libc/test/src/math/CMakeLists.txt
+++ b/libc/test/src/math/CMakeLists.txt
@@ -73,6 +73,18 @@ add_fp_unittest(
 )
 
 add_fp_unittest(
+  sincos_test
+  NEED_MPFR
+  SUITE
+    libc-math-unittests
+  SRCS
+    sincos_test.cpp
+  DEPENDS
+    libc.src.math.sincos
+    libc.src.__support.FPUtil.fp_bits
+)
+
+add_fp_unittest(
   tanf_test
   NEED_MPFR
   SUITE
diff --git a/libc/test/src/math/sincos_test.cpp b/libc/test/src/math/sincos_test.cpp
new file mode 100644
index 0000000..c0cbff7
--- /dev/null
+++ b/libc/test/src/math/sincos_test.cpp
@@ -0,0 +1,120 @@
+//===-- Unittests for sincos ----------------------------------------------===//
+//
+// 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/FPUtil/FPBits.h"
+#include "src/math/sincos.h"
+#include "test/UnitTest/FPMatcher.h"
+#include "test/UnitTest/Test.h"
+#include "utils/MPFRWrapper/MPFRUtils.h"
+
+using LlvmLibcSincosTest = LIBC_NAMESPACE::testing::FPTest<double>;
+
+namespace mpfr = LIBC_NAMESPACE::testing::mpfr;
+
+using LIBC_NAMESPACE::testing::tlog;
+
+#define ASSERT_SINCOS_MATCH_ALL_ROUNDING(input)                                \
+  do {                                                                         \
+    double sin_x, cos_x;                                                       \
+    namespace mpfr = LIBC_NAMESPACE::testing::mpfr;                            \
+                                                                               \
+    mpfr::ForceRoundingMode __r1(mpfr::RoundingMode::Nearest);                 \
+    if (__r1.success) {                                                        \
+      LIBC_NAMESPACE::sincos(input, &sin_x, &cos_x);                           \
+      ASSERT_MPFR_MATCH(mpfr::Operation::Sin, input, sin_x, 0.5,               \
+                        mpfr::RoundingMode::Nearest);                          \
+      ASSERT_MPFR_MATCH(mpfr::Operation::Cos, input, cos_x, 0.5,               \
+                        mpfr::RoundingMode::Nearest);                          \
+    }                                                                          \
+                                                                               \
+    mpfr::ForceRoundingMode __r2(mpfr::RoundingMode::Upward);                  \
+    if (__r2.success) {                                                        \
+      LIBC_NAMESPACE::sincos(input, &sin_x, &cos_x);                           \
+      ASSERT_MPFR_MATCH(mpfr::Operation::Sin, input, sin_x, 0.5,               \
+                        mpfr::RoundingMode::Upward);                           \
+      ASSERT_MPFR_MATCH(mpfr::Operation::Cos, input, cos_x, 0.5,               \
+                        mpfr::RoundingMode::Upward);                           \
+    }                                                                          \
+                                                                               \
+    mpfr::ForceRoundingMode __r3(mpfr::RoundingMode::Downward);                \
+    if (__r3.success) {                                                        \
+      LIBC_NAMESPACE::sincos(input, &sin_x, &cos_x);                           \
+      ASSERT_MPFR_MATCH(mpfr::Operation::Sin, input, sin_x, 0.5,               \
+                        mpfr::RoundingMode::Downward);                         \
+      ASSERT_MPFR_MATCH(mpfr::Operation::Cos, input, cos_x, 0.5,               \
+                        mpfr::RoundingMode::Downward);                         \
+    }                                                                          \
+                                                                               \
+    mpfr::ForceRoundingMode __r4(mpfr::RoundingMode::TowardZero);              \
+    if (__r4.success) {                                                        \
+      LIBC_NAMESPACE::sincos(input, &sin_x, &cos_x);                           \
+      ASSERT_MPFR_MATCH(mpfr::Operation::Sin, input, sin_x, 0.5,               \
+                        mpfr::RoundingMode::TowardZero);                       \
+      ASSERT_MPFR_MATCH(mpfr::Operation::Cos, input, cos_x, 0.5,               \
+                        mpfr::RoundingMode::TowardZero);                       \
+    }                                                                          \
+  } while (0)
+
+TEST_F(LlvmLibcSincosTest, TrickyInputs) {
+  constexpr double INPUTS[] = {
+      0x1.8000000000009p-23,    0x1.8000000000024p-22,
+      0x1.800000000009p-21,     0x1.20000000000f3p-20,
+      0x1.800000000024p-20,     0x1.e0000000001c2p-20,
+      0x1.940c877fb7dacp-7,     -0x1.f42fb19b5b9b2p-6,
+      -0x1.0285070f9f1bcp-5,    0x1.23f40dccdef72p+0,
+      0x1.43cf16358c9d7p+0,     0x1.addf3b9722265p+0,
+      0x1.ae78d360afa15p+0,     0x1.e31b55306f22cp+2,
+      0x1.e639103a05997p+2,     -0x1.f7898d5a756ddp+2,
+      0x1.1685973506319p+3,     0x1.5f09cad750ab1p+3,
+      -0x1.aaf85537ea4c7p+3,    0x1.4f2b874135d27p+4,
+      0x1.13114266f9764p+4,     0x1.a211877de55dbp+4,
+      -0x1.a5eece87e8606p+4,    0x1.a65d441ea6dcep+4,
+      0x1.1ffb509f3db15p+5,     0x1.2345d1e090529p+5,
+      0x1.c96e28eb679f8p+5,     0x1.be886d9c2324dp+6,
+      -0x1.ab514bfc61c76p+7,    -0x1.14823229799c2p+7,
+      0x1.48ff1782ca91dp+8,     0x1.dcbfda0c7559ep+8,
+      0x1.dcbfda0c7559ep+8,     0x1.2e566149bf5fdp+9,
+      0x1.cb996c60f437ep+9,     0x1.ae945054939c2p+10,
+      -0x1.119471e9216cdp+10,   0x1.ae945054939c2p+10,
+      0x1.fffffffffdb6p+24,     0x1.fd4da4ef37075p+29,
+      0x1.55202aefde314p+31,    0x1.b951f1572eba5p+31,
+      0x1.7776c2343ba4ep+101,   0x1.85fc0f04c0128p+101,
+      0x1.678309fa50d58p+110,   0x1.fffffffffef4ep+199,
+      0x1.3eec5912ea7cdp+331,   -0x1.3eec5912ea7cdp+331,
+      -0x1.6deb37da81129p+205,  0x1.08087e9aad90bp+887,
+      -0x1.08087e9aad90bp+887,  -0x1.8bb5847d49973p+845,
+      0x1.6ac5b262ca1ffp+849,   0x1.f08b14e1c4d0fp+890,
+      0x1.2b5fe88a9d8d5p+903,   0x1.f6d7518808571p+1023,
+      -0x1.a880417b7b119p+1023, 0x1.00a33764a0a83p-7,
+      0x1.fe81868fc47fep+1,     0x1.0da8cc189b47dp-10,
+      0x1.da1838053b866p+5,
+
+  };
+  constexpr int N = sizeof(INPUTS) / sizeof(INPUTS[0]);
+
+  for (int i = 0; i < N; ++i) {
+    ASSERT_SINCOS_MATCH_ALL_ROUNDING(INPUTS[i]);
+  }
+}
+
+TEST_F(LlvmLibcSincosTest, InDoubleRange) {
+  constexpr uint64_t COUNT = 123'451;
+  uint64_t START = LIBC_NAMESPACE::fputil::FPBits<double>(0x1.0p-50).uintval();
+  uint64_t STOP = LIBC_NAMESPACE::fputil::FPBits<double>(0x1.0p200).uintval();
+  uint64_t STEP = (STOP - START) / COUNT;
+
+  auto test = [&](mpfr::RoundingMode rounding_mode) {
+    for (uint64_t i = 0, v = START; i <= COUNT; ++i, v += STEP) {
+      double x = FPBits(v).get_val();
+      if (isnan(x) || isinf(x))
+        continue;
+
+      ASSERT_SINCOS_MATCH_ALL_ROUNDING(x);
+    }
+  };
+}
diff --git a/libc/test/src/math/smoke/CMakeLists.txt b/libc/test/src/math/smoke/CMakeLists.txt
index d79e296..1ec5853 100644
--- a/libc/test/src/math/smoke/CMakeLists.txt
+++ b/libc/test/src/math/smoke/CMakeLists.txt
@@ -3687,3 +3687,13 @@ add_fp_unittest(
   DEPENDS
     libc.src.math.cos
 )
+
+add_fp_unittest(
+  sincos_test
+  SUITE
+    libc-math-smoke-tests
+  SRCS
+    sincos_test.cpp
+  DEPENDS
+    libc.src.math.sincos
+)
diff --git a/libc/test/src/math/smoke/sincos_test.cpp b/libc/test/src/math/smoke/sincos_test.cpp
new file mode 100644
index 0000000..371c0ad
--- /dev/null
+++ b/libc/test/src/math/smoke/sincos_test.cpp
@@ -0,0 +1,41 @@
+//===-- Unittests for sincos ----------------------------------------------===//
+//
+// 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/sincos.h"
+#include "test/UnitTest/FPMatcher.h"
+#include "test/UnitTest/Test.h"
+
+using LlvmLibcSincosTest = LIBC_NAMESPACE::testing::FPTest<double>;
+
+TEST_F(LlvmLibcSincosTest, SpecialNumbers) {
+  double sin_x, cos_x;
+
+  LIBC_NAMESPACE::sincos(aNaN, &sin_x, &cos_x);
+  EXPECT_FP_EQ_ALL_ROUNDING(aNaN, cos_x);
+  EXPECT_FP_EQ_ALL_ROUNDING(aNaN, sin_x);
+
+  LIBC_NAMESPACE::sincos(zero, &sin_x, &cos_x);
+  EXPECT_FP_EQ_ALL_ROUNDING(1.0, cos_x);
+  EXPECT_FP_EQ_ALL_ROUNDING(0.0, sin_x);
+
+  LIBC_NAMESPACE::sincos(neg_zero, &sin_x, &cos_x);
+  EXPECT_FP_EQ_ALL_ROUNDING(1.0, cos_x);
+  EXPECT_FP_EQ_ALL_ROUNDING(neg_zero, sin_x);
+
+  LIBC_NAMESPACE::sincos(inf, &sin_x, &cos_x);
+  EXPECT_FP_EQ_ALL_ROUNDING(aNaN, cos_x);
+  EXPECT_FP_EQ_ALL_ROUNDING(aNaN, sin_x);
+
+  LIBC_NAMESPACE::sincos(neg_inf, &sin_x, &cos_x);
+  EXPECT_FP_EQ_ALL_ROUNDING(aNaN, cos_x);
+  EXPECT_FP_EQ_ALL_ROUNDING(aNaN, sin_x);
+
+  LIBC_NAMESPACE::sincos(0x1.0p-28, &sin_x, &cos_x);
+  EXPECT_FP_EQ(1.0, cos_x);
+  EXPECT_FP_EQ(0x1.0p-28, sin_x);
+}