| // 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" |
| #include "src/base/safe_math.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; |
| return lhs / rhs; |
| } |
| |
| |
| int32_t SignedMod32(int32_t lhs, int32_t rhs) { |
| if (rhs == 0 || rhs == -1) return 0; |
| return lhs % rhs; |
| } |
| |
| |
| int64_t FromCheckedNumeric(const internal::CheckedNumeric<int64_t> value) { |
| if (value.IsValid()) |
| return value.ValueUnsafe(); |
| |
| // We could return max/min but we don't really expose what the maximum delta |
| // is. Instead, return max/(-max), which is something that clients can reason |
| // about. |
| // TODO(rvargas) crbug.com/332611: don't use internal values. |
| int64_t limit = std::numeric_limits<int64_t>::max(); |
| if (value.validity() == internal::RANGE_UNDERFLOW) |
| limit = -limit; |
| return value.ValueOrDefault(limit); |
| } |
| |
| |
| int64_t SignedSaturatedAdd64(int64_t lhs, int64_t rhs) { |
| internal::CheckedNumeric<int64_t> rv(lhs); |
| rv += rhs; |
| return FromCheckedNumeric(rv); |
| } |
| |
| |
| int64_t SignedSaturatedSub64(int64_t lhs, int64_t rhs) { |
| internal::CheckedNumeric<int64_t> rv(lhs); |
| rv -= rhs; |
| return FromCheckedNumeric(rv); |
| } |
| |
| bool SignedMulOverflow32(int32_t lhs, int32_t rhs, int32_t* val) { |
| internal::CheckedNumeric<int32_t> rv(lhs); |
| rv *= rhs; |
| int32_t limit = std::numeric_limits<int32_t>::max(); |
| *val = rv.ValueOrDefault(limit); |
| return !rv.IsValid(); |
| } |
| |
| bool SignedMulOverflow64(int64_t lhs, int64_t rhs, int64_t* val) { |
| internal::CheckedNumeric<int64_t> rv(lhs); |
| rv *= rhs; |
| int64_t limit = std::numeric_limits<int64_t>::max(); |
| *val = rv.ValueOrDefault(limit); |
| return !rv.IsValid(); |
| } |
| |
| } // namespace bits |
| } // namespace base |
| } // namespace v8 |