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// 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
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