tor-browser

The Tor Browser
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WhileEmitter.h (2855B)

      1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
      2 * vim: set ts=8 sts=2 et sw=2 tw=80:
      3 * This Source Code Form is subject to the terms of the Mozilla Public
      4 * License, v. 2.0. If a copy of the MPL was not distributed with this
      5 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
      6 
      7 #ifndef frontend_WhileEmitter_h
      8 #define frontend_WhileEmitter_h
      9 
     10 #include "mozilla/Attributes.h"
     11 #include "mozilla/Maybe.h"
     12 
     13 #include <stdint.h>
     14 
     15 #include "frontend/BytecodeControlStructures.h"
     16 #include "frontend/TDZCheckCache.h"
     17 
     18 namespace js {
     19 namespace frontend {
     20 
     21 struct BytecodeEmitter;
     22 
     23 // Class for emitting bytecode for while loop.
     24 //
     25 // Usage: (check for the return value is omitted for simplicity)
     26 //
     27 //   `while (cond) body`
     28 //     WhileEmitter wh(this);
     29 //     wh.emitCond(offset_of_while,
     30 //                 offset_of_body,
     31 //                 offset_of_end);
     32 //     emit(cond);
     33 //     wh.emitBody();
     34 //     emit(body);
     35 //     wh.emitEnd();
     36 //
     37 class MOZ_STACK_CLASS WhileEmitter {
     38 #if defined(ENABLE_DECORATORS) || defined(ENABLE_EXPLICIT_RESOURCE_MANAGEMENT)
     39 protected:
     40 #endif
     41  BytecodeEmitter* bce_;
     42 
     43  mozilla::Maybe<LoopControl> loopInfo_;
     44 
     45  // Cache for the loop body, which is enclosed by the cache in `loopInfo_`,
     46  // which is effectively for the loop condition.
     47  mozilla::Maybe<TDZCheckCache> tdzCacheForBody_;
     48 
     49 #ifdef DEBUG
     50  // The state of this emitter.
     51  //
     52  // +-------+ emitCond +------+ emitBody +------+ emitEnd  +-----+
     53  // | Start |--------->| Cond |--------->| Body |--------->| End |
     54  // +-------+          +------+          +------+          +-----+
     55  enum class State {
     56    // The initial state.
     57    Start,
     58 
     59    // After calling emitCond.
     60    Cond,
     61 
     62    // After calling emitBody.
     63    Body,
     64 
     65    // After calling emitEnd.
     66    End
     67  };
     68  State state_ = State::Start;
     69 #endif
     70 
     71 public:
     72  explicit WhileEmitter(BytecodeEmitter* bce);
     73 
     74  // Parameters are the offset in the source code for each character below:
     75  //
     76  //   while ( x < 20 ) { ... }
     77  //   ^       ^              ^
     78  //   |       |              |
     79  //   |       |              endPos_
     80  //   |       |
     81  //   |       condPos_
     82  //   |
     83  //   whilePos_
     84  [[nodiscard]] bool emitCond(uint32_t whilePos, uint32_t condPos,
     85                              uint32_t endPos);
     86  [[nodiscard]] bool emitBody();
     87  [[nodiscard]] bool emitEnd();
     88 };
     89 
     90 #if defined(ENABLE_DECORATORS) || defined(ENABLE_EXPLICIT_RESOURCE_MANAGEMENT)
     91 // This version is for emitting the condition in synthesized code that
     92 // does not have a corresponding location in the source code.
     93 class MOZ_STACK_CLASS InternalWhileEmitter : public WhileEmitter {
     94 public:
     95  explicit InternalWhileEmitter(BytecodeEmitter* bce) : WhileEmitter(bce) {}
     96  [[nodiscard]] bool emitCond();
     97 };
     98 #endif
     99 
    100 } /* namespace frontend */
    101 } /* namespace js */
    102 
    103 #endif /* frontend_WhileEmitter_h */