1// Copyright 2017 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#ifndef V8_INTERPRETER_BYTECODE_JUMP_TABLE_H_
6#define V8_INTERPRETER_BYTECODE_JUMP_TABLE_H_
7
8#include "src/utils/bit-vector.h"
9#include "src/zone/zone.h"
10
11namespace v8 {
12namespace internal {
13namespace interpreter {
14
15class ConstantArrayBuilder;
16
17// A jump table for a set of targets in a bytecode array. When an entry in the
18// table is bound, it represents a known position in the bytecode array. If no
19// entries match, the switch falls through.
20class V8_EXPORT_PRIVATE BytecodeJumpTable final : public ZoneObject {
21 public:
22  // Constructs a new BytecodeJumpTable starting at |constant_pool_index|, with
23  // the given |size|, where the case values of the table start at
24  // |case_value_base|.
25  BytecodeJumpTable(size_t constant_pool_index, int size, int case_value_base,
26                    Zone* zone)
27      :
28#ifdef DEBUG
29        bound_(size, zone),
30#endif
31        constant_pool_index_(constant_pool_index),
32        switch_bytecode_offset_(kInvalidOffset),
33        size_(size),
34        case_value_base_(case_value_base) {
35  }
36
37  size_t constant_pool_index() const { return constant_pool_index_; }
38  size_t switch_bytecode_offset() const { return switch_bytecode_offset_; }
39  int case_value_base() const { return case_value_base_; }
40  int size() const { return size_; }
41#ifdef DEBUG
42  bool is_bound(int case_value) const {
43    DCHECK_GE(case_value, case_value_base_);
44    DCHECK_LT(case_value, case_value_base_ + size());
45    return bound_.Contains(case_value - case_value_base_);
46  }
47#endif
48
49  size_t ConstantPoolEntryFor(int case_value) {
50    DCHECK_GE(case_value, case_value_base_);
51    return constant_pool_index_ + case_value - case_value_base_;
52  }
53
54 private:
55  static const size_t kInvalidIndex = static_cast<size_t>(-1);
56  static const size_t kInvalidOffset = static_cast<size_t>(-1);
57
58  void mark_bound(int case_value) {
59#ifdef DEBUG
60    DCHECK_GE(case_value, case_value_base_);
61    DCHECK_LT(case_value, case_value_base_ + size());
62    bound_.Add(case_value - case_value_base_);
63#endif
64  }
65
66  void set_switch_bytecode_offset(size_t offset) {
67    DCHECK_EQ(switch_bytecode_offset_, kInvalidOffset);
68    switch_bytecode_offset_ = offset;
69  }
70
71#ifdef DEBUG
72  // This bit vector is only used for DCHECKS, so only store the field in debug
73  // builds.
74  BitVector bound_;
75#endif
76  size_t constant_pool_index_;
77  size_t switch_bytecode_offset_;
78  int size_;
79  int case_value_base_;
80
81  friend class BytecodeArrayWriter;
82};
83
84}  // namespace interpreter
85}  // namespace internal
86}  // namespace v8
87
88#endif  // V8_INTERPRETER_BYTECODE_JUMP_TABLE_H_
89