1 // Copyright 2015 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_CONSTANT_ARRAY_BUILDER_H_
6 #define V8_INTERPRETER_CONSTANT_ARRAY_BUILDER_H_
7 
8 #include "src/globals.h"
9 #include "src/identity-map.h"
10 #include "src/interpreter/bytecodes.h"
11 #include "src/zone/zone-containers.h"
12 
13 namespace v8 {
14 namespace internal {
15 
16 class Isolate;
17 
18 namespace interpreter {
19 
20 // A helper class for constructing constant arrays for the
21 // interpreter. Each instance of this class is intended to be used to
22 // generate exactly one FixedArray of constants via the ToFixedArray
23 // method.
24 class V8_EXPORT_PRIVATE ConstantArrayBuilder final BASE_EMBEDDED {
25  public:
26   // Capacity of the 8-bit operand slice.
27   static const size_t k8BitCapacity = 1u << kBitsPerByte;
28 
29   // Capacity of the 16-bit operand slice.
30   static const size_t k16BitCapacity = (1u << 2 * kBitsPerByte) - k8BitCapacity;
31 
32   // Capacity of the 32-bit operand slice.
33   static const size_t k32BitCapacity =
34       kMaxUInt32 - k16BitCapacity - k8BitCapacity + 1;
35 
36   ConstantArrayBuilder(Zone* zone, Handle<Object> the_hole_value);
37 
38   // Generate a fixed array of constants based on inserted objects.
39   Handle<FixedArray> ToFixedArray(Isolate* isolate);
40 
41   // Returns the object in the constant pool array that at index
42   // |index|.
43   Handle<Object> At(size_t index) const;
44 
45   // Returns the number of elements in the array.
46   size_t size() const;
47 
48   // Insert an object into the constants array if it is not already
49   // present. Returns the array index associated with the object.
50   size_t Insert(Handle<Object> object);
51 
52   // Allocates an empty entry and returns the array index associated with the
53   // reservation. Entry can be inserted by calling InsertReservedEntry().
54   size_t AllocateEntry();
55 
56   // Inserts the given object into an allocated entry.
57   void InsertAllocatedEntry(size_t index, Handle<Object> object);
58 
59   // Creates a reserved entry in the constant pool and returns
60   // the size of the operand that'll be required to hold the entry
61   // when committed.
62   OperandSize CreateReservedEntry();
63 
64   // Commit reserved entry and returns the constant pool index for the
65   // SMI value.
66   size_t CommitReservedEntry(OperandSize operand_size, Smi* value);
67 
68   // Discards constant pool reservation.
69   void DiscardReservedEntry(OperandSize operand_size);
70 
71  private:
72   typedef uint32_t index_t;
73 
74   index_t AllocateIndex(Handle<Object> object);
75   index_t AllocateReservedEntry(Smi* value);
76 
77   struct ConstantArraySlice final : public ZoneObject {
78     ConstantArraySlice(Zone* zone, size_t start_index, size_t capacity,
79                        OperandSize operand_size);
80     void Reserve();
81     void Unreserve();
82     size_t Allocate(Handle<Object> object);
83     Handle<Object> At(size_t index) const;
84     void InsertAt(size_t index, Handle<Object> object);
85     bool AllElementsAreUnique() const;
86 
availablefinal87     inline size_t available() const { return capacity() - reserved() - size(); }
reservedfinal88     inline size_t reserved() const { return reserved_; }
capacityfinal89     inline size_t capacity() const { return capacity_; }
sizefinal90     inline size_t size() const { return constants_.size(); }
start_indexfinal91     inline size_t start_index() const { return start_index_; }
max_indexfinal92     inline size_t max_index() const { return start_index_ + capacity() - 1; }
operand_sizefinal93     inline OperandSize operand_size() const { return operand_size_; }
94 
95    private:
96     const size_t start_index_;
97     const size_t capacity_;
98     size_t reserved_;
99     OperandSize operand_size_;
100     ZoneVector<Handle<Object>> constants_;
101 
102     DISALLOW_COPY_AND_ASSIGN(ConstantArraySlice);
103   };
104 
105   ConstantArraySlice* IndexToSlice(size_t index) const;
106   ConstantArraySlice* OperandSizeToSlice(OperandSize operand_size) const;
107 
the_hole_value()108   Handle<Object> the_hole_value() const { return the_hole_value_; }
109 
110   ConstantArraySlice* idx_slice_[3];
111   base::TemplateHashMapImpl<Address, index_t, base::KeyEqualityMatcher<Address>,
112                             ZoneAllocationPolicy>
113       constants_map_;
114   ZoneMap<Smi*, index_t> smi_map_;
115   ZoneVector<std::pair<Smi*, index_t>> smi_pairs_;
116   Zone* zone_;
117   Handle<Object> the_hole_value_;
118 };
119 
120 }  // namespace interpreter
121 }  // namespace internal
122 }  // namespace v8
123 
124 #endif  // V8_INTERPRETER_CONSTANT_ARRAY_BUILDER_H_
125