| // Copyright 2014 the V8 project authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #ifndef V8_BASE_BITS_H_ |
| #define V8_BASE_BITS_H_ |
| |
| #include <stdint.h> |
| #include <type_traits> |
| |
| #include "src/base/base-export.h" |
| #include "src/base/macros.h" |
| #if V8_CC_MSVC |
| #include <intrin.h> |
| #endif |
| #if V8_OS_WIN32 |
| #include "src/base/win32-headers.h" |
| #endif |
| |
| namespace v8 { |
| namespace base { |
| namespace bits { |
| |
| // CountPopulation(value) returns the number of bits set in |value|. |
| template <typename T> |
| constexpr inline |
| typename std::enable_if<std::is_unsigned<T>::value && sizeof(T) <= 8, |
| unsigned>::type |
| CountPopulation(T value) { |
| #if V8_HAS_BUILTIN_POPCOUNT |
| return sizeof(T) == 8 ? __builtin_popcountll(static_cast<uint64_t>(value)) |
| : __builtin_popcount(static_cast<uint32_t>(value)); |
| #else |
| constexpr uint64_t mask[] = {0x5555555555555555, 0x3333333333333333, |
| 0x0f0f0f0f0f0f0f0f, 0x00ff00ff00ff00ff, |
| 0x0000ffff0000ffff, 0x00000000ffffffff}; |
| value = ((value >> 1) & mask[0]) + (value & mask[0]); |
| value = ((value >> 2) & mask[1]) + (value & mask[1]); |
| value = ((value >> 4) & mask[2]) + (value & mask[2]); |
| if (sizeof(T) > 1) |
| value = ((value >> (sizeof(T) > 1 ? 8 : 0)) & mask[3]) + (value & mask[3]); |
| if (sizeof(T) > 2) |
| value = ((value >> (sizeof(T) > 2 ? 16 : 0)) & mask[4]) + (value & mask[4]); |
| if (sizeof(T) > 4) |
| value = ((value >> (sizeof(T) > 4 ? 32 : 0)) & mask[5]) + (value & mask[5]); |
| return static_cast<unsigned>(value); |
| #endif |
| } |
| |
| // ReverseBits(value) returns |value| in reverse bit order. |
| template <typename T> |
| T ReverseBits(T value) { |
| DCHECK((sizeof(value) == 1) || (sizeof(value) == 2) || (sizeof(value) == 4) || |
| (sizeof(value) == 8)); |
| T result = 0; |
| for (unsigned i = 0; i < (sizeof(value) * 8); i++) { |
| result = (result << 1) | (value & 1); |
| value >>= 1; |
| } |
| return result; |
| } |
| |
| // CountLeadingZeros(value) returns the number of zero bits following the most |
| // significant 1 bit in |value| if |value| is non-zero, otherwise it returns |
| // {sizeof(T) * 8}. |
| template <typename T, unsigned bits = sizeof(T) * 8> |
| inline constexpr |
| typename std::enable_if<std::is_unsigned<T>::value && sizeof(T) <= 8, |
| unsigned>::type |
| CountLeadingZeros(T value) { |
| static_assert(bits > 0, "invalid instantiation"); |
| #if V8_HAS_BUILTIN_CLZ |
| return value == 0 |
| ? bits |
| : bits == 64 |
| ? __builtin_clzll(static_cast<uint64_t>(value)) |
| : __builtin_clz(static_cast<uint32_t>(value)) - (32 - bits); |
| #else |
| // Binary search algorithm taken from "Hacker's Delight" (by Henry S. Warren, |
| // Jr.), figures 5-11 and 5-12. |
| if (bits == 1) return static_cast<unsigned>(value) ^ 1; |
| T upper_half = value >> (bits / 2); |
| T next_value = upper_half != 0 ? upper_half : value; |
| unsigned add = upper_half != 0 ? 0 : bits / 2; |
| constexpr unsigned next_bits = bits == 1 ? 1 : bits / 2; |
| return CountLeadingZeros<T, next_bits>(next_value) + add; |
| #endif |
| } |
| |
| inline constexpr unsigned CountLeadingZeros32(uint32_t value) { |
| return CountLeadingZeros(value); |
| } |
| inline constexpr unsigned CountLeadingZeros64(uint64_t value) { |
| return CountLeadingZeros(value); |
| } |
| |
| // CountTrailingZeros(value) returns the number of zero bits preceding the |
| // least significant 1 bit in |value| if |value| is non-zero, otherwise it |
| // returns {sizeof(T) * 8}. |
| template <typename T, unsigned bits = sizeof(T) * 8> |
| inline constexpr |
| typename std::enable_if<std::is_integral<T>::value && sizeof(T) <= 8, |
| unsigned>::type |
| CountTrailingZeros(T value) { |
| #if V8_HAS_BUILTIN_CTZ |
| return value == 0 ? bits |
| : bits == 64 ? __builtin_ctzll(static_cast<uint64_t>(value)) |
| : __builtin_ctz(static_cast<uint32_t>(value)); |
| #else |
| // Fall back to popcount (see "Hacker's Delight" by Henry S. Warren, Jr.), |
| // chapter 5-4. On x64, since is faster than counting in a loop and faster |
| // than doing binary search. |
| using U = typename std::make_unsigned<T>::type; |
| U u = value; |
| return CountPopulation(static_cast<U>(~u & (u - 1u))); |
| #endif |
| } |
| |
| inline constexpr unsigned CountTrailingZeros32(uint32_t value) { |
| return CountTrailingZeros(value); |
| } |
| inline constexpr unsigned CountTrailingZeros64(uint64_t value) { |
| return CountTrailingZeros(value); |
| } |
| |
| // Returns true iff |value| is a power of 2. |
| template <typename T, |
| typename = typename std::enable_if<std::is_integral<T>::value || |
| std::is_enum<T>::value>::type> |
| constexpr inline bool IsPowerOfTwo(T value) { |
| return value > 0 && (value & (value - 1)) == 0; |
| } |
| |
| // RoundUpToPowerOfTwo32(value) returns the smallest power of two which is |
| // greater than or equal to |value|. If you pass in a |value| that is already a |
| // power of two, it is returned as is. |value| must be less than or equal to |
| // 0x80000000u. Uses computation based on leading zeros if we have compiler |
| // support for that. Falls back to the implementation from "Hacker's Delight" by |
| // Henry S. Warren, Jr., figure 3-3, page 48, where the function is called clp2. |
| V8_BASE_EXPORT uint32_t RoundUpToPowerOfTwo32(uint32_t value); |
| // Same for 64 bit integers. |value| must be <= 2^63 |
| V8_BASE_EXPORT uint64_t RoundUpToPowerOfTwo64(uint64_t value); |
| // Same for size_t integers. |
| inline size_t RoundUpToPowerOfTwo(size_t value) { |
| if (sizeof(size_t) == sizeof(uint64_t)) { |
| return RoundUpToPowerOfTwo64(value); |
| } else { |
| return RoundUpToPowerOfTwo32(value); |
| } |
| } |
| |
| // RoundDownToPowerOfTwo32(value) returns the greatest power of two which is |
| // less than or equal to |value|. If you pass in a |value| that is already a |
| // power of two, it is returned as is. |
| inline uint32_t RoundDownToPowerOfTwo32(uint32_t value) { |
| if (value > 0x80000000u) return 0x80000000u; |
| uint32_t result = RoundUpToPowerOfTwo32(value); |
| if (result > value) result >>= 1; |
| return result; |
| } |
| |
| |
| // Precondition: 0 <= shift < 32 |
| inline uint32_t RotateRight32(uint32_t value, uint32_t shift) { |
| if (shift == 0) return value; |
| return (value >> shift) | (value << (32 - shift)); |
| } |
| |
| // Precondition: 0 <= shift < 32 |
| inline uint32_t RotateLeft32(uint32_t value, uint32_t shift) { |
| if (shift == 0) return value; |
| return (value << shift) | (value >> (32 - shift)); |
| } |
| |
| // Precondition: 0 <= shift < 64 |
| inline uint64_t RotateRight64(uint64_t value, uint64_t shift) { |
| if (shift == 0) return value; |
| return (value >> shift) | (value << (64 - shift)); |
| } |
| |
| // Precondition: 0 <= shift < 64 |
| inline uint64_t RotateLeft64(uint64_t value, uint64_t shift) { |
| if (shift == 0) return value; |
| return (value << shift) | (value >> (64 - shift)); |
| } |
| |
| |
| // SignedAddOverflow32(lhs,rhs,val) performs a signed summation of |lhs| and |
| // |rhs| and stores the result into the variable pointed to by |val| and |
| // returns true if the signed summation resulted in an overflow. |
| inline bool SignedAddOverflow32(int32_t lhs, int32_t rhs, int32_t* val) { |
| #if V8_HAS_BUILTIN_SADD_OVERFLOW |
| return __builtin_sadd_overflow(lhs, rhs, val); |
| #else |
| uint32_t res = static_cast<uint32_t>(lhs) + static_cast<uint32_t>(rhs); |
| *val = bit_cast<int32_t>(res); |
| return ((res ^ lhs) & (res ^ rhs) & (1U << 31)) != 0; |
| #endif |
| } |
| |
| |
| // SignedSubOverflow32(lhs,rhs,val) performs a signed subtraction of |lhs| and |
| // |rhs| and stores the result into the variable pointed to by |val| and |
| // returns true if the signed subtraction resulted in an overflow. |
| inline bool SignedSubOverflow32(int32_t lhs, int32_t rhs, int32_t* val) { |
| #if V8_HAS_BUILTIN_SSUB_OVERFLOW |
| return __builtin_ssub_overflow(lhs, rhs, val); |
| #else |
| uint32_t res = static_cast<uint32_t>(lhs) - static_cast<uint32_t>(rhs); |
| *val = bit_cast<int32_t>(res); |
| return ((res ^ lhs) & (res ^ ~rhs) & (1U << 31)) != 0; |
| #endif |
| } |
| |
| // SignedMulOverflow32(lhs,rhs,val) performs a signed multiplication of |lhs| |
| // and |rhs| and stores the result into the variable pointed to by |val| and |
| // returns true if the signed multiplication resulted in an overflow. |
| V8_BASE_EXPORT bool SignedMulOverflow32(int32_t lhs, int32_t rhs, int32_t* val); |
| |
| // SignedAddOverflow64(lhs,rhs,val) performs a signed summation of |lhs| and |
| // |rhs| and stores the result into the variable pointed to by |val| and |
| // returns true if the signed summation resulted in an overflow. |
| inline bool SignedAddOverflow64(int64_t lhs, int64_t rhs, int64_t* val) { |
| uint64_t res = static_cast<uint64_t>(lhs) + static_cast<uint64_t>(rhs); |
| *val = bit_cast<int64_t>(res); |
| return ((res ^ lhs) & (res ^ rhs) & (1ULL << 63)) != 0; |
| } |
| |
| |
| // SignedSubOverflow64(lhs,rhs,val) performs a signed subtraction of |lhs| and |
| // |rhs| and stores the result into the variable pointed to by |val| and |
| // returns true if the signed subtraction resulted in an overflow. |
| inline bool SignedSubOverflow64(int64_t lhs, int64_t rhs, int64_t* val) { |
| uint64_t res = static_cast<uint64_t>(lhs) - static_cast<uint64_t>(rhs); |
| *val = bit_cast<int64_t>(res); |
| return ((res ^ lhs) & (res ^ ~rhs) & (1ULL << 63)) != 0; |
| } |
| |
| // SignedMulHigh32(lhs, rhs) multiplies two signed 32-bit values |lhs| and |
| // |rhs|, extracts the most significant 32 bits of the result, and returns |
| // those. |
| V8_BASE_EXPORT int32_t SignedMulHigh32(int32_t lhs, int32_t rhs); |
| |
| // SignedMulHighAndAdd32(lhs, rhs, acc) multiplies two signed 32-bit values |
| // |lhs| and |rhs|, extracts the most significant 32 bits of the result, and |
| // adds the accumulate value |acc|. |
| V8_BASE_EXPORT int32_t SignedMulHighAndAdd32(int32_t lhs, int32_t rhs, |
| int32_t acc); |
| |
| // SignedDiv32(lhs, rhs) divides |lhs| by |rhs| and returns the quotient |
| // truncated to int32. If |rhs| is zero, then zero is returned. If |lhs| |
| // is minint and |rhs| is -1, it returns minint. |
| V8_BASE_EXPORT int32_t SignedDiv32(int32_t lhs, int32_t rhs); |
| |
| // SignedMod32(lhs, rhs) divides |lhs| by |rhs| and returns the remainder |
| // truncated to int32. If either |rhs| is zero or |lhs| is minint and |rhs| |
| // is -1, it returns zero. |
| V8_BASE_EXPORT int32_t SignedMod32(int32_t lhs, int32_t rhs); |
| |
| // UnsignedAddOverflow32(lhs,rhs,val) performs an unsigned summation of |lhs| |
| // and |rhs| and stores the result into the variable pointed to by |val| and |
| // returns true if the unsigned summation resulted in an overflow. |
| inline bool UnsignedAddOverflow32(uint32_t lhs, uint32_t rhs, uint32_t* val) { |
| #if V8_HAS_BUILTIN_SADD_OVERFLOW |
| return __builtin_uadd_overflow(lhs, rhs, val); |
| #else |
| *val = lhs + rhs; |
| return *val < (lhs | rhs); |
| #endif |
| } |
| |
| |
| // UnsignedDiv32(lhs, rhs) divides |lhs| by |rhs| and returns the quotient |
| // truncated to uint32. If |rhs| is zero, then zero is returned. |
| inline uint32_t UnsignedDiv32(uint32_t lhs, uint32_t rhs) { |
| return rhs ? lhs / rhs : 0u; |
| } |
| |
| |
| // UnsignedMod32(lhs, rhs) divides |lhs| by |rhs| and returns the remainder |
| // truncated to uint32. If |rhs| is zero, then zero is returned. |
| inline uint32_t UnsignedMod32(uint32_t lhs, uint32_t rhs) { |
| return rhs ? lhs % rhs : 0u; |
| } |
| |
| |
| // SignedSaturatedAdd64(lhs, rhs) adds |lhs| and |rhs|, |
| // checks and returns the result. |
| V8_BASE_EXPORT int64_t SignedSaturatedAdd64(int64_t lhs, int64_t rhs); |
| |
| // SignedSaturatedSub64(lhs, rhs) subtracts |lhs| by |rhs|, |
| // checks and returns the result. |
| V8_BASE_EXPORT int64_t SignedSaturatedSub64(int64_t lhs, int64_t rhs); |
| |
| } // namespace bits |
| } // namespace base |
| } // namespace v8 |
| |
| #endif // V8_BASE_BITS_H_ |