| // Copyright 2006-2008 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_COMPILER_INTRINSICS_H_ |
| #define V8_COMPILER_INTRINSICS_H_ |
| |
| namespace v8 { |
| namespace internal { |
| |
| class CompilerIntrinsics { |
| public: |
| // Returns number of zero bits preceding least significant 1 bit. |
| // Undefined for zero value. |
| INLINE(static int CountTrailingZeros(uint32_t value)); |
| |
| // Returns number of zero bits following most significant 1 bit. |
| // Undefined for zero value. |
| INLINE(static int CountLeadingZeros(uint32_t value)); |
| |
| // Returns the number of bits set. |
| INLINE(static int CountSetBits(uint32_t value)); |
| }; |
| |
| #ifdef __GNUC__ |
| int CompilerIntrinsics::CountTrailingZeros(uint32_t value) { |
| return __builtin_ctz(value); |
| } |
| |
| int CompilerIntrinsics::CountLeadingZeros(uint32_t value) { |
| return __builtin_clz(value); |
| } |
| |
| int CompilerIntrinsics::CountSetBits(uint32_t value) { |
| return __builtin_popcount(value); |
| } |
| |
| #elif defined(_MSC_VER) |
| |
| #pragma intrinsic(_BitScanForward) |
| #pragma intrinsic(_BitScanReverse) |
| |
| int CompilerIntrinsics::CountTrailingZeros(uint32_t value) { |
| unsigned long result; //NOLINT |
| _BitScanForward(&result, static_cast<long>(value)); //NOLINT |
| return static_cast<int>(result); |
| } |
| |
| int CompilerIntrinsics::CountLeadingZeros(uint32_t value) { |
| unsigned long result; //NOLINT |
| _BitScanReverse(&result, static_cast<long>(value)); //NOLINT |
| return 31 - static_cast<int>(result); |
| } |
| |
| int CompilerIntrinsics::CountSetBits(uint32_t value) { |
| // Manually count set bits. |
| 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; |
| } |
| |
| #else |
| #error Unsupported compiler |
| #endif |
| |
| } } // namespace v8::internal |
| |
| #endif // V8_COMPILER_INTRINSICS_H_ |