libc/test/src/__support/math_extras_test.cpp

//===-- Unittests for math_extras -----------------------------------------===//
//
// 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/integer_literals.h"
#include "src/__support/macros/config.h"
#include "src/__support/math_extras.h"
#include "src/__support/uint128.h" // UInt<128>
#include "test/UnitTest/Test.h"

namespace LIBC_NAMESPACE_DECL {

// TODO: add UInt<128> support.
using UnsignedTypesNoBigInt = testing::TypeList<
#if defined(LIBC_TYPES_HAS_INT128)
    __uint128_t,
#endif // LIBC_TYPES_HAS_INT128
    unsigned char, unsigned short, unsigned int, unsigned long,
    unsigned long long, UInt<128>>;

TEST(LlvmLibcBlockMathExtrasTest, mask_trailing_ones) {
  EXPECT_EQ(0_u8, (mask_leading_ones<uint8_t, 0>()));
  EXPECT_EQ(0_u8, (mask_trailing_ones<uint8_t, 0>()));
  EXPECT_EQ(0_u16, (mask_leading_ones<uint16_t, 0>()));
  EXPECT_EQ(0_u16, (mask_trailing_ones<uint16_t, 0>()));
  EXPECT_EQ(0_u32, (mask_leading_ones<uint32_t, 0>()));
  EXPECT_EQ(0_u32, (mask_trailing_ones<uint32_t, 0>()));
  EXPECT_EQ(0_u64, (mask_leading_ones<uint64_t, 0>()));
  EXPECT_EQ(0_u64, (mask_trailing_ones<uint64_t, 0>()));

  EXPECT_EQ(0x00000003_u32, (mask_trailing_ones<uint32_t, 2>()));
  EXPECT_EQ(0xC0000000_u32, (mask_leading_ones<uint32_t, 2>()));

  EXPECT_EQ(0x000007FF_u32, (mask_trailing_ones<uint32_t, 11>()));
  EXPECT_EQ(0xFFE00000_u32, (mask_leading_ones<uint32_t, 11>()));

  EXPECT_EQ(0xFFFFFFFF_u32, (mask_trailing_ones<uint32_t, 32>()));
  EXPECT_EQ(0xFFFFFFFF_u32, (mask_leading_ones<uint32_t, 32>()));
  EXPECT_EQ(0xFFFFFFFFFFFFFFFF_u64, (mask_trailing_ones<uint64_t, 64>()));
  EXPECT_EQ(0xFFFFFFFFFFFFFFFF_u64, (mask_leading_ones<uint64_t, 64>()));

  EXPECT_EQ(0x0000FFFFFFFFFFFF_u64, (mask_trailing_ones<uint64_t, 48>()));
  EXPECT_EQ(0xFFFFFFFFFFFF0000_u64, (mask_leading_ones<uint64_t, 48>()));

  EXPECT_EQ(0_u128, (mask_trailing_ones<UInt128, 0>()));
  EXPECT_EQ(0_u128, (mask_leading_ones<UInt128, 0>()));

  EXPECT_EQ(0x00000000000000007FFFFFFFFFFFFFFF_u128,
            (mask_trailing_ones<UInt128, 63>()));
  EXPECT_EQ(0xFFFFFFFFFFFFFFFE0000000000000000_u128,
            (mask_leading_ones<UInt128, 63>()));

  EXPECT_EQ(0x0000000000000000FFFFFFFFFFFFFFFF_u128,
            (mask_trailing_ones<UInt128, 64>()));
  EXPECT_EQ(0xFFFFFFFFFFFFFFFF0000000000000000_u128,
            (mask_leading_ones<UInt128, 64>()));

  EXPECT_EQ(0x0000000000000001FFFFFFFFFFFFFFFF_u128,
            (mask_trailing_ones<UInt128, 65>()));
  EXPECT_EQ(0xFFFFFFFFFFFFFFFF8000000000000000_u128,
            (mask_leading_ones<UInt128, 65>()));

  EXPECT_EQ(0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF_u128,
            (mask_trailing_ones<UInt128, 128>()));
  EXPECT_EQ(0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF_u128,
            (mask_leading_ones<UInt128, 128>()));
}

TYPED_TEST(LlvmLibcBitTest, FirstLeadingZero, UnsignedTypesNoBigInt) {
  EXPECT_EQ(first_leading_zero<T>(cpp::numeric_limits<T>::max()), 0);
  for (int i = 0U; i != cpp::numeric_limits<T>::digits; ++i) {
    auto lhs = T(~(T(1) << size_t(i)));
    EXPECT_EQ(first_leading_zero<T>(lhs), cpp::numeric_limits<T>::digits - i);
  }
}

TYPED_TEST(LlvmLibcBitTest, FirstLeadingOne, UnsignedTypesNoBigInt) {
  EXPECT_EQ(first_leading_one<T>(static_cast<T>(0)), 0);
  for (int i = 0U; i != cpp::numeric_limits<T>::digits; ++i) {
    auto lhs = T(T(1) << size_t(i));
    EXPECT_EQ(first_leading_one<T>(lhs), cpp::numeric_limits<T>::digits - i);
  }
}

TYPED_TEST(LlvmLibcBitTest, FirstTrailingZero, UnsignedTypesNoBigInt) {
  EXPECT_EQ(first_trailing_zero<T>(cpp::numeric_limits<T>::max()), 0);
  for (int i = 0U; i != cpp::numeric_limits<T>::digits; ++i) {
    auto lhs = T(~(T(1) << size_t(i)));
    EXPECT_EQ(first_trailing_zero<T>(lhs), i + 1);
  }
}

TYPED_TEST(LlvmLibcBitTest, FirstTrailingOne, UnsignedTypesNoBigInt) {
  EXPECT_EQ(first_trailing_one<T>(static_cast<T>(0)), 0);
  EXPECT_EQ(first_trailing_one<T>(cpp::numeric_limits<T>::max()), 1);
  for (int i = 0U; i != cpp::numeric_limits<T>::digits; ++i) {
    auto lhs = T(T(1) << size_t(i));
    EXPECT_EQ(first_trailing_one<T>(lhs), i + 1);
  }
}

TYPED_TEST(LlvmLibcBitTest, CountZeros, UnsignedTypesNoBigInt) {
  EXPECT_EQ(count_zeros(T(0)), cpp::numeric_limits<T>::digits);
  for (int i = 0; i != cpp::numeric_limits<T>::digits; ++i)
    EXPECT_EQ(count_zeros<T>(cpp::numeric_limits<T>::max() >> size_t(i)), i);
}

using UnsignedTypes = testing::TypeList<
#if defined(LIBC_TYPES_HAS_INT128)
    __uint128_t,
#endif
    unsigned char, unsigned short, unsigned int, unsigned long,
    unsigned long long>;

TYPED_TEST(LlvmLibcBlockMathExtrasTest, add_overflow, UnsignedTypes) {
  constexpr T ZERO = cpp::numeric_limits<T>::min();
  constexpr T ONE(1);
  constexpr T MAX = cpp::numeric_limits<T>::max();
  constexpr T BEFORE_MAX = MAX - 1;

  const struct {
    T lhs;
    T rhs;
    T sum;
    bool carry;
  } TESTS[] = {
      {ZERO, ONE, ONE, false},       // 0x00 + 0x01 = 0x01
      {BEFORE_MAX, ONE, MAX, false}, // 0xFE + 0x01 = 0xFF
      {MAX, ONE, ZERO, true},        // 0xFF + 0x01 = 0x00 (carry)
      {MAX, MAX, BEFORE_MAX, true},  // 0xFF + 0xFF = 0xFE (carry)
  };
  for (auto tc : TESTS) {
    T sum;
    bool carry = add_overflow<T>(tc.lhs, tc.rhs, sum);
    EXPECT_EQ(sum, tc.sum);
    EXPECT_EQ(carry, tc.carry);
  }
}

TYPED_TEST(LlvmLibcBlockMathExtrasTest, sub_overflow, UnsignedTypes) {
  constexpr T ZERO = cpp::numeric_limits<T>::min();
  constexpr T ONE(1);
  constexpr T MAX = cpp::numeric_limits<T>::max();
  constexpr T BEFORE_MAX = MAX - 1;

  const struct {
    T lhs;
    T rhs;
    T sub;
    bool carry;
  } TESTS[] = {
      {ONE, ZERO, ONE, false},      // 0x01 - 0x00 = 0x01
      {MAX, MAX, ZERO, false},      // 0xFF - 0xFF = 0x00
      {ZERO, ONE, MAX, true},       // 0x00 - 0x01 = 0xFF (carry)
      {BEFORE_MAX, MAX, MAX, true}, // 0xFE - 0xFF = 0xFF (carry)
  };
  for (auto tc : TESTS) {
    T sub;
    bool carry = sub_overflow<T>(tc.lhs, tc.rhs, sub);
    EXPECT_EQ(sub, tc.sub);
    EXPECT_EQ(carry, tc.carry);
  }
}

} // namespace LIBC_NAMESPACE_DECL