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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
* vim: set ts=8 sts=2 et sw=2 tw=80:
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#ifndef frontend_ForInEmitter_h
#define frontend_ForInEmitter_h
#include "mozilla/Attributes.h"
#include "mozilla/Maybe.h"
#include <stdint.h>
#include "frontend/BytecodeControlStructures.h"
#include "frontend/TDZCheckCache.h"
namespace js {
namespace frontend {
struct BytecodeEmitter;
class EmitterScope;
// Class for emitting bytecode for for-in loop.
//
// Usage: (check for the return value is omitted for simplicity)
//
// `for (init in iterated) body`
// // headLexicalEmitterScope: lexical scope for init
// ForInEmitter forIn(this, headLexicalEmitterScope);
// forIn.emitIterated();
// emit(iterated);
// forIn.emitInitialize();
// emit(init);
// forIn.emitBody();
// emit(body);
// forIn.emitEnd(offset_of_for);
//
class MOZ_STACK_CLASS ForInEmitter {
BytecodeEmitter* bce_;
#ifdef DEBUG
// The stack depth before emitting initialize code inside loop.
int32_t loopDepth_ = 0;
#endif
mozilla::Maybe<LoopControl> loopInfo_;
// The lexical scope to be freshened for each iteration. See the comment
// in `emitBody` for more details. Can be nullptr if there's no lexical
// scope.
const EmitterScope* headLexicalEmitterScope_;
// Cache for the iterated value.
// (The cache for the iteration body is inside `loopInfo_`)
//
// The iterated value needs its own TDZCheckCache, separated from both the
// enclosing block and the iteration body, in order to make the sanity check
// in Ion work properly.
// In term of the execution order, the TDZCheckCache for the iterated value
// dominates the one for the iteration body, that means the checks in the
// iteration body is dead, and we can optimize them away. But the sanity
// check in Ion doesn't know it's dead.
// (see bug 1368360 for more context)
mozilla::Maybe<TDZCheckCache> tdzCacheForIteratedValue_;
#ifdef DEBUG
// The state of this emitter.
//
// +-------+ emitIterated +----------+ emitInitialize +------------+
// | Start |------------->| Iterated |--------------->| Initialize |-+
// +-------+ +----------+ +------------+ |
// |
// +----------------------------------+
// |
// | emitBody +------+ emitEnd +-----+
// +----------| Body |--------->| End |
// +------+ +-----+
enum class State {
// The initial state.
Start,
// After calling emitIterated.
Iterated,
// After calling emitInitialize.
Initialize,
// After calling emitBody.
Body,
// After calling emitEnd.
End
};
State state_ = State::Start;
#endif
public:
ForInEmitter(BytecodeEmitter* bce,
const EmitterScope* headLexicalEmitterScope);
// Parameters are the offset in the source code for each character below:
//
// for ( var x in obj ) { ... }
// ^
// |
// forPos
[[nodiscard]] bool emitIterated();
[[nodiscard]] bool emitInitialize();
[[nodiscard]] bool emitBody();
[[nodiscard]] bool emitEnd(uint32_t forPos);
};
} /* namespace frontend */
} /* namespace js */
#endif /* frontend_ForInEmitter_h */
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