// 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. #include "src/base/bits.h" #include <limits> #include "src/base/logging.h" namespace v8 { namespace base { namespace bits { uint32_t RoundUpToPowerOfTwo32(uint32_t value) { DCHECK_LE(value, uint32_t{1} << 31); if (value) --value; // Use computation based on leading zeros if we have compiler support for that. #if V8_HAS_BUILTIN_CLZ || V8_CC_MSVC return 1u << (32 - CountLeadingZeros(value)); #else value |= value >> 1; value |= value >> 2; value |= value >> 4; value |= value >> 8; value |= value >> 16; return value + 1; #endif } uint64_t RoundUpToPowerOfTwo64(uint64_t value) { DCHECK_LE(value, uint64_t{1} << 63); if (value) --value; // Use computation based on leading zeros if we have compiler support for that. #if V8_HAS_BUILTIN_CLZ return uint64_t{1} << (64 - CountLeadingZeros(value)); #else value |= value >> 1; value |= value >> 2; value |= value >> 4; value |= value >> 8; value |= value >> 16; value |= value >> 32; return value + 1; #endif } int32_t SignedMulHigh32(int32_t lhs, int32_t rhs) { int64_t const value = static_cast<int64_t>(lhs) * static_cast<int64_t>(rhs); return bit_cast<int32_t, uint32_t>(bit_cast<uint64_t>(value) >> 32u); } int32_t SignedMulHighAndAdd32(int32_t lhs, int32_t rhs, int32_t acc) { return bit_cast<int32_t>(bit_cast<uint32_t>(acc) + bit_cast<uint32_t>(SignedMulHigh32(lhs, rhs))); } int32_t SignedDiv32(int32_t lhs, int32_t rhs) { if (rhs == 0) return 0; if (rhs == -1) return lhs == std::numeric_limits<int32_t>::min() ? lhs : -lhs; return lhs / rhs; } int32_t SignedMod32(int32_t lhs, int32_t rhs) { if (rhs == 0 || rhs == -1) return 0; return lhs % rhs; } int64_t SignedSaturatedAdd64(int64_t lhs, int64_t rhs) { using limits = std::numeric_limits<int64_t>; // Underflow if {lhs + rhs < min}. In that case, return {min}. if (rhs < 0 && lhs < limits::min() - rhs) return limits::min(); // Overflow if {lhs + rhs > max}. In that case, return {max}. if (rhs >= 0 && lhs > limits::max() - rhs) return limits::max(); return lhs + rhs; } int64_t SignedSaturatedSub64(int64_t lhs, int64_t rhs) { using limits = std::numeric_limits<int64_t>; // Underflow if {lhs - rhs < min}. In that case, return {min}. if (rhs > 0 && lhs < limits::min() + rhs) return limits::min(); // Overflow if {lhs - rhs > max}. In that case, return {max}. if (rhs <= 0 && lhs > limits::max() + rhs) return limits::max(); return lhs - rhs; } bool SignedMulOverflow32(int32_t lhs, int32_t rhs, int32_t* val) { // Compute the result as {int64_t}, then check for overflow. int64_t result = int64_t{lhs} * int64_t{rhs}; *val = static_cast<int32_t>(result); using limits = std::numeric_limits<int32_t>; return result < limits::min() || result > limits::max(); } } // namespace bits } // namespace base } // namespace v8