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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
* 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_LexicalScopeEmitter_h
#define frontend_LexicalScopeEmitter_h
#include "mozilla/Assertions.h" // MOZ_ASSERT
#include "mozilla/Attributes.h" // MOZ_STACK_CLASS, MOZ_MUST_USE
#include "mozilla/Maybe.h" // Maybe
#include "frontend/EmitterScope.h" // EmitterScope
#include "frontend/TDZCheckCache.h" // TDZCheckCache
#include "gc/Rooting.h" // JS::Handle
#include "vm/Scope.h" // ScopeKind, LexicalScope
namespace js {
namespace frontend {
struct BytecodeEmitter;
// Class for emitting bytecode for lexical scope.
//
// In addition to emitting code for entering and leaving a scope, this RAII
// guard affects the code emitted for `break` and other non-structured
// control flow. See NonLocalExitControl::prepareForNonLocalJump().
//
// Usage: (check for the return value is omitted for simplicity)
//
// `{ ... }` -- lexical scope with no bindings
// LexicalScopeEmitter lse(this);
// lse.emitEmptyScope();
// emit(scopeBody);
// lse.emitEnd();
//
// `{ let a; body }`
// LexicalScopeEmitter lse(this);
// lse.emitScope(ScopeKind::Lexical, scopeBinding);
// emit(let_and_body);
// lse.emitEnd();
//
// `catch (e) { body }`
// LexicalScopeEmitter lse(this);
// lse.emitScope(ScopeKind::SimpleCatch, scopeBinding);
// emit(body);
// lse.emitEnd();
//
// `catch ([a, b]) { body }`
// LexicalScopeEmitter lse(this);
// lse.emitScope(ScopeKind::Catch, scopeBinding);
// emit(body);
// lse.emitEnd();
class MOZ_STACK_CLASS LexicalScopeEmitter
{
BytecodeEmitter* bce_;
mozilla::Maybe<TDZCheckCache> tdzCache_;
mozilla::Maybe<EmitterScope> emitterScope_;
#ifdef DEBUG
// The state of this emitter.
//
// +-------+ emitScope +-------+ emitEnd +-----+
// | Start |----------->| Scope |--------->| End |
// +-------+ +-------+ +-----+
enum class State {
// The initial state.
Start,
// After calling emitScope/emitEmptyScope.
Scope,
// After calling emitEnd.
End,
};
State state_ = State::Start;
#endif
public:
explicit LexicalScopeEmitter(BytecodeEmitter* bce);
// Returns the scope object for non-empty scope.
const EmitterScope& emitterScope() const {
return *emitterScope_;
}
MOZ_MUST_USE bool emitScope(ScopeKind kind,
JS::Handle<LexicalScope::Data*> bindings);
MOZ_MUST_USE bool emitEmptyScope();
MOZ_MUST_USE bool emitEnd();
};
} /* namespace frontend */
} /* namespace js */
#endif /* frontend_LexicalScopeEmitter_h */
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