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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/. */
#include "frontend/CForEmitter.h"
#include "frontend/BytecodeEmitter.h" // BytecodeEmitter
#include "frontend/EmitterScope.h" // EmitterScope
#include "vm/Opcodes.h" // JSOp
#include "vm/Scope.h" // ScopeKind
#include "vm/StencilEnums.h" // TryNoteKind
using namespace js;
using namespace js::frontend;
using mozilla::Maybe;
CForEmitter::CForEmitter(BytecodeEmitter* bce,
const EmitterScope* headLexicalEmitterScopeForLet)
: bce_(bce),
headLexicalEmitterScopeForLet_(headLexicalEmitterScopeForLet) {}
bool CForEmitter::emitInit(const Maybe<uint32_t>& initPos) {
MOZ_ASSERT(state_ == State::Start);
loopInfo_.emplace(bce_, StatementKind::ForLoop);
if (initPos) {
if (!bce_->updateSourceCoordNotes(*initPos)) {
return false;
}
}
#ifdef DEBUG
state_ = State::Init;
#endif
return true;
}
bool CForEmitter::emitCond(const Maybe<uint32_t>& condPos) {
MOZ_ASSERT(state_ == State::Init);
// ES 13.7.4.8 step 2. The initial freshening.
//
// If an initializer let-declaration may be captured during loop
// iteration, the current scope has an environment. If so, freshen the
// current environment to expose distinct bindings for each loop
// iteration.
if (headLexicalEmitterScopeForLet_) {
// The environment chain only includes an environment for the
// for(;;) loop head's let-declaration *if* a scope binding is
// captured, thus requiring a fresh environment each iteration. If
// a lexical scope exists for the head, it must be the innermost
// one. If that scope has closed-over bindings inducing an
// environment, recreate the current environment.
MOZ_ASSERT(headLexicalEmitterScopeForLet_ == bce_->innermostEmitterScope());
MOZ_ASSERT(headLexicalEmitterScopeForLet_->scope(bce_).kind() ==
ScopeKind::Lexical);
if (headLexicalEmitterScopeForLet_->hasEnvironment()) {
if (!bce_->emit1(JSOp::FreshenLexicalEnv)) {
return false;
}
}
}
if (!loopInfo_->emitLoopHead(bce_, condPos)) {
// [stack]
return false;
}
#ifdef DEBUG
state_ = State::Cond;
#endif
return true;
}
bool CForEmitter::emitBody(Cond cond) {
MOZ_ASSERT(state_ == State::Cond);
cond_ = cond;
if (cond_ == Cond::Present) {
if (!bce_->emitJump(JSOp::IfEq, &loopInfo_->breaks)) {
return false;
}
}
tdzCache_.emplace(bce_);
#ifdef DEBUG
state_ = State::Body;
#endif
return true;
}
bool CForEmitter::emitUpdate(Update update, const Maybe<uint32_t>& updatePos) {
MOZ_ASSERT(state_ == State::Body);
update_ = update;
tdzCache_.reset();
// Set loop and enclosing "update" offsets, for continue. Note that we
// continue to immediately *before* the block-freshening: continuing must
// refresh the block.
if (!loopInfo_->emitContinueTarget(bce_)) {
return false;
}
// ES 13.7.4.8 step 3.e. The per-iteration freshening.
if (headLexicalEmitterScopeForLet_) {
MOZ_ASSERT(headLexicalEmitterScopeForLet_ == bce_->innermostEmitterScope());
MOZ_ASSERT(headLexicalEmitterScopeForLet_->scope(bce_).kind() ==
ScopeKind::Lexical);
if (headLexicalEmitterScopeForLet_->hasEnvironment()) {
if (!bce_->emit1(JSOp::FreshenLexicalEnv)) {
return false;
}
}
}
// The update code may not be executed at all; it needs its own TDZ
// cache.
if (update_ == Update::Present) {
tdzCache_.emplace(bce_);
if (updatePos) {
if (!bce_->updateSourceCoordNotes(*updatePos)) {
return false;
}
}
}
#ifdef DEBUG
state_ = State::Update;
#endif
return true;
}
bool CForEmitter::emitEnd(const Maybe<uint32_t>& forPos) {
MOZ_ASSERT(state_ == State::Update);
if (update_ == Update::Present) {
tdzCache_.reset();
// [stack] UPDATE
if (!bce_->emit1(JSOp::Pop)) {
// [stack]
return false;
}
}
if (cond_ == Cond::Missing && update_ == Update::Missing) {
// If there is no condition clause and no update clause, mark
// the loop-ending "goto" with the location of the "for".
// This ensures that the debugger will stop on each loop
// iteration.
if (forPos) {
if (!bce_->updateSourceCoordNotes(*forPos)) {
return false;
}
}
}
// Emit the loop-closing jump.
if (!loopInfo_->emitLoopEnd(bce_, JSOp::Goto, TryNoteKind::Loop)) {
// [stack]
return false;
}
loopInfo_.reset();
#ifdef DEBUG
state_ = State::End;
#endif
return true;
}
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