1 // Copyright 2014 the V8 project authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #include "src/base/bits.h" 6 7 #include <limits> 8 9 #include "src/base/logging.h" 10 #include "src/base/safe_math.h" 11 12 namespace v8 { 13 namespace base { 14 namespace bits { 15 16 uint32_t RoundUpToPowerOfTwo32(uint32_t value) { 17 DCHECK_LE(value, 0x80000000u); 18 value = value - 1; 19 value = value | (value >> 1); 20 value = value | (value >> 2); 21 value = value | (value >> 4); 22 value = value | (value >> 8); 23 value = value | (value >> 16); 24 return value + 1; 25 } 26 27 28 int32_t SignedMulHigh32(int32_t lhs, int32_t rhs) { 29 int64_t const value = static_cast<int64_t>(lhs) * static_cast<int64_t>(rhs); 30 return bit_cast<int32_t, uint32_t>(bit_cast<uint64_t>(value) >> 32u); 31 } 32 33 34 int32_t SignedMulHighAndAdd32(int32_t lhs, int32_t rhs, int32_t acc) { 35 return bit_cast<int32_t>(bit_cast<uint32_t>(acc) + 36 bit_cast<uint32_t>(SignedMulHigh32(lhs, rhs))); 37 } 38 39 40 int32_t SignedDiv32(int32_t lhs, int32_t rhs) { 41 if (rhs == 0) return 0; 42 if (rhs == -1) return -lhs; 43 return lhs / rhs; 44 } 45 46 47 int32_t SignedMod32(int32_t lhs, int32_t rhs) { 48 if (rhs == 0 || rhs == -1) return 0; 49 return lhs % rhs; 50 } 51 52 53 int64_t FromCheckedNumeric(const internal::CheckedNumeric<int64_t> value) { 54 if (value.IsValid()) 55 return value.ValueUnsafe(); 56 57 // We could return max/min but we don't really expose what the maximum delta 58 // is. Instead, return max/(-max), which is something that clients can reason 59 // about. 60 // TODO(rvargas) crbug.com/332611: don't use internal values. 61 int64_t limit = std::numeric_limits<int64_t>::max(); 62 if (value.validity() == internal::RANGE_UNDERFLOW) 63 limit = -limit; 64 return value.ValueOrDefault(limit); 65 } 66 67 68 int64_t SignedSaturatedAdd64(int64_t lhs, int64_t rhs) { 69 internal::CheckedNumeric<int64_t> rv(lhs); 70 rv += rhs; 71 return FromCheckedNumeric(rv); 72 } 73 74 75 int64_t SignedSaturatedSub64(int64_t lhs, int64_t rhs) { 76 internal::CheckedNumeric<int64_t> rv(lhs); 77 rv -= rhs; 78 return FromCheckedNumeric(rv); 79 } 80 81 bool SignedMulOverflow32(int32_t lhs, int32_t rhs, int32_t* val) { 82 internal::CheckedNumeric<int32_t> rv(lhs); 83 rv *= rhs; 84 int32_t limit = std::numeric_limits<int32_t>::max(); 85 *val = rv.ValueOrDefault(limit); 86 return !rv.IsValid(); 87 } 88 89 bool SignedMulOverflow64(int64_t lhs, int64_t rhs, int64_t* val) { 90 internal::CheckedNumeric<int64_t> rv(lhs); 91 rv *= rhs; 92 int64_t limit = std::numeric_limits<int64_t>::max(); 93 *val = rv.ValueOrDefault(limit); 94 return !rv.IsValid(); 95 } 96 97 } // namespace bits 98 } // namespace base 99 } // namespace v8 100
