/* -*- 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 "jit/WarpBuilder.h"

#include "mozilla/DebugOnly.h"

#include "jit/BaselineFrame.h"
#include "jit/CacheIR.h"
#include "jit/CompileInfo.h"
#include "jit/InlineScriptTree.h"
#include "jit/MIR.h"
#include "jit/MIRGenerator.h"
#include "jit/MIRGraph.h"
#include "jit/WarpCacheIRTranspiler.h"
#include "jit/WarpSnapshot.h"
#include "js/friend/ErrorMessages.h"  // JSMSG_BAD_CONST_ASSIGN
#include "vm/GeneratorObject.h"
#include "vm/Interpreter.h"
#include "vm/Opcodes.h"

#include "gc/ObjectKind-inl.h"
#include "vm/BytecodeIterator-inl.h"
#include "vm/BytecodeLocation-inl.h"
#include "vm/JSObject-inl.h"

using namespace js;
using namespace js::jit;

// Used for building the outermost script.
WarpBuilder::WarpBuilder(WarpSnapshot& snapshot, MIRGenerator& mirGen,
                         WarpCompilation* warpCompilation)
    : WarpBuilderShared(snapshot, mirGen, nullptr),
      warpCompilation_(warpCompilation),
      graph_(mirGen.graph()),
      info_(mirGen.outerInfo()),
      scriptSnapshot_(snapshot.rootScript()),
      script_(snapshot.rootScript()->script()),
      loopStack_(mirGen.alloc()) {
  opSnapshotIter_ = scriptSnapshot_->opSnapshots().getFirst();
}

// Used for building inlined scripts.
WarpBuilder::WarpBuilder(WarpBuilder* caller, WarpScriptSnapshot* snapshot,
                         CompileInfo& compileInfo, CallInfo* inlineCallInfo,
                         MResumePoint* callerResumePoint)
    : WarpBuilderShared(caller->snapshot(), caller->mirGen(), nullptr),
      warpCompilation_(caller->warpCompilation()),
      graph_(caller->mirGen().graph()),
      info_(compileInfo),
      scriptSnapshot_(snapshot),
      script_(snapshot->script()),
      loopStack_(caller->mirGen().alloc()),
      callerBuilder_(caller),
      callerResumePoint_(callerResumePoint),
      inlineCallInfo_(inlineCallInfo) {
  opSnapshotIter_ = snapshot->opSnapshots().getFirst();
}

BytecodeSite* WarpBuilder::newBytecodeSite(BytecodeLocation loc) {
  jsbytecode* pc = loc.toRawBytecode();
  MOZ_ASSERT(info().inlineScriptTree()->script()->containsPC(pc));
  return new (alloc()) BytecodeSite(info().inlineScriptTree(), pc);
}

const WarpOpSnapshot* WarpBuilder::getOpSnapshotImpl(
    BytecodeLocation loc, WarpOpSnapshot::Kind kind) {
  uint32_t offset = loc.bytecodeToOffset(script_);

  // Skip snapshots until we get to a snapshot with offset >= offset. This is
  // a loop because WarpBuilder can skip unreachable bytecode ops.
  while (opSnapshotIter_ && opSnapshotIter_->offset() < offset) {
    opSnapshotIter_ = opSnapshotIter_->getNext();
  }

  if (!opSnapshotIter_ || opSnapshotIter_->offset() != offset ||
      opSnapshotIter_->kind() != kind) {
    return nullptr;
  }

  return opSnapshotIter_;
}

void WarpBuilder::initBlock(MBasicBlock* block) {
  graph().addBlock(block);

  block->setLoopDepth(loopDepth());

  current = block;
}

bool WarpBuilder::startNewBlock(MBasicBlock* predecessor, BytecodeLocation loc,
                                size_t numToPop) {
  MBasicBlock* block =
      MBasicBlock::NewPopN(graph(), info(), predecessor, newBytecodeSite(loc),
                           MBasicBlock::NORMAL, numToPop);
  if (!block) {
    return false;
  }

  initBlock(block);
  return true;
}

bool WarpBuilder::startNewEntryBlock(size_t stackDepth, BytecodeLocation loc) {
  MBasicBlock* block =
      MBasicBlock::New(graph(), stackDepth, info(), /* maybePred = */ nullptr,
                       newBytecodeSite(loc), MBasicBlock::NORMAL);
  if (!block) {
    return false;
  }

  initBlock(block);
  return true;
}

bool WarpBuilder::startNewLoopHeaderBlock(BytecodeLocation loopHead) {
  MBasicBlock* header = MBasicBlock::NewPendingLoopHeader(
      graph(), info(), current, newBytecodeSite(loopHead));
  if (!header) {
    return false;
  }

  initBlock(header);
  return loopStack_.emplaceBack(header);
}

bool WarpBuilder::startNewOsrPreHeaderBlock(BytecodeLocation loopHead) {
  MOZ_ASSERT(loopHead.is(JSOp::LoopHead));
  MOZ_ASSERT(loopHead.toRawBytecode() == info().osrPc());

  // Create two blocks:
  // * The OSR entry block. This is always the graph's second block and has no
  //   predecessors. This is the entry point for OSR from the Baseline JIT.
  // * The OSR preheader block. This has two predecessors: the OSR entry block
  //   and the current block.

  MBasicBlock* pred = current;

  // Create the OSR entry block.
  if (!startNewEntryBlock(pred->stackDepth(), loopHead)) {
    return false;
  }

  MBasicBlock* osrBlock = current;
  graph().setOsrBlock(osrBlock);
  graph().moveBlockAfter(*graph().begin(), osrBlock);

  MOsrEntry* entry = MOsrEntry::New(alloc());
  osrBlock->add(entry);

  // Initialize environment chain.
  {
    uint32_t slot = info().environmentChainSlot();
    MInstruction* envv;
    if (usesEnvironmentChain()) {
      envv = MOsrEnvironmentChain::New(alloc(), entry);
    } else {
      // Use an undefined value if the script does not need its environment
      // chain, to match the main entry point.
      envv = MConstant::New(alloc(), UndefinedValue());
    }
    osrBlock->add(envv);
    osrBlock->initSlot(slot, envv);
  }

  // Initialize return value.
  {
    MInstruction* returnValue;
    if (!script_->noScriptRval()) {
      returnValue = MOsrReturnValue::New(alloc(), entry);
    } else {
      returnValue = MConstant::New(alloc(), UndefinedValue());
    }
    osrBlock->add(returnValue);
    osrBlock->initSlot(info().returnValueSlot(), returnValue);
  }

  // Initialize arguments object.
  MInstruction* argsObj = nullptr;
  if (info().needsArgsObj()) {
    argsObj = MOsrArgumentsObject::New(alloc(), entry);
    osrBlock->add(argsObj);
    osrBlock->initSlot(info().argsObjSlot(), argsObj);
  }

  if (info().hasFunMaybeLazy()) {
    // Initialize |this| parameter.
    MParameter* thisv = MParameter::New(alloc(), MParameter::THIS_SLOT);
    osrBlock->add(thisv);
    osrBlock->initSlot(info().thisSlot(), thisv);

    // Initialize arguments. There are three cases:
    //
    // 1) There's no ArgumentsObject or it doesn't alias formals. In this case
    //    we can just use the frame's argument slot.
    // 2) The ArgumentsObject aliases formals and the argument is stored in the
    //    CallObject. Use |undefined| because we can't load from the arguments
    //    object and code will use the CallObject anyway.
    // 3) The ArgumentsObject aliases formals and the argument isn't stored in
    //    the CallObject. We have to load it from the ArgumentsObject.
    for (uint32_t i = 0; i < info().nargs(); i++) {
      uint32_t slot = info().argSlotUnchecked(i);
      MInstruction* osrv;
      if (!info().argsObjAliasesFormals()) {
        osrv = MParameter::New(alloc().fallible(), i);
      } else if (script_->formalIsAliased(i)) {
        osrv = MConstant::New(alloc().fallible(), UndefinedValue());
      } else {
        osrv = MGetArgumentsObjectArg::New(alloc().fallible(), argsObj, i);
      }
      if (!osrv) {
        return false;
      }
      current->add(osrv);
      current->initSlot(slot, osrv);
    }
  }

  // Initialize locals.
  uint32_t nlocals = info().nlocals();
  for (uint32_t i = 0; i < nlocals; i++) {
    uint32_t slot = info().localSlot(i);
    ptrdiff_t offset = BaselineFrame::reverseOffsetOfLocal(i);
    MOsrValue* osrv = MOsrValue::New(alloc().fallible(), entry, offset);
    if (!osrv) {
      return false;
    }
    current->add(osrv);
    current->initSlot(slot, osrv);
  }

  // Initialize expression stack slots.
  uint32_t numStackSlots = current->stackDepth() - info().firstStackSlot();
  for (uint32_t i = 0; i < numStackSlots; i++) {
    uint32_t slot = info().stackSlot(i);
    ptrdiff_t offset = BaselineFrame::reverseOffsetOfLocal(nlocals + i);
    MOsrValue* osrv = MOsrValue::New(alloc().fallible(), entry, offset);
    if (!osrv) {
      return false;
    }
    current->add(osrv);
    current->initSlot(slot, osrv);
  }

  MStart* start = MStart::New(alloc());
  current->add(start);

  // Note: phi specialization can add type guard instructions to the OSR entry
  // block if needed. See TypeAnalyzer::shouldSpecializeOsrPhis.

  // Create the preheader block, with the predecessor block and OSR block as
  // predecessors.
  if (!startNewBlock(pred, loopHead)) {
    return false;
  }

  pred->end(MGoto::New(alloc(), current));
  osrBlock->end(MGoto::New(alloc(), current));

  if (!current->addPredecessor(alloc(), osrBlock)) {
    return false;
  }

  return true;
}

bool WarpBuilder::addPendingEdge(BytecodeLocation target, MBasicBlock* block,
                                 uint32_t successor, uint32_t numToPop) {
  MOZ_ASSERT(successor < block->lastIns()->numSuccessors());
  MOZ_ASSERT(numToPop <= block->stackDepth());

  jsbytecode* targetPC = target.toRawBytecode();
  PendingEdgesMap::AddPtr p = pendingEdges_.lookupForAdd(targetPC);
  if (p) {
    return p->value().emplaceBack(block, successor, numToPop);
  }

  PendingEdges edges;
  static_assert(PendingEdges::InlineLength >= 1,
                "Appending one element should be infallible");
  MOZ_ALWAYS_TRUE(edges.emplaceBack(block, successor, numToPop));

  return pendingEdges_.add(p, targetPC, std::move(edges));
}

bool WarpBuilder::build() {
  if (!buildPrologue()) {
    return false;
  }

  if (!buildBody()) {
    return false;
  }

  if (!MPhi::markIteratorPhis(*iterators())) {
    return false;
  }

  MOZ_ASSERT_IF(info().osrPc(), graph().osrBlock());
  MOZ_ASSERT(loopStack_.empty());
  MOZ_ASSERT(loopDepth() == 0);

  return true;
}

bool WarpBuilder::buildInline() {
  if (!buildInlinePrologue()) {
    return false;
  }

  if (!buildBody()) {
    return false;
  }

  MOZ_ASSERT(loopStack_.empty());
  return true;
}

MInstruction* WarpBuilder::buildNamedLambdaEnv(MDefinition* callee,
                                               MDefinition* env,
                                               NamedLambdaObject* templateObj) {
  MOZ_ASSERT(templateObj->numDynamicSlots() == 0);

  MInstruction* namedLambda = MNewNamedLambdaObject::New(alloc(), templateObj);
  current->add(namedLambda);

#ifdef DEBUG
  // Assert in debug mode we can elide the post write barriers.
  current->add(MAssertCanElidePostWriteBarrier::New(alloc(), namedLambda, env));
  current->add(
      MAssertCanElidePostWriteBarrier::New(alloc(), namedLambda, callee));
#endif

  // Initialize the object's reserved slots. No post barrier is needed here:
  // the object will be allocated in the nursery if possible, and if the
  // tenured heap is used instead, a minor collection will have been performed
  // that moved env/callee to the tenured heap.
  size_t enclosingSlot = NamedLambdaObject::enclosingEnvironmentSlot();
  size_t lambdaSlot = NamedLambdaObject::lambdaSlot();
  current->add(MStoreFixedSlot::NewUnbarriered(alloc(), namedLambda,
                                               enclosingSlot, env));
  current->add(MStoreFixedSlot::NewUnbarriered(alloc(), namedLambda, lambdaSlot,
                                               callee));

  return namedLambda;
}

MInstruction* WarpBuilder::buildCallObject(MDefinition* callee,
                                           MDefinition* env,
                                           CallObject* templateObj) {
  MConstant* templateCst = constant(ObjectValue(*templateObj));

  MNewCallObject* callObj = MNewCallObject::New(alloc(), templateCst);
  current->add(callObj);

#ifdef DEBUG
  // Assert in debug mode we can elide the post write barriers.
  current->add(MAssertCanElidePostWriteBarrier::New(alloc(), callObj, env));
  current->add(MAssertCanElidePostWriteBarrier::New(alloc(), callObj, callee));
#endif

  // Initialize the object's reserved slots. No post barrier is needed here,
  // for the same reason as in buildNamedLambdaEnv.
  size_t enclosingSlot = CallObject::enclosingEnvironmentSlot();
  size_t calleeSlot = CallObject::calleeSlot();
  current->add(
      MStoreFixedSlot::NewUnbarriered(alloc(), callObj, enclosingSlot, env));
  current->add(
      MStoreFixedSlot::NewUnbarriered(alloc(), callObj, calleeSlot, callee));

  return callObj;
}

bool WarpBuilder::buildEnvironmentChain() {
  const WarpEnvironment& env = scriptSnapshot()->environment();

  if (env.is<NoEnvironment>()) {
    return true;
  }

  MInstruction* envDef = env.match(
      [](const NoEnvironment&) -> MInstruction* {
        MOZ_CRASH("Already handled");
      },
      [this](JSObject* obj) -> MInstruction* {
        return constant(ObjectValue(*obj));
      },
      [this](const FunctionEnvironment& env) -> MInstruction* {
        MDefinition* callee = getCallee();
        MInstruction* envDef = MFunctionEnvironment::New(alloc(), callee);
        current->add(envDef);
        if (NamedLambdaObject* obj = env.namedLambdaTemplate) {
          envDef = buildNamedLambdaEnv(callee, envDef, obj);
        }
        if (CallObject* obj = env.callObjectTemplate) {
          envDef = buildCallObject(callee, envDef, obj);
          if (!envDef) {
            return nullptr;
          }
        }
        return envDef;
      });
  if (!envDef) {
    return false;
  }

  // Update the environment slot from UndefinedValue only after the initial
  // environment is created so that bailout doesn't see a partial environment.
  // See: |BaselineStackBuilder::buildBaselineFrame|
  current->setEnvironmentChain(envDef);
  return true;
}

bool WarpBuilder::buildPrologue() {
  BytecodeLocation startLoc(script_, script_->code());
  if (!startNewEntryBlock(info().firstStackSlot(), startLoc)) {
    return false;
  }

  if (info().hasFunMaybeLazy()) {
    // Initialize |this|.
    MParameter* param = MParameter::New(alloc(), MParameter::THIS_SLOT);
    current->add(param);
    current->initSlot(info().thisSlot(), param);

    // Initialize arguments.
    for (uint32_t i = 0; i < info().nargs(); i++) {
      MParameter* param = MParameter::New(alloc().fallible(), i);
      if (!param) {
        return false;
      }
      current->add(param);
      current->initSlot(info().argSlotUnchecked(i), param);
    }
  }

  MConstant* undef = constant(UndefinedValue());

  // Initialize local slots.
  for (uint32_t i = 0; i < info().nlocals(); i++) {
    current->initSlot(info().localSlot(i), undef);
  }

  // Initialize the environment chain, return value, and arguments object slots.
  current->initSlot(info().environmentChainSlot(), undef);
  current->initSlot(info().returnValueSlot(), undef);
  if (info().needsArgsObj()) {
    current->initSlot(info().argsObjSlot(), undef);
  }

  current->add(MStart::New(alloc()));

  // Guard against over-recursion.
  MCheckOverRecursed* check = MCheckOverRecursed::New(alloc());
  current->add(check);

  if (!buildEnvironmentChain()) {
    return false;
  }

#ifdef JS_CACHEIR_SPEW
  if (snapshot().needsFinalWarmUpCount()) {
    MIncrementWarmUpCounter* ins =
        MIncrementWarmUpCounter::New(alloc(), script_);
    current->add(ins);
  }
#endif

  return true;
}

bool WarpBuilder::buildInlinePrologue() {
  // Generate entry block.
  BytecodeLocation startLoc(script_, script_->code());
  if (!startNewEntryBlock(info().firstStackSlot(), startLoc)) {
    return false;
  }
  current->setCallerResumePoint(callerResumePoint());

  // Connect the entry block to the last block in the caller's graph.
  MBasicBlock* pred = callerBuilder()->current;
  MOZ_ASSERT(pred == callerResumePoint()->block());

  pred->end(MGoto::New(alloc(), current));
  if (!current->addPredecessorWithoutPhis(pred)) {
    return false;
  }

  MConstant* undef = constant(UndefinedValue());

  // Initialize env chain slot to Undefined.  It's set later by
  // |buildEnvironmentChain|.
  current->initSlot(info().environmentChainSlot(), undef);

  // Initialize |return value| slot.
  current->initSlot(info().returnValueSlot(), undef);

  // Initialize |arguments| slot if needed.
  if (info().needsArgsObj()) {
    current->initSlot(info().argsObjSlot(), undef);
  }

  // Initialize |this| slot.
  current->initSlot(info().thisSlot(), inlineCallInfo()->thisArg());

  uint32_t callerArgs = inlineCallInfo()->argc();
  uint32_t actualArgs = info().nargs();
  uint32_t passedArgs = std::min<uint32_t>(callerArgs, actualArgs);

  // Initialize actually set arguments.
  for (uint32_t i = 0; i < passedArgs; i++) {
    MDefinition* arg = inlineCallInfo()->getArg(i);
    current->initSlot(info().argSlotUnchecked(i), arg);
  }

  // Pass undefined for missing arguments.
  for (uint32_t i = passedArgs; i < actualArgs; i++) {
    current->initSlot(info().argSlotUnchecked(i), undef);
  }

  // Initialize local slots.
  for (uint32_t i = 0; i < info().nlocals(); i++) {
    current->initSlot(info().localSlot(i), undef);
  }

  MOZ_ASSERT(current->entryResumePoint()->stackDepth() == info().totalSlots());

  if (!buildEnvironmentChain()) {
    return false;
  }

  return true;
}

#ifdef DEBUG
// In debug builds, after compiling a bytecode op, this class is used to check
// that all values popped by this opcode either:
//
//   (1) Have the ImplicitlyUsed flag set on them.
//   (2) Have more uses than before compiling this op (the value is
//       used as operand of a new MIR instruction).
//
// This is used to catch problems where WarpBuilder pops a value without
// adding any SSA uses and doesn't call setImplicitlyUsedUnchecked on it.
class MOZ_RAII WarpPoppedValueUseChecker {
  Vector<MDefinition*, 4, SystemAllocPolicy> popped_;
  Vector<size_t, 4, SystemAllocPolicy> poppedUses_;
  MBasicBlock* current_;
  BytecodeLocation loc_;

 public:
  WarpPoppedValueUseChecker(MBasicBlock* current, BytecodeLocation loc)
      : current_(current), loc_(loc) {}

  [[nodiscard]] bool init() {
    // Don't require SSA uses for values popped by these ops.
    switch (loc_.getOp()) {
      case JSOp::Pop:
      case JSOp::PopN:
      case JSOp::DupAt:
      case JSOp::Dup:
      case JSOp::Dup2:
      case JSOp::Pick:
      case JSOp::Unpick:
      case JSOp::Swap:
      case JSOp::SetArg:
      case JSOp::SetLocal:
      case JSOp::InitLexical:
      case JSOp::SetRval:
      case JSOp::Void:
        // Basic stack/local/argument management opcodes.
        return true;

      case JSOp::Case:
      case JSOp::Default:
        // These ops have to pop the switch value when branching but don't
        // actually use it.
        return true;

      default:
        break;
    }

    unsigned nuses = loc_.useCount();

    for (unsigned i = 0; i < nuses; i++) {
      MDefinition* def = current_->peek(-int32_t(i + 1));
      if (!popped_.append(def) || !poppedUses_.append(def->defUseCount())) {
        return false;
      }
    }

    return true;
  }

  void checkAfterOp() {
    for (size_t i = 0; i < popped_.length(); i++) {
      // First value popped by JSOp::EndIter is not used at all, it's similar
      // to JSOp::Pop above.
      if (loc_.is(JSOp::EndIter) && i == 0) {
        continue;
      }
      MOZ_ASSERT(popped_[i]->isImplicitlyUsed() ||
                 popped_[i]->defUseCount() > poppedUses_[i]);
    }
  }
};
#endif

bool WarpBuilder::buildBody() {
  for (BytecodeLocation loc : AllBytecodesIterable(script_)) {
    if (mirGen().shouldCancel("WarpBuilder (opcode loop)")) {
      return false;
    }

    // Skip unreachable ops (for example code after a 'return' or 'throw') until
    // we get to the next jump target.
    if (hasTerminatedBlock()) {
      // Finish any "broken" loops with an unreachable backedge. For example:
      //
      //   do {
      //     ...
      //     return;
      //     ...
      //   } while (x);
      //
      // This loop never actually loops.
      if (loc.isBackedge() && !loopStack_.empty()) {
        BytecodeLocation loopHead(script_, loopStack_.back().header()->pc());
        if (loc.isBackedgeForLoophead(loopHead)) {
          decLoopDepth();
          loopStack_.popBack();
        }
      }
      if (!loc.isJumpTarget()) {
        continue;
      }
    }

    if (!alloc().ensureBallast()) {
      return false;
    }

#ifdef DEBUG
    WarpPoppedValueUseChecker useChecker(current, loc);
    if (!useChecker.init()) {
      return false;
    }
#endif

    JSOp op = loc.getOp();

#define BUILD_OP(OP, ...)                       \
  case JSOp::OP:                                \
    if (MOZ_UNLIKELY(!this->build_##OP(loc))) { \
      return false;                             \
    }                                           \
    break;
    switch (op) { FOR_EACH_OPCODE(BUILD_OP) }
#undef BUILD_OP

#ifdef DEBUG
    useChecker.checkAfterOp();
#endif
  }

  return true;
}

#define DEF_OP(OP)                                 \
  bool WarpBuilder::build_##OP(BytecodeLocation) { \
    MOZ_CRASH("Unsupported op");                   \
  }
WARP_UNSUPPORTED_OPCODE_LIST(DEF_OP)
#undef DEF_OP

bool WarpBuilder::build_Nop(BytecodeLocation) { return true; }

bool WarpBuilder::build_NopDestructuring(BytecodeLocation) { return true; }

bool WarpBuilder::build_TryDestructuring(BytecodeLocation) {
  // Set the hasTryBlock flag to turn off optimizations that eliminate dead
  // resume points operands because the exception handler code for
  // TryNoteKind::Destructuring is effectively a (specialized) catch-block.
  graph().setHasTryBlock();
  return true;
}

bool WarpBuilder::build_Lineno(BytecodeLocation) { return true; }

bool WarpBuilder::build_DebugLeaveLexicalEnv(BytecodeLocation) { return true; }

bool WarpBuilder::build_Undefined(BytecodeLocation) {
  pushConstant(UndefinedValue());
  return true;
}

bool WarpBuilder::build_Void(BytecodeLocation) {
  current->pop();
  pushConstant(UndefinedValue());
  return true;
}

bool WarpBuilder::build_Null(BytecodeLocation) {
  pushConstant(NullValue());
  return true;
}

bool WarpBuilder::build_Hole(BytecodeLocation) {
  pushConstant(MagicValue(JS_ELEMENTS_HOLE));
  return true;
}

bool WarpBuilder::build_Uninitialized(BytecodeLocation) {
  pushConstant(MagicValue(JS_UNINITIALIZED_LEXICAL));
  return true;
}

bool WarpBuilder::build_IsConstructing(BytecodeLocation) {
  pushConstant(MagicValue(JS_IS_CONSTRUCTING));
  return true;
}

bool WarpBuilder::build_False(BytecodeLocation) {
  pushConstant(BooleanValue(false));
  return true;
}

bool WarpBuilder::build_True(BytecodeLocation) {
  pushConstant(BooleanValue(true));
  return true;
}

bool WarpBuilder::build_Pop(BytecodeLocation) {
  current->pop();
  return true;
}

bool WarpBuilder::build_PopN(BytecodeLocation loc) {
  for (uint32_t i = 0, n = loc.getPopCount(); i < n; i++) {
    current->pop();
  }
  return true;
}

bool WarpBuilder::build_Dup(BytecodeLocation) {
  current->pushSlot(current->stackDepth() - 1);
  return true;
}

bool WarpBuilder::build_Dup2(BytecodeLocation) {
  uint32_t lhsSlot = current->stackDepth() - 2;
  uint32_t rhsSlot = current->stackDepth() - 1;
  current->pushSlot(lhsSlot);
  current->pushSlot(rhsSlot);
  return true;
}

bool WarpBuilder::build_DupAt(BytecodeLocation loc) {
  current->pushSlot(current->stackDepth() - 1 - loc.getDupAtIndex());
  return true;
}

bool WarpBuilder::build_Swap(BytecodeLocation) {
  current->swapAt(-1);
  return true;
}

bool WarpBuilder::build_Pick(BytecodeLocation loc) {
  int32_t depth = -int32_t(loc.getPickDepth());
  current->pick(depth);
  return true;
}

bool WarpBuilder::build_Unpick(BytecodeLocation loc) {
  int32_t depth = -int32_t(loc.getUnpickDepth());
  current->unpick(depth);
  return true;
}

bool WarpBuilder::build_Zero(BytecodeLocation) {
  pushConstant(Int32Value(0));
  return true;
}

bool WarpBuilder::build_One(BytecodeLocation) {
  pushConstant(Int32Value(1));
  return true;
}

bool WarpBuilder::build_Int8(BytecodeLocation loc) {
  pushConstant(Int32Value(loc.getInt8()));
  return true;
}

bool WarpBuilder::build_Uint16(BytecodeLocation loc) {
  pushConstant(Int32Value(loc.getUint16()));
  return true;
}

bool WarpBuilder::build_Uint24(BytecodeLocation loc) {
  pushConstant(Int32Value(loc.getUint24()));
  return true;
}

bool WarpBuilder::build_Int32(BytecodeLocation loc) {
  pushConstant(Int32Value(loc.getInt32()));
  return true;
}

bool WarpBuilder::build_Double(BytecodeLocation loc) {
  pushConstant(loc.getInlineValue());
  return true;
}

bool WarpBuilder::build_BigInt(BytecodeLocation loc) {
  BigInt* bi = loc.getBigInt(script_);
  pushConstant(BigIntValue(bi));
  return true;
}

bool WarpBuilder::build_String(BytecodeLocation loc) {
  JSString* str = loc.getString(script_);
  pushConstant(StringValue(str));
  return true;
}

bool WarpBuilder::build_Symbol(BytecodeLocation loc) {
  uint32_t which = loc.getSymbolIndex();
  JS::Symbol* sym = mirGen().runtime->wellKnownSymbols().get(which);
  pushConstant(SymbolValue(sym));
  return true;
}

bool WarpBuilder::build_RegExp(BytecodeLocation loc) {
  RegExpObject* reObj = loc.getRegExp(script_);

  auto* snapshot = getOpSnapshot<WarpRegExp>(loc);

  MRegExp* regexp = MRegExp::New(alloc(), reObj, snapshot->hasShared());
  current->add(regexp);
  current->push(regexp);

  return true;
}

bool WarpBuilder::build_Return(BytecodeLocation) {
  MDefinition* def = current->pop();

  MReturn* ret = MReturn::New(alloc(), def);
  current->end(ret);

  if (!graph().addReturn(current)) {
    return false;
  }

  setTerminatedBlock();
  return true;
}

bool WarpBuilder::build_RetRval(BytecodeLocation) {
  MDefinition* rval;
  if (script_->noScriptRval()) {
    rval = constant(UndefinedValue());
  } else {
    rval = current->getSlot(info().returnValueSlot());
  }

  MReturn* ret = MReturn::New(alloc(), rval);
  current->end(ret);

  if (!graph().addReturn(current)) {
    return false;
  }

  setTerminatedBlock();
  return true;
}

bool WarpBuilder::build_SetRval(BytecodeLocation) {
  MOZ_ASSERT(!script_->noScriptRval());
  MDefinition* rval = current->pop();
  current->setSlot(info().returnValueSlot(), rval);
  return true;
}

bool WarpBuilder::build_GetRval(BytecodeLocation) {
  MOZ_ASSERT(!script_->noScriptRval());
  MDefinition* rval = current->getSlot(info().returnValueSlot());
  current->push(rval);
  return true;
}

bool WarpBuilder::build_GetLocal(BytecodeLocation loc) {
  current->pushLocal(loc.local());
  return true;
}

bool WarpBuilder::build_SetLocal(BytecodeLocation loc) {
  current->setLocal(loc.local());
  return true;
}

bool WarpBuilder::build_InitLexical(BytecodeLocation loc) {
  current->setLocal(loc.local());
  return true;
}

bool WarpBuilder::build_GetArg(BytecodeLocation loc) {
  uint32_t arg = loc.arg();
  if (info().argsObjAliasesFormals()) {
    MDefinition* argsObj = current->argumentsObject();
    auto* getArg = MGetArgumentsObjectArg::New(alloc(), argsObj, arg);
    current->add(getArg);
    current->push(getArg);
  } else {
    current->pushArg(arg);
  }
  return true;
}

bool WarpBuilder::build_GetFrameArg(BytecodeLocation loc) {
  current->pushArgUnchecked(loc.arg());
  return true;
}

bool WarpBuilder::build_SetArg(BytecodeLocation loc) {
  uint32_t arg = loc.arg();
  MDefinition* val = current->peek(-1);

  if (!info().argsObjAliasesFormals()) {
    // Either |arguments| is never referenced within this function, or
    // it doesn't map to the actual arguments values. Either way, we
    // don't need to worry about synchronizing the argument values
    // when writing to them.
    current->setArg(arg);
    return true;
  }

  // If an arguments object is in use, and it aliases formals, then all SetArgs
  // must go through the arguments object.
  MDefinition* argsObj = current->argumentsObject();
  current->add(MPostWriteBarrier::New(alloc(), argsObj, val));
  auto* ins = MSetArgumentsObjectArg::New(alloc(), argsObj, val, arg);
  current->add(ins);
  return resumeAfter(ins, loc);
}

bool WarpBuilder::build_ArgumentsLength(BytecodeLocation) {
  if (inlineCallInfo()) {
    pushConstant(Int32Value(inlineCallInfo()->argc()));
  } else {
    auto* argsLength = MArgumentsLength::New(alloc());
    current->add(argsLength);
    current->push(argsLength);
  }
  return true;
}

bool WarpBuilder::build_GetActualArg(BytecodeLocation) {
  MDefinition* index = current->pop();
  MInstruction* arg;
  if (inlineCallInfo()) {
    arg = MGetInlinedArgument::New(alloc(), index, *inlineCallInfo());
  } else {
    arg = MGetFrameArgument::New(alloc(), index);
  }
  current->add(arg);
  current->push(arg);
  return true;
}

bool WarpBuilder::build_ToNumeric(BytecodeLocation loc) {
  return buildUnaryOp(loc);
}

bool WarpBuilder::buildUnaryOp(BytecodeLocation loc) {
  MDefinition* value = current->pop();
  return buildIC(loc, CacheKind::UnaryArith, {value});
}

bool WarpBuilder::build_Inc(BytecodeLocation loc) { return buildUnaryOp(loc); }

bool WarpBuilder::build_Dec(BytecodeLocation loc) { return buildUnaryOp(loc); }

bool WarpBuilder::build_Pos(BytecodeLocation loc) { return buildUnaryOp(loc); }

bool WarpBuilder::build_Neg(BytecodeLocation loc) { return buildUnaryOp(loc); }

bool WarpBuilder::build_BitNot(BytecodeLocation loc) {
  return buildUnaryOp(loc);
}

bool WarpBuilder::buildBinaryOp(BytecodeLocation loc) {
  MDefinition* right = current->pop();
  MDefinition* left = current->pop();
  return buildIC(loc, CacheKind::BinaryArith, {left, right});
}

bool WarpBuilder::build_Add(BytecodeLocation loc) { return buildBinaryOp(loc); }

bool WarpBuilder::build_Sub(BytecodeLocation loc) { return buildBinaryOp(loc); }

bool WarpBuilder::build_Mul(BytecodeLocation loc) { return buildBinaryOp(loc); }

bool WarpBuilder::build_Div(BytecodeLocation loc) { return buildBinaryOp(loc); }

bool WarpBuilder::build_Mod(BytecodeLocation loc) { return buildBinaryOp(loc); }

bool WarpBuilder::build_Pow(BytecodeLocation loc) { return buildBinaryOp(loc); }

bool WarpBuilder::build_BitAnd(BytecodeLocation loc) {
  return buildBinaryOp(loc);
}

bool WarpBuilder::build_BitOr(BytecodeLocation loc) {
  return buildBinaryOp(loc);
}

bool WarpBuilder::build_BitXor(BytecodeLocation loc) {
  return buildBinaryOp(loc);
}

bool WarpBuilder::build_Lsh(BytecodeLocation loc) { return buildBinaryOp(loc); }

bool WarpBuilder::build_Rsh(BytecodeLocation loc) { return buildBinaryOp(loc); }

bool WarpBuilder::build_Ursh(BytecodeLocation loc) {
  return buildBinaryOp(loc);
}

bool WarpBuilder::buildCompareOp(BytecodeLocation loc) {
  MDefinition* right = current->pop();
  MDefinition* left = current->pop();
  return buildIC(loc, CacheKind::Compare, {left, right});
}

bool WarpBuilder::build_Eq(BytecodeLocation loc) { return buildCompareOp(loc); }

bool WarpBuilder::build_Ne(BytecodeLocation loc) { return buildCompareOp(loc); }

bool WarpBuilder::build_Lt(BytecodeLocation loc) { return buildCompareOp(loc); }

bool WarpBuilder::build_Le(BytecodeLocation loc) { return buildCompareOp(loc); }

bool WarpBuilder::build_Gt(BytecodeLocation loc) { return buildCompareOp(loc); }

bool WarpBuilder::build_Ge(BytecodeLocation loc) { return buildCompareOp(loc); }

bool WarpBuilder::build_StrictEq(BytecodeLocation loc) {
  return buildCompareOp(loc);
}

bool WarpBuilder::build_StrictNe(BytecodeLocation loc) {
  return buildCompareOp(loc);
}

// Returns true iff the MTest added for |op| has a true-target corresponding
// with the join point in the bytecode.
static bool TestTrueTargetIsJoinPoint(JSOp op) {
  switch (op) {
    case JSOp::JumpIfTrue:
    case JSOp::Or:
    case JSOp::Case:
      return true;

    case JSOp::JumpIfFalse:
    case JSOp::And:
    case JSOp::Coalesce:
      return false;

    default:
      MOZ_CRASH("Unexpected op");
  }
}

bool WarpBuilder::build_JumpTarget(BytecodeLocation loc) {
  PendingEdgesMap::Ptr p = pendingEdges_.lookup(loc.toRawBytecode());
  if (!p) {
    // No (reachable) jumps so this is just a no-op.
    return true;
  }

  PendingEdges edges(std::move(p->value()));
  pendingEdges_.remove(p);

  MOZ_ASSERT(!edges.empty());

  // Create join block if there's fall-through from the previous bytecode op.
  if (!hasTerminatedBlock()) {
    MBasicBlock* pred = current;
    if (!startNewBlock(pred, loc)) {
      return false;
    }
    pred->end(MGoto::New(alloc(), current));
  }

  for (const PendingEdge& edge : edges) {
    MBasicBlock* source = edge.block();
    uint32_t numToPop = edge.numToPop();

    if (hasTerminatedBlock()) {
      if (!startNewBlock(source, loc, numToPop)) {
        return false;
      }
    } else {
      MOZ_ASSERT(source->stackDepth() - numToPop == current->stackDepth());
      if (!current->addPredecessorPopN(alloc(), source, numToPop)) {
        return false;
      }
    }

    MOZ_ASSERT(source->lastIns()->isTest() || source->lastIns()->isGoto() ||
               source->lastIns()->isTableSwitch());
    source->lastIns()->initSuccessor(edge.successor(), current);
  }

  MOZ_ASSERT(!hasTerminatedBlock());
  return true;
}

bool WarpBuilder::addIteratorLoopPhis(BytecodeLocation loopHead) {
  // When unwinding the stack for a thrown exception, the exception handler must
  // close live iterators. For ForIn and Destructuring loops, the exception
  // handler needs access to values on the stack. To prevent them from being
  // optimized away (and replaced with the JS_OPTIMIZED_OUT MagicValue), we need
  // to mark the phis (and phis they flow into) as having implicit uses.
  // See ProcessTryNotes in vm/Interpreter.cpp and CloseLiveIteratorIon in
  // jit/JitFrames.cpp

  MOZ_ASSERT(current->stackDepth() >= info().firstStackSlot());

  bool emptyStack = current->stackDepth() == info().firstStackSlot();
  if (emptyStack) {
    return true;
  }

  jsbytecode* loopHeadPC = loopHead.toRawBytecode();

  for (TryNoteIterAllNoGC tni(script_, loopHeadPC); !tni.done(); ++tni) {
    const TryNote& tn = **tni;

    // Stop if we reach an outer loop because outer loops were already
    // processed when we visited their loop headers.
    if (tn.isLoop()) {
      BytecodeLocation tnStart = script_->offsetToLocation(tn.start);
      if (tnStart != loopHead) {
        MOZ_ASSERT(tnStart.is(JSOp::LoopHead));
        MOZ_ASSERT(tnStart < loopHead);
        return true;
      }
    }

    switch (tn.kind()) {
      case TryNoteKind::Destructuring:
      case TryNoteKind::ForIn: {
        // For for-in loops we add the iterator object to iterators(). For
        // destructuring loops we add the "done" value that's on top of the
        // stack and used in the exception handler.
        MOZ_ASSERT(tn.stackDepth >= 1);
        uint32_t slot = info().stackSlot(tn.stackDepth - 1);
        MPhi* phi = current->getSlot(slot)->toPhi();
        if (!iterators()->append(phi)) {
          return false;
        }
        break;
      }
      case TryNoteKind::Loop:
      case TryNoteKind::ForOf:
        // Regular loops do not have iterators to close. ForOf loops handle
        // unwinding using catch blocks.
        break;
      default:
        break;
    }
  }

  return true;
}

bool WarpBuilder::build_LoopHead(BytecodeLocation loc) {
  // All loops have the following bytecode structure:
  //
  //    LoopHead
  //    ...
  //    JumpIfTrue/Goto to LoopHead

  if (hasTerminatedBlock()) {
    // The whole loop is unreachable.
    return true;
  }

  // Handle OSR from Baseline JIT code.
  if (loc.toRawBytecode() == info().osrPc()) {
    if (!startNewOsrPreHeaderBlock(loc)) {
      return false;
    }
  }

  incLoopDepth();

  MBasicBlock* pred = current;
  if (!startNewLoopHeaderBlock(loc)) {
    return false;
  }

  pred->end(MGoto::New(alloc(), current));

  if (!addIteratorLoopPhis(loc)) {
    return false;
  }

  MInterruptCheck* check = MInterruptCheck::New(alloc());
  current->add(check);

#ifdef JS_CACHEIR_SPEW
  if (snapshot().needsFinalWarmUpCount()) {
    MIncrementWarmUpCounter* ins =
        MIncrementWarmUpCounter::New(alloc(), script_);
    current->add(ins);
  }
#endif

  return true;
}

bool WarpBuilder::buildTestOp(BytecodeLocation loc) {
  MDefinition* originalValue = current->peek(-1);

  if (auto* cacheIRSnapshot = getOpSnapshot<WarpCacheIR>(loc)) {
    // If we have CacheIR, we can use it to refine the input. Note that
    // the transpiler doesn't generate any control instructions. Instead,
    // we fall through and generate them below.
    MDefinition* value = current->pop();
    if (!TranspileCacheIRToMIR(this, loc, cacheIRSnapshot, {value})) {
      return false;
    }
  }

  if (loc.isBackedge()) {
    return buildTestBackedge(loc);
  }

  JSOp op = loc.getOp();
  BytecodeLocation target1 = loc.next();
  BytecodeLocation target2 = loc.getJumpTarget();

  if (TestTrueTargetIsJoinPoint(op)) {
    std::swap(target1, target2);
  }

  MDefinition* value = current->pop();

  // JSOp::And and JSOp::Or leave the top stack value unchanged.  The
  // top stack value may have been converted to bool by a transpiled
  // ToBool IC, so we push the original value.
  bool mustKeepCondition = (op == JSOp::And || op == JSOp::Or);
  if (mustKeepCondition) {
    current->push(originalValue);
  }

  // If this op always branches to the same location we treat this as a
  // JSOp::Goto.
  if (target1 == target2) {
    value->setImplicitlyUsedUnchecked();
    return buildForwardGoto(target1);
  }

  MTest* test = MTest::New(alloc(), value, /* ifTrue = */ nullptr,
                           /* ifFalse = */ nullptr);
  current->end(test);

  // JSOp::Case must pop a second value on the true-branch (the input to the
  // switch-statement).
  uint32_t numToPop = (loc.getOp() == JSOp::Case) ? 1 : 0;

  if (!addPendingEdge(target1, current, MTest::TrueBranchIndex, numToPop)) {
    return false;
  }
  if (!addPendingEdge(target2, current, MTest::FalseBranchIndex)) {
    return false;
  }

  if (const auto* typesSnapshot = getOpSnapshot<WarpPolymorphicTypes>(loc)) {
    test->setObservedTypes(typesSnapshot->list());
  }

  setTerminatedBlock();
  return true;
}

bool WarpBuilder::buildTestBackedge(BytecodeLocation loc) {
  MOZ_ASSERT(loc.is(JSOp::JumpIfTrue));
  MOZ_ASSERT(loopDepth() > 0);

  MDefinition* value = current->pop();

  BytecodeLocation loopHead = loc.getJumpTarget();
  MOZ_ASSERT(loopHead.is(JSOp::LoopHead));

  BytecodeLocation successor = loc.next();

  // We can finish the loop now. Use the loophead pc instead of the current pc
  // because the stack depth at the start of that op matches the current stack
  // depth (after popping our operand).
  MBasicBlock* pred = current;
  if (!startNewBlock(current, loopHead)) {
    return false;
  }

  MTest* test = MTest::New(alloc(), value, /* ifTrue = */ current,
                           /* ifFalse = */ nullptr);
  pred->end(test);

  if (const auto* typesSnapshot = getOpSnapshot<WarpPolymorphicTypes>(loc)) {
    test->setObservedTypes(typesSnapshot->list());
  }

  if (!addPendingEdge(successor, pred, MTest::FalseBranchIndex)) {
    return false;
  }

  return buildBackedge();
}

bool WarpBuilder::build_JumpIfFalse(BytecodeLocation loc) {
  return buildTestOp(loc);
}

bool WarpBuilder::build_JumpIfTrue(BytecodeLocation loc) {
  return buildTestOp(loc);
}

bool WarpBuilder::build_And(BytecodeLocation loc) { return buildTestOp(loc); }

bool WarpBuilder::build_Or(BytecodeLocation loc) { return buildTestOp(loc); }

bool WarpBuilder::build_Case(BytecodeLocation loc) { return buildTestOp(loc); }

bool WarpBuilder::build_Default(BytecodeLocation loc) {
  current->pop();
  return buildForwardGoto(loc.getJumpTarget());
}

bool WarpBuilder::build_Coalesce(BytecodeLocation loc) {
  BytecodeLocation target1 = loc.next();
  BytecodeLocation target2 = loc.getJumpTarget();
  MOZ_ASSERT(target2 > target1);

  MDefinition* value = current->peek(-1);

  MInstruction* isNullOrUndefined = MIsNullOrUndefined::New(alloc(), value);
  current->add(isNullOrUndefined);

  current->end(MTest::New(alloc(), isNullOrUndefined, /* ifTrue = */ nullptr,
                          /* ifFalse = */ nullptr));

  if (!addPendingEdge(target1, current, MTest::TrueBranchIndex)) {
    return false;
  }
  if (!addPendingEdge(target2, current, MTest::FalseBranchIndex)) {
    return false;
  }

  setTerminatedBlock();
  return true;
}

bool WarpBuilder::buildBackedge() {
  decLoopDepth();

  MBasicBlock* header = loopStack_.popCopy().header();
  current->end(MGoto::New(alloc(), header));

  if (!header->setBackedge(current)) {
    return false;
  }

  setTerminatedBlock();
  return true;
}

bool WarpBuilder::buildForwardGoto(BytecodeLocation target) {
  current->end(MGoto::New(alloc(), nullptr));

  if (!addPendingEdge(target, current, MGoto::TargetIndex)) {
    return false;
  }

  setTerminatedBlock();
  return true;
}

bool WarpBuilder::build_Goto(BytecodeLocation loc) {
  if (loc.isBackedge()) {
    return buildBackedge();
  }

  return buildForwardGoto(loc.getJumpTarget());
}

bool WarpBuilder::build_IsNullOrUndefined(BytecodeLocation loc) {
  MDefinition* value = current->peek(-1);
  auto* isNullOrUndef = MIsNullOrUndefined::New(alloc(), value);
  current->add(isNullOrUndef);
  current->push(isNullOrUndef);
  return true;
}

bool WarpBuilder::build_DebugCheckSelfHosted(BytecodeLocation loc) {
#ifdef DEBUG
  MDefinition* val = current->pop();
  MDebugCheckSelfHosted* check = MDebugCheckSelfHosted::New(alloc(), val);
  current->add(check);
  current->push(check);
  if (!resumeAfter(check, loc)) {
    return false;
  }
#endif
  return true;
}

bool WarpBuilder::build_DynamicImport(BytecodeLocation loc) {
  MDefinition* options = current->pop();
  MDefinition* specifier = current->pop();
  MDynamicImport* ins = MDynamicImport::New(alloc(), specifier, options);
  current->add(ins);
  current->push(ins);
  return resumeAfter(ins, loc);
}

bool WarpBuilder::build_Not(BytecodeLocation loc) {
  if (auto* cacheIRSnapshot = getOpSnapshot<WarpCacheIR>(loc)) {
    // If we have CacheIR, we can use it to refine the input before
    // emitting the MNot.
    MDefinition* value = current->pop();
    if (!TranspileCacheIRToMIR(this, loc, cacheIRSnapshot, {value})) {
      return false;
    }
  }

  MDefinition* value = current->pop();
  MNot* ins = MNot::New(alloc(), value);
  current->add(ins);
  current->push(ins);

  if (const auto* typesSnapshot = getOpSnapshot<WarpPolymorphicTypes>(loc)) {
    ins->setObservedTypes(typesSnapshot->list());
  }

  return true;
}

bool WarpBuilder::build_ToString(BytecodeLocation loc) {
  MDefinition* value = current->pop();

  if (value->type() == MIRType::String) {
    value->setImplicitlyUsedUnchecked();
    current->push(value);
    return true;
  }

  MToString* ins =
      MToString::New(alloc(), value, MToString::SideEffectHandling::Supported);
  current->add(ins);
  current->push(ins);
  if (ins->isEffectful()) {
    return resumeAfter(ins, loc);
  }
  return true;
}

bool WarpBuilder::usesEnvironmentChain() const {
  return script_->jitScript()->usesEnvironmentChain();
}

bool WarpBuilder::build_GlobalOrEvalDeclInstantiation(BytecodeLocation loc) {
  MOZ_ASSERT(!script_->isForEval(), "Eval scripts not supported");
  auto* redeclCheck = MGlobalDeclInstantiation::New(alloc());
  current->add(redeclCheck);
  return resumeAfter(redeclCheck, loc);
}

bool WarpBuilder::build_BindVar(BytecodeLocation) {
  MOZ_ASSERT(usesEnvironmentChain());

  MDefinition* env = current->environmentChain();
  MCallBindVar* ins = MCallBindVar::New(alloc(), env);
  current->add(ins);
  current->push(ins);
  return true;
}

bool WarpBuilder::build_MutateProto(BytecodeLocation loc) {
  MDefinition* value = current->pop();
  MDefinition* obj = current->peek(-1);
  MMutateProto* mutate = MMutateProto::New(alloc(), obj, value);
  current->add(mutate);
  return resumeAfter(mutate, loc);
}

MDefinition* WarpBuilder::getCallee() {
  if (inlineCallInfo()) {
    return inlineCallInfo()->callee();
  }

  MInstruction* callee = MCallee::New(alloc());
  current->add(callee);
  return callee;
}

bool WarpBuilder::build_Callee(BytecodeLocation) {
  MDefinition* callee = getCallee();
  current->push(callee);
  return true;
}

bool WarpBuilder::build_ToAsyncIter(BytecodeLocation loc) {
  MDefinition* nextMethod = current->pop();
  MDefinition* iterator = current->pop();
  MToAsyncIter* ins = MToAsyncIter::New(alloc(), iterator, nextMethod);
  current->add(ins);
  current->push(ins);
  return resumeAfter(ins, loc);
}

bool WarpBuilder::build_ToPropertyKey(BytecodeLocation loc) {
  MDefinition* value = current->pop();
  return buildIC(loc, CacheKind::ToPropertyKey, {value});
}

bool WarpBuilder::build_Typeof(BytecodeLocation loc) {
  MDefinition* input = current->pop();

  if (const auto* typesSnapshot = getOpSnapshot<WarpPolymorphicTypes>(loc)) {
    auto* typeOf = MTypeOf::New(alloc(), input);
    typeOf->setObservedTypes(typesSnapshot->list());
    current->add(typeOf);

    auto* ins = MTypeOfName::New(alloc(), typeOf);
    current->add(ins);
    current->push(ins);
    return true;
  }

  return buildIC(loc, CacheKind::TypeOf, {input});
}

bool WarpBuilder::build_TypeofExpr(BytecodeLocation loc) {
  return build_Typeof(loc);
}

bool WarpBuilder::build_Arguments(BytecodeLocation loc) {
  auto* snapshot = getOpSnapshot<WarpArguments>(loc);
  MOZ_ASSERT(info().needsArgsObj());
  MOZ_ASSERT(snapshot);
  MOZ_ASSERT(usesEnvironmentChain());

  ArgumentsObject* templateObj = snapshot->templateObj();
  MDefinition* env = current->environmentChain();

  MInstruction* argsObj;
  if (inlineCallInfo()) {
    argsObj = MCreateInlinedArgumentsObject::New(
        alloc(), env, getCallee(), inlineCallInfo()->argv(), templateObj);
    if (!argsObj) {
      return false;
    }
  } else {
    argsObj = MCreateArgumentsObject::New(alloc(), env, templateObj);
  }
  current->add(argsObj);
  current->setArgumentsObject(argsObj);
  current->push(argsObj);

  return true;
}

bool WarpBuilder::build_ObjWithProto(BytecodeLocation loc) {
  MDefinition* proto = current->pop();
  MInstruction* ins = MObjectWithProto::New(alloc(), proto);
  current->add(ins);
  current->push(ins);
  return resumeAfter(ins, loc);
}

MDefinition* WarpBuilder::walkEnvironmentChain(uint32_t numHops) {
  MDefinition* env = current->environmentChain();

  for (uint32_t i = 0; i < numHops; i++) {
    if (!alloc().ensureBallast()) {
      return nullptr;
    }

    MInstruction* ins = MEnclosingEnvironment::New(alloc(), env);
    current->add(ins);
    env = ins;
  }

  return env;
}

bool WarpBuilder::build_GetAliasedVar(BytecodeLocation loc) {
  EnvironmentCoordinate ec = loc.getEnvironmentCoordinate();
  MDefinition* obj = walkEnvironmentChain(ec.hops());
  if (!obj) {
    return false;
  }

  MInstruction* load;
  if (EnvironmentObject::nonExtensibleIsFixedSlot(ec)) {
    load = MLoadFixedSlot::New(alloc(), obj, ec.slot());
  } else {
    MInstruction* slots = MSlots::New(alloc(), obj);
    current->add(slots);

    uint32_t slot = EnvironmentObject::nonExtensibleDynamicSlotIndex(ec);
    load = MLoadDynamicSlot::New(alloc(), slots, slot);
  }

  current->add(load);
  current->push(load);
  return true;
}

bool WarpBuilder::build_SetAliasedVar(BytecodeLocation loc) {
  EnvironmentCoordinate ec = loc.getEnvironmentCoordinate();
  MDefinition* val = current->peek(-1);
  MDefinition* obj = walkEnvironmentChain(ec.hops());
  if (!obj) {
    return false;
  }

  current->add(MPostWriteBarrier::New(alloc(), obj, val));

  MInstruction* store;
  if (EnvironmentObject::nonExtensibleIsFixedSlot(ec)) {
    store = MStoreFixedSlot::NewBarriered(alloc(), obj, ec.slot(), val);
  } else {
    MInstruction* slots = MSlots::New(alloc(), obj);
    current->add(slots);

    uint32_t slot = EnvironmentObject::nonExtensibleDynamicSlotIndex(ec);
    store = MStoreDynamicSlot::NewBarriered(alloc(), slots, slot, val);
  }

  current->add(store);
  return resumeAfter(store, loc);
}

bool WarpBuilder::build_InitAliasedLexical(BytecodeLocation loc) {
  return build_SetAliasedVar(loc);
}

bool WarpBuilder::build_EnvCallee(BytecodeLocation loc) {
  uint32_t numHops = loc.getEnvCalleeNumHops();
  MDefinition* env = walkEnvironmentChain(numHops);
  if (!env) {
    return false;
  }

  auto* callee = MLoadFixedSlot::New(alloc(), env, CallObject::calleeSlot());
  current->add(callee);
  current->push(callee);
  return true;
}

bool WarpBuilder::build_Iter(BytecodeLocation loc) {
  MDefinition* obj = current->pop();
  return buildIC(loc, CacheKind::GetIterator, {obj});
}

bool WarpBuilder::build_MoreIter(BytecodeLocation loc) {
  MDefinition* iter = current->peek(-1);
  MInstruction* ins = MIteratorMore::New(alloc(), iter);
  current->add(ins);
  current->push(ins);
  return resumeAfter(ins, loc);
}

bool WarpBuilder::build_EndIter(BytecodeLocation loc) {
  current->pop();  // Iterator value is not used.
  MDefinition* iter = current->pop();
  MInstruction* ins = MIteratorEnd::New(alloc(), iter);
  current->add(ins);
  return resumeAfter(ins, loc);
}

bool WarpBuilder::build_CloseIter(BytecodeLocation loc) {
  MDefinition* iter = current->pop();
  return buildIC(loc, CacheKind::CloseIter, {iter});
}

bool WarpBuilder::build_IsNoIter(BytecodeLocation) {
  MDefinition* def = current->peek(-1);
  MOZ_ASSERT(def->isIteratorMore());
  MInstruction* ins = MIsNoIter::New(alloc(), def);
  current->add(ins);
  current->push(ins);
  return true;
}

bool WarpBuilder::transpileCall(BytecodeLocation loc,
                                const WarpCacheIR* cacheIRSnapshot,
                                CallInfo* callInfo) {
  // Synthesize the constant number of arguments for this call op.
  auto* argc = MConstant::New(alloc(), Int32Value(callInfo->argc()));
  current->add(argc);

  return TranspileCacheIRToMIR(this, loc, cacheIRSnapshot, {argc}, callInfo);
}

void WarpBuilder::buildCreateThis(CallInfo& callInfo) {
  MOZ_ASSERT(callInfo.constructing());

  // Inline the this-object allocation on the caller-side.
  MDefinition* callee = callInfo.callee();
  MDefinition* newTarget = callInfo.getNewTarget();
  auto* createThis = MCreateThis::New(alloc(), callee, newTarget);
  current->add(createThis);
  callInfo.thisArg()->setImplicitlyUsedUnchecked();
  callInfo.setThis(createThis);
}

bool WarpBuilder::buildCallOp(BytecodeLocation loc) {
  uint32_t argc = loc.getCallArgc();
  JSOp op = loc.getOp();
  bool constructing = IsConstructOp(op);
  bool ignoresReturnValue = (op == JSOp::CallIgnoresRv || loc.resultIsPopped());

  CallInfo callInfo(alloc(), constructing, ignoresReturnValue);
  if (!callInfo.init(current, argc)) {
    return false;
  }

  if (const auto* inliningSnapshot = getOpSnapshot<WarpInlinedCall>(loc)) {
    // Transpile the CacheIR to generate the correct guards before
    // inlining.  In this case, CacheOp::CallInlinedFunction updates
    // the CallInfo, but does not generate a call.
    callInfo.markAsInlined();
    if (!transpileCall(loc, inliningSnapshot->cacheIRSnapshot(), &callInfo)) {
      return false;
    }

    // Generate the body of the inlined function.
    return buildInlinedCall(loc, inliningSnapshot, callInfo);
  }

  if (auto* cacheIRSnapshot = getOpSnapshot<WarpCacheIR>(loc)) {
    return transpileCall(loc, cacheIRSnapshot, &callInfo);
  }

  if (getOpSnapshot<WarpBailout>(loc)) {
    callInfo.setImplicitlyUsedUnchecked();
    return buildBailoutForColdIC(loc, CacheKind::Call);
  }

  bool needsThisCheck = false;
  if (callInfo.constructing()) {
    buildCreateThis(callInfo);
    needsThisCheck = true;
  }

  MCall* call = makeCall(callInfo, needsThisCheck);
  if (!call) {
    return false;
  }

  current->add(call);
  current->push(call);
  return resumeAfter(call, loc);
}

bool WarpBuilder::build_Call(BytecodeLocation loc) { return buildCallOp(loc); }

bool WarpBuilder::build_CallContent(BytecodeLocation loc) {
  return buildCallOp(loc);
}

bool WarpBuilder::build_CallIgnoresRv(BytecodeLocation loc) {
  return buildCallOp(loc);
}

bool WarpBuilder::build_CallIter(BytecodeLocation loc) {
  return buildCallOp(loc);
}

bool WarpBuilder::build_CallContentIter(BytecodeLocation loc) {
  return buildCallOp(loc);
}

bool WarpBuilder::build_New(BytecodeLocation loc) { return buildCallOp(loc); }

bool WarpBuilder::build_NewContent(BytecodeLocation loc) {
  return buildCallOp(loc);
}

bool WarpBuilder::build_SuperCall(BytecodeLocation loc) {
  return buildCallOp(loc);
}

bool WarpBuilder::build_FunctionThis(BytecodeLocation loc) {
  MOZ_ASSERT(info().hasFunMaybeLazy());

  if (script_->strict()) {
    // No need to wrap primitive |this| in strict mode.
    current->pushSlot(info().thisSlot());
    return true;
  }

  MOZ_ASSERT(!script_->hasNonSyntacticScope(),
             "WarpOracle should have aborted compilation");

  MDefinition* def = current->getSlot(info().thisSlot());
  JSObject* globalThis = snapshot().globalLexicalEnvThis();

  auto* thisObj = MBoxNonStrictThis::New(alloc(), def, globalThis);
  current->add(thisObj);
  current->push(thisObj);

  return true;
}

bool WarpBuilder::build_GlobalThis(BytecodeLocation loc) {
  MOZ_ASSERT(!script_->hasNonSyntacticScope());
  JSObject* obj = snapshot().globalLexicalEnvThis();
  pushConstant(ObjectValue(*obj));
  return true;
}

MConstant* WarpBuilder::globalLexicalEnvConstant() {
  JSObject* globalLexical = snapshot().globalLexicalEnv();
  return constant(ObjectValue(*globalLexical));
}

bool WarpBuilder::build_GetName(BytecodeLocation loc) {
  MOZ_ASSERT(usesEnvironmentChain());

  MDefinition* env = current->environmentChain();
  return buildIC(loc, CacheKind::GetName, {env});
}

bool WarpBuilder::build_GetGName(BytecodeLocation loc) {
  MOZ_ASSERT(!script_->hasNonSyntacticScope());

  MDefinition* env = globalLexicalEnvConstant();
  return buildIC(loc, CacheKind::GetName, {env});
}

bool WarpBuilder::build_BindName(BytecodeLocation loc) {
  MOZ_ASSERT(usesEnvironmentChain());

  MDefinition* env = current->environmentChain();
  return buildIC(loc, CacheKind::BindName, {env});
}

bool WarpBuilder::build_BindGName(BytecodeLocation loc) {
  MOZ_ASSERT(!script_->hasNonSyntacticScope());

  if (const auto* snapshot = getOpSnapshot<WarpBindGName>(loc)) {
    JSObject* globalEnv = snapshot->globalEnv();
    pushConstant(ObjectValue(*globalEnv));
    return true;
  }

  MDefinition* env = globalLexicalEnvConstant();
  return buildIC(loc, CacheKind::BindName, {env});
}

bool WarpBuilder::build_GetProp(BytecodeLocation loc) {
  MDefinition* val = current->pop();
  return buildIC(loc, CacheKind::GetProp, {val});
}

bool WarpBuilder::build_GetElem(BytecodeLocation loc) {
  MDefinition* id = current->pop();
  MDefinition* val = current->pop();
  return buildIC(loc, CacheKind::GetElem, {val, id});
}

bool WarpBuilder::build_SetProp(BytecodeLocation loc) {
  MDefinition* val = current->pop();
  MDefinition* obj = current->pop();
  current->push(val);
  return buildIC(loc, CacheKind::SetProp, {obj, val});
}

bool WarpBuilder::build_StrictSetProp(BytecodeLocation loc) {
  return build_SetProp(loc);
}

bool WarpBuilder::build_SetName(BytecodeLocation loc) {
  return build_SetProp(loc);
}

bool WarpBuilder::build_StrictSetName(BytecodeLocation loc) {
  return build_SetProp(loc);
}

bool WarpBuilder::build_SetGName(BytecodeLocation loc) {
  return build_SetProp(loc);
}

bool WarpBuilder::build_StrictSetGName(BytecodeLocation loc) {
  return build_SetProp(loc);
}

bool WarpBuilder::build_InitGLexical(BytecodeLocation loc) {
  MOZ_ASSERT(!script_->hasNonSyntacticScope());

  MDefinition* globalLexical = globalLexicalEnvConstant();
  MDefinition* val = current->peek(-1);

  return buildIC(loc, CacheKind::SetProp, {globalLexical, val});
}

bool WarpBuilder::build_SetElem(BytecodeLocation loc) {
  MDefinition* val = current->pop();
  MDefinition* id = current->pop();
  MDefinition* obj = current->pop();
  current->push(val);
  return buildIC(loc, CacheKind::SetElem, {obj, id, val});
}

bool WarpBuilder::build_StrictSetElem(BytecodeLocation loc) {
  return build_SetElem(loc);
}

bool WarpBuilder::build_DelProp(BytecodeLocation loc) {
  PropertyName* name = loc.getPropertyName(script_);
  MDefinition* obj = current->pop();
  bool strict = loc.getOp() == JSOp::StrictDelProp;

  MInstruction* ins = MDeleteProperty::New(alloc(), obj, name, strict);
  current->add(ins);
  current->push(ins);
  return resumeAfter(ins, loc);
}

bool WarpBuilder::build_StrictDelProp(BytecodeLocation loc) {
  return build_DelProp(loc);
}

bool WarpBuilder::build_DelElem(BytecodeLocation loc) {
  MDefinition* id = current->pop();
  MDefinition* obj = current->pop();
  bool strict = loc.getOp() == JSOp::StrictDelElem;

  MInstruction* ins = MDeleteElement::New(alloc(), obj, id, strict);
  current->add(ins);
  current->push(ins);
  return resumeAfter(ins, loc);
}

bool WarpBuilder::build_StrictDelElem(BytecodeLocation loc) {
  return build_DelElem(loc);
}

bool WarpBuilder::build_SetFunName(BytecodeLocation loc) {
  FunctionPrefixKind prefixKind = loc.getFunctionPrefixKind();
  MDefinition* name = current->pop();
  MDefinition* fun = current->pop();

  MSetFunName* ins = MSetFunName::New(alloc(), fun, name, uint8_t(prefixKind));
  current->add(ins);
  current->push(fun);
  return resumeAfter(ins, loc);
}

bool WarpBuilder::build_PushLexicalEnv(BytecodeLocation loc) {
  MOZ_ASSERT(usesEnvironmentChain());

  const auto* snapshot = getOpSnapshot<WarpLexicalEnvironment>(loc);
  MOZ_ASSERT(snapshot);

  MDefinition* env = current->environmentChain();
  MConstant* templateCst = constant(ObjectValue(*snapshot->templateObj()));

  auto* ins = MNewLexicalEnvironmentObject::New(alloc(), templateCst);
  current->add(ins);

#ifdef DEBUG
  // Assert in debug mode we can elide the post write barrier.
  current->add(MAssertCanElidePostWriteBarrier::New(alloc(), ins, env));
#endif

  // Initialize the object's reserved slots. No post barrier is needed here,
  // for the same reason as in buildNamedLambdaEnv.
  current->add(MStoreFixedSlot::NewUnbarriered(
      alloc(), ins, EnvironmentObject::enclosingEnvironmentSlot(), env));

  current->setEnvironmentChain(ins);
  return true;
}

bool WarpBuilder::build_PushClassBodyEnv(BytecodeLocation loc) {
  MOZ_ASSERT(usesEnvironmentChain());

  const auto* snapshot = getOpSnapshot<WarpClassBodyEnvironment>(loc);
  MOZ_ASSERT(snapshot);

  MDefinition* env = current->environmentChain();
  MConstant* templateCst = constant(ObjectValue(*snapshot->templateObj()));

  auto* ins = MNewClassBodyEnvironmentObject::New(alloc(), templateCst);
  current->add(ins);

#ifdef DEBUG
  // Assert in debug mode we can elide the post write barrier.
  current->add(MAssertCanElidePostWriteBarrier::New(alloc(), ins, env));
#endif

  // Initialize the object's reserved slots. No post barrier is needed here,
  // for the same reason as in buildNamedLambdaEnv.
  current->add(MStoreFixedSlot::NewUnbarriered(
      alloc(), ins, EnvironmentObject::enclosingEnvironmentSlot(), env));

  current->setEnvironmentChain(ins);
  return true;
}

bool WarpBuilder::build_PopLexicalEnv(BytecodeLocation) {
  MDefinition* enclosingEnv = walkEnvironmentChain(1);
  if (!enclosingEnv) {
    return false;
  }
  current->setEnvironmentChain(enclosingEnv);
  return true;
}

bool WarpBuilder::build_FreshenLexicalEnv(BytecodeLocation loc) {
  MOZ_ASSERT(usesEnvironmentChain());

  const auto* snapshot = getOpSnapshot<WarpLexicalEnvironment>(loc);
  MOZ_ASSERT(snapshot);

  MDefinition* enclosingEnv = walkEnvironmentChain(1);
  if (!enclosingEnv) {
    return false;
  }

  MDefinition* env = current->environmentChain();
  MConstant* templateCst = constant(ObjectValue(*snapshot->templateObj()));

  auto* templateObj = snapshot->templateObj();
  auto* scope = &templateObj->scope();
  MOZ_ASSERT(scope->hasEnvironment());

  auto* ins = MNewLexicalEnvironmentObject::New(alloc(), templateCst);
  current->add(ins);

#ifdef DEBUG
  // Assert in debug mode we can elide the post write barrier.
  current->add(
      MAssertCanElidePostWriteBarrier::New(alloc(), ins, enclosingEnv));
#endif

  // Initialize the object's reserved slots. No post barrier is needed here,
  // for the same reason as in buildNamedLambdaEnv.
  current->add(MStoreFixedSlot::NewUnbarriered(
      alloc(), ins, EnvironmentObject::enclosingEnvironmentSlot(),
      enclosingEnv));

  // Copy environment slots.
  MSlots* envSlots = nullptr;
  MSlots* slots = nullptr;
  for (BindingIter iter(scope); iter; iter++) {
    auto loc = iter.location();
    if (loc.kind() != BindingLocation::Kind::Environment) {
      MOZ_ASSERT(loc.kind() == BindingLocation::Kind::Frame);
      continue;
    }

    if (!alloc().ensureBallast()) {
      return false;
    }

    uint32_t slot = loc.slot();
    uint32_t numFixedSlots = templateObj->numFixedSlots();
    if (slot >= numFixedSlots) {
      if (!envSlots) {
        envSlots = MSlots::New(alloc(), env);
        current->add(envSlots);
      }
      if (!slots) {
        slots = MSlots::New(alloc(), ins);
        current->add(slots);
      }

      uint32_t dynamicSlot = slot - numFixedSlots;

      auto* load = MLoadDynamicSlot::New(alloc(), envSlots, dynamicSlot);
      current->add(load);

#ifdef DEBUG
      // Assert in debug mode we can elide the post write barrier.
      current->add(MAssertCanElidePostWriteBarrier::New(alloc(), ins, load));
#endif

      current->add(
          MStoreDynamicSlot::NewUnbarriered(alloc(), slots, dynamicSlot, load));
    } else {
      auto* load = MLoadFixedSlot::New(alloc(), env, slot);
      current->add(load);

#ifdef DEBUG
      // Assert in debug mode we can elide the post write barrier.
      current->add(MAssertCanElidePostWriteBarrier::New(alloc(), ins, load));
#endif

      current->add(MStoreFixedSlot::NewUnbarriered(alloc(), ins, slot, load));
    }
  }

  current->setEnvironmentChain(ins);
  return true;
}

bool WarpBuilder::build_RecreateLexicalEnv(BytecodeLocation loc) {
  MOZ_ASSERT(usesEnvironmentChain());

  const auto* snapshot = getOpSnapshot<WarpLexicalEnvironment>(loc);
  MOZ_ASSERT(snapshot);

  MDefinition* enclosingEnv = walkEnvironmentChain(1);
  if (!enclosingEnv) {
    return false;
  }

  MConstant* templateCst = constant(ObjectValue(*snapshot->templateObj()));

  auto* ins = MNewLexicalEnvironmentObject::New(alloc(), templateCst);
  current->add(ins);

#ifdef DEBUG
  // Assert in debug mode we can elide the post write barrier.
  current->add(
      MAssertCanElidePostWriteBarrier::New(alloc(), ins, enclosingEnv));
#endif

  // Initialize the object's reserved slots. No post barrier is needed here,
  // for the same reason as in buildNamedLambdaEnv.
  current->add(MStoreFixedSlot::NewUnbarriered(
      alloc(), ins, EnvironmentObject::enclosingEnvironmentSlot(),
      enclosingEnv));

  current->setEnvironmentChain(ins);
  return true;
}

bool WarpBuilder::build_PushVarEnv(BytecodeLocation loc) {
  MOZ_ASSERT(usesEnvironmentChain());

  const auto* snapshot = getOpSnapshot<WarpVarEnvironment>(loc);
  MOZ_ASSERT(snapshot);

  MDefinition* env = current->environmentChain();
  MConstant* templateCst = constant(ObjectValue(*snapshot->templateObj()));

  auto* ins = MNewVarEnvironmentObject::New(alloc(), templateCst);
  current->add(ins);

#ifdef DEBUG
  // Assert in debug mode we can elide the post write barrier.
  current->add(MAssertCanElidePostWriteBarrier::New(alloc(), ins, env));
#endif

  // Initialize the object's reserved slots. No post barrier is needed here,
  // for the same reason as in buildNamedLambdaEnv.
  current->add(MStoreFixedSlot::NewUnbarriered(
      alloc(), ins, EnvironmentObject::enclosingEnvironmentSlot(), env));

  current->setEnvironmentChain(ins);
  return true;
}

bool WarpBuilder::build_ImplicitThis(BytecodeLocation loc) {
  MOZ_ASSERT(usesEnvironmentChain());

  PropertyName* name = loc.getPropertyName(script_);
  MDefinition* env = current->environmentChain();

  auto* ins = MImplicitThis::New(alloc(), env, name);
  current->add(ins);
  current->push(ins);
  return resumeAfter(ins, loc);
}

bool WarpBuilder::build_CheckClassHeritage(BytecodeLocation loc) {
  MDefinition* def = current->pop();
  auto* ins = MCheckClassHeritage::New(alloc(), def);
  current->add(ins);
  current->push(ins);
  return resumeAfter(ins, loc);
}

bool WarpBuilder::build_CheckThis(BytecodeLocation loc) {
  MDefinition* def = current->pop();
  auto* ins = MCheckThis::New(alloc(), def);
  current->add(ins);
  current->push(ins);
  return resumeAfter(ins, loc);
}

bool WarpBuilder::build_CheckThisReinit(BytecodeLocation loc) {
  MDefinition* def = current->pop();
  auto* ins = MCheckThisReinit::New(alloc(), def);
  current->add(ins);
  current->push(ins);
  return resumeAfter(ins, loc);
}

bool WarpBuilder::build_Generator(BytecodeLocation loc) {
  MOZ_ASSERT(usesEnvironmentChain());

  MDefinition* callee = getCallee();
  MDefinition* environmentChain = current->environmentChain();
  MDefinition* argsObj = info().needsArgsObj() ? current->argumentsObject()
                                               : constant(Int32Value(0));

  MGenerator* generator =
      MGenerator::New(alloc(), callee, environmentChain, argsObj);

  current->add(generator);
  current->push(generator);
  return resumeAfter(generator, loc);
}

bool WarpBuilder::build_AfterYield(BytecodeLocation loc) {
  // Unreachable blocks don't need to generate a bail.
  if (hasTerminatedBlock()) {
    return true;
  }

  // This comes after a yield, which we generate as a return,
  // so we know this should be unreachable code.
  //
  // We emit an unreachable bail for this, which will assert if we
  // ever execute this.
  //
  // An Unreachable bail, instead of MUnreachable, because MUnreachable
  // is a control instruction, and injecting it in the middle of a block
  // causes various graph state assertions to fail.
  MBail* bail = MBail::New(alloc(), BailoutKind::Unreachable);
  current->add(bail);

  return true;
}

bool WarpBuilder::build_FinalYieldRval(BytecodeLocation loc) {
  MDefinition* gen = current->pop();

  auto setSlotNull = [this, gen](size_t slot) {
    auto* ins = MStoreFixedSlot::NewBarriered(alloc(), gen, slot,
                                              constant(NullValue()));
    current->add(ins);
  };

  // Close the generator
  setSlotNull(AbstractGeneratorObject::calleeSlot());
  setSlotNull(AbstractGeneratorObject::envChainSlot());
  setSlotNull(AbstractGeneratorObject::argsObjectSlot());
  setSlotNull(AbstractGeneratorObject::stackStorageSlot());
  setSlotNull(AbstractGeneratorObject::resumeIndexSlot());

  // Return
  return build_RetRval(loc);
}

bool WarpBuilder::build_AsyncResolve(BytecodeLocation loc) {
  MDefinition* generator = current->pop();
  MDefinition* valueOrReason = current->pop();
  auto resolveKind = loc.getAsyncFunctionResolveKind();

  MAsyncResolve* resolve =
      MAsyncResolve::New(alloc(), generator, valueOrReason, resolveKind);
  current->add(resolve);
  current->push(resolve);
  return resumeAfter(resolve, loc);
}

bool WarpBuilder::build_ResumeKind(BytecodeLocation loc) {
  GeneratorResumeKind resumeKind = loc.resumeKind();

  current->push(constant(Int32Value(static_cast<int32_t>(resumeKind))));
  return true;
}

bool WarpBuilder::build_CheckResumeKind(BytecodeLocation loc) {
  // Outside of `yield*`, this is normally unreachable code in Warp,
  // so we just manipulate the stack appropriately to ensure correct
  // MIR generation.
  //
  // However, `yield*` emits a forced generator return which can be
  // warp compiled, so in order to correctly handle these semantics
  // we also generate a bailout, so that the forced generator return
  // runs in baseline.
  MDefinition* resumeKind = current->pop();
  MDefinition* gen = current->pop();
  MDefinition* rval = current->peek(-1);

  // Mark operands as implicitly used.
  resumeKind->setImplicitlyUsedUnchecked();
  gen->setImplicitlyUsedUnchecked();
  rval->setImplicitlyUsedUnchecked();

  // Bail out if we encounter CheckResumeKind.
  MBail* bail = MBail::New(alloc(), BailoutKind::Inevitable);
  current->add(bail);
  current->setAlwaysBails();

  return true;
}

bool WarpBuilder::build_CanSkipAwait(BytecodeLocation loc) {
  MDefinition* val = current->pop();

  MCanSkipAwait* canSkip = MCanSkipAwait::New(alloc(), val);
  current->add(canSkip);

  current->push(val);
  current->push(canSkip);

  return resumeAfter(canSkip, loc);
}

bool WarpBuilder::build_MaybeExtractAwaitValue(BytecodeLocation loc) {
  MDefinition* canSkip = current->pop();
  MDefinition* value = current->pop();

  MMaybeExtractAwaitValue* extracted =
      MMaybeExtractAwaitValue::New(alloc(), value, canSkip);
  current->add(extracted);

  current->push(extracted);
  current->push(canSkip);

  return resumeAfter(extracted, loc);
}

bool WarpBuilder::build_InitialYield(BytecodeLocation loc) {
  MDefinition* gen = current->pop();
  return buildSuspend(loc, gen, gen);
}

bool WarpBuilder::build_Await(BytecodeLocation loc) {
  MDefinition* gen = current->pop();
  MDefinition* promiseOrGenerator = current->pop();

  return buildSuspend(loc, gen, promiseOrGenerator);
}
bool WarpBuilder::build_Yield(BytecodeLocation loc) { return build_Await(loc); }

bool WarpBuilder::buildSuspend(BytecodeLocation loc, MDefinition* gen,
                               MDefinition* retVal) {
  // If required, unbox the generator object explicitly and infallibly.
  //
  // This is done to avoid fuzz-bugs where ApplyTypeInformation does the
  // unboxing, and generates fallible unboxes which can lead to torn object
  // state due to `bailAfter`.
  MDefinition* genObj = gen;
  if (genObj->type() != MIRType::Object) {
    auto* unbox =
        MUnbox::New(alloc(), gen, MIRType::Object, MUnbox::Mode::Infallible);
    current->add(unbox);

    genObj = unbox;
  }

  int32_t slotsToCopy = current->stackDepth() - info().firstLocalSlot();
  MOZ_ASSERT(slotsToCopy >= 0);
  if (slotsToCopy > 0) {
    auto* arrayObj = MLoadFixedSlotAndUnbox::New(
        alloc(), genObj, AbstractGeneratorObject::stackStorageSlot(),
        MUnbox::Mode::Infallible, MIRType::Object);
    current->add(arrayObj);

    auto* stackStorage = MElements::New(alloc(), arrayObj);
    current->add(stackStorage);

    for (int32_t i = 0; i < slotsToCopy; i++) {
      if (!alloc().ensureBallast()) {
        return false;
      }
      // Use peekUnchecked because we're also writing out the argument slots
      int32_t peek = -slotsToCopy + i;
      MDefinition* stackElem = current->peekUnchecked(peek);
      auto* store = MStoreElement::NewUnbarriered(
          alloc(), stackStorage, constant(Int32Value(i)), stackElem,
          /* needsHoleCheck = */ false);

      current->add(store);
      current->add(MPostWriteBarrier::New(alloc(), arrayObj, stackElem));
    }

    auto* len = constant(Int32Value(slotsToCopy - 1));

    auto* setInitLength =
        MSetInitializedLength::New(alloc(), stackStorage, len);
    current->add(setInitLength);

    auto* setLength = MSetArrayLength::New(alloc(), stackStorage, len);
    current->add(setLength);
  }

  // Update Generator Object state
  uint32_t resumeIndex = loc.getResumeIndex();

  // This store is unbarriered, as it's only ever storing an integer, and as
  // such doesn't partake of object tracing.
  current->add(MStoreFixedSlot::NewUnbarriered(
      alloc(), genObj, AbstractGeneratorObject::resumeIndexSlot(),
      constant(Int32Value(resumeIndex))));

  // This store is barriered because it stores an object value.
  current->add(MStoreFixedSlot::NewBarriered(
      alloc(), genObj, AbstractGeneratorObject::envChainSlot(),
      current->environmentChain()));

  current->add(
      MPostWriteBarrier::New(alloc(), genObj, current->environmentChain()));

  // GeneratorReturn will return from the method, however to support MIR
  // generation isn't treated like the end of a block
  MGeneratorReturn* ret = MGeneratorReturn::New(alloc(), retVal);
  current->add(ret);

  // To ensure the rest of the MIR generation looks correct, fill the stack with
  // the appropriately typed MUnreachable's for the stack pushes from this
  // opcode.
  auto* unreachableResumeKind =
      MUnreachableResult::New(alloc(), MIRType::Int32);
  current->add(unreachableResumeKind);
  current->push(unreachableResumeKind);

  auto* unreachableGenerator =
      MUnreachableResult::New(alloc(), MIRType::Object);
  current->add(unreachableGenerator);
  current->push(unreachableGenerator);

  auto* unreachableRval = MUnreachableResult::New(alloc(), MIRType::Value);
  current->add(unreachableRval);
  current->push(unreachableRval);

  return true;
}

bool WarpBuilder::build_AsyncAwait(BytecodeLocation loc) {
  MDefinition* gen = current->pop();
  MDefinition* value = current->pop();

  MAsyncAwait* asyncAwait = MAsyncAwait::New(alloc(), value, gen);
  current->add(asyncAwait);
  current->push(asyncAwait);
  return resumeAfter(asyncAwait, loc);
}

bool WarpBuilder::build_CheckReturn(BytecodeLocation loc) {
  MOZ_ASSERT(!script_->noScriptRval());

  MDefinition* returnValue = current->getSlot(info().returnValueSlot());
  MDefinition* thisValue = current->pop();

  auto* ins = MCheckReturn::New(alloc(), returnValue, thisValue);
  current->add(ins);
  current->push(ins);
  return resumeAfter(ins, loc);
}

void WarpBuilder::buildCheckLexicalOp(BytecodeLocation loc) {
  JSOp op = loc.getOp();
  MOZ_ASSERT(op == JSOp::CheckLexical || op == JSOp::CheckAliasedLexical);

  MDefinition* input = current->pop();
  MInstruction* lexicalCheck = MLexicalCheck::New(alloc(), input);
  current->add(lexicalCheck);
  current->push(lexicalCheck);

  if (snapshot().bailoutInfo().failedLexicalCheck()) {
    // If we have previously had a failed lexical check in Ion, we want to avoid
    // hoisting any lexical checks, which can cause spurious failures. In this
    // case, we also have to be careful not to hoist any loads of this lexical
    // past the check. For unaliased lexical variables, we can set the local
    // slot to create a dependency (see below). For aliased lexicals, that
    // doesn't work, so we disable LICM instead.
    lexicalCheck->setNotMovable();
    if (op == JSOp::CheckAliasedLexical) {
      mirGen().disableLICM();
    }
  }

  if (op == JSOp::CheckLexical) {
    // Set the local slot so that a subsequent GetLocal without a CheckLexical
    // (the frontend can elide lexical checks) doesn't let a definition with
    // MIRType::MagicUninitializedLexical escape to arbitrary MIR instructions.
    // Note that in this case the GetLocal would be unreachable because we throw
    // an exception here, but we still generate MIR instructions for it.
    uint32_t slot = info().localSlot(loc.local());
    current->setSlot(slot, lexicalCheck);
  }
}

bool WarpBuilder::build_CheckLexical(BytecodeLocation loc) {
  buildCheckLexicalOp(loc);
  return true;
}

bool WarpBuilder::build_CheckAliasedLexical(BytecodeLocation loc) {
  buildCheckLexicalOp(loc);
  return true;
}

bool WarpBuilder::build_InitHomeObject(BytecodeLocation loc) {
  MDefinition* homeObject = current->pop();
  MDefinition* function = current->pop();

  current->add(MPostWriteBarrier::New(alloc(), function, homeObject));

  auto* ins = MInitHomeObject::New(alloc(), function, homeObject);
  current->add(ins);
  current->push(ins);
  return true;
}

bool WarpBuilder::build_SuperBase(BytecodeLocation) {
  MDefinition* callee = current->pop();

  auto* homeObject = MHomeObject::New(alloc(), callee);
  current->add(homeObject);

  auto* superBase = MHomeObjectSuperBase::New(alloc(), homeObject);
  current->add(superBase);
  current->push(superBase);
  return true;
}

bool WarpBuilder::build_SuperFun(BytecodeLocation) {
  MDefinition* callee = current->pop();
  auto* ins = MSuperFunction::New(alloc(), callee);
  current->add(ins);
  current->push(ins);
  return true;
}

bool WarpBuilder::build_BuiltinObject(BytecodeLocation loc) {
  if (auto* snapshot = getOpSnapshot<WarpBuiltinObject>(loc)) {
    JSObject* builtin = snapshot->builtin();
    pushConstant(ObjectValue(*builtin));
    return true;
  }

  auto kind = loc.getBuiltinObjectKind();
  auto* ins = MBuiltinObject::New(alloc(), kind);
  current->add(ins);
  current->push(ins);
  return resumeAfter(ins, loc);
}

bool WarpBuilder::build_GetIntrinsic(BytecodeLocation loc) {
  if (auto* snapshot = getOpSnapshot<WarpGetIntrinsic>(loc)) {
    Value intrinsic = snapshot->intrinsic();
    pushConstant(intrinsic);
    return true;
  }

  PropertyName* name = loc.getPropertyName(script_);
  MCallGetIntrinsicValue* ins = MCallGetIntrinsicValue::New(alloc(), name);
  current->add(ins);
  current->push(ins);
  return resumeAfter(ins, loc);
}

bool WarpBuilder::build_ImportMeta(BytecodeLocation loc) {
  ModuleObject* moduleObj = scriptSnapshot()->moduleObject();
  MOZ_ASSERT(moduleObj);

  MModuleMetadata* ins = MModuleMetadata::New(alloc(), moduleObj);
  current->add(ins);
  current->push(ins);
  return resumeAfter(ins, loc);
}

bool WarpBuilder::build_CallSiteObj(BytecodeLocation loc) {
  return build_Object(loc);
}

bool WarpBuilder::build_NewArray(BytecodeLocation loc) {
  return buildIC(loc, CacheKind::NewArray, {});
}

bool WarpBuilder::build_NewObject(BytecodeLocation loc) {
  return buildIC(loc, CacheKind::NewObject, {});
}

bool WarpBuilder::build_NewInit(BytecodeLocation loc) {
  return build_NewObject(loc);
}

bool WarpBuilder::build_Object(BytecodeLocation loc) {
  JSObject* obj = loc.getObject(script_);
  MConstant* objConst = constant(ObjectValue(*obj));

  current->push(objConst);
  return true;
}

bool WarpBuilder::buildInitPropGetterSetterOp(BytecodeLocation loc) {
  PropertyName* name = loc.getPropertyName(script_);
  MDefinition* value = current->pop();
  MDefinition* obj = current->peek(-1);

  auto* ins = MInitPropGetterSetter::New(alloc(), obj, value, name);
  current->add(ins);
  return resumeAfter(ins, loc);
}

bool WarpBuilder::build_InitPropGetter(BytecodeLocation loc) {
  return buildInitPropGetterSetterOp(loc);
}

bool WarpBuilder::build_InitPropSetter(BytecodeLocation loc) {
  return buildInitPropGetterSetterOp(loc);
}

bool WarpBuilder::build_InitHiddenPropGetter(BytecodeLocation loc) {
  return buildInitPropGetterSetterOp(loc);
}

bool WarpBuilder::build_InitHiddenPropSetter(BytecodeLocation loc) {
  return buildInitPropGetterSetterOp(loc);
}

bool WarpBuilder::buildInitElemGetterSetterOp(BytecodeLocation loc) {
  MDefinition* value = current->pop();
  MDefinition* id = current->pop();
  MDefinition* obj = current->peek(-1);

  auto* ins = MInitElemGetterSetter::New(alloc(), obj, id, value);
  current->add(ins);
  return resumeAfter(ins, loc);
}

bool WarpBuilder::build_InitElemGetter(BytecodeLocation loc) {
  return buildInitElemGetterSetterOp(loc);
}

bool WarpBuilder::build_InitElemSetter(BytecodeLocation loc) {
  return buildInitElemGetterSetterOp(loc);
}

bool WarpBuilder::build_InitHiddenElemGetter(BytecodeLocation loc) {
  return buildInitElemGetterSetterOp(loc);
}

bool WarpBuilder::build_InitHiddenElemSetter(BytecodeLocation loc) {
  return buildInitElemGetterSetterOp(loc);
}

bool WarpBuilder::build_In(BytecodeLocation loc) {
  MDefinition* obj = current->pop();
  MDefinition* id = current->pop();
  return buildIC(loc, CacheKind::In, {id, obj});
}

bool WarpBuilder::build_HasOwn(BytecodeLocation loc) {
  MDefinition* obj = current->pop();
  MDefinition* id = current->pop();
  return buildIC(loc, CacheKind::HasOwn, {id, obj});
}

bool WarpBuilder::build_CheckPrivateField(BytecodeLocation loc) {
  MDefinition* id = current->peek(-1);
  MDefinition* obj = current->peek(-2);
  return buildIC(loc, CacheKind::CheckPrivateField, {obj, id});
}

bool WarpBuilder::build_NewPrivateName(BytecodeLocation loc) {
  JSAtom* name = loc.getAtom(script_);

  auto* ins = MNewPrivateName::New(alloc(), name);
  current->add(ins);
  current->push(ins);
  return resumeAfter(ins, loc);
}

bool WarpBuilder::build_Instanceof(BytecodeLocation loc) {
  MDefinition* rhs = current->pop();
  MDefinition* obj = current->pop();
  return buildIC(loc, CacheKind::InstanceOf, {obj, rhs});
}

bool WarpBuilder::build_NewTarget(BytecodeLocation loc) {
  MOZ_ASSERT(script_->isFunction());
  MOZ_ASSERT(info().hasFunMaybeLazy());
  MOZ_ASSERT(!scriptSnapshot()->isArrowFunction());

  if (inlineCallInfo()) {
    if (inlineCallInfo()->constructing()) {
      current->push(inlineCallInfo()->getNewTarget());
    } else {
      pushConstant(UndefinedValue());
    }
    return true;
  }

  MNewTarget* ins = MNewTarget::New(alloc());
  current->add(ins);
  current->push(ins);
  return true;
}

bool WarpBuilder::build_CheckIsObj(BytecodeLocation loc) {
  CheckIsObjectKind kind = loc.getCheckIsObjectKind();

  MDefinition* toCheck = current->peek(-1);
  if (toCheck->type() == MIRType::Object) {
    toCheck->setImplicitlyUsedUnchecked();
    return true;
  }

  MDefinition* val = current->pop();
  MCheckIsObj* ins = MCheckIsObj::New(alloc(), val, uint8_t(kind));
  current->add(ins);
  current->push(ins);
  return true;
}

bool WarpBuilder::build_CheckObjCoercible(BytecodeLocation loc) {
  MDefinition* val = current->pop();
  MCheckObjCoercible* ins = MCheckObjCoercible::New(alloc(), val);
  current->add(ins);
  current->push(ins);
  return resumeAfter(ins, loc);
}

MInstruction* WarpBuilder::buildLoadSlot(MDefinition* obj,
                                         uint32_t numFixedSlots,
                                         uint32_t slot) {
  if (slot < numFixedSlots) {
    MLoadFixedSlot* load = MLoadFixedSlot::New(alloc(), obj, slot);
    current->add(load);
    return load;
  }

  MSlots* slots = MSlots::New(alloc(), obj);
  current->add(slots);

  MLoadDynamicSlot* load =
      MLoadDynamicSlot::New(alloc(), slots, slot - numFixedSlots);
  current->add(load);
  return load;
}

bool WarpBuilder::build_GetImport(BytecodeLocation loc) {
  auto* snapshot = getOpSnapshot<WarpGetImport>(loc);

  ModuleEnvironmentObject* targetEnv = snapshot->targetEnv();

  // Load the target environment slot.
  MConstant* obj = constant(ObjectValue(*targetEnv));
  auto* load = buildLoadSlot(obj, snapshot->numFixedSlots(), snapshot->slot());

  if (snapshot->needsLexicalCheck()) {
    // TODO: IonBuilder has code to mark non-movable. See buildCheckLexicalOp.
    MInstruction* lexicalCheck = MLexicalCheck::New(alloc(), load);
    current->add(lexicalCheck);
    current->push(lexicalCheck);
  } else {
    current->push(load);
  }

  return true;
}

bool WarpBuilder::build_GetPropSuper(BytecodeLocation loc) {
  MDefinition* obj = current->pop();
  MDefinition* receiver = current->pop();
  return buildIC(loc, CacheKind::GetPropSuper, {obj, receiver});
}

bool WarpBuilder::build_GetElemSuper(BytecodeLocation loc) {
  MDefinition* obj = current->pop();
  MDefinition* id = current->pop();
  MDefinition* receiver = current->pop();
  return buildIC(loc, CacheKind::GetElemSuper, {obj, id, receiver});
}

bool WarpBuilder::build_InitProp(BytecodeLocation loc) {
  MDefinition* val = current->pop();
  MDefinition* obj = current->peek(-1);
  return buildIC(loc, CacheKind::SetProp, {obj, val});
}

bool WarpBuilder::build_InitLockedProp(BytecodeLocation loc) {
  return build_InitProp(loc);
}

bool WarpBuilder::build_InitHiddenProp(BytecodeLocation loc) {
  return build_InitProp(loc);
}

bool WarpBuilder::build_InitElem(BytecodeLocation loc) {
  MDefinition* val = current->pop();
  MDefinition* id = current->pop();
  MDefinition* obj = current->peek(-1);
  return buildIC(loc, CacheKind::SetElem, {obj, id, val});
}

bool WarpBuilder::build_InitLockedElem(BytecodeLocation loc) {
  return build_InitElem(loc);
}

bool WarpBuilder::build_InitHiddenElem(BytecodeLocation loc) {
  return build_InitElem(loc);
}

bool WarpBuilder::build_InitElemArray(BytecodeLocation loc) {
  MDefinition* val = current->pop();
  MDefinition* obj = current->peek(-1);

  // Note: getInitElemArrayIndex asserts the index fits in int32_t.
  uint32_t index = loc.getInitElemArrayIndex();
  MConstant* indexConst = constant(Int32Value(index));

  // Note: InitArrayElemOperation asserts the index does not exceed the array's
  // dense element capacity.

  auto* elements = MElements::New(alloc(), obj);
  current->add(elements);

  if (val->type() == MIRType::MagicHole) {
    val->setImplicitlyUsedUnchecked();
    auto* store = MStoreHoleValueElement::New(alloc(), elements, indexConst);
    current->add(store);
  } else {
    current->add(MPostWriteBarrier::New(alloc(), obj, val));
    auto* store =
        MStoreElement::NewUnbarriered(alloc(), elements, indexConst, val,
                                      /* needsHoleCheck = */ false);
    current->add(store);
  }

  auto* setLength = MSetInitializedLength::New(alloc(), elements, indexConst);
  current->add(setLength);

  return resumeAfter(setLength, loc);
}

bool WarpBuilder::build_InitElemInc(BytecodeLocation loc) {
  MDefinition* val = current->pop();
  MDefinition* index = current->pop();
  MDefinition* obj = current->peek(-1);

  // Push index + 1.
  MConstant* constOne = constant(Int32Value(1));
  MAdd* nextIndex = MAdd::New(alloc(), index, constOne, TruncateKind::Truncate);
  current->add(nextIndex);
  current->push(nextIndex);

  return buildIC(loc, CacheKind::SetElem, {obj, index, val});
}

bool WarpBuilder::build_Lambda(BytecodeLocation loc) {
  MOZ_ASSERT(usesEnvironmentChain());

  MDefinition* env = current->environmentChain();

  JSFunction* fun = loc.getFunction(script_);
  MConstant* funConst = constant(ObjectValue(*fun));

  auto* ins = MLambda::New(alloc(), env, funConst);
  current->add(ins);
  current->push(ins);
  return resumeAfter(ins, loc);
}

bool WarpBuilder::build_FunWithProto(BytecodeLocation loc) {
  MOZ_ASSERT(usesEnvironmentChain());

  MDefinition* proto = current->pop();
  MDefinition* env = current->environmentChain();

  JSFunction* fun = loc.getFunction(script_);
  MConstant* funConst = constant(ObjectValue(*fun));

  auto* ins = MFunctionWithProto::New(alloc(), env, proto, funConst);
  current->add(ins);
  current->push(ins);
  return resumeAfter(ins, loc);
}

bool WarpBuilder::build_SpreadCall(BytecodeLocation loc) {
  bool constructing = false;
  CallInfo callInfo(alloc(), constructing, loc.resultIsPopped());
  callInfo.initForSpreadCall(current);

  if (auto* cacheIRSnapshot = getOpSnapshot<WarpCacheIR>(loc)) {
    return transpileCall(loc, cacheIRSnapshot, &callInfo);
  }

  bool needsThisCheck = false;
  MInstruction* call = makeSpreadCall(callInfo, needsThisCheck);
  if (!call) {
    return false;
  }
  call->setBailoutKind(BailoutKind::TooManyArguments);
  current->add(call);
  current->push(call);
  return resumeAfter(call, loc);
}

bool WarpBuilder::build_SpreadNew(BytecodeLocation loc) {
  bool constructing = true;
  CallInfo callInfo(alloc(), constructing, loc.resultIsPopped());
  callInfo.initForSpreadCall(current);

  if (auto* cacheIRSnapshot = getOpSnapshot<WarpCacheIR>(loc)) {
    return transpileCall(loc, cacheIRSnapshot, &callInfo);
  }

  buildCreateThis(callInfo);

  bool needsThisCheck = true;
  MInstruction* call = makeSpreadCall(callInfo, needsThisCheck);
  if (!call) {
    return false;
  }
  call->setBailoutKind(BailoutKind::TooManyArguments);
  current->add(call);
  current->push(call);
  return resumeAfter(call, loc);
}

bool WarpBuilder::build_SpreadSuperCall(BytecodeLocation loc) {
  return build_SpreadNew(loc);
}

bool WarpBuilder::build_OptimizeSpreadCall(BytecodeLocation loc) {
  MDefinition* value = current->pop();
  return buildIC(loc, CacheKind::OptimizeSpreadCall, {value});
}

bool WarpBuilder::build_Debugger(BytecodeLocation loc) {
  // The |debugger;| statement will bail out to Baseline if the realm is a
  // debuggee realm with an onDebuggerStatement hook.
  MDebugger* debugger = MDebugger::New(alloc());
  current->add(debugger);
  return resumeAfter(debugger, loc);
}

bool WarpBuilder::build_TableSwitch(BytecodeLocation loc) {
  int32_t low = loc.getTableSwitchLow();
  int32_t high = loc.getTableSwitchHigh();
  size_t numCases = high - low + 1;

  MDefinition* input = current->pop();
  MTableSwitch* tableswitch = MTableSwitch::New(alloc(), input, low, high);
  current->end(tableswitch);

  // Table mapping from target bytecode offset to MTableSwitch successor index.
  // This prevents adding multiple predecessor/successor edges to the same
  // target block, which isn't valid in MIR.
  using TargetToSuccessorMap =
      InlineMap<uint32_t, uint32_t, 8, DefaultHasher<uint32_t>,
                SystemAllocPolicy>;
  TargetToSuccessorMap targetToSuccessor;

  // Create |default| edge.
  {
    BytecodeLocation defaultLoc = loc.getTableSwitchDefaultTarget();
    uint32_t defaultOffset = defaultLoc.bytecodeToOffset(script_);

    size_t index;
    if (!tableswitch->addDefault(nullptr, &index)) {
      return false;
    }
    if (!addPendingEdge(defaultLoc, current, index)) {
      return false;
    }
    if (!targetToSuccessor.put(defaultOffset, index)) {
      return false;
    }
  }

  // Add all cases.
  for (size_t i = 0; i < numCases; i++) {
    BytecodeLocation caseLoc = loc.getTableSwitchCaseTarget(script_, i);
    uint32_t caseOffset = caseLoc.bytecodeToOffset(script_);

    size_t index;
    if (auto p = targetToSuccessor.lookupForAdd(caseOffset)) {
      index = p->value();
    } else {
      if (!tableswitch->addSuccessor(nullptr, &index)) {
        return false;
      }
      if (!addPendingEdge(caseLoc, current, index)) {
        return false;
      }
      if (!targetToSuccessor.add(p, caseOffset, index)) {
        return false;
      }
    }
    if (!tableswitch->addCase(index)) {
      return false;
    }
  }

  setTerminatedBlock();
  return true;
}

bool WarpBuilder::build_Rest(BytecodeLocation loc) {
  auto* snapshot = getOpSnapshot<WarpRest>(loc);
  Shape* shape = snapshot ? snapshot->shape() : nullptr;

  // NOTE: Keep this code in sync with |ArgumentsReplacer|.

  if (inlineCallInfo()) {
    // If we are inlining, we know the actual arguments.
    unsigned numActuals = inlineCallInfo()->argc();
    unsigned numFormals = info().nargs() - 1;
    unsigned numRest = numActuals > numFormals ? numActuals - numFormals : 0;

    // TODO: support pre-tenuring.
    gc::Heap heap = gc::Heap::Default;

    // Allocate an array of the correct size.
    MInstruction* newArray;
    if (shape && gc::CanUseFixedElementsForArray(numRest)) {
      auto* shapeConstant = MConstant::NewShape(alloc(), shape);
      current->add(shapeConstant);
      newArray = MNewArrayObject::New(alloc(), shapeConstant, numRest, heap);
    } else {
      MConstant* templateConst = constant(NullValue());
      newArray = MNewArray::NewVM(alloc(), numRest, templateConst, heap);
    }
    current->add(newArray);
    current->push(newArray);

    if (numRest == 0) {
      // No more updating to do.
      return true;
    }

    MElements* elements = MElements::New(alloc(), newArray);
    current->add(elements);

    // Unroll the argument copy loop. We don't need to do any bounds or hole
    // checking here.
    MConstant* index = nullptr;
    for (uint32_t i = numFormals; i < numActuals; i++) {
      if (!alloc().ensureBallast()) {
        return false;
      }

      index = MConstant::New(alloc(), Int32Value(i - numFormals));
      current->add(index);

      MDefinition* arg = inlineCallInfo()->argv()[i];
      MStoreElement* store =
          MStoreElement::NewUnbarriered(alloc(), elements, index, arg,
                                        /* needsHoleCheck = */ false);
      current->add(store);
      current->add(MPostWriteBarrier::New(alloc(), newArray, arg));
    }

    // Update the initialized length for all the (necessarily non-hole)
    // elements added.
    MSetInitializedLength* initLength =
        MSetInitializedLength::New(alloc(), elements, index);
    current->add(initLength);

    return true;
  }

  MArgumentsLength* numActuals = MArgumentsLength::New(alloc());
  current->add(numActuals);

  // Pass in the number of actual arguments, the number of formals (not
  // including the rest parameter slot itself), and the shape.
  unsigned numFormals = info().nargs() - 1;
  MRest* rest = MRest::New(alloc(), numActuals, numFormals, shape);
  current->add(rest);
  current->push(rest);
  return true;
}

bool WarpBuilder::build_Try(BytecodeLocation loc) {
  graph().setHasTryBlock();

  MBasicBlock* pred = current;
  if (!startNewBlock(pred, loc.next())) {
    return false;
  }

  pred->end(MGoto::New(alloc(), current));
  return true;
}

bool WarpBuilder::build_Finally(BytecodeLocation loc) {
  MOZ_ASSERT(graph().hasTryBlock());
  return true;
}

bool WarpBuilder::build_Exception(BytecodeLocation) {
  MOZ_CRASH("Unreachable because we skip catch-blocks");
}

bool WarpBuilder::build_Throw(BytecodeLocation loc) {
  MDefinition* def = current->pop();

  MThrow* ins = MThrow::New(alloc(), def);
  current->add(ins);
  if (!resumeAfter(ins, loc)) {
    return false;
  }

  // Terminate the block.
  current->end(MUnreachable::New(alloc()));
  setTerminatedBlock();
  return true;
}

bool WarpBuilder::build_ThrowSetConst(BytecodeLocation loc) {
  auto* ins = MThrowRuntimeLexicalError::New(alloc(), JSMSG_BAD_CONST_ASSIGN);
  current->add(ins);
  if (!resumeAfter(ins, loc)) {
    return false;
  }

  // Terminate the block.
  current->end(MUnreachable::New(alloc()));
  setTerminatedBlock();
  return true;
}

bool WarpBuilder::build_ThrowMsg(BytecodeLocation loc) {
  auto* ins = MThrowMsg::New(alloc(), loc.throwMsgKind());
  current->add(ins);
  if (!resumeAfter(ins, loc)) {
    return false;
  }

  // Terminate the block.
  current->end(MUnreachable::New(alloc()));
  setTerminatedBlock();
  return true;
}

bool WarpBuilder::buildIC(BytecodeLocation loc, CacheKind kind,
                          std::initializer_list<MDefinition*> inputs) {
  MOZ_ASSERT(loc.opHasIC());

  mozilla::DebugOnly<size_t> numInputs = inputs.size();
  MOZ_ASSERT(numInputs == NumInputsForCacheKind(kind));

  if (auto* cacheIRSnapshot = getOpSnapshot<WarpCacheIR>(loc)) {
    return TranspileCacheIRToMIR(this, loc, cacheIRSnapshot, inputs);
  }

  if (getOpSnapshot<WarpBailout>(loc)) {
    for (MDefinition* input : inputs) {
      input->setImplicitlyUsedUnchecked();
    }
    return buildBailoutForColdIC(loc, kind);
  }

  if (const auto* inliningSnapshot = getOpSnapshot<WarpInlinedCall>(loc)) {
    // The CallInfo will be initialized by the transpiler.
    bool ignoresRval = BytecodeIsPopped(loc.toRawBytecode());
    CallInfo callInfo(alloc(), /*constructing =*/false, ignoresRval);
    callInfo.markAsInlined();

    if (!TranspileCacheIRToMIR(this, loc, inliningSnapshot->cacheIRSnapshot(),
                               inputs, &callInfo)) {
      return false;
    }
    return buildInlinedCall(loc, inliningSnapshot, callInfo);
  }

  // Work around std::initializer_list not defining operator[].
  auto getInput = [&](size_t index) -> MDefinition* {
    MOZ_ASSERT(index < numInputs);
    return inputs.begin()[index];
  };

  switch (kind) {
    case CacheKind::UnaryArith: {
      MOZ_ASSERT(numInputs == 1);
      auto* ins = MUnaryCache::New(alloc(), getInput(0));
      current->add(ins);
      current->push(ins);
      return resumeAfter(ins, loc);
    }
    case CacheKind::ToPropertyKey: {
      MOZ_ASSERT(numInputs == 1);
      auto* ins = MToPropertyKeyCache::New(alloc(), getInput(0));
      current->add(ins);
      current->push(ins);
      return resumeAfter(ins, loc);
    }
    case CacheKind::BinaryArith: {
      MOZ_ASSERT(numInputs == 2);
      auto* ins =
          MBinaryCache::New(alloc(), getInput(0), getInput(1), MIRType::Value);
      current->add(ins);
      current->push(ins);
      return resumeAfter(ins, loc);
    }
    case CacheKind::Compare: {
      MOZ_ASSERT(numInputs == 2);
      auto* ins = MBinaryCache::New(alloc(), getInput(0), getInput(1),
                                    MIRType::Boolean);
      current->add(ins);
      current->push(ins);
      return resumeAfter(ins, loc);
    }
    case CacheKind::In: {
      MOZ_ASSERT(numInputs == 2);
      auto* ins = MInCache::New(alloc(), getInput(0), getInput(1));
      current->add(ins);
      current->push(ins);
      return resumeAfter(ins, loc);
    }
    case CacheKind::HasOwn: {
      MOZ_ASSERT(numInputs == 2);
      // Note: the MHasOwnCache constructor takes obj/id instead of id/obj.
      auto* ins = MHasOwnCache::New(alloc(), getInput(1), getInput(0));
      current->add(ins);
      current->push(ins);
      return resumeAfter(ins, loc);
    }
    case CacheKind::CheckPrivateField: {
      MOZ_ASSERT(numInputs == 2);
      auto* ins =
          MCheckPrivateFieldCache::New(alloc(), getInput(0), getInput(1));
      current->add(ins);
      current->push(ins);
      return resumeAfter(ins, loc);
    }
    case CacheKind::InstanceOf: {
      MOZ_ASSERT(numInputs == 2);
      auto* ins = MInstanceOfCache::New(alloc(), getInput(0), getInput(1));
      current->add(ins);
      current->push(ins);
      return resumeAfter(ins, loc);
    }
    case CacheKind::BindName: {
      MOZ_ASSERT(numInputs == 1);
      auto* ins = MBindNameCache::New(alloc(), getInput(0));
      current->add(ins);
      current->push(ins);
      return resumeAfter(ins, loc);
    }
    case CacheKind::GetIterator: {
      MOZ_ASSERT(numInputs == 1);
      auto* ins = MGetIteratorCache::New(alloc(), getInput(0));
      current->add(ins);
      current->push(ins);
      return resumeAfter(ins, loc);
    }
    case CacheKind::GetName: {
      MOZ_ASSERT(numInputs == 1);
      auto* ins = MGetNameCache::New(alloc(), getInput(0));
      current->add(ins);
      current->push(ins);
      return resumeAfter(ins, loc);
    }
    case CacheKind::GetProp: {
      MOZ_ASSERT(numInputs == 1);
      PropertyName* name = loc.getPropertyName(script_);
      MConstant* id = constant(StringValue(name));
      MDefinition* val = getInput(0);
      auto* ins = MGetPropertyCache::New(alloc(), val, id);
      current->add(ins);
      current->push(ins);
      return resumeAfter(ins, loc);
    }
    case CacheKind::GetElem: {
      MOZ_ASSERT(numInputs == 2);
      MDefinition* val = getInput(0);
      auto* ins = MGetPropertyCache::New(alloc(), val, getInput(1));
      current->add(ins);
      current->push(ins);
      return resumeAfter(ins, loc);
    }
    case CacheKind::SetProp: {
      MOZ_ASSERT(numInputs == 2);
      PropertyName* name = loc.getPropertyName(script_);
      MConstant* id = constant(StringValue(name));
      bool strict = loc.isStrictSetOp();
      auto* ins =
          MSetPropertyCache::New(alloc(), getInput(0), id, getInput(1), strict);
      current->add(ins);
      return resumeAfter(ins, loc);
    }
    case CacheKind::SetElem: {
      MOZ_ASSERT(numInputs == 3);
      bool strict = loc.isStrictSetOp();
      auto* ins = MSetPropertyCache::New(alloc(), getInput(0), getInput(1),
                                         getInput(2), strict);
      current->add(ins);
      return resumeAfter(ins, loc);
    }
    case CacheKind::GetPropSuper: {
      MOZ_ASSERT(numInputs == 2);
      PropertyName* name = loc.getPropertyName(script_);
      MConstant* id = constant(StringValue(name));
      auto* ins =
          MGetPropSuperCache::New(alloc(), getInput(0), getInput(1), id);
      current->add(ins);
      current->push(ins);
      return resumeAfter(ins, loc);
    }
    case CacheKind::GetElemSuper: {
      MOZ_ASSERT(numInputs == 3);
      // Note: CacheIR expects obj/id/receiver but MGetPropSuperCache takes
      // obj/receiver/id so swap the last two inputs.
      auto* ins = MGetPropSuperCache::New(alloc(), getInput(0), getInput(2),
                                          getInput(1));
      current->add(ins);
      current->push(ins);
      return resumeAfter(ins, loc);
    }
    case CacheKind::OptimizeSpreadCall: {
      MOZ_ASSERT(numInputs == 1);
      auto* ins = MOptimizeSpreadCallCache::New(alloc(), getInput(0));
      current->add(ins);
      current->push(ins);
      return resumeAfter(ins, loc);
    }
    case CacheKind::TypeOf: {
      // Note: Warp does not have a TypeOf IC, it just inlines the operation.
      MOZ_ASSERT(numInputs == 1);
      auto* typeOf = MTypeOf::New(alloc(), getInput(0));
      current->add(typeOf);

      auto* ins = MTypeOfName::New(alloc(), typeOf);
      current->add(ins);
      current->push(ins);
      return true;
    }
    case CacheKind::NewObject: {
      auto* templateConst = constant(NullValue());
      MNewObject* ins = MNewObject::NewVM(
          alloc(), templateConst, gc::Heap::Default, MNewObject::ObjectLiteral);
      current->add(ins);
      current->push(ins);
      return resumeAfter(ins, loc);
    }
    case CacheKind::NewArray: {
      uint32_t length = loc.getNewArrayLength();
      MConstant* templateConst = constant(NullValue());
      MNewArray* ins =
          MNewArray::NewVM(alloc(), length, templateConst, gc::Heap::Default);
      current->add(ins);
      current->push(ins);
      return true;
    }
    case CacheKind::CloseIter: {
      MOZ_ASSERT(numInputs == 1);
      static_assert(sizeof(CompletionKind) == sizeof(uint8_t));
      CompletionKind kind = loc.getCompletionKind();
      auto* ins = MCloseIterCache::New(alloc(), getInput(0), uint8_t(kind));
      current->add(ins);
      return resumeAfter(ins, loc);
    }
    case CacheKind::GetIntrinsic:
    case CacheKind::ToBool:
    case CacheKind::Call:
      // We're currently not using an IC or transpiling CacheIR for these kinds.
      MOZ_CRASH("Unexpected kind");
  }

  return true;
}

bool WarpBuilder::buildBailoutForColdIC(BytecodeLocation loc, CacheKind kind) {
  MOZ_ASSERT(loc.opHasIC());

  MBail* bail = MBail::New(alloc(), BailoutKind::FirstExecution);
  current->add(bail);
  current->setAlwaysBails();

  MIRType resultType;
  switch (kind) {
    case CacheKind::UnaryArith:
    case CacheKind::BinaryArith:
    case CacheKind::GetName:
    case CacheKind::GetProp:
    case CacheKind::GetElem:
    case CacheKind::GetPropSuper:
    case CacheKind::GetElemSuper:
    case CacheKind::GetIntrinsic:
    case CacheKind::Call:
    case CacheKind::ToPropertyKey:
    case CacheKind::OptimizeSpreadCall:
      resultType = MIRType::Value;
      break;
    case CacheKind::BindName:
    case CacheKind::GetIterator:
    case CacheKind::NewArray:
    case CacheKind::NewObject:
      resultType = MIRType::Object;
      break;
    case CacheKind::TypeOf:
      resultType = MIRType::String;
      break;
    case CacheKind::ToBool:
    case CacheKind::Compare:
    case CacheKind::In:
    case CacheKind::HasOwn:
    case CacheKind::CheckPrivateField:
    case CacheKind::InstanceOf:
      resultType = MIRType::Boolean;
      break;
    case CacheKind::SetProp:
    case CacheKind::SetElem:
    case CacheKind::CloseIter:
      return true;  // No result.
  }

  auto* ins = MUnreachableResult::New(alloc(), resultType);
  current->add(ins);
  current->push(ins);

  return true;
}

class MOZ_RAII AutoAccumulateReturns {
  MIRGraph& graph_;
  MIRGraphReturns* prev_;

 public:
  AutoAccumulateReturns(MIRGraph& graph, MIRGraphReturns& returns)
      : graph_(graph) {
    prev_ = graph_.returnAccumulator();
    graph_.setReturnAccumulator(&returns);
  }
  ~AutoAccumulateReturns() { graph_.setReturnAccumulator(prev_); }
};

bool WarpBuilder::buildInlinedCall(BytecodeLocation loc,
                                   const WarpInlinedCall* inlineSnapshot,
                                   CallInfo& callInfo) {
  jsbytecode* pc = loc.toRawBytecode();

  if (callInfo.isSetter()) {
    // build_SetProp pushes the rhs argument onto the stack. Remove it
    // in preparation for pushCallStack.
    current->pop();
  }

  callInfo.setImplicitlyUsedUnchecked();

  // Capture formals in the outer resume point.
  if (!callInfo.pushCallStack(current)) {
    return false;
  }
  MResumePoint* outerResumePoint =
      MResumePoint::New(alloc(), current, pc, callInfo.inliningResumeMode());
  if (!outerResumePoint) {
    return false;
  }
  current->setOuterResumePoint(outerResumePoint);

  // Pop formals again, except leave |callee| on stack for duration of call.
  callInfo.popCallStack(current);
  current->push(callInfo.callee());

  // Build the graph.
  CompileInfo* calleeCompileInfo = inlineSnapshot->info();
  MIRGraphReturns returns(alloc());
  AutoAccumulateReturns aar(graph(), returns);
  WarpBuilder inlineBuilder(this, inlineSnapshot->scriptSnapshot(),
                            *calleeCompileInfo, &callInfo, outerResumePoint);
  if (!inlineBuilder.buildInline()) {
    // Note: Inlining only aborts on OOM.  If inlining would fail for
    // any other reason, we detect it in advance and don't inline.
    return false;
  }

  // We mark scripts as uninlineable in BytecodeAnalysis if we cannot
  // reach a return statement (without going through a catch/finally).
  MOZ_ASSERT(!returns.empty());

  // Create return block
  BytecodeLocation postCall = loc.next();
  MBasicBlock* prev = current;
  if (!startNewEntryBlock(prev->stackDepth(), postCall)) {
    return false;
  }
  // Restore previous value of callerResumePoint.
  current->setCallerResumePoint(callerResumePoint());
  current->inheritSlots(prev);

  // Pop |callee|.
  current->pop();

  // Accumulate return values.
  MDefinition* returnValue =
      patchInlinedReturns(calleeCompileInfo, callInfo, returns, current);
  if (!returnValue) {
    return false;
  }
  current->push(returnValue);

  // Initialize entry slots
  if (!current->initEntrySlots(alloc())) {
    return false;
  }

  return true;
}

MDefinition* WarpBuilder::patchInlinedReturns(CompileInfo* calleeCompileInfo,
                                              CallInfo& callInfo,
                                              MIRGraphReturns& exits,
                                              MBasicBlock* returnBlock) {
  if (exits.length() == 1) {
    return patchInlinedReturn(calleeCompileInfo, callInfo, exits[0],
                              returnBlock);
  }

  // Accumulate multiple returns with a phi.
  MPhi* phi = MPhi::New(alloc());
  if (!phi->reserveLength(exits.length())) {
    return nullptr;
  }

  for (auto* exit : exits) {
    MDefinition* rdef =
        patchInlinedReturn(calleeCompileInfo, callInfo, exit, returnBlock);
    if (!rdef) {
      return nullptr;
    }
    phi->addInput(rdef);
  }
  returnBlock->addPhi(phi);
  return phi;
}

MDefinition* WarpBuilder::patchInlinedReturn(CompileInfo* calleeCompileInfo,
                                             CallInfo& callInfo,
                                             MBasicBlock* exit,
                                             MBasicBlock* returnBlock) {
  // Replace the MReturn in the exit block with an MGoto branching to
  // the return block.
  MDefinition* rdef = exit->lastIns()->toReturn()->input();
  exit->discardLastIns();

  // Constructors must be patched by the caller to always return an object.
  // Derived class constructors contain extra bytecode to ensure an object
  // is always returned, so no additional patching is needed.
  if (callInfo.constructing() &&
      !calleeCompileInfo->isDerivedClassConstructor()) {
    auto* filter = MReturnFromCtor::New(alloc(), rdef, callInfo.thisArg());
    exit->add(filter);
    rdef = filter;
  } else if (callInfo.isSetter()) {
    // Setters return the rhs argument, not whatever value is returned.
    rdef = callInfo.getArg(0);
  }

  exit->end(MGoto::New(alloc(), returnBlock));
  if (!returnBlock->addPredecessorWithoutPhis(exit)) {
    return nullptr;
  }

  return rdef;
}