Line data    Source code

       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_BYTECODE_LABEL_H_
       6             : #define V8_INTERPRETER_BYTECODE_LABEL_H_
       7             : 
       8             : #include "src/zone/zone-containers.h"
       9             : 
      10             : namespace v8 {
      11             : namespace internal {
      12             : namespace interpreter {
      13             : 
      14             : class BytecodeArrayBuilder;
      15             : 
      16             : // A label representing a branch target in a bytecode array. When a
      17             : // label is bound, it represents a known position in the bytecode
      18             : // array. For labels that are forward references there can be at most
      19             : // one reference whilst it is unbound.
      20             : class V8_EXPORT_PRIVATE BytecodeLabel final {
      21             :  public:
      22    11811197 :   BytecodeLabel() : bound_(false), offset_(kInvalidOffset) {}
      23             : 
      24             :   bool is_bound() const { return bound_; }
      25             :   size_t offset() const { return offset_; }
      26             : 
      27             :  private:
      28             :   static const size_t kInvalidOffset = static_cast<size_t>(-1);
      29             : 
      30             :   void bind_to(size_t offset) {
      31             :     DCHECK(!bound_ && offset != kInvalidOffset);
      32     4749872 :     offset_ = offset;
      33     4749872 :     bound_ = true;
      34             :   }
      35             : 
      36             :   void set_referrer(size_t offset) {
      37             :     DCHECK(!bound_ && offset != kInvalidOffset && offset_ == kInvalidOffset);
      38     2877989 :     offset_ = offset;
      39             :   }
      40             : 
      41     7627863 :   bool is_forward_target() const {
      42     7627863 :     return offset() != kInvalidOffset && !is_bound();
      43             :   }
      44             : 
      45             :   // There are three states for a label:
      46             :   //                    bound_   offset_
      47             :   //  UNSET             false    kInvalidOffset
      48             :   //  FORWARD_TARGET    false    Offset of referring jump
      49             :   //  BACKWARD_TARGET    true    Offset of label in bytecode array when bound
      50             :   bool bound_;
      51             :   size_t offset_;
      52             : 
      53             :   friend class BytecodeArrayWriter;
      54             : };
      55             : 
      56             : // Class representing a branch target of multiple jumps.
      57             : class V8_EXPORT_PRIVATE BytecodeLabels {
      58             :  public:
      59             :   explicit BytecodeLabels(Zone* zone) : labels_(zone) {}
      60             : 
      61             :   BytecodeLabel* New();
      62             : 
      63             :   void Bind(BytecodeArrayBuilder* builder);
      64             : 
      65             :   void BindToLabel(BytecodeArrayBuilder* builder, const BytecodeLabel& target);
      66             : 
      67             :   bool is_bound() const {
      68             :     bool is_bound = !labels_.empty() && labels_.at(0).is_bound();
      69             :     DCHECK(!is_bound ||
      70             :            std::all_of(labels_.begin(), labels_.end(),
      71             :                        [](const BytecodeLabel& l) { return l.is_bound(); }));
      72             :     return is_bound;
      73             :   }
      74             : 
      75             :   bool empty() const { return labels_.empty(); }
      76             : 
      77             :  private:
      78             :   ZoneVector<BytecodeLabel> labels_;
      79             : 
      80             :   DISALLOW_COPY_AND_ASSIGN(BytecodeLabels);
      81             : };
      82             : 
      83             : }  // namespace interpreter
      84             : }  // namespace internal
      85             : }  // namespace v8
      86             : 
      87             : #endif  // V8_INTERPRETER_BYTECODE_LABEL_H_