| // 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 "include/v8stdint.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 { |
| |
| // CountPopulation32(value) returns the number of bits set in |value|. |
| inline uint32_t CountPopulation32(uint32_t value) { |
| #if V8_HAS_BUILTIN_POPCOUNT |
| return __builtin_popcount(value); |
| #else |
| value = ((value >> 1) & 0x55555555) + (value & 0x55555555); |
| value = ((value >> 2) & 0x33333333) + (value & 0x33333333); |
| value = ((value >> 4) & 0x0f0f0f0f) + (value & 0x0f0f0f0f); |
| value = ((value >> 8) & 0x00ff00ff) + (value & 0x00ff00ff); |
| value = ((value >> 16) & 0x0000ffff) + (value & 0x0000ffff); |
| return value; |
| #endif |
| } |
| |
| |
| // CountLeadingZeros32(value) returns the number of zero bits following the most |
| // significant 1 bit in |value| if |value| is non-zero, otherwise it returns 32. |
| inline uint32_t CountLeadingZeros32(uint32_t value) { |
| #if V8_HAS_BUILTIN_CLZ |
| return value ? __builtin_clz(value) : 32; |
| #elif V8_CC_MSVC |
| unsigned long result; // NOLINT(runtime/int) |
| if (!_BitScanReverse(&result, value)) return 32; |
| return static_cast<uint32_t>(31 - result); |
| #else |
| value = value | (value >> 1); |
| value = value | (value >> 2); |
| value = value | (value >> 4); |
| value = value | (value >> 8); |
| value = value | (value >> 16); |
| return CountPopulation32(~value); |
| #endif |
| } |
| |
| |
| // CountTrailingZeros32(value) returns the number of zero bits preceding the |
| // least significant 1 bit in |value| if |value| is non-zero, otherwise it |
| // returns 32. |
| inline uint32_t CountTrailingZeros32(uint32_t value) { |
| #if V8_HAS_BUILTIN_CTZ |
| return value ? __builtin_ctz(value) : 32; |
| #elif V8_CC_MSVC |
| unsigned long result; // NOLINT(runtime/int) |
| if (!_BitScanForward(&result, value)) return 32; |
| return static_cast<uint32_t>(result); |
| #else |
| if (value == 0) return 32; |
| unsigned count = 0; |
| for (value ^= value - 1; value >>= 1; ++count) |
| ; |
| return count; |
| #endif |
| } |
| |
| |
| inline uint32_t RotateRight32(uint32_t value, uint32_t shift) { |
| if (shift == 0) return value; |
| return (value >> shift) | (value << (32 - shift)); |
| } |
| |
| |
| inline uint64_t RotateRight64(uint64_t value, uint64_t shift) { |
| if (shift == 0) return value; |
| return (value >> shift) | (value << (64 - shift)); |
| } |
| |
| } // namespace bits |
| } // namespace base |
| } // namespace v8 |
| |
| #endif // V8_BASE_BITS_H_ |