src/frontend/BytecodeEmitter.h

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 * vim: set ts=8 sts=4 et sw=4 tw=99:
 * 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/. */

/* JS bytecode generation. */

#ifndef frontend_BytecodeEmitter_h
#define frontend_BytecodeEmitter_h

#include "mozilla/Attributes.h"

#include "ds/InlineTable.h"
#include "frontend/EitherParser.h"
#include "frontend/SharedContext.h"
#include "frontend/SourceNotes.h"
#include "vm/BytecodeUtil.h"
#include "vm/Interpreter.h"
#include "vm/Iteration.h"
#include "vm/JSContext.h"
#include "vm/JSScript.h"

namespace js {
namespace frontend {

class CGConstList {
  Vector<Value> list;

 public:
  explicit CGConstList(JSContext* cx) : list(cx) {}
  MOZ_MUST_USE bool append(const Value& v) {
    MOZ_ASSERT_IF(v.isString(), v.toString()->isAtom());
    return list.append(v);
  }
  size_t length() const { return list.length(); }
  void finish(ConstArray* array);
};

struct CGObjectList {
  uint32_t length;    /* number of emitted so far objects */
  ObjectBox* lastbox; /* last emitted object */

  CGObjectList() : length(0), lastbox(nullptr) {}

  unsigned add(ObjectBox* objbox);
  unsigned indexOf(JSObject* obj);
  void finish(ObjectArray* array);
  ObjectBox* find(uint32_t index);
};

struct MOZ_STACK_CLASS CGScopeList {
  Rooted<GCVector<Scope*>> vector;

  explicit CGScopeList(JSContext* cx) : vector(cx, GCVector<Scope*>(cx)) {}

  bool append(Scope* scope) { return vector.append(scope); }
  uint32_t length() const { return vector.length(); }
  void finish(ScopeArray* array);
};

struct CGTryNoteList {
  Vector<JSTryNote> list;
  explicit CGTryNoteList(JSContext* cx) : list(cx) {}

  MOZ_MUST_USE bool append(JSTryNoteKind kind, uint32_t stackDepth,
                           size_t start, size_t end);
  size_t length() const { return list.length(); }
  void finish(TryNoteArray* array);
};

struct CGScopeNote : public ScopeNote {
  // The end offset. Used to compute the length; may need adjusting first if
  // in the prologue.
  uint32_t end;

  // Is the start offset in the prologue?
  bool startInPrologue;

  // Is the end offset in the prologue?
  bool endInPrologue;
};

struct CGScopeNoteList {
  Vector<CGScopeNote> list;
  explicit CGScopeNoteList(JSContext* cx) : list(cx) {}

  MOZ_MUST_USE bool append(uint32_t scopeIndex, uint32_t offset,
                           bool inPrologue, uint32_t parent);
  void recordEnd(uint32_t index, uint32_t offset, bool inPrologue);
  size_t length() const { return list.length(); }
  void finish(ScopeNoteArray* array, uint32_t prologueLength);
};

struct CGYieldAndAwaitOffsetList {
  Vector<uint32_t> list;
  uint32_t numYields;
  uint32_t numAwaits;
  explicit CGYieldAndAwaitOffsetList(JSContext* cx)
      : list(cx), numYields(0), numAwaits(0) {}

  MOZ_MUST_USE bool append(uint32_t offset) { return list.append(offset); }
  size_t length() const { return list.length(); }
  void finish(YieldAndAwaitOffsetArray& array, uint32_t prologueLength);
};

static constexpr size_t MaxBytecodeLength = INT32_MAX;
static constexpr size_t MaxSrcNotesLength = INT32_MAX;

// Have a few inline elements, so as to avoid heap allocation for tiny
// sequences.  See bug 1390526.
typedef Vector<jsbytecode, 64> BytecodeVector;
typedef Vector<jssrcnote, 64> SrcNotesVector;

// Linked list of jump instructions that need to be patched. The linked list is
// stored in the bytes of the incomplete bytecode that will be patched, so no
// extra memory is needed, and patching the instructions destroys the list.
//
// Example:
//
//     JumpList brList;
//     if (!emitJump(JSOP_IFEQ, &brList))
//         return false;
//     ...
//     JumpTarget label;
//     if (!emitJumpTarget(&label))
//         return false;
//     ...
//     if (!emitJump(JSOP_GOTO, &brList))
//         return false;
//     ...
//     patchJumpsToTarget(brList, label);
//
//                 +-> -1
//                 |
//                 |
//    ifeq ..   <+ +                +-+   ifeq ..
//    ..         |                  |     ..
//  label:       |                  +-> label:
//    jumptarget |                  |     jumptarget
//    ..         |                  |     ..
//    goto .. <+ +                  +-+   goto .. <+
//             |                                   |
//             |                                   |
//             +                                   +
//           brList                              brList
//
//       |                                  ^
//       +------- patchJumpsToTarget -------+
//

// Offset of a jump target instruction, used for patching jump instructions.
struct JumpTarget {
  ptrdiff_t offset;
};

struct JumpList {
  // -1 is used to mark the end of jump lists.
  JumpList() : offset(-1) {}
  ptrdiff_t offset;

  // Add a jump instruction to the list.
  void push(jsbytecode* code, ptrdiff_t jumpOffset);

  // Patch all jump instructions in this list to jump to `target`.  This
  // clobbers the list.
  void patchAll(jsbytecode* code, JumpTarget target);
};

// Used to control whether JSOP_CALL_IGNORES_RV is emitted for function calls.
enum class ValueUsage {
  // Assume the value of the current expression may be used. This is always
  // correct but prohibits JSOP_CALL_IGNORES_RV.
  WantValue,

  // Pass this when emitting an expression if the expression's value is
  // definitely unused by later instructions. You must make sure the next
  // instruction is JSOP_POP, a jump to a JSOP_POP, or something similar.
  IgnoreValue
};

struct MOZ_STACK_CLASS BytecodeEmitter {
  class TDZCheckCache;
  class NestableControl;
  class EmitterScope;

  SharedContext* const
      sc; /* context shared between parsing and bytecode generation */

  JSContext* const cx;

  BytecodeEmitter* const parent; /* enclosing function or global context */

  Rooted<JSScript*> script; /* the JSScript we're ultimately producing */

  Rooted<LazyScript*> lazyScript; /* the lazy script if mode is LazyFunction,
                                      nullptr otherwise. */

  struct EmitSection {
    BytecodeVector code;      /* bytecode */
    SrcNotesVector notes;     /* source notes, see below */
    ptrdiff_t lastNoteOffset; /* code offset for last source note */

    // Line number for srcnotes.
    //
    // WARNING: If this becomes out of sync with already-emitted srcnotes,
    // we can get undefined behavior.
    uint32_t currentLine;

    // Zero-based column index on currentLine of last SRC_COLSPAN-annotated
    // opcode.
    //
    // WARNING: If this becomes out of sync with already-emitted srcnotes,
    // we can get undefined behavior.
    uint32_t lastColumn;

    JumpTarget lastTarget;  // Last jump target emitted.

    EmitSection(JSContext* cx, uint32_t lineNum)
        : code(cx),
          notes(cx),
          lastNoteOffset(0),
          currentLine(lineNum),
          lastColumn(0),
          lastTarget{-1 - ptrdiff_t(JSOP_JUMPTARGET_LENGTH)} {}
  };
  EmitSection prologue, main, *current;

  EitherParser<FullParseHandler> parser;

  PooledMapPtr<AtomIndexMap> atomIndices; /* literals indexed for mapping */
  unsigned firstLine; /* first line, for JSScript::initFromEmitter */

  uint32_t maxFixedSlots; /* maximum number of fixed frame slots so far */
  uint32_t maxStackDepth; /* maximum number of expression stack slots so far */

  int32_t stackDepth; /* current stack depth in script frame */

  unsigned emitLevel; /* emitTree recursion level */

  uint32_t bodyScopeIndex; /* index into scopeList of the body scope */

  EmitterScope* varEmitterScope;
  NestableControl* innermostNestableControl;
  EmitterScope* innermostEmitterScope_;
  TDZCheckCache* innermostTDZCheckCache;

#ifdef DEBUG
  bool unstableEmitterScope;

  friend class AutoCheckUnstableEmitterScope;
#endif

  EmitterScope* innermostEmitterScope() const {
    MOZ_ASSERT(!unstableEmitterScope);
    return innermostEmitterScopeNoCheck();
  }
  EmitterScope* innermostEmitterScopeNoCheck() const {
    return innermostEmitterScope_;
  }

  CGConstList constList;         /* constants to be included with the script */
  CGObjectList objectList;       /* list of emitted objects */
  CGScopeList scopeList;         /* list of emitted scopes */
  CGTryNoteList tryNoteList;     /* list of emitted try notes */
  CGScopeNoteList scopeNoteList; /* list of emitted block scope notes */

  /*
   * For each yield or await op, map the yield and await index (stored as
   * bytecode operand) to the offset of the next op.
   */
  CGYieldAndAwaitOffsetList yieldAndAwaitOffsetList;

  uint16_t typesetCount; /* Number of JOF_TYPESET opcodes generated */

  bool
      hasSingletons : 1; /* script contains singleton initializer JSOP_OBJECT */

  bool hasTryFinally : 1; /* script contains finally block */

  bool emittingRunOnceLambda : 1; /* true while emitting a lambda which is only
                                     expected to run once. */

  bool isRunOnceLambda();

  enum EmitterMode {
    Normal,

    /*
     * Emit JSOP_GETINTRINSIC instead of JSOP_GETNAME and assert that
     * JSOP_GETNAME and JSOP_*GNAME don't ever get emitted. See the comment
     * for the field |selfHostingMode| in Parser.h for details.
     */
    SelfHosting,

    /*
     * Check the static scope chain of the root function for resolving free
     * variable accesses in the script.
     */
    LazyFunction
  };

  const EmitterMode emitterMode;

  // The end location of a function body that is being emitted.
  MOZ_INIT_OUTSIDE_CTOR uint32_t functionBodyEndPos;
  // Whether functionBodyEndPos was set.
  bool functionBodyEndPosSet;

  /*
   * Note that BytecodeEmitters are magic: they own the arena "top-of-stack"
   * space above their tempMark points. This means that you cannot alloc from
   * tempLifoAlloc and save the pointer beyond the next BytecodeEmitter
   * destruction.
   */
  BytecodeEmitter(BytecodeEmitter* parent,
                  const EitherParser<FullParseHandler>& parser,
                  SharedContext* sc, HandleScript script,
                  Handle<LazyScript*> lazyScript, uint32_t lineNum,
                  EmitterMode emitterMode = Normal);

  template <typename CharT>
  BytecodeEmitter(BytecodeEmitter* parent,
                  Parser<FullParseHandler, CharT>* parser, SharedContext* sc,
                  HandleScript script, Handle<LazyScript*> lazyScript,
                  uint32_t lineNum, EmitterMode emitterMode = Normal)
      : BytecodeEmitter(parent, EitherParser<FullParseHandler>(parser), sc,
                        script, lazyScript, lineNum, emitterMode) {}

  // An alternate constructor that uses a TokenPos for the starting
  // line and that sets functionBodyEndPos as well.
  BytecodeEmitter(BytecodeEmitter* parent,
                  const EitherParser<FullParseHandler>& parser,
                  SharedContext* sc, HandleScript script,
                  Handle<LazyScript*> lazyScript, TokenPos bodyPosition,
                  EmitterMode emitterMode = Normal);

  template <typename CharT>
  BytecodeEmitter(BytecodeEmitter* parent,
                  Parser<FullParseHandler, CharT>* parser, SharedContext* sc,
                  HandleScript script, Handle<LazyScript*> lazyScript,
                  TokenPos bodyPosition, EmitterMode emitterMode = Normal)
      : BytecodeEmitter(parent, EitherParser<FullParseHandler>(parser), sc,
                        script, lazyScript, bodyPosition, emitterMode) {}

  MOZ_MUST_USE bool init();

  template <typename Predicate /* (NestableControl*) -> bool */>
  NestableControl* findInnermostNestableControl(Predicate predicate) const;

  template <typename T>
  T* findInnermostNestableControl() const;

  template <typename T, typename Predicate /* (T*) -> bool */>
  T* findInnermostNestableControl(Predicate predicate) const;

  NameLocation lookupName(JSAtom* name);

  // To implement Annex B and the formal parameter defaults scope semantics
  // requires accessing names that would otherwise be shadowed. This method
  // returns the access location of a name that is known to be bound in a
  // target scope.
  mozilla::Maybe<NameLocation> locationOfNameBoundInScope(JSAtom* name,
                                                          EmitterScope* target);

  // Get the location of a name known to be bound in the function scope,
  // starting at the source scope.
  mozilla::Maybe<NameLocation> locationOfNameBoundInFunctionScope(
      JSAtom* name, EmitterScope* source);

  mozilla::Maybe<NameLocation> locationOfNameBoundInFunctionScope(
      JSAtom* name) {
    return locationOfNameBoundInFunctionScope(name, innermostEmitterScope());
  }

  void setVarEmitterScope(EmitterScope* emitterScope) {
    MOZ_ASSERT(emitterScope);
    MOZ_ASSERT(!varEmitterScope);
    varEmitterScope = emitterScope;
  }

  Scope* outermostScope() const { return scopeList.vector[0]; }
  Scope* innermostScope() const;

  MOZ_ALWAYS_INLINE
  MOZ_MUST_USE bool makeAtomIndex(JSAtom* atom, uint32_t* indexp) {
    MOZ_ASSERT(atomIndices);
    AtomIndexMap::AddPtr p = atomIndices->lookupForAdd(atom);
    if (p) {
      *indexp = p->value();
      return true;
    }

    uint32_t index = atomIndices->count();
    if (!atomIndices->add(p, atom, index)) return false;

    *indexp = index;
    return true;
  }

  bool isInLoop();
  MOZ_MUST_USE bool checkSingletonContext();

  // Check whether our function is in a run-once context (a toplevel
  // run-one script or a run-once lambda).
  MOZ_MUST_USE bool checkRunOnceContext();

  bool needsImplicitThis();

  MOZ_MUST_USE bool maybeSetDisplayURL();
  MOZ_MUST_USE bool maybeSetSourceMap();
  void tellDebuggerAboutCompiledScript(JSContext* cx);

  inline TokenStreamAnyChars& tokenStream();

  BytecodeVector& code() const { return current->code; }
  jsbytecode* code(ptrdiff_t offset) const {
    return current->code.begin() + offset;
  }
  ptrdiff_t offset() const {
    return current->code.end() - current->code.begin();
  }
  ptrdiff_t prologueOffset() const {
    return prologue.code.end() - prologue.code.begin();
  }
  void switchToMain() { current = &main; }
  void switchToPrologue() { current = &prologue; }
  bool inPrologue() const { return current == &prologue; }

  SrcNotesVector& notes() const { return current->notes; }
  ptrdiff_t lastNoteOffset() const { return current->lastNoteOffset; }
  unsigned currentLine() const { return current->currentLine; }

  // Check if the last emitted opcode is a jump target.
  bool lastOpcodeIsJumpTarget() const {
    return offset() - current->lastTarget.offset ==
           ptrdiff_t(JSOP_JUMPTARGET_LENGTH);
  }

  // JumpTarget should not be part of the emitted statement, as they can be
  // aliased by multiple statements. If we included the jump target as part of
  // the statement we might have issues where the enclosing statement might
  // not contain all the opcodes of the enclosed statements.
  ptrdiff_t lastNonJumpTargetOffset() const {
    return lastOpcodeIsJumpTarget() ? current->lastTarget.offset : offset();
  }

  void setFunctionBodyEndPos(TokenPos pos) {
    functionBodyEndPos = pos.end;
    functionBodyEndPosSet = true;
  }

  void reportError(ParseNode* pn, unsigned errorNumber, ...);
  bool reportExtraWarning(ParseNode* pn, unsigned errorNumber, ...);

  // If pn contains a useful expression, return true with *answer set to true.
  // If pn contains a useless expression, return true with *answer set to
  // false. Return false on error.
  //
  // The caller should initialize *answer to false and invoke this function on
  // an expression statement or similar subtree to decide whether the tree
  // could produce code that has any side effects.  For an expression
  // statement, we define useless code as code with no side effects, because
  // the main effect, the value left on the stack after the code executes,
  // will be discarded by a pop bytecode.
  MOZ_MUST_USE bool checkSideEffects(ParseNode* pn, bool* answer);

#ifdef DEBUG
  MOZ_MUST_USE bool checkStrictOrSloppy(JSOp op);
#endif

  // Append a new source note of the given type (and therefore size) to the
  // notes dynamic array, updating noteCount. Return the new note's index
  // within the array pointed at by current->notes as outparam.
  MOZ_MUST_USE bool newSrcNote(SrcNoteType type, unsigned* indexp = nullptr);
  MOZ_MUST_USE bool newSrcNote2(SrcNoteType type, ptrdiff_t offset,
                                unsigned* indexp = nullptr);
  MOZ_MUST_USE bool newSrcNote3(SrcNoteType type, ptrdiff_t offset1,
                                ptrdiff_t offset2, unsigned* indexp = nullptr);

  void copySrcNotes(jssrcnote* destination, uint32_t nsrcnotes);
  MOZ_MUST_USE bool setSrcNoteOffset(unsigned index, unsigned which,
                                     ptrdiff_t offset);

  // NB: this function can add at most one extra extended delta note.
  MOZ_MUST_USE bool addToSrcNoteDelta(jssrcnote* sn, ptrdiff_t delta);

  // Finish taking source notes in cx's notePool. If successful, the final
  // source note count is stored in the out outparam.
  MOZ_MUST_USE bool finishTakingSrcNotes(uint32_t* out);

  // Control whether emitTree emits a line number note.
  enum EmitLineNumberNote { EMIT_LINENOTE, SUPPRESS_LINENOTE };

  // Emit code for the tree rooted at pn.
  MOZ_MUST_USE bool emitTree(ParseNode* pn,
                             ValueUsage valueUsage = ValueUsage::WantValue,
                             EmitLineNumberNote emitLineNote = EMIT_LINENOTE);

  // Emit code for the tree rooted at pn with its own TDZ cache.
  MOZ_MUST_USE bool emitTreeInBranch(
      ParseNode* pn, ValueUsage valueUsage = ValueUsage::WantValue);

  // Emit global, eval, or module code for tree rooted at body. Always
  // encompasses the entire source.
  MOZ_MUST_USE bool emitScript(ParseNode* body);

  // Emit function code for the tree rooted at body.
  MOZ_MUST_USE bool emitFunctionScript(ParseNode* body);

  // If op is JOF_TYPESET (see the type barriers comment in TypeInference.h),
  // reserve a type set to store its result.
  void checkTypeSet(JSOp op);

  void updateDepth(ptrdiff_t target);
  MOZ_MUST_USE bool updateLineNumberNotes(uint32_t offset);
  MOZ_MUST_USE bool updateSourceCoordNotes(uint32_t offset);

  JSOp strictifySetNameOp(JSOp op);

  MOZ_MUST_USE bool emitCheck(ptrdiff_t delta, ptrdiff_t* offset);

  // Emit one bytecode.
  MOZ_MUST_USE bool emit1(JSOp op);

  // Emit two bytecodes, an opcode (op) with a byte of immediate operand
  // (op1).
  MOZ_MUST_USE bool emit2(JSOp op, uint8_t op1);

  // Emit three bytecodes, an opcode with two bytes of immediate operands.
  MOZ_MUST_USE bool emit3(JSOp op, jsbytecode op1, jsbytecode op2);

  // Helper to emit JSOP_DUPAT. The argument is the value's depth on the
  // JS stack, as measured from the top.
  MOZ_MUST_USE bool emitDupAt(unsigned slotFromTop);

  // Helper to emit JSOP_POP or JSOP_POPN.
  MOZ_MUST_USE bool emitPopN(unsigned n);

  // Helper to emit JSOP_CHECKISOBJ.
  MOZ_MUST_USE bool emitCheckIsObj(CheckIsObjectKind kind);

  // Helper to emit JSOP_CHECKISCALLABLE.
  MOZ_MUST_USE bool emitCheckIsCallable(CheckIsCallableKind kind);

  // Push whether the value atop of the stack is non-undefined and non-null.
  MOZ_MUST_USE bool emitPushNotUndefinedOrNull();

  // Emit a bytecode followed by an uint16 immediate operand stored in
  // big-endian order.
  MOZ_MUST_USE bool emitUint16Operand(JSOp op, uint32_t operand);

  // Emit a bytecode followed by an uint32 immediate operand.
  MOZ_MUST_USE bool emitUint32Operand(JSOp op, uint32_t operand);

  // Emit (1 + extra) bytecodes, for N bytes of op and its immediate operand.
  MOZ_MUST_USE bool emitN(JSOp op, size_t extra, ptrdiff_t* offset = nullptr);

  MOZ_MUST_USE bool emitNumberOp(double dval);

  MOZ_MUST_USE bool emitThisLiteral(ParseNode* pn);
  MOZ_MUST_USE bool emitGetFunctionThis(ParseNode* pn);
  MOZ_MUST_USE bool emitGetThisForSuperBase(ParseNode* pn);
  MOZ_MUST_USE bool emitSetThis(ParseNode* pn);
  MOZ_MUST_USE bool emitCheckDerivedClassConstructorReturn();

  // Handle jump opcodes and jump targets.
  MOZ_MUST_USE bool emitJumpTarget(JumpTarget* target);
  MOZ_MUST_USE bool emitJumpNoFallthrough(JSOp op, JumpList* jump);
  MOZ_MUST_USE bool emitJump(JSOp op, JumpList* jump);
  MOZ_MUST_USE bool emitBackwardJump(JSOp op, JumpTarget target, JumpList* jump,
                                     JumpTarget* fallthrough);
  void patchJumpsToTarget(JumpList jump, JumpTarget target);
  MOZ_MUST_USE bool emitJumpTargetAndPatch(JumpList jump);

  MOZ_MUST_USE bool emitCall(JSOp op, uint16_t argc, ParseNode* pn = nullptr);
  MOZ_MUST_USE bool emitCallIncDec(ParseNode* incDec);

  MOZ_MUST_USE bool emitLoopHead(ParseNode* nextpn, JumpTarget* top);
  MOZ_MUST_USE bool emitLoopEntry(ParseNode* nextpn, JumpList entryJump);

  MOZ_MUST_USE bool emitGoto(NestableControl* target, JumpList* jumplist,
                             SrcNoteType noteType = SRC_NULL);

  MOZ_MUST_USE bool emitIndex32(JSOp op, uint32_t index);
  MOZ_MUST_USE bool emitIndexOp(JSOp op, uint32_t index);

  MOZ_MUST_USE bool emitAtomOp(JSAtom* atom, JSOp op);
  MOZ_MUST_USE bool emitAtomOp(ParseNode* pn, JSOp op);

  MOZ_MUST_USE bool emitArrayLiteral(ParseNode* pn);
  MOZ_MUST_USE bool emitArray(ParseNode* pn, uint32_t count);

  MOZ_MUST_USE bool emitInternedScopeOp(uint32_t index, JSOp op);
  MOZ_MUST_USE bool emitInternedObjectOp(uint32_t index, JSOp op);
  MOZ_MUST_USE bool emitObjectOp(ObjectBox* objbox, JSOp op);
  MOZ_MUST_USE bool emitObjectPairOp(ObjectBox* objbox1, ObjectBox* objbox2,
                                     JSOp op);
  MOZ_MUST_USE bool emitRegExp(uint32_t index);

  MOZ_NEVER_INLINE MOZ_MUST_USE bool emitFunction(ParseNode* pn,
                                                  bool needsProto = false);
  MOZ_NEVER_INLINE MOZ_MUST_USE bool emitObject(ParseNode* pn);

  MOZ_MUST_USE bool replaceNewInitWithNewObject(JSObject* obj,
                                                ptrdiff_t offset);

  MOZ_MUST_USE bool emitHoistedFunctionsInList(ParseNode* pn);

  MOZ_MUST_USE bool emitPropertyList(ParseNode* pn,
                                     MutableHandlePlainObject objp,
                                     PropListType type);

  // To catch accidental misuse, emitUint16Operand/emit3 assert that they are
  // not used to unconditionally emit JSOP_GETLOCAL. Variable access should
  // instead be emitted using EmitVarOp. In special cases, when the caller
  // definitely knows that a given local slot is unaliased, this function may be
  // used as a non-asserting version of emitUint16Operand.
  MOZ_MUST_USE bool emitLocalOp(JSOp op, uint32_t slot);

  MOZ_MUST_USE bool emitArgOp(JSOp op, uint16_t slot);
  MOZ_MUST_USE bool emitEnvCoordOp(JSOp op, EnvironmentCoordinate ec);

  MOZ_MUST_USE bool emitGetNameAtLocation(JSAtom* name, const NameLocation& loc,
                                          bool callContext = false);
  MOZ_MUST_USE bool emitGetNameAtLocationForCompoundAssignment(
      JSAtom* name, const NameLocation& loc);
  MOZ_MUST_USE bool emitGetName(JSAtom* name, bool callContext = false) {
    return emitGetNameAtLocation(name, lookupName(name), callContext);
  }
  MOZ_MUST_USE bool emitGetName(ParseNode* pn, bool callContext = false);

  template <typename RHSEmitter>
  MOZ_MUST_USE bool emitSetOrInitializeNameAtLocation(HandleAtom name,
                                                      const NameLocation& loc,
                                                      RHSEmitter emitRhs,
                                                      bool initialize);
  template <typename RHSEmitter>
  MOZ_MUST_USE bool emitSetOrInitializeName(HandleAtom name, RHSEmitter emitRhs,
                                            bool initialize) {
    return emitSetOrInitializeNameAtLocation(name, lookupName(name), emitRhs,
                                             initialize);
  }
  template <typename RHSEmitter>
  MOZ_MUST_USE bool emitSetName(ParseNode* pn, RHSEmitter emitRhs) {
    RootedAtom name(cx, pn->name());
    return emitSetName(name, emitRhs);
  }
  template <typename RHSEmitter>
  MOZ_MUST_USE bool emitSetName(HandleAtom name, RHSEmitter emitRhs) {
    return emitSetOrInitializeName(name, emitRhs, false);
  }
  template <typename RHSEmitter>
  MOZ_MUST_USE bool emitInitializeName(ParseNode* pn, RHSEmitter emitRhs) {
    RootedAtom name(cx, pn->name());
    return emitInitializeName(name, emitRhs);
  }
  template <typename RHSEmitter>
  MOZ_MUST_USE bool emitInitializeName(HandleAtom name, RHSEmitter emitRhs) {
    return emitSetOrInitializeName(name, emitRhs, true);
  }

  MOZ_MUST_USE bool emitTDZCheckIfNeeded(JSAtom* name, const NameLocation& loc);

  MOZ_MUST_USE bool emitNameIncDec(ParseNode* pn);

  MOZ_MUST_USE bool emitDeclarationList(ParseNode* decls);
  MOZ_MUST_USE bool emitSingleDeclaration(ParseNode* decls, ParseNode* decl,
                                          ParseNode* initializer);

  MOZ_MUST_USE bool emitNewInit(JSProtoKey key);
  MOZ_MUST_USE bool emitSingletonInitialiser(ParseNode* pn);

  MOZ_MUST_USE bool emitPrepareIteratorResult();
  MOZ_MUST_USE bool emitFinishIteratorResult(bool done);
  MOZ_MUST_USE bool iteratorResultShape(unsigned* shape);

  MOZ_MUST_USE bool emitGetDotGeneratorInInnermostScope() {
    return emitGetDotGeneratorInScope(*innermostEmitterScope());
  }
  MOZ_MUST_USE bool emitGetDotGeneratorInScope(EmitterScope& currentScope);

  MOZ_MUST_USE bool emitInitialYield(ParseNode* pn);
  MOZ_MUST_USE bool emitYield(ParseNode* pn);
  MOZ_MUST_USE bool emitYieldOp(JSOp op);
  MOZ_MUST_USE bool emitYieldStar(ParseNode* iter);
  MOZ_MUST_USE bool emitAwaitInInnermostScope() {
    return emitAwaitInScope(*innermostEmitterScope());
  }
  MOZ_MUST_USE bool emitAwaitInInnermostScope(ParseNode* pn);
  MOZ_MUST_USE bool emitAwaitInScope(EmitterScope& currentScope);

  MOZ_MUST_USE bool emitPropLHS(ParseNode* pn);
  MOZ_MUST_USE bool emitPropOp(ParseNode* pn, JSOp op);
  MOZ_MUST_USE bool emitPropIncDec(ParseNode* pn);

  MOZ_MUST_USE bool emitAsyncWrapperLambda(unsigned index, bool isArrow);
  MOZ_MUST_USE bool emitAsyncWrapper(unsigned index, bool needsHomeObject,
                                     bool isArrow, bool isGenerator);

  MOZ_MUST_USE bool emitComputedPropertyName(ParseNode* computedPropName);

  // Emit bytecode to put operands for a JSOP_GETELEM/CALLELEM/SETELEM/DELELEM
  // opcode onto the stack in the right order. In the case of SETELEM, the
  // value to be assigned must already be pushed.
  enum class EmitElemOption { Get, Set, Call, IncDec, CompoundAssign, Ref };
  MOZ_MUST_USE bool emitElemOperands(ParseNode* pn, EmitElemOption opts);

  MOZ_MUST_USE bool emitElemOpBase(JSOp op);
  MOZ_MUST_USE bool emitElemOp(ParseNode* pn, JSOp op);
  MOZ_MUST_USE bool emitElemIncDec(ParseNode* pn);

  MOZ_MUST_USE bool emitCatch(ParseNode* pn);
  MOZ_MUST_USE bool emitIf(ParseNode* pn);
  MOZ_MUST_USE bool emitWith(ParseNode* pn);

  MOZ_NEVER_INLINE MOZ_MUST_USE bool emitLabeledStatement(
      const LabeledStatement* pn);
  MOZ_NEVER_INLINE MOZ_MUST_USE bool emitLexicalScope(ParseNode* pn);
  MOZ_MUST_USE bool emitLexicalScopeBody(
      ParseNode* body, EmitLineNumberNote emitLineNote = EMIT_LINENOTE);
  MOZ_NEVER_INLINE MOZ_MUST_USE bool emitSwitch(ParseNode* pn);
  MOZ_NEVER_INLINE MOZ_MUST_USE bool emitTry(ParseNode* pn);

  enum DestructuringFlavor {
    // Destructuring into a declaration.
    DestructuringDeclaration,

    // Destructuring into a formal parameter, when the formal parameters
    // contain an expression that might be evaluated, and thus require
    // this destructuring to assign not into the innermost scope that
    // contains the function body's vars, but into its enclosing scope for
    // parameter expressions.
    DestructuringFormalParameterInVarScope,

    // Destructuring as part of an AssignmentExpression.
    DestructuringAssignment
  };

  // emitDestructuringLHSRef emits the lhs expression's reference.
  // If the lhs expression is object property |OBJ.prop|, it emits |OBJ|.
  // If it's object element |OBJ[ELEM]|, it emits |OBJ| and |ELEM|.
  // If there's nothing to evaluate for the reference, it emits nothing.
  // |emitted| parameter receives the number of values pushed onto the stack.
  MOZ_MUST_USE bool emitDestructuringLHSRef(ParseNode* target, size_t* emitted);

  // emitSetOrInitializeDestructuring assumes the lhs expression's reference
  // and the to-be-destructured value has been pushed on the stack.  It emits
  // code to destructure a single lhs expression (either a name or a compound
  // []/{} expression).
  MOZ_MUST_USE bool emitSetOrInitializeDestructuring(ParseNode* target,
                                                     DestructuringFlavor flav);

  // emitDestructuringObjRestExclusionSet emits the property exclusion set
  // for the rest-property in an object pattern.
  MOZ_MUST_USE bool emitDestructuringObjRestExclusionSet(ParseNode* pattern);

  // emitDestructuringOps assumes the to-be-destructured value has been
  // pushed on the stack and emits code to destructure each part of a [] or
  // {} lhs expression.
  MOZ_MUST_USE bool emitDestructuringOps(ParseNode* pattern,
                                         DestructuringFlavor flav);
  MOZ_MUST_USE bool emitDestructuringOpsArray(ParseNode* pattern,
                                              DestructuringFlavor flav);
  MOZ_MUST_USE bool emitDestructuringOpsObject(ParseNode* pattern,
                                               DestructuringFlavor flav);

  typedef bool (*DestructuringDeclEmitter)(BytecodeEmitter* bce, ParseNode* pn);

  template <typename NameEmitter>
  MOZ_MUST_USE bool emitDestructuringDeclsWithEmitter(ParseNode* pattern,
                                                      NameEmitter emitName);

  enum class CopyOption { Filtered, Unfiltered };

  // Calls either the |CopyDataProperties| or the
  // |CopyDataPropertiesUnfiltered| intrinsic function, consumes three (or
  // two in the latter case) elements from the stack.
  MOZ_MUST_USE bool emitCopyDataProperties(CopyOption option);

  // emitIterator expects the iterable to already be on the stack.
  // It will replace that stack value with the corresponding iterator
  MOZ_MUST_USE bool emitIterator();

  MOZ_MUST_USE bool emitAsyncIterator();

  // Pops iterator from the top of the stack. Pushes the result of |.next()|
  // onto the stack.
  MOZ_MUST_USE bool emitIteratorNext(ParseNode* pn,
                                     IteratorKind kind = IteratorKind::Sync,
                                     bool allowSelfHosted = false);
  MOZ_MUST_USE bool emitIteratorCloseInScope(
      EmitterScope& currentScope, IteratorKind iterKind = IteratorKind::Sync,
      CompletionKind completionKind = CompletionKind::Normal,
      bool allowSelfHosted = false);
  MOZ_MUST_USE bool emitIteratorCloseInInnermostScope(
      IteratorKind iterKind = IteratorKind::Sync,
      CompletionKind completionKind = CompletionKind::Normal,
      bool allowSelfHosted = false) {
    return emitIteratorCloseInScope(*innermostEmitterScope(), iterKind,
                                    completionKind, allowSelfHosted);
  }

  template <typename InnerEmitter>
  MOZ_MUST_USE bool wrapWithDestructuringIteratorCloseTryNote(
      int32_t iterDepth, InnerEmitter emitter);

  // Check if the value on top of the stack is "undefined". If so, replace
  // that value on the stack with the value defined by |defaultExpr|.
  // |pattern| is a lhs node of the default expression.  If it's an
  // identifier and |defaultExpr| is an anonymous function, |SetFunctionName|
  // is called at compile time.
  MOZ_MUST_USE bool emitDefault(ParseNode* defaultExpr, ParseNode* pattern);

  MOZ_MUST_USE bool setOrEmitSetFunName(ParseNode* maybeFun, HandleAtom name,
                                        FunctionPrefixKind prefixKind);

  MOZ_MUST_USE bool emitInitializer(ParseNode* initializer, ParseNode* pattern);
  MOZ_MUST_USE bool emitInitializerInBranch(ParseNode* initializer,
                                            ParseNode* pattern);

  MOZ_MUST_USE bool emitCallSiteObject(ParseNode* pn);
  MOZ_MUST_USE bool emitTemplateString(ParseNode* pn);
  MOZ_MUST_USE bool emitAssignment(ParseNode* lhs, ParseNodeKind pnk,
                                   ParseNode* rhs);

  MOZ_MUST_USE bool emitReturn(ParseNode* pn);
  MOZ_MUST_USE bool emitExpressionStatement(ParseNode* pn);
  MOZ_MUST_USE bool emitStatementList(ParseNode* pn);

  MOZ_MUST_USE bool emitDeleteName(ParseNode* pn);
  MOZ_MUST_USE bool emitDeleteProperty(ParseNode* pn);
  MOZ_MUST_USE bool emitDeleteElement(ParseNode* pn);
  MOZ_MUST_USE bool emitDeleteExpression(ParseNode* pn);

  // |op| must be JSOP_TYPEOF or JSOP_TYPEOFEXPR.
  MOZ_MUST_USE bool emitTypeof(ParseNode* node, JSOp op);

  MOZ_MUST_USE bool emitUnary(ParseNode* pn);
  MOZ_MUST_USE bool emitRightAssociative(ParseNode* pn);
  MOZ_MUST_USE bool emitLeftAssociative(ParseNode* pn);
  MOZ_MUST_USE bool emitLogical(ParseNode* pn);
  MOZ_MUST_USE bool emitSequenceExpr(
      ParseNode* pn, ValueUsage valueUsage = ValueUsage::WantValue);

  MOZ_NEVER_INLINE MOZ_MUST_USE bool emitIncOrDec(ParseNode* pn);

  MOZ_MUST_USE bool emitConditionalExpression(
      ConditionalExpression& conditional,
      ValueUsage valueUsage = ValueUsage::WantValue);

  bool isRestParameter(ParseNode* pn);

  MOZ_MUST_USE bool emitCallOrNew(
      ParseNode* pn, ValueUsage valueUsage = ValueUsage::WantValue);
  MOZ_MUST_USE bool emitSelfHostedCallFunction(ParseNode* pn);
  MOZ_MUST_USE bool emitSelfHostedResumeGenerator(ParseNode* pn);
  MOZ_MUST_USE bool emitSelfHostedForceInterpreter();
  MOZ_MUST_USE bool emitSelfHostedAllowContentIter(ParseNode* pn);
  MOZ_MUST_USE bool emitSelfHostedDefineDataProperty(ParseNode* pn);
  MOZ_MUST_USE bool emitSelfHostedGetPropertySuper(ParseNode* pn);
  MOZ_MUST_USE bool emitSelfHostedHasOwn(ParseNode* pn);

  MOZ_MUST_USE bool emitDo(ParseNode* pn);
  MOZ_MUST_USE bool emitWhile(ParseNode* pn);

  MOZ_MUST_USE bool emitFor(ParseNode* pn,
                            EmitterScope* headLexicalEmitterScope = nullptr);
  MOZ_MUST_USE bool emitCStyleFor(ParseNode* pn,
                                  EmitterScope* headLexicalEmitterScope);
  MOZ_MUST_USE bool emitForIn(ParseNode* pn,
                              EmitterScope* headLexicalEmitterScope);
  MOZ_MUST_USE bool emitForOf(ParseNode* pn,
                              EmitterScope* headLexicalEmitterScope);

  MOZ_MUST_USE bool emitInitializeForInOrOfTarget(ParseNode* forHead);

  MOZ_MUST_USE bool emitBreak(PropertyName* label);
  MOZ_MUST_USE bool emitContinue(PropertyName* label);

  MOZ_MUST_USE bool emitFunctionFormalParametersAndBody(ParseNode* pn);
  MOZ_MUST_USE bool emitFunctionFormalParameters(ParseNode* pn);
  MOZ_MUST_USE bool emitInitializeFunctionSpecialNames();
  MOZ_MUST_USE bool emitFunctionBody(ParseNode* pn);
  MOZ_MUST_USE bool emitLexicalInitialization(ParseNode* pn);

  // Emit bytecode for the spread operator.
  //
  // emitSpread expects the current index (I) of the array, the array itself
  // and the iterator to be on the stack in that order (iterator on the bottom).
  // It will pop the iterator and I, then iterate over the iterator by calling
  // |.next()| and put the results into the I-th element of array with
  // incrementing I, then push the result I (it will be original I +
  // iteration count). The stack after iteration will look like |ARRAY INDEX|.
  MOZ_MUST_USE bool emitSpread(bool allowSelfHosted = false);

  MOZ_MUST_USE bool emitClass(ParseNode* pn);
  MOZ_MUST_USE bool emitSuperPropLHS(ParseNode* superBase, bool isCall = false);
  MOZ_MUST_USE bool emitSuperPropOp(ParseNode* pn, JSOp op,
                                    bool isCall = false);
  MOZ_MUST_USE bool emitSuperElemOperands(
      ParseNode* pn, EmitElemOption opts = EmitElemOption::Get);
  MOZ_MUST_USE bool emitSuperElemOp(ParseNode* pn, JSOp op,
                                    bool isCall = false);

  MOZ_MUST_USE bool emitCallee(ParseNode* callee, ParseNode* call,
                               bool* callop);

  MOZ_MUST_USE bool emitPipeline(ParseNode* pn);

  MOZ_MUST_USE bool emitExportDefault(ParseNode* pn);
};

class MOZ_RAII AutoCheckUnstableEmitterScope {
#ifdef DEBUG
  bool prev_;
  BytecodeEmitter* bce_;
#endif

 public:
  AutoCheckUnstableEmitterScope() = delete;
  explicit AutoCheckUnstableEmitterScope(BytecodeEmitter* bce)
#ifdef DEBUG
      : bce_(bce)
#endif
  {
#ifdef DEBUG
    prev_ = bce_->unstableEmitterScope;
    bce_->unstableEmitterScope = true;
#endif
  }
  ~AutoCheckUnstableEmitterScope() {
#ifdef DEBUG
    bce_->unstableEmitterScope = prev_;
#endif
  }
};

} /* namespace frontend */
} /* namespace js */

#endif /* frontend_BytecodeEmitter_h */