summaryrefslogtreecommitdiffstats
path: root/js/src/regexp/regexp-stack.h
blob: 0b452c005911e16054aeb250f4c0236c8f77f007 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
// 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_

#include "regexp/regexp-shim.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:
  RegExpStack();
  ~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 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:
  // 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_