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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 */
#ifndef frontend_BytecodeControlStructures_h
#define frontend_BytecodeControlStructures_h
#include "mozilla/Assertions.h" // MOZ_ASSERT
#include "mozilla/Maybe.h" // mozilla::Maybe
#include <stdint.h> // int32_t, uint32_t
#include "ds/Nestable.h" // Nestable
#include "frontend/BytecodeOffset.h" // BytecodeOffset
#include "frontend/JumpList.h" // JumpList, JumpTarget
#include "frontend/ParserAtom.h" // TaggedParserAtomIndex
#include "frontend/SharedContext.h" // StatementKind, StatementKindIsLoop, StatementKindIsUnlabeledBreakTarget
#include "frontend/TDZCheckCache.h" // TDZCheckCache
#include "vm/StencilEnums.h" // TryNoteKind
namespace js {
namespace frontend {
struct BytecodeEmitter;
class EmitterScope;
class NestableControl : public Nestable<NestableControl> {
StatementKind kind_;
// The innermost scope when this was pushed.
EmitterScope* emitterScope_;
NestableControl(BytecodeEmitter* bce, StatementKind kind);
using Nestable<NestableControl>::enclosing;
using Nestable<NestableControl>::findNearest;
StatementKind kind() const { return kind_; }
EmitterScope* emitterScope() const { return emitterScope_; }
template <typename T>
bool is() const;
template <typename T>
T& as() {
return static_cast<T&>(*this);
class BreakableControl : public NestableControl {
// Offset of the last break.
JumpList breaks;
BreakableControl(BytecodeEmitter* bce, StatementKind kind);
[[nodiscard]] bool patchBreaks(BytecodeEmitter* bce);
template <>
inline bool NestableControl::is<BreakableControl>() const {
return StatementKindIsUnlabeledBreakTarget(kind_) ||
kind_ == StatementKind::Label;
class LabelControl : public BreakableControl {
TaggedParserAtomIndex label_;
// The code offset when this was pushed. Used for effectfulness checking.
BytecodeOffset startOffset_;
LabelControl(BytecodeEmitter* bce, TaggedParserAtomIndex label,
BytecodeOffset startOffset);
TaggedParserAtomIndex label() const { return label_; }
BytecodeOffset startOffset() const { return startOffset_; }
template <>
inline bool NestableControl::is<LabelControl>() const {
return kind_ == StatementKind::Label;
class LoopControl : public BreakableControl {
// Loops' children are emitted in dominance order, so they can always
// have a TDZCheckCache.
TDZCheckCache tdzCache_;
// Here's the basic structure of a loop:
// head:
// JSOp::LoopHead
// {loop condition/body}
// continueTarget:
// {loop update if present}
// # Loop end, backward jump
// JSOp::Goto/JSOp::JumpIfTrue head
// breakTarget:
// The bytecode offset of JSOp::LoopHead.
JumpTarget head_;
// Stack depth when this loop was pushed on the control stack.
int32_t stackDepth_;
// The loop nesting depth. Used as a hint to Ion.
uint32_t loopDepth_;
// Offset of the last continue in the loop.
JumpList continues;
LoopControl(BytecodeEmitter* bce, StatementKind loopKind);
BytecodeOffset headOffset() const { return head_.offset; }
[[nodiscard]] bool emitContinueTarget(BytecodeEmitter* bce);
// `nextPos` is the offset in the source code for the character that
// corresponds to the next instruction after JSOp::LoopHead.
// Can be Nothing() if not available.
[[nodiscard]] bool emitLoopHead(BytecodeEmitter* bce,
const mozilla::Maybe<uint32_t>& nextPos);
[[nodiscard]] bool emitLoopEnd(BytecodeEmitter* bce, JSOp op,
TryNoteKind tryNoteKind);
template <>
inline bool NestableControl::is<LoopControl>() const {
return StatementKindIsLoop(kind_);
enum class NonLocalExitKind { Continue, Break, Return };
class TryFinallyContinuation {
TryFinallyContinuation(NestableControl* target, NonLocalExitKind kind)
: target_(target), kind_(kind) {}
NestableControl* target_;
NonLocalExitKind kind_;
class TryFinallyControl : public NestableControl {
bool emittingSubroutine_ = false;
// Offset of the last jump to this `finally`.
JumpList finallyJumps_;
js::Vector<TryFinallyContinuation, 4, SystemAllocPolicy> continuations_;
TryFinallyControl(BytecodeEmitter* bce, StatementKind kind);
void setEmittingSubroutine() { emittingSubroutine_ = true; }
bool emittingSubroutine() const { return emittingSubroutine_; }
enum SpecialContinuations { Fallthrough, Count };
bool allocateContinuation(NestableControl* target, NonLocalExitKind kind,
uint32_t* idx);
bool emitContinuations(BytecodeEmitter* bce);
template <>
inline bool NestableControl::is<TryFinallyControl>() const {
return kind_ == StatementKind::Try || kind_ == StatementKind::Finally;
class NonLocalExitControl {
BytecodeEmitter* bce_;
const uint32_t savedScopeNoteIndex_;
const int savedDepth_;
uint32_t openScopeNoteIndex_;
NonLocalExitKind kind_;
// The offset of a `JSOp::SetRval` that can be rewritten as a
// `JSOp::Return` if we don't generate any code for this
// NonLocalExitControl.
BytecodeOffset setRvalOffset_ = BytecodeOffset::invalidOffset();
[[nodiscard]] bool leaveScope(EmitterScope* es);
NonLocalExitControl(const NonLocalExitControl&) = delete;
NonLocalExitControl(BytecodeEmitter* bce, NonLocalExitKind kind);
[[nodiscard]] bool emitNonLocalJump(NestableControl* target,
NestableControl* startingAfter = nullptr);
[[nodiscard]] bool emitReturn(BytecodeOffset setRvalOffset);
} /* namespace frontend */
} /* namespace js */
#endif /* frontend_BytecodeControlStructures_h */