js/src/frontend/LabelEmitter.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_LabelEmitter_h
   8 #define frontend_LabelEmitter_h
   9
  10 #include "mozilla/Attributes.h"  // MOZ_STACK_CLASS
  11 #include "mozilla/Maybe.h"       // Maybe
  12
  13 #include "frontend/BytecodeControlStructures.h"  // LabelControl
  14
  15 namespace js {
  16 namespace frontend {
  17
  18 struct BytecodeEmitter;
  19 class TaggedParserAtomIndex;
  20
  21 // Class for emitting labeled statement.
  22 //
  23 // Usage: (check for the return value is omitted for simplicity)
  24 //
  25 //   `label: expr;`
  26 //     LabelEmitter le(this);
  27 //     le.emitLabel(name_of_label);
  28 //     emit(expr);
  29 //     le.emitEnd();
  30 //
  31 class MOZ_STACK_CLASS LabelEmitter {
  32   BytecodeEmitter* bce_;
  33
  34   mozilla::Maybe<LabelControl> controlInfo_;
  35
  36 #ifdef DEBUG
  37   // The state of this emitter.
  38   //
  39   // +-------+ emitLabel +-------+ emitEnd +-----+
  40   // | Start |---------->| Label |-------->| End |
  41   // +-------+           +-------+         +-----+
  42   enum class State {
  43     // The initial state.
  44     Start,
  45
  46     // After calling emitLabel.
  47     Label,
  48
  49     // After calling emitEnd.
  50     End
  51   };
  52   State state_ = State::Start;
  53 #endif
  54
  55  public:
  56   explicit LabelEmitter(BytecodeEmitter* bce) : bce_(bce) {}
  57
  58   void emitLabel(TaggedParserAtomIndex name);
  59   [[nodiscard]] bool emitEnd();
  60 };
  61
  62 } /* namespace frontend */
  63 } /* namespace js */
  64
  65 #endif /* frontend_LabelEmitter_h */