Adding upstream version 115.8.0esr.upstream/115.8.0esr

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 3576 insertions, 0 deletions

diff --git a/js/src/jit/WarpBuilder.cpp b/js/src/jit/WarpBuilder.cpp
new file mode 100644
index 0000000000..f005a6ea5e
--- /dev/null
+++ b/js/src/jit/WarpBuilder.cpp
@@ -0,0 +1,3576 @@
+/* -*- 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;
+}