blob: b1d45717602f713111ae2be130ef521c6dc93e0b [file] [log] [blame]
// Copyright 2009 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/logging.h"
#include "src/base/macros.h"
#include "src/common/globals.h"
namespace v8 {
namespace internal {
class RegExpStack;
// Maintains a per-v8thread stack area that can be used by irregexp
// implementation for its backtracking stack.
// Since there is only one stack area, the Irregexp implementation is not
// re-entrant. I.e., no regular expressions may be executed in the same thread
// during a preempted Irregexp execution.
class RegExpStackScope {
// Create and delete an instance to control the life-time of a growing stack.
// Initializes the stack memory area if necessary.
explicit RegExpStackScope(Isolate* isolate);
~RegExpStackScope(); // Releases the stack if it has grown.
RegExpStack* stack() const { return regexp_stack_; }
RegExpStack* regexp_stack_;
class RegExpStack {
// Number of allocated locations on the stack below the limit.
// No sequence of pushes must be longer that this without doing a stack-limit
// check.
static const int kStackLimitSlack = 32;
// Gives the top of the memory used as stack.
Address stack_base() {
DCHECK_NE(0, thread_local_.memory_size_);
return reinterpret_cast<Address>(thread_local_.memory_) +
// The total size of the memory allocated for the stack.
size_t stack_capacity() { return thread_local_.memory_size_; }
// If the stack pointer gets below the limit, we should react and
// either grow the stack or report an out-of-stack exception.
// There is only a limited number of locations below the stack limit,
// so users of the stack should check the stack limit during any
// sequence of pushes longer that this.
Address* limit_address() { return &(thread_local_.limit_); }
// Ensures that there is a memory area with at least the specified size.
// If passing zero, the default/minimum size buffer is allocated.
Address EnsureCapacity(size_t size);
// Thread local archiving.
static int ArchiveSpacePerThread() {
return static_cast<int>(sizeof(ThreadLocal));
char* ArchiveStack(char* to);
char* RestoreStack(char* from);
void FreeThreadResources() { thread_local_.Free(); }
// Artificial limit used when no memory has been allocated.
static const Address kMemoryTop =
// Minimal size of allocated stack area.
static const size_t kMinimumStackSize = 1 * KB;
// Maximal size of allocated stack area.
static const size_t kMaximumStackSize = 64 * MB;
// Structure holding the allocated memory, size and limit.
struct ThreadLocal {
ThreadLocal() { Clear(); }
// If memory_size_ > 0 then memory_ must be non-nullptr.
byte* memory_;
size_t memory_size_;
Address limit_;
void Clear() {
memory_ = nullptr;
memory_size_ = 0;
limit_ = kMemoryTop;
void Free();
// Address of allocated memory.
Address memory_address() {
return reinterpret_cast<Address>(&thread_local_.memory_);
// Address of size of allocated memory.
Address memory_size_address() {
return reinterpret_cast<Address>(&thread_local_.memory_size_);
// Resets the buffer if it has grown beyond the default/minimum size.
// After this, the buffer is either the default size, or it is empty, so
// you have to call EnsureCapacity before using it again.
void Reset();
ThreadLocal thread_local_;
Isolate* isolate_;
friend class ExternalReference;
friend class Isolate;
friend class RegExpStackScope;
} // namespace internal
} // namespace v8