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 <algorithm>
       9             : 
      10             : #include "src/zone/zone-containers.h"
      11             : 
      12             : namespace v8 {
      13             : namespace internal {
      14             : namespace interpreter {
      15             : 
      16             : class BytecodeArrayBuilder;
      17             : 
      18             : // A label representing a loop header in a bytecode array. It is bound before
      19             : // the jump is seen, so its position is always known by the time the jump is
      20             : // reached.
      21             : class V8_EXPORT_PRIVATE BytecodeLoopHeader final {
      22             :  public:
      23      278400 :   BytecodeLoopHeader() : offset_(kInvalidOffset) {}
      24             : 
      25             :   size_t offset() const {
      26             :     DCHECK_NE(offset_, kInvalidOffset);
      27      254099 :     return offset_;
      28             :   }
      29             : 
      30             :  private:
      31             :   static const size_t kInvalidOffset = static_cast<size_t>(-1);
      32             : 
      33             :   void bind_to(size_t offset) {
      34             :     DCHECK_NE(offset, kInvalidOffset);
      35             :     DCHECK_EQ(offset_, kInvalidOffset);
      36      262480 :     offset_ = offset;
      37             :   }
      38             : 
      39             :   // The bytecode offset of the loop header.
      40             :   size_t offset_;
      41             : 
      42             :   friend class BytecodeArrayWriter;
      43             : };
      44             : 
      45             : // A label representing a forward branch target in a bytecode array. When a
      46             : // label is bound, it represents a known position in the bytecode array. A label
      47             : // can only have at most one referrer jump.
      48             : class V8_EXPORT_PRIVATE BytecodeLabel final {
      49             :  public:
      50     1865502 :   BytecodeLabel() : bound_(false), jump_offset_(kInvalidOffset) {}
      51             : 
      52             :   bool is_bound() const { return bound_; }
      53             :   size_t jump_offset() const {
      54             :     DCHECK_NE(jump_offset_, kInvalidOffset);
      55             :     return jump_offset_;
      56             :   }
      57             : 
      58           1 :   bool has_referrer_jump() const { return jump_offset_ != kInvalidOffset; }
      59             : 
      60             :  private:
      61             :   static const size_t kInvalidOffset = static_cast<size_t>(-1);
      62             : 
      63             :   void bind() {
      64             :     DCHECK(!bound_);
      65     1823454 :     bound_ = true;
      66             :   }
      67             : 
      68             :   void set_referrer(size_t offset) {
      69             :     DCHECK(!bound_);
      70             :     DCHECK_NE(offset, kInvalidOffset);
      71             :     DCHECK_EQ(jump_offset_, kInvalidOffset);
      72     1823469 :     jump_offset_ = offset;
      73             :   }
      74             : 
      75             :   // Set when the label is bound (i.e. the start of the target basic block).
      76             :   bool bound_;
      77             :   // Set when the jump referrer is set (i.e. the location of the jump).
      78             :   size_t jump_offset_;
      79             : 
      80             :   friend class BytecodeArrayWriter;
      81             : };
      82             : 
      83             : // Class representing a branch target of multiple jumps.
      84     8146625 : class V8_EXPORT_PRIVATE BytecodeLabels {
      85             :  public:
      86     8146441 :   explicit BytecodeLabels(Zone* zone) : labels_(zone), is_bound_(false) {}
      87             : 
      88             :   BytecodeLabel* New();
      89             : 
      90             :   void Bind(BytecodeArrayBuilder* builder);
      91             : 
      92             :   bool is_bound() const {
      93             :     DCHECK_IMPLIES(
      94             :         is_bound_,
      95             :         std::all_of(labels_.begin(), labels_.end(), [](const BytecodeLabel& l) {
      96             :           return !l.has_referrer_jump() || l.is_bound();
      97             :         }));
      98             :     return is_bound_;
      99             :   }
     100             : 
     101             :   bool empty() const { return labels_.empty(); }
     102             : 
     103             :  private:
     104             :   ZoneLinkedList<BytecodeLabel> labels_;
     105             :   bool is_bound_;
     106             : 
     107             :   DISALLOW_COPY_AND_ASSIGN(BytecodeLabels);
     108             : };
     109             : 
     110             : }  // namespace interpreter
     111             : }  // namespace internal
     112             : }  // namespace v8
     113             : 
     114             : #endif  // V8_INTERPRETER_BYTECODE_LABEL_H_