[libc][math][c23] Add f16divf C23 math function (#96131)

Part of #93566.

6 files changed, 298 insertions, 0 deletions

diff --git a/libc/test/src/math/CMakeLists.txt b/libc/test/src/math/CMakeLists.txt
index bb364c3..ba58866 100644
--- a/libc/test/src/math/CMakeLists.txt
+++ b/libc/test/src/math/CMakeLists.txt
@@ -1891,6 +1891,19 @@ add_fp_unittest(
 )
 
 add_fp_unittest(
+  f16divf_test
+  NEED_MPFR
+  SUITE
+    libc-math-unittests
+  SRCS
+    f16divf_test.cpp
+  HDRS
+    DivTest.h
+  DEPENDS
+    libc.src.math.f16divf
+)
+
+add_fp_unittest(
   f16fmaf_test
   NEED_MPFR
   SUITE
diff --git a/libc/test/src/math/DivTest.h b/libc/test/src/math/DivTest.h
new file mode 100644
index 0000000..1cdc139
--- /dev/null
+++ b/libc/test/src/math/DivTest.h
@@ -0,0 +1,74 @@
+//===-- Utility class to test different flavors of float div ----*- 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_TEST_SRC_MATH_DIVTEST_H
+#define LLVM_LIBC_TEST_SRC_MATH_DIVTEST_H
+
+#include "test/UnitTest/FEnvSafeTest.h"
+#include "test/UnitTest/FPMatcher.h"
+#include "test/UnitTest/Test.h"
+#include "utils/MPFRWrapper/MPFRUtils.h"
+
+namespace mpfr = LIBC_NAMESPACE::testing::mpfr;
+
+template <typename OutType, typename InType>
+class DivTest : public LIBC_NAMESPACE::testing::FEnvSafeTest {
+
+  struct InConstants {
+    DECLARE_SPECIAL_CONSTANTS(InType)
+  };
+
+  using InFPBits = typename InConstants::FPBits;
+  using InStorageType = typename InConstants::StorageType;
+
+  static constexpr InStorageType IN_MAX_NORMAL_U =
+      InFPBits::max_normal().uintval();
+  static constexpr InStorageType IN_MIN_NORMAL_U =
+      InFPBits::min_normal().uintval();
+  static constexpr InStorageType IN_MAX_SUBNORMAL_U =
+      InFPBits::max_subnormal().uintval();
+  static constexpr InStorageType IN_MIN_SUBNORMAL_U =
+      InFPBits::min_subnormal().uintval();
+
+public:
+  using DivFunc = OutType (*)(InType, InType);
+
+  void test_subnormal_range(DivFunc func) {
+    constexpr InStorageType COUNT = 100'001;
+    constexpr InStorageType STEP =
+        (IN_MAX_SUBNORMAL_U - IN_MIN_SUBNORMAL_U) / COUNT;
+    for (InStorageType i = 0, v = 0, w = IN_MAX_SUBNORMAL_U; i <= COUNT;
+         ++i, v += STEP, w -= STEP) {
+      InType x = InFPBits(v).get_val();
+      InType y = InFPBits(w).get_val();
+      mpfr::BinaryInput<InType> input{x, y};
+      EXPECT_MPFR_MATCH_ALL_ROUNDING(mpfr::Operation::Div, input, func(x, y),
+                                     0.5);
+    }
+  }
+
+  void test_normal_range(DivFunc func) {
+    constexpr InStorageType COUNT = 100'001;
+    constexpr InStorageType STEP = (IN_MAX_NORMAL_U - IN_MIN_NORMAL_U) / COUNT;
+    for (InStorageType i = 0, v = 0, w = IN_MAX_NORMAL_U; i <= COUNT;
+         ++i, v += STEP, w -= STEP) {
+      InType x = InFPBits(v).get_val();
+      InType y = InFPBits(w).get_val();
+      mpfr::BinaryInput<InType> input{x, y};
+      EXPECT_MPFR_MATCH_ALL_ROUNDING(mpfr::Operation::Div, input, func(x, y),
+                                     0.5);
+    }
+  }
+};
+
+#define LIST_DIV_TESTS(OutType, InType, func)                                  \
+  using LlvmLibcDivTest = DivTest<OutType, InType>;                            \
+  TEST_F(LlvmLibcDivTest, SubnormalRange) { test_subnormal_range(&func); }     \
+  TEST_F(LlvmLibcDivTest, NormalRange) { test_normal_range(&func); }
+
+#endif // LLVM_LIBC_TEST_SRC_MATH_DIVTEST_H
diff --git a/libc/test/src/math/f16divf_test.cpp b/libc/test/src/math/f16divf_test.cpp
new file mode 100644
index 0000000..85be1eb
--- /dev/null
+++ b/libc/test/src/math/f16divf_test.cpp
@@ -0,0 +1,13 @@
+//===-- Unittests for f16divf ---------------------------------------------===//
+//
+// 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 "DivTest.h"
+
+#include "src/math/f16divf.h"
+
+LIST_DIV_TESTS(float16, float, LIBC_NAMESPACE::f16divf)
diff --git a/libc/test/src/math/smoke/CMakeLists.txt b/libc/test/src/math/smoke/CMakeLists.txt
index ffa8ba1..ee99fb9 100644
--- a/libc/test/src/math/smoke/CMakeLists.txt
+++ b/libc/test/src/math/smoke/CMakeLists.txt
@@ -3631,6 +3631,20 @@ add_fp_unittest(
 )
 
 add_fp_unittest(
+  f16divf_test
+  SUITE
+    libc-math-smoke-tests
+  SRCS
+    f16divf_test.cpp
+  HDRS
+    DivTest.h
+  DEPENDS
+    libc.hdr.fenv_macros
+    libc.src.__support.FPUtil.basic_operations
+    libc.src.math.f16divf
+)
+
+add_fp_unittest(
   f16fmaf_test
   SUITE
     libc-math-smoke-tests
diff --git a/libc/test/src/math/smoke/DivTest.h b/libc/test/src/math/smoke/DivTest.h
new file mode 100644
index 0000000..71cfb32
--- /dev/null
+++ b/libc/test/src/math/smoke/DivTest.h
@@ -0,0 +1,171 @@
+//===-- Utility class to test different flavors of float div --------------===//
+//
+// 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_TEST_SRC_MATH_SMOKE_DIVTEST_H
+#define LLVM_LIBC_TEST_SRC_MATH_SMOKE_DIVTEST_H
+
+#include "hdr/fenv_macros.h"
+#include "src/__support/FPUtil/BasicOperations.h"
+#include "test/UnitTest/FEnvSafeTest.h"
+#include "test/UnitTest/FPMatcher.h"
+#include "test/UnitTest/RoundingModeUtils.h"
+#include "test/UnitTest/Test.h"
+
+template <typename OutType, typename InType>
+class DivTest : public LIBC_NAMESPACE::testing::FEnvSafeTest {
+
+  DECLARE_SPECIAL_CONSTANTS(OutType)
+
+  struct InConstants {
+    DECLARE_SPECIAL_CONSTANTS(InType)
+  };
+
+  using InFPBits = typename InConstants::FPBits;
+  using InStorageType = typename InConstants::StorageType;
+
+public:
+  using DivFunc = OutType (*)(InType, InType);
+
+  void test_special_numbers(DivFunc func) {
+    EXPECT_FP_IS_NAN(func(aNaN, aNaN));
+    EXPECT_FP_IS_NAN_WITH_EXCEPTION(func(sNaN, sNaN), FE_INVALID);
+
+    InType qnan_42 = InFPBits::quiet_nan(Sign::POS, 0x42).get_val();
+    EXPECT_FP_EQ(InType(0x42.0p+0),
+                 LIBC_NAMESPACE::fputil::getpayload(func(qnan_42, zero)));
+    EXPECT_FP_EQ(InType(0x42.0p+0),
+                 LIBC_NAMESPACE::fputil::getpayload(func(zero, qnan_42)));
+
+    if constexpr (sizeof(OutType) < sizeof(InType)) {
+      InStorageType max_payload = InFPBits::FRACTION_MASK >> 1;
+      InType qnan_max = InFPBits::quiet_nan(Sign::POS, max_payload).get_val();
+      EXPECT_FP_EQ(zero,
+                   LIBC_NAMESPACE::fputil::getpayload(func(qnan_max, zero)));
+      EXPECT_FP_EQ(zero,
+                   LIBC_NAMESPACE::fputil::getpayload(func(zero, qnan_max)));
+      EXPECT_FP_EQ(InType(0x42.0p+0),
+                   LIBC_NAMESPACE::fputil::getpayload(func(qnan_max, qnan_42)));
+      EXPECT_FP_EQ(InType(0x42.0p+0),
+                   LIBC_NAMESPACE::fputil::getpayload(func(qnan_42, qnan_max)));
+    }
+
+    EXPECT_FP_EQ(inf, func(inf, zero));
+    EXPECT_FP_EQ(neg_inf, func(neg_inf, zero));
+    EXPECT_FP_EQ(neg_inf, func(inf, neg_zero));
+    EXPECT_FP_EQ(inf, func(neg_inf, neg_zero));
+  }
+
+  void test_division_by_zero(DivFunc func) {
+    EXPECT_FP_EQ_WITH_EXCEPTION(inf, func(InType(1.0), zero), FE_DIVBYZERO);
+    EXPECT_FP_EQ_WITH_EXCEPTION(neg_inf, func(InType(-1.0), zero),
+                                FE_DIVBYZERO);
+    EXPECT_FP_EQ_WITH_EXCEPTION(neg_inf, func(InType(1.0), neg_zero),
+                                FE_DIVBYZERO);
+    EXPECT_FP_EQ_WITH_EXCEPTION(inf, func(InType(1.0), zero), FE_DIVBYZERO);
+  }
+
+  void test_invalid_operations(DivFunc func) {
+    EXPECT_FP_IS_NAN_WITH_EXCEPTION(func(zero, zero), FE_INVALID);
+    EXPECT_FP_IS_NAN_WITH_EXCEPTION(func(neg_zero, zero), FE_INVALID);
+    EXPECT_FP_IS_NAN_WITH_EXCEPTION(func(zero, neg_zero), FE_INVALID);
+    EXPECT_FP_IS_NAN_WITH_EXCEPTION(func(neg_zero, neg_zero), FE_INVALID);
+
+    EXPECT_FP_IS_NAN_WITH_EXCEPTION(func(inf, inf), FE_INVALID);
+    EXPECT_MATH_ERRNO(EDOM);
+    EXPECT_FP_IS_NAN_WITH_EXCEPTION(func(neg_inf, inf), FE_INVALID);
+    EXPECT_MATH_ERRNO(EDOM);
+    EXPECT_FP_IS_NAN_WITH_EXCEPTION(func(inf, neg_inf), FE_INVALID);
+    EXPECT_MATH_ERRNO(EDOM);
+    EXPECT_FP_IS_NAN_WITH_EXCEPTION(func(neg_inf, neg_inf), FE_INVALID);
+    EXPECT_MATH_ERRNO(EDOM);
+  }
+
+  void test_range_errors(DivFunc func) {
+    using namespace LIBC_NAMESPACE::fputil::testing;
+
+    if (ForceRoundingMode r(RoundingMode::Nearest); r.success) {
+      EXPECT_FP_EQ_WITH_EXCEPTION(inf, func(max_normal, min_normal),
+                                  FE_OVERFLOW | FE_INEXACT);
+      EXPECT_MATH_ERRNO(ERANGE);
+      EXPECT_FP_EQ_WITH_EXCEPTION(-inf, func(neg_max_normal, min_denormal),
+                                  FE_OVERFLOW | FE_INEXACT);
+      EXPECT_MATH_ERRNO(ERANGE);
+
+      EXPECT_FP_EQ_WITH_EXCEPTION(zero, func(min_denormal, max_normal),
+                                  FE_UNDERFLOW | FE_INEXACT);
+      EXPECT_MATH_ERRNO(ERANGE);
+      EXPECT_FP_EQ_WITH_EXCEPTION(neg_zero, func(neg_min_denormal, max_normal),
+                                  FE_UNDERFLOW | FE_INEXACT);
+      EXPECT_MATH_ERRNO(ERANGE);
+    }
+
+    if (ForceRoundingMode r(RoundingMode::TowardZero); r.success) {
+      EXPECT_FP_EQ_WITH_EXCEPTION(max_normal, func(max_normal, min_normal),
+                                  FE_OVERFLOW | FE_INEXACT);
+      EXPECT_FP_EQ_WITH_EXCEPTION(neg_max_normal,
+                                  func(neg_max_normal, min_denormal),
+                                  FE_OVERFLOW | FE_INEXACT);
+
+      EXPECT_FP_EQ_WITH_EXCEPTION(zero, func(min_denormal, max_normal),
+                                  FE_UNDERFLOW | FE_INEXACT);
+      EXPECT_MATH_ERRNO(ERANGE);
+      EXPECT_FP_EQ_WITH_EXCEPTION(neg_zero, func(neg_min_denormal, max_normal),
+                                  FE_UNDERFLOW | FE_INEXACT);
+      EXPECT_MATH_ERRNO(ERANGE);
+    }
+
+    if (ForceRoundingMode r(RoundingMode::Downward); r.success) {
+      EXPECT_FP_EQ_WITH_EXCEPTION(max_normal, func(max_normal, min_normal),
+                                  FE_OVERFLOW | FE_INEXACT);
+      EXPECT_FP_EQ_WITH_EXCEPTION(-inf, func(neg_max_normal, min_denormal),
+                                  FE_OVERFLOW | FE_INEXACT);
+      EXPECT_MATH_ERRNO(ERANGE);
+
+      EXPECT_FP_EQ_WITH_EXCEPTION(zero, func(min_denormal, max_normal),
+                                  FE_UNDERFLOW | FE_INEXACT);
+      EXPECT_MATH_ERRNO(ERANGE);
+      EXPECT_FP_EQ_WITH_EXCEPTION(neg_min_denormal,
+                                  func(neg_min_denormal, max_normal),
+                                  FE_UNDERFLOW | FE_INEXACT);
+      EXPECT_MATH_ERRNO(ERANGE);
+    }
+
+    if (ForceRoundingMode r(RoundingMode::Upward); r.success) {
+      EXPECT_FP_EQ_WITH_EXCEPTION(inf, func(max_normal, min_normal),
+                                  FE_OVERFLOW | FE_INEXACT);
+      EXPECT_MATH_ERRNO(ERANGE);
+      EXPECT_FP_EQ_WITH_EXCEPTION(neg_max_normal,
+                                  func(neg_max_normal, min_denormal),
+                                  FE_OVERFLOW | FE_INEXACT);
+
+      EXPECT_FP_EQ_WITH_EXCEPTION(min_denormal, func(min_denormal, max_normal),
+                                  FE_UNDERFLOW | FE_INEXACT);
+      EXPECT_MATH_ERRNO(ERANGE);
+      EXPECT_FP_EQ_WITH_EXCEPTION(neg_zero, func(neg_min_denormal, max_normal),
+                                  FE_UNDERFLOW | FE_INEXACT);
+      EXPECT_MATH_ERRNO(ERANGE);
+    }
+  }
+
+  void test_inexact_results(DivFunc func) {
+    func(InType(1.0), InType(3.0));
+    EXPECT_FP_EXCEPTION(FE_INEXACT);
+  }
+};
+
+#define LIST_DIV_TESTS(OutType, InType, func)                                  \
+  using LlvmLibcDivTest = DivTest<OutType, InType>;                            \
+  TEST_F(LlvmLibcDivTest, SpecialNumbers) { test_special_numbers(&func); }     \
+  TEST_F(LlvmLibcDivTest, DivisionByZero) { test_division_by_zero(&func); }    \
+  TEST_F(LlvmLibcDivTest, InvalidOperations) {                                 \
+    test_invalid_operations(&func);                                            \
+  }                                                                            \
+  TEST_F(LlvmLibcDivTest, RangeErrors) { test_range_errors(&func); }           \
+  TEST_F(LlvmLibcDivTest, InexactResults) { test_inexact_results(&func); }
+
+#endif // LLVM_LIBC_TEST_SRC_MATH_SMOKE_DIVTEST_H
diff --git a/libc/test/src/math/smoke/f16divf_test.cpp b/libc/test/src/math/smoke/f16divf_test.cpp
new file mode 100644
index 0000000..85be1eb
--- /dev/null
+++ b/libc/test/src/math/smoke/f16divf_test.cpp
@@ -0,0 +1,13 @@
+//===-- Unittests for f16divf ---------------------------------------------===//
+//
+// 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 "DivTest.h"
+
+#include "src/math/f16divf.h"
+
+LIST_DIV_TESTS(float16, float, LIBC_NAMESPACE::f16divf)