Line data    Source code

       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     2891194 : uint32_t RoundUpToPowerOfTwo32(uint32_t value) {
      17             :   DCHECK_LE(value, uint32_t{1} << 31);
      18     2891194 :   if (value) --value;
      19             : // Use computation based on leading zeros if we have compiler support for that.
      20             : #if V8_HAS_BUILTIN_CLZ || V8_CC_MSVC
      21     2891194 :   return 1u << (32 - CountLeadingZeros(value));
      22             : #else
      23             :   value |= value >> 1;
      24             :   value |= value >> 2;
      25             :   value |= value >> 4;
      26             :   value |= value >> 8;
      27             :   value |= value >> 16;
      28             :   return value + 1;
      29             : #endif
      30             : }
      31             : 
      32     2333504 : uint64_t RoundUpToPowerOfTwo64(uint64_t value) {
      33             :   DCHECK_LE(value, uint64_t{1} << 63);
      34     2333504 :   if (value) --value;
      35             : // Use computation based on leading zeros if we have compiler support for that.
      36             : #if V8_HAS_BUILTIN_CLZ
      37     2333504 :   return uint64_t{1} << (64 - CountLeadingZeros(value));
      38             : #else
      39             :   value |= value >> 1;
      40             :   value |= value >> 2;
      41             :   value |= value >> 4;
      42             :   value |= value >> 8;
      43             :   value |= value >> 16;
      44             :   value |= value >> 32;
      45             :   return value + 1;
      46             : #endif
      47             : }
      48             : 
      49             : 
      50        1280 : int32_t SignedMulHigh32(int32_t lhs, int32_t rhs) {
      51        1280 :   int64_t const value = static_cast<int64_t>(lhs) * static_cast<int64_t>(rhs);
      52        3935 :   return bit_cast<int32_t, uint32_t>(bit_cast<uint64_t>(value) >> 32u);
      53             : }
      54             : 
      55             : 
      56        1375 : int32_t SignedMulHighAndAdd32(int32_t lhs, int32_t rhs, int32_t acc) {
      57        1375 :   return bit_cast<int32_t>(bit_cast<uint32_t>(acc) +
      58        1375 :                            bit_cast<uint32_t>(SignedMulHigh32(lhs, rhs)));
      59             : }
      60             : 
      61             : 
      62       19892 : int32_t SignedDiv32(int32_t lhs, int32_t rhs) {
      63       19892 :   if (rhs == 0) return 0;
      64       19841 :   if (rhs == -1) return lhs == std::numeric_limits<int32_t>::min() ? lhs : -lhs;
      65       19505 :   return lhs / rhs;
      66             : }
      67             : 
      68             : 
      69       39444 : int32_t SignedMod32(int32_t lhs, int32_t rhs) {
      70       39444 :   if (rhs == 0 || rhs == -1) return 0;
      71       39242 :   return lhs % rhs;
      72             : }
      73             : 
      74             : 
      75           0 : int64_t FromCheckedNumeric(const internal::CheckedNumeric<int64_t> value) {
      76       42101 :   if (value.IsValid())
      77             :     return value.ValueUnsafe();
      78             : 
      79             :   // We could return max/min but we don't really expose what the maximum delta
      80             :   // is. Instead, return max/(-max), which is something that clients can reason
      81             :   // about.
      82             :   // TODO(rvargas) crbug.com/332611: don't use internal values.
      83             :   int64_t limit = std::numeric_limits<int64_t>::max();
      84           0 :   if (value.validity() == internal::RANGE_UNDERFLOW)
      85             :     limit = -limit;
      86           0 :   return value.ValueOrDefault(limit);
      87             : }
      88             : 
      89             : 
      90       42101 : int64_t SignedSaturatedAdd64(int64_t lhs, int64_t rhs) {
      91             :   internal::CheckedNumeric<int64_t> rv(lhs);
      92             :   rv += rhs;
      93       42101 :   return FromCheckedNumeric(rv);
      94             : }
      95             : 
      96             : 
      97           0 : int64_t SignedSaturatedSub64(int64_t lhs, int64_t rhs) {
      98             :   internal::CheckedNumeric<int64_t> rv(lhs);
      99             :   rv -= rhs;
     100           0 :   return FromCheckedNumeric(rv);
     101             : }
     102             : 
     103      114412 : bool SignedMulOverflow32(int32_t lhs, int32_t rhs, int32_t* val) {
     104             :   internal::CheckedNumeric<int32_t> rv(lhs);
     105             :   rv *= rhs;
     106             :   int32_t limit = std::numeric_limits<int32_t>::max();
     107      114412 :   *val = rv.ValueOrDefault(limit);
     108      114412 :   return !rv.IsValid();
     109             : }
     110             : 
     111           0 : bool SignedMulOverflow64(int64_t lhs, int64_t rhs, int64_t* val) {
     112             :   internal::CheckedNumeric<int64_t> rv(lhs);
     113             :   rv *= rhs;
     114             :   int64_t limit = std::numeric_limits<int64_t>::max();
     115           0 :   *val = rv.ValueOrDefault(limit);
     116           0 :   return !rv.IsValid();
     117             : }
     118             : 
     119             : }  // namespace bits
     120             : }  // namespace base
     121             : }  // namespace v8