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             : 
      11             : namespace v8 {
      12             : namespace base {
      13             : namespace bits {
      14             : 
      15     2948447 : uint32_t RoundUpToPowerOfTwo32(uint32_t value) {
      16             :   DCHECK_LE(value, uint32_t{1} << 31);
      17     2948447 :   if (value) --value;
      18             : // Use computation based on leading zeros if we have compiler support for that.
      19             : #if V8_HAS_BUILTIN_CLZ || V8_CC_MSVC
      20     2948447 :   return 1u << (32 - CountLeadingZeros(value));
      21             : #else
      22             :   value |= value >> 1;
      23             :   value |= value >> 2;
      24             :   value |= value >> 4;
      25             :   value |= value >> 8;
      26             :   value |= value >> 16;
      27             :   return value + 1;
      28             : #endif
      29             : }
      30             : 
      31     1918076 : uint64_t RoundUpToPowerOfTwo64(uint64_t value) {
      32             :   DCHECK_LE(value, uint64_t{1} << 63);
      33     1918076 :   if (value) --value;
      34             : // Use computation based on leading zeros if we have compiler support for that.
      35             : #if V8_HAS_BUILTIN_CLZ
      36     1918076 :   return uint64_t{1} << (64 - CountLeadingZeros(value));
      37             : #else
      38             :   value |= value >> 1;
      39             :   value |= value >> 2;
      40             :   value |= value >> 4;
      41             :   value |= value >> 8;
      42             :   value |= value >> 16;
      43             :   value |= value >> 32;
      44             :   return value + 1;
      45             : #endif
      46             : }
      47             : 
      48             : 
      49        1280 : int32_t SignedMulHigh32(int32_t lhs, int32_t rhs) {
      50        2655 :   int64_t const value = static_cast<int64_t>(lhs) * static_cast<int64_t>(rhs);
      51        2655 :   return bit_cast<int32_t, uint32_t>(bit_cast<uint64_t>(value) >> 32u);
      52             : }
      53             : 
      54             : 
      55        1375 : int32_t SignedMulHighAndAdd32(int32_t lhs, int32_t rhs, int32_t acc) {
      56        1375 :   return bit_cast<int32_t>(bit_cast<uint32_t>(acc) +
      57        1375 :                            bit_cast<uint32_t>(SignedMulHigh32(lhs, rhs)));
      58             : }
      59             : 
      60             : 
      61       19838 : int32_t SignedDiv32(int32_t lhs, int32_t rhs) {
      62       19838 :   if (rhs == 0) return 0;
      63       19787 :   if (rhs == -1) return lhs == std::numeric_limits<int32_t>::min() ? lhs : -lhs;
      64       19451 :   return lhs / rhs;
      65             : }
      66             : 
      67             : 
      68       39384 : int32_t SignedMod32(int32_t lhs, int32_t rhs) {
      69       39384 :   if (rhs == 0 || rhs == -1) return 0;
      70       39182 :   return lhs % rhs;
      71             : }
      72             : 
      73      139950 : int64_t SignedSaturatedAdd64(int64_t lhs, int64_t rhs) {
      74             :   using limits = std::numeric_limits<int64_t>;
      75             :   // Underflow if {lhs + rhs < min}. In that case, return {min}.
      76      139950 :   if (rhs < 0 && lhs < limits::min() - rhs) return limits::min();
      77             :   // Overflow if {lhs + rhs > max}. In that case, return {max}.
      78      139950 :   if (rhs >= 0 && lhs > limits::max() - rhs) return limits::max();
      79      139950 :   return lhs + rhs;
      80             : }
      81             : 
      82           0 : int64_t SignedSaturatedSub64(int64_t lhs, int64_t rhs) {
      83             :   using limits = std::numeric_limits<int64_t>;
      84             :   // Underflow if {lhs - rhs < min}. In that case, return {min}.
      85           0 :   if (rhs > 0 && lhs < limits::min() + rhs) return limits::min();
      86             :   // Overflow if {lhs - rhs > max}. In that case, return {max}.
      87           0 :   if (rhs <= 0 && lhs > limits::max() + rhs) return limits::max();
      88           0 :   return lhs - rhs;
      89             : }
      90             : 
      91       97702 : bool SignedMulOverflow32(int32_t lhs, int32_t rhs, int32_t* val) {
      92             :   // Compute the result as {int64_t}, then check for overflow.
      93       97702 :   int64_t result = int64_t{lhs} * int64_t{rhs};
      94       97702 :   *val = static_cast<int32_t>(result);
      95             :   using limits = std::numeric_limits<int32_t>;
      96       97702 :   return result < limits::min() || result > limits::max();
      97             : }
      98             : 
      99             : }  // namespace bits
     100             : }  // namespace base
     101             : }  // namespace v8