//===-- Utility class to test different flavors of [l|ll]round --*- 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_ROUNDTOINTEGERTEST_H
#define LLVM_LIBC_TEST_SRC_MATH_ROUNDTOINTEGERTEST_H

#include "src/__support/CPP/algorithm.h"
#include "src/__support/FPUtil/FEnvImpl.h"
#include "src/__support/FPUtil/FPBits.h"
#include "test/UnitTest/FEnvSafeTest.h"
#include "test/UnitTest/FPMatcher.h"
#include "test/UnitTest/Test.h"
#include "utils/MPFRWrapper/MPFRUtils.h"

#include "hdr/math_macros.h"
#include <errno.h>

namespace mpfr = LIBC_NAMESPACE::testing::mpfr;

static constexpr int ROUNDING_MODES[4] = {FE_UPWARD, FE_DOWNWARD, FE_TOWARDZERO,
                                          FE_TONEAREST};

template <typename F, typename I, bool TestModes = false>
class RoundToIntegerTestTemplate
    : public LIBC_NAMESPACE::testing::FEnvSafeTest {
public:
  typedef I (*RoundToIntegerFunc)(F);

private:
  using FPBits = LIBC_NAMESPACE::fputil::FPBits<F>;
  using StorageType = typename FPBits::StorageType;

  const F zero = FPBits::zero().get_val();
  const F neg_zero = FPBits::zero(Sign::NEG).get_val();
  const F inf = FPBits::inf().get_val();
  const F neg_inf = FPBits::inf(Sign::NEG).get_val();
  const F nan = FPBits::quiet_nan().get_val();

  static constexpr StorageType MAX_NORMAL = FPBits::max_normal().uintval();
  static constexpr StorageType MIN_NORMAL = FPBits::min_normal().uintval();
  static constexpr StorageType MAX_SUBNORMAL =
      FPBits::max_subnormal().uintval();
  static constexpr StorageType MIN_SUBNORMAL =
      FPBits::min_subnormal().uintval();

  static constexpr I INTEGER_MIN = I(1) << (sizeof(I) * 8 - 1);
  static constexpr I INTEGER_MAX = -(INTEGER_MIN + 1);

  void test_one_input(RoundToIntegerFunc func, F input, I expected,
                      bool expectError) {
    LIBC_NAMESPACE::libc_errno = 0;
    LIBC_NAMESPACE::fputil::clear_except(FE_ALL_EXCEPT);

    ASSERT_EQ(func(input), expected);

    // TODO: Handle the !expectError case. It used to expect
    // 0 for errno and exceptions, but this doesn't hold for
    // all math functions using RoundToInteger test:
    // https://github.com/llvm/llvm-project/pull/88816
    if (expectError) {
      ASSERT_FP_EXCEPTION(FE_INVALID);
      ASSERT_MATH_ERRNO(EDOM);
    }
  }

  static inline mpfr::RoundingMode to_mpfr_rounding_mode(int mode) {
    switch (mode) {
    case FE_UPWARD:
      return mpfr::RoundingMode::Upward;
    case FE_DOWNWARD:
      return mpfr::RoundingMode::Downward;
    case FE_TOWARDZERO:
      return mpfr::RoundingMode::TowardZero;
    case FE_TONEAREST:
      return mpfr::RoundingMode::Nearest;
    default:
      __builtin_unreachable();
    }
  }

public:
  void SetUp() override {
    LIBC_NAMESPACE::testing::FEnvSafeTest::SetUp();

    if (math_errhandling & MATH_ERREXCEPT) {
      // We will disable all exceptions so that the test will not
      // crash with SIGFPE. We can still use fetestexcept to check
      // if the appropriate flag was raised.
      LIBC_NAMESPACE::fputil::disable_except(FE_ALL_EXCEPT);
    }
  }

  void do_infinity_and_na_n_test(RoundToIntegerFunc func) {
    test_one_input(func, inf, INTEGER_MAX, true);
    test_one_input(func, neg_inf, INTEGER_MIN, true);
    // This is currently never enabled, the
    // LLVM_LIBC_IMPLEMENTATION_DEFINED_TEST_BEHAVIOR CMake option in
    // libc/CMakeLists.txt is not forwarded to C++.
#if LIBC_COPT_IMPLEMENTATION_DEFINED_TEST_BEHAVIOR
    // Result is not well-defined, we always returns INTEGER_MAX
    test_one_input(func, nan, INTEGER_MAX, true);
#endif // LIBC_COPT_IMPLEMENTATION_DEFINED_TEST_BEHAVIOR
  }

  void testInfinityAndNaN(RoundToIntegerFunc func) {
    if (TestModes) {
      for (int mode : ROUNDING_MODES) {
        LIBC_NAMESPACE::fputil::set_round(mode);
        do_infinity_and_na_n_test(func);
      }
    } else {
      do_infinity_and_na_n_test(func);
    }
  }

  void do_round_numbers_test(RoundToIntegerFunc func) {
    test_one_input(func, zero, I(0), false);
    test_one_input(func, neg_zero, I(0), false);
    test_one_input(func, F(1.0), I(1), false);
    test_one_input(func, F(-1.0), I(-1), false);
    test_one_input(func, F(10.0), I(10), false);
    test_one_input(func, F(-10.0), I(-10), false);
    test_one_input(func, F(1234.0), I(1234), false);
    test_one_input(func, F(-1234.0), I(-1234), false);

    // The rest of this function compares with an equivalent MPFR function
    // which rounds floating point numbers to long values. There is no MPFR
    // function to round to long long or wider integer values. So, we will
    // the remaining tests only if the width of I less than equal to that of
    // long.
    if (sizeof(I) > sizeof(long))
      return;

    constexpr int EXPONENT_LIMIT = sizeof(I) * 8 - 1;
    constexpr int BIASED_EXPONENT_LIMIT = EXPONENT_LIMIT + FPBits::EXP_BIAS;
    if (BIASED_EXPONENT_LIMIT > FPBits::MAX_BIASED_EXPONENT)
      return;
    // We start with 1.0 so that the implicit bit for x86 long doubles
    // is set.
    FPBits bits(F(1.0));
    bits.set_biased_exponent(BIASED_EXPONENT_LIMIT);
    bits.set_sign(Sign::NEG);
    bits.set_mantissa(0);

    F x = bits.get_val();
    long mpfr_result;
    bool erangeflag = mpfr::round_to_long(x, mpfr_result);
    ASSERT_FALSE(erangeflag);
    test_one_input(func, x, mpfr_result, false);
  }

  void testRoundNumbers(RoundToIntegerFunc func) {
    if (TestModes) {
      for (int mode : ROUNDING_MODES) {
        LIBC_NAMESPACE::fputil::set_round(mode);
        do_round_numbers_test(func);
      }
    } else {
      do_round_numbers_test(func);
    }
  }

  void do_fractions_test(RoundToIntegerFunc func, int mode) {
    constexpr F FRACTIONS[] = {0.5, -0.5, 0.115, -0.115, 0.715, -0.715};
    for (F x : FRACTIONS) {
      long mpfr_long_result;
      bool erangeflag;
      if (TestModes)
        erangeflag = mpfr::round_to_long(x, to_mpfr_rounding_mode(mode),
                                         mpfr_long_result);
      else
        erangeflag = mpfr::round_to_long(x, mpfr_long_result);
      ASSERT_FALSE(erangeflag);
      I mpfr_result = mpfr_long_result;
      test_one_input(func, x, mpfr_result, false);
    }
  }

  void testFractions(RoundToIntegerFunc func) {
    if (TestModes) {
      for (int mode : ROUNDING_MODES) {
        LIBC_NAMESPACE::fputil::set_round(mode);
        do_fractions_test(func, mode);
      }
    } else {
      // Passing 0 for mode has no effect as it is not used in doFractionsTest
      // when `TestModes` is false;
      do_fractions_test(func, 0);
    }
  }

  void testIntegerOverflow(RoundToIntegerFunc func) {
    // This function compares with an equivalent MPFR function which rounds
    // floating point numbers to long values. There is no MPFR function to
    // round to long long or wider integer values. So, we will peform the
    // comparisons in this function only if the width of I less than equal to
    // that of long.
    if (sizeof(I) > sizeof(long))
      return;

    constexpr int EXPONENT_LIMIT = sizeof(I) * 8 - 1;
    constexpr int BIASED_EXPONENT_LIMIT = EXPONENT_LIMIT + FPBits::EXP_BIAS;
    if (BIASED_EXPONENT_LIMIT > FPBits::MAX_BIASED_EXPONENT)
      return;
    // We start with 1.0 so that the implicit bit for x86 long doubles
    // is set.
    FPBits bits(F(1.0));
    bits.set_biased_exponent(BIASED_EXPONENT_LIMIT);
    bits.set_sign(Sign::NEG);
    bits.set_mantissa(FPBits::FRACTION_MASK);

    F x = bits.get_val();
    if (TestModes) {
      for (int m : ROUNDING_MODES) {
        LIBC_NAMESPACE::fputil::set_round(m);
        long mpfr_long_result;
        bool erangeflag =
            mpfr::round_to_long(x, to_mpfr_rounding_mode(m), mpfr_long_result);
        ASSERT_TRUE(erangeflag);
        test_one_input(func, x, INTEGER_MIN, true);
      }
    } else {
      long mpfr_long_result;
      bool erangeflag = mpfr::round_to_long(x, mpfr_long_result);
      ASSERT_TRUE(erangeflag);
      test_one_input(func, x, INTEGER_MIN, true);
    }
  }

  void testSubnormalRange(RoundToIntegerFunc func) {
    constexpr int COUNT = 1'000'001;
    constexpr StorageType STEP = LIBC_NAMESPACE::cpp::max(
        static_cast<StorageType>((MAX_SUBNORMAL - MIN_SUBNORMAL) / COUNT),
        StorageType(1));
    for (StorageType i = MIN_SUBNORMAL; i <= MAX_SUBNORMAL; i += STEP) {
      F x = FPBits(i).get_val();
      if (x == F(0.0))
        continue;
      // All subnormal numbers should round to zero.
      if (TestModes) {
        if (x > 0) {
          LIBC_NAMESPACE::fputil::set_round(FE_UPWARD);
          test_one_input(func, x, I(1), false);
          LIBC_NAMESPACE::fputil::set_round(FE_DOWNWARD);
          test_one_input(func, x, I(0), false);
          LIBC_NAMESPACE::fputil::set_round(FE_TOWARDZERO);
          test_one_input(func, x, I(0), false);
          LIBC_NAMESPACE::fputil::set_round(FE_TONEAREST);
          test_one_input(func, x, I(0), false);
        } else {
          LIBC_NAMESPACE::fputil::set_round(FE_UPWARD);
          test_one_input(func, x, I(0), false);
          LIBC_NAMESPACE::fputil::set_round(FE_DOWNWARD);
          test_one_input(func, x, I(-1), false);
          LIBC_NAMESPACE::fputil::set_round(FE_TOWARDZERO);
          test_one_input(func, x, I(0), false);
          LIBC_NAMESPACE::fputil::set_round(FE_TONEAREST);
          test_one_input(func, x, I(0), false);
        }
      } else {
        test_one_input(func, x, 0L, false);
      }
    }
  }

  void testNormalRange(RoundToIntegerFunc func) {
    // This function compares with an equivalent MPFR function which rounds
    // floating point numbers to long values. There is no MPFR function to
    // round to long long or wider integer values. So, we will peform the
    // comparisons in this function only if the width of I less than equal to
    // that of long.
    if (sizeof(I) > sizeof(long))
      return;

    constexpr int COUNT = 1'000'001;
    constexpr StorageType STEP = LIBC_NAMESPACE::cpp::max(
        static_cast<StorageType>((MAX_NORMAL - MIN_NORMAL) / COUNT),
        StorageType(1));
    for (StorageType i = MIN_NORMAL; i <= MAX_NORMAL; i += STEP) {
      FPBits xbits(i);
      F x = xbits.get_val();
      // In normal range on x86 platforms, the long double implicit 1 bit can be
      // zero making the numbers NaN. We will skip them.
      if (xbits.is_nan())
        continue;

      if (TestModes) {
        for (int m : ROUNDING_MODES) {
          long mpfr_long_result;
          bool erangeflag = mpfr::round_to_long(x, to_mpfr_rounding_mode(m),
                                                mpfr_long_result);
          I mpfr_result = mpfr_long_result;
          LIBC_NAMESPACE::fputil::set_round(m);
          if (erangeflag)
            test_one_input(func, x, x > 0 ? INTEGER_MAX : INTEGER_MIN, true);
          else
            test_one_input(func, x, mpfr_result, false);
        }
      } else {
        long mpfr_long_result;
        bool erangeflag = mpfr::round_to_long(x, mpfr_long_result);
        I mpfr_result = mpfr_long_result;
        if (erangeflag)
          test_one_input(func, x, x > 0 ? INTEGER_MAX : INTEGER_MIN, true);
        else
          test_one_input(func, x, mpfr_result, false);
      }
    }
  }
};

#define LIST_ROUND_TO_INTEGER_TESTS_HELPER(F, I, func, TestModes)              \
  using LlvmLibcRoundToIntegerTest =                                           \
      RoundToIntegerTestTemplate<F, I, TestModes>;                             \
  TEST_F(LlvmLibcRoundToIntegerTest, InfinityAndNaN) {                         \
    testInfinityAndNaN(&func);                                                 \
  }                                                                            \
  TEST_F(LlvmLibcRoundToIntegerTest, RoundNumbers) {                           \
    testRoundNumbers(&func);                                                   \
  }                                                                            \
  TEST_F(LlvmLibcRoundToIntegerTest, Fractions) { testFractions(&func); }      \
  TEST_F(LlvmLibcRoundToIntegerTest, IntegerOverflow) {                        \
    testIntegerOverflow(&func);                                                \
  }                                                                            \
  TEST_F(LlvmLibcRoundToIntegerTest, SubnormalRange) {                         \
    testSubnormalRange(&func);                                                 \
  }                                                                            \
  TEST_F(LlvmLibcRoundToIntegerTest, NormalRange) { testNormalRange(&func); }

#define LIST_ROUND_TO_INTEGER_TESTS(F, I, func)                                \
  LIST_ROUND_TO_INTEGER_TESTS_HELPER(F, I, func, false)

#define LIST_ROUND_TO_INTEGER_TESTS_WITH_MODES(F, I, func)                     \
  LIST_ROUND_TO_INTEGER_TESTS_HELPER(F, I, func, true)

#endif // LLVM_LIBC_TEST_SRC_MATH_ROUNDTOINTEGERTEST_H