js/src/frontend/WhileEmitter.h

   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 #ifdef ENABLE_DECORATORS
  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 #ifdef ENABLE_DECORATORS
  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 */