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// 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.
#ifndef V8_REGEXP_REGEXP_STACK_H_
#define V8_REGEXP_REGEXP_STACK_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 {
public:
// 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_; }
private:
RegExpStack* regexp_stack_;
DISALLOW_COPY_AND_ASSIGN(RegExpStackScope);
};
class RegExpStack {
public:
// 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 constexpr int kStackLimitSlack = 32;
// Gives the top of the memory used as stack.
Address stack_base() {
DCHECK_NE(0, thread_local_.memory_size_);
DCHECK_EQ(thread_local_.memory_top_,
thread_local_.memory_ + thread_local_.memory_size_);
return reinterpret_cast<Address>(thread_local_.memory_top_);
}
// 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_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 constexpr int ArchiveSpacePerThread() {
return static_cast<int>(sizeof(ThreadLocal));
}
char* ArchiveStack(char* to);
char* RestoreStack(char* from);
void FreeThreadResources() { thread_local_.ResetToStaticStack(this); }
// Maximal size of allocated stack area.
static constexpr size_t kMaximumStackSize = 64 * MB;
private:
RegExpStack();
~RegExpStack();
// Artificial limit used when the thread-local state has been destroyed.
static const Address kMemoryTop =
static_cast<Address>(static_cast<uintptr_t>(-1));
// Minimal size of dynamically-allocated stack area.
static constexpr size_t kMinimumDynamicStackSize = 1 * KB;
// In addition to dynamically-allocated, variable-sized stacks, we also have
// a statically allocated and sized area that is used whenever no dynamic
// stack is allocated. This guarantees that a stack is always available and
// we can skip availability-checks later on.
// It's double the slack size to ensure that we have a bit of breathing room
// before NativeRegExpMacroAssembler::GrowStack must be called.
static constexpr size_t kStaticStackSize =
2 * kStackLimitSlack * kSystemPointerSize;
byte static_stack_[kStaticStackSize] = {0};
STATIC_ASSERT(kStaticStackSize <= kMaximumStackSize);
// Structure holding the allocated memory, size and limit.
struct ThreadLocal {
explicit ThreadLocal(RegExpStack* regexp_stack) {
ResetToStaticStack(regexp_stack);
}
// If memory_size_ > 0 then memory_ and memory_top_ must be non-nullptr
// and memory_top_ = memory_ + memory_size_
byte* memory_ = nullptr;
byte* memory_top_ = nullptr;
size_t memory_size_ = 0;
Address limit_ = kNullAddress;
bool owns_memory_ = false; // Whether memory_ is owned and must be freed.
void ResetToStaticStack(RegExpStack* regexp_stack);
void FreeAndInvalidate();
};
// Address of top of memory used as stack.
Address memory_top_address_address() {
return reinterpret_cast<Address>(&thread_local_.memory_top_);
}
// 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;
DISALLOW_COPY_AND_ASSIGN(RegExpStack);
};
} // namespace internal
} // namespace v8
#endif // V8_REGEXP_REGEXP_STACK_H_
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