diff --git a/src/maglev/maglev-code-generator.cc b/src/maglev/maglev-code-generator.cc
index 295d7a0e72..3d14d65391 100644
--- a/src/maglev/maglev-code-generator.cc
+++ b/src/maglev/maglev-code-generator.cc
@@ -479,13 +479,18 @@ class ExceptionHandlerTrampolineBuilder {
     // values are tagged and b) the stack walk treats unknown stack slots as
     // tagged.
 
+    const InterpretedDeoptFrame& lazy_frame =
+        deopt_info->top_frame().type() ==
+                DeoptFrame::FrameType::kBuiltinContinuationFrame
+            ? deopt_info->top_frame().parent()->as_interpreted()
+            : deopt_info->top_frame().as_interpreted();
+
     // TODO(v8:7700): Handle inlining.
 
     ParallelMoveResolver<Register> direct_moves(masm_);
     MoveVector materialising_moves;
     bool save_accumulator = false;
-    RecordMoves(deopt_info->top_frame().as_interpreted().unit(), catch_block,
-                deopt_info->top_frame().as_interpreted().frame_state(),
+    RecordMoves(lazy_frame.unit(), catch_block, lazy_frame.frame_state(),
                 &direct_moves, &materialising_moves, &save_accumulator);
 
     __ bind(&handler_info->trampoline_entry);
@@ -981,7 +986,29 @@ class SafepointingNodeProcessor {
 
 namespace {
 int GetFrameCount(const DeoptFrame& deopt_frame) {
-  return 1 + deopt_frame.as_interpreted().unit().inlining_depth();
+  switch (deopt_frame.type()) {
+    case DeoptFrame::FrameType::kInterpretedFrame:
+      return 1 + deopt_frame.as_interpreted().unit().inlining_depth();
+    case DeoptFrame::FrameType::kBuiltinContinuationFrame:
+      return 1 + GetFrameCount(*deopt_frame.parent());
+  }
+}
+BytecodeOffset GetBytecodeOffset(const DeoptFrame& deopt_frame) {
+  switch (deopt_frame.type()) {
+    case DeoptFrame::FrameType::kInterpretedFrame:
+      return deopt_frame.as_interpreted().bytecode_position();
+    case DeoptFrame::FrameType::kBuiltinContinuationFrame:
+      return Builtins::GetContinuationBytecodeOffset(
+          deopt_frame.as_builtin_continuation().builtin_id());
+  }
+}
+SourcePosition GetSourcePosition(const DeoptFrame& deopt_frame) {
+  switch (deopt_frame.type()) {
+    case DeoptFrame::FrameType::kInterpretedFrame:
+      return deopt_frame.as_interpreted().source_position();
+    case DeoptFrame::FrameType::kBuiltinContinuationFrame:
+      return SourcePosition::Unknown();
+  }
 }
 }  // namespace
 
@@ -1067,6 +1094,34 @@ class MaglevTranslationArrayBuilder {
             deopt_info->result_size());
         break;
       }
+      case DeoptFrame::FrameType::kBuiltinContinuationFrame: {
+        const BuiltinContinuationDeoptFrame& builtin_continuation_frame =
+            top_frame.as_builtin_continuation();
+
+        translation_array_builder_->BeginBuiltinContinuationFrame(
+            Builtins::GetContinuationBytecodeOffset(
+                builtin_continuation_frame.builtin_id()),
+            GetDeoptLiteral(*builtin_continuation_frame.parent()
+                                 ->as_interpreted()
+                                 .unit()
+                                 .shared_function_info()
+                                 .object()),
+            builtin_continuation_frame.parameters().length());
+
+        // Closure
+        translation_array_builder_->StoreOptimizedOut();
+
+        // Parameters
+        for (ValueNode* value : builtin_continuation_frame.parameters()) {
+          BuildDeoptFrameSingleValue(value, *current_input_location);
+          current_input_location++;
+        }
+
+        // Context
+        ValueNode* value = builtin_continuation_frame.context();
+        BuildDeoptFrameSingleValue(value, *current_input_location);
+        current_input_location++;
+      }
     }
   }
 
@@ -1117,6 +1172,36 @@ class MaglevTranslationArrayBuilder {
             return_count);
         break;
       }
+      case DeoptFrame::FrameType::kBuiltinContinuationFrame: {
+        const BuiltinContinuationDeoptFrame& builtin_continuation_frame =
+            frame.as_builtin_continuation();
+
+        translation_array_builder_->BeginBuiltinContinuationFrame(
+            Builtins::GetContinuationBytecodeOffset(
+                builtin_continuation_frame.builtin_id()),
+            GetDeoptLiteral(*builtin_continuation_frame.parent()
+                                 ->as_interpreted()
+                                 .unit()
+                                 .shared_function_info()
+                                 .object()),
+            builtin_continuation_frame.parameters().length());
+
+        // Closure
+        translation_array_builder_->StoreOptimizedOut();
+
+        // Parameters
+        for (ValueNode* value : builtin_continuation_frame.parameters()) {
+          BuildDeoptFrameSingleValue(value, *current_input_location);
+          current_input_location++;
+        }
+
+        // Context
+        ValueNode* value = builtin_continuation_frame.context();
+        BuildDeoptFrameSingleValue(value, *current_input_location);
+        current_input_location++;
+
+        break;
+      }
     }
   }
 
@@ -1322,10 +1407,9 @@ void MaglevCodeGenerator::EmitDeopts() {
     translation_builder.BuildEagerDeopt(deopt_info);
 
     if (masm_.compilation_info()->collect_source_positions()) {
-      __ RecordDeoptReason(
-          deopt_info->reason(), 0,
-          deopt_info->top_frame().as_interpreted().source_position(),
-          deopt_index);
+      __ RecordDeoptReason(deopt_info->reason(), 0,
+                           GetSourcePosition(deopt_info->top_frame()),
+                           deopt_index);
     }
     __ bind(deopt_info->deopt_entry_label());
     __ CallForDeoptimization(Builtin::kDeoptimizationEntry_Eager, deopt_index,
@@ -1341,10 +1425,9 @@ void MaglevCodeGenerator::EmitDeopts() {
     translation_builder.BuildLazyDeopt(deopt_info);
 
     if (masm_.compilation_info()->collect_source_positions()) {
-      __ RecordDeoptReason(
-          DeoptimizeReason::kUnknown, 0,
-          deopt_info->top_frame().as_interpreted().source_position(),
-          deopt_index);
+      __ RecordDeoptReason(DeoptimizeReason::kUnknown, 0,
+                           GetSourcePosition(deopt_info->top_frame()),
+                           deopt_index);
     }
     __ bind(deopt_info->deopt_entry_label());
     __ CallForDeoptimization(Builtin::kDeoptimizationEntry_Lazy, deopt_index,
@@ -1462,8 +1545,7 @@ Handle<DeoptimizationData> MaglevCodeGenerator::GenerateDeoptimizationData(
   int i = 0;
   for (EagerDeoptInfo* deopt_info : code_gen_state_.eager_deopts()) {
     DCHECK_NE(deopt_info->translation_index(), -1);
-    raw_data.SetBytecodeOffset(
-        i, deopt_info->top_frame().as_interpreted().bytecode_position());
+    raw_data.SetBytecodeOffset(i, GetBytecodeOffset(deopt_info->top_frame()));
     raw_data.SetTranslationIndex(i,
                                  Smi::FromInt(deopt_info->translation_index()));
     raw_data.SetPc(i, Smi::FromInt(deopt_info->deopt_entry_label()->pos()));
@@ -1474,8 +1556,7 @@ Handle<DeoptimizationData> MaglevCodeGenerator::GenerateDeoptimizationData(
   }
   for (LazyDeoptInfo* deopt_info : code_gen_state_.lazy_deopts()) {
     DCHECK_NE(deopt_info->translation_index(), -1);
-    raw_data.SetBytecodeOffset(
-        i, deopt_info->top_frame().as_interpreted().bytecode_position());
+    raw_data.SetBytecodeOffset(i, GetBytecodeOffset(deopt_info->top_frame()));
     raw_data.SetTranslationIndex(i,
                                  Smi::FromInt(deopt_info->translation_index()));
     raw_data.SetPc(i, Smi::FromInt(deopt_info->deopt_entry_label()->pos()));
diff --git a/src/maglev/maglev-compiler.cc b/src/maglev/maglev-compiler.cc
index ee8448f886..2e78016581 100644
--- a/src/maglev/maglev-compiler.cc
+++ b/src/maglev/maglev-compiler.cc
@@ -180,21 +180,19 @@ class UseMarkingProcessor {
                            LoopUsedNodes* loop_used_nodes,
                            const ProcessingState& state) {
     int use_id = node->id();
-    detail::DeepForEachInput(
-        deopt_info,
-        [&](ValueNode* node, interpreter::Register reg, InputLocation* input) {
-          MarkUse(node, use_id, input, loop_used_nodes);
-        });
+    detail::DeepForEachInput(deopt_info,
+                             [&](ValueNode* node, InputLocation* input) {
+                               MarkUse(node, use_id, input, loop_used_nodes);
+                             });
   }
   void MarkCheckpointNodes(NodeBase* node, const LazyDeoptInfo* deopt_info,
                            LoopUsedNodes* loop_used_nodes,
                            const ProcessingState& state) {
     int use_id = node->id();
-    detail::DeepForEachInput(
-        deopt_info,
-        [&](ValueNode* node, interpreter::Register reg, InputLocation* input) {
-          MarkUse(node, use_id, input, loop_used_nodes);
-        });
+    detail::DeepForEachInput(deopt_info,
+                             [&](ValueNode* node, InputLocation* input) {
+                               MarkUse(node, use_id, input, loop_used_nodes);
+                             });
   }
 
   MaglevCompilationInfo* compilation_info_;
diff --git a/src/maglev/maglev-graph-builder.cc b/src/maglev/maglev-graph-builder.cc
index 271a935b44..d9bf030b17 100644
--- a/src/maglev/maglev-graph-builder.cc
+++ b/src/maglev/maglev-graph-builder.cc
@@ -3093,6 +3093,274 @@ void MaglevGraphBuilder::VisitTestGreaterThanOrEqual() {
   VisitCompareOperation<Operation::kGreaterThanOrEqual>();
 }
 
+MaglevGraphBuilder::InferHasInPrototypeChainResult
+MaglevGraphBuilder::InferHasInPrototypeChain(
+    ValueNode* receiver, compiler::HeapObjectRef prototype) {
+  auto stable_it = known_node_aspects().stable_maps.find(receiver);
+  auto unstable_it = known_node_aspects().unstable_maps.find(receiver);
+  auto stable_end = known_node_aspects().stable_maps.end();
+  auto unstable_end = known_node_aspects().unstable_maps.end();
+  // If either of the map sets is not found, then we don't know anything about
+  // the map of the receiver, so bail.
+  if (stable_it == stable_end || unstable_it == unstable_end) {
+    return kMayBeInPrototypeChain;
+  }
+
+  ZoneVector<compiler::MapRef> receiver_map_refs(zone());
+
+  // Try to determine either that all of the {receiver_maps} have the given
+  // {prototype} in their chain, or that none do. If we can't tell, return
+  // kMayBeInPrototypeChain.
+  bool all = true;
+  bool none = true;
+  for (const ZoneHandleSet<Map>& map_set :
+       {stable_it->second, unstable_it->second}) {
+    for (Handle<Map> map_handle : map_set) {
+      compiler::MapRef map = MakeRefAssumeMemoryFence(broker(), map_handle);
+      receiver_map_refs.push_back(map);
+      while (true) {
+        if (IsSpecialReceiverInstanceType(map.instance_type())) {
+          return kMayBeInPrototypeChain;
+        }
+        if (!map.IsJSObjectMap()) {
+          all = false;
+          break;
+        }
+        compiler::HeapObjectRef map_prototype = map.prototype();
+        if (map_prototype.equals(prototype)) {
+          none = false;
+          break;
+        }
+        map = map_prototype.map();
+        // TODO(v8:11457) Support dictionary mode protoypes here.
+        if (!map.is_stable() || map.is_dictionary_map()) {
+          return kMayBeInPrototypeChain;
+        }
+        if (map.oddball_type() == compiler::OddballType::kNull) {
+          all = false;
+          break;
+        }
+      }
+    }
+  }
+  DCHECK_IMPLIES(all, !none);
+  if (!all && !none) return kMayBeInPrototypeChain;
+
+  {
+    base::Optional<compiler::JSObjectRef> last_prototype;
+    if (all) {
+      // We don't need to protect the full chain if we found the prototype, we
+      // can stop at {prototype}.  In fact we could stop at the one before
+      // {prototype} but since we're dealing with multiple receiver maps this
+      // might be a different object each time, so it's much simpler to include
+      // {prototype}. That does, however, mean that we must check {prototype}'s
+      // map stability.
+      if (!prototype.map().is_stable()) return kMayBeInPrototypeChain;
+      last_prototype = prototype.AsJSObject();
+    }
+    broker()->dependencies()->DependOnStablePrototypeChains(
+        receiver_map_refs, kStartAtPrototype, last_prototype);
+  }
+
+  DCHECK_EQ(all, !none);
+  return all ? kIsInPrototypeChain : kIsNotInPrototypeChain;
+}
+
+bool MaglevGraphBuilder::TryBuildFastHasInPrototypeChain(
+    ValueNode* object, compiler::ObjectRef prototype) {
+  if (!prototype.IsHeapObject()) return false;
+  auto in_prototype_chain =
+      InferHasInPrototypeChain(object, prototype.AsHeapObject());
+  if (in_prototype_chain == kMayBeInPrototypeChain) return false;
+
+  SetAccumulator(GetBooleanConstant(in_prototype_chain == kIsInPrototypeChain));
+  return true;
+}
+
+void MaglevGraphBuilder::BuildHasInPrototypeChain(
+    ValueNode* object, compiler::ObjectRef prototype) {
+  if (TryBuildFastHasInPrototypeChain(object, prototype)) return;
+
+  SetAccumulator(BuildCallRuntime(Runtime::kHasInPrototypeChain,
+                                  {object, GetConstant(prototype)}));
+}
+
+bool MaglevGraphBuilder::TryBuildFastOrdinaryHasInstance(
+    ValueNode* object, compiler::JSObjectRef callable,
+    ValueNode* callable_node_if_not_constant) {
+  const bool is_constant = callable_node_if_not_constant == nullptr;
+  if (!is_constant) return false;
+
+  if (callable.IsJSBoundFunction()) {
+    // OrdinaryHasInstance on bound functions turns into a recursive
+    // invocation of the instanceof operator again.
+    compiler::JSBoundFunctionRef function = callable.AsJSBoundFunction();
+    compiler::JSReceiverRef bound_target_function =
+        function.bound_target_function();
+
+    if (!bound_target_function.IsJSObject() ||
+        !TryBuildFastInstanceOf(object, bound_target_function.AsJSObject(),
+                                nullptr)) {
+      // If we can't build a fast instance-of, build a slow one with the
+      // partial optimisation of using the bound target function constant.
+      SetAccumulator(BuildCallBuiltin<Builtin::kInstanceOf>(
+          {object, GetConstant(bound_target_function)}));
+    }
+    return true;
+  }
+
+  if (callable.IsJSFunction()) {
+    // Optimize if we currently know the "prototype" property.
+    compiler::JSFunctionRef function = callable.AsJSFunction();
+
+    // TODO(v8:7700): Remove the has_prototype_slot condition once the broker
+    // is always enabled.
+    if (!function.map().has_prototype_slot() ||
+        !function.has_instance_prototype(broker()->dependencies()) ||
+        function.PrototypeRequiresRuntimeLookup(broker()->dependencies())) {
+      return false;
+    }
+
+    compiler::ObjectRef prototype =
+        broker()->dependencies()->DependOnPrototypeProperty(function);
+    BuildHasInPrototypeChain(object, prototype);
+    return true;
+  }
+
+  return false;
+}
+
+void MaglevGraphBuilder::BuildOrdinaryHasInstance(
+    ValueNode* object, compiler::JSObjectRef callable,
+    ValueNode* callable_node_if_not_constant) {
+  if (TryBuildFastOrdinaryHasInstance(object, callable,
+                                      callable_node_if_not_constant))
+    return;
+
+  SetAccumulator(BuildCallBuiltin<Builtin::kOrdinaryHasInstance>(
+      {object, callable_node_if_not_constant ? callable_node_if_not_constant
+                                             : GetConstant(callable)}));
+}
+
+bool MaglevGraphBuilder::TryBuildFastInstanceOf(
+    ValueNode* object, compiler::JSObjectRef callable,
+    ValueNode* callable_node_if_not_constant) {
+  compiler::MapRef receiver_map = callable.map();
+  compiler::NameRef name =
+      MakeRef(broker(), local_isolate()->factory()->has_instance_symbol());
+  compiler::PropertyAccessInfo access_info = broker()->GetPropertyAccessInfo(
+      receiver_map, name, compiler::AccessMode::kLoad,
+      broker()->dependencies());
+
+  // TODO(v8:11457) Support dictionary mode holders here.
+  if (access_info.IsInvalid() || access_info.HasDictionaryHolder()) {
+    return false;
+  }
+  access_info.RecordDependencies(broker()->dependencies());
+
+  if (access_info.IsNotFound()) {
+    // If there's no @@hasInstance handler, the OrdinaryHasInstance operation
+    // takes over, but that requires the constructor to be callable.
+    if (!receiver_map.is_callable()) {
+      return false;
+    }
+
+    broker()->dependencies()->DependOnStablePrototypeChains(
+        access_info.lookup_start_object_maps(), kStartAtPrototype);
+
+    // Monomorphic property access.
+    if (callable_node_if_not_constant) {
+      BuildCheckMaps(callable_node_if_not_constant,
+                     access_info.lookup_start_object_maps());
+    }
+
+    BuildOrdinaryHasInstance(object, callable, callable_node_if_not_constant);
+    return true;
+  }
+
+  if (access_info.IsFastDataConstant()) {
+    base::Optional<compiler::JSObjectRef> holder = access_info.holder();
+    bool found_on_proto = holder.has_value();
+    compiler::JSObjectRef holder_ref =
+        found_on_proto ? holder.value() : callable;
+    base::Optional<compiler::ObjectRef> has_instance_field =
+        holder_ref.GetOwnFastDataProperty(access_info.field_representation(),
+                                          access_info.field_index(),
+                                          broker()->dependencies());
+    if (!has_instance_field.has_value() ||
+        !has_instance_field->IsHeapObject() ||
+        !has_instance_field->AsHeapObject().map().is_callable()) {
+      return false;
+    }
+
+    if (found_on_proto) {
+      broker()->dependencies()->DependOnStablePrototypeChains(
+          access_info.lookup_start_object_maps(), kStartAtPrototype,
+          holder.value());
+    }
+
+    ValueNode* callable_node;
+    if (callable_node_if_not_constant) {
+      // Check that {callable_node_if_not_constant} is actually {callable}.
+      AddNewNode<CheckValue>({callable_node_if_not_constant}, callable);
+      callable_node = callable_node_if_not_constant;
+    } else {
+      callable_node = GetConstant(callable);
+    }
+
+    // Call @@hasInstance
+    Call* call = AddNewNode<Call>(
+        Call::kFixedInputCount + 2, ConvertReceiverMode::kNotNullOrUndefined,
+        Call::TargetType::kJSFunction, compiler::FeedbackSource(),
+        GetConstant(*has_instance_field), GetContext());
+    call->set_arg(0, callable_node);
+    call->set_arg(1, object);
+
+    // Make sure that a lazy deopt after the @@hasInstance call also performs
+    // ToBoolean before returning to the interpreter.
+    // TODO(leszeks): Wrap this in a helper.
+    new (call->lazy_deopt_info()) LazyDeoptInfo(
+        zone(),
+        BuiltinContinuationDeoptFrame(
+            Builtin::kToBooleanLazyDeoptContinuation, {}, GetContext(),
+            zone()->New<InterpretedDeoptFrame>(
+                call->lazy_deopt_info()->top_frame().as_interpreted())));
+
+    SetAccumulator(AddNewNode<ToBoolean>({call}));
+    return true;
+  }
+
+  return false;
+}
+
+bool MaglevGraphBuilder::TryBuildFastInstanceOfWithFeedback(
+    ValueNode* object, ValueNode* callable,
+    compiler::FeedbackSource feedback_source) {
+  compiler::ProcessedFeedback const& feedback =
+      broker()->GetFeedbackForInstanceOf(feedback_source);
+
+  // TurboFan emits generic code when there's no feedback, rather than
+  // deopting.
+  if (feedback.IsInsufficient()) return false;
+
+  // Check if the right hand side is a known receiver, or
+  // we have feedback from the InstanceOfIC.
+  if (callable->Is<Constant>() &&
+      callable->Cast<Constant>()->object().IsJSObject()) {
+    compiler::JSObjectRef callable_ref =
+        callable->Cast<Constant>()->object().AsJSObject();
+    return TryBuildFastInstanceOf(object, callable_ref, nullptr);
+  }
+  if (feedback_source.IsValid()) {
+    base::Optional<compiler::JSObjectRef> callable_from_feedback =
+        feedback.AsInstanceOf().value();
+    if (callable_from_feedback) {
+      return TryBuildFastInstanceOf(object, *callable_from_feedback, callable);
+    }
+  }
+  return false;
+}
+
 void MaglevGraphBuilder::VisitTestInstanceOf() {
   // TestInstanceOf <src> <feedback_slot>
   ValueNode* object = LoadRegisterTagged(0);
@@ -3100,8 +3368,10 @@ void MaglevGraphBuilder::VisitTestInstanceOf() {
   FeedbackSlot slot = GetSlotOperand(1);
   compiler::FeedbackSource feedback_source{feedback(), slot};
 
-  // TODO(victorgomes): Check feedback slot and a do static lookup for
-  // @@hasInstance.
+  if (TryBuildFastInstanceOfWithFeedback(object, callable, feedback_source)) {
+    return;
+  }
+
   ValueNode* context = GetContext();
   SetAccumulator(
       AddNewNode<TestInstanceOf>({context, object, callable}, feedback_source));
diff --git a/src/maglev/maglev-graph-builder.h b/src/maglev/maglev-graph-builder.h
index fd1d29c90e..6b4335c405 100644
--- a/src/maglev/maglev-graph-builder.h
+++ b/src/maglev/maglev-graph-builder.h
@@ -1058,6 +1058,30 @@ class MaglevGraphBuilder {
   bool TryReuseKnownPropertyLoad(ValueNode* lookup_start_object,
                                  compiler::NameRef name);
 
+  enum InferHasInPrototypeChainResult {
+    kMayBeInPrototypeChain,
+    kIsInPrototypeChain,
+    kIsNotInPrototypeChain
+  };
+  InferHasInPrototypeChainResult InferHasInPrototypeChain(
+      ValueNode* receiver, compiler::HeapObjectRef prototype);
+  bool TryBuildFastHasInPrototypeChain(ValueNode* object,
+                                       compiler::ObjectRef prototype);
+  void BuildHasInPrototypeChain(ValueNode* object,
+                                compiler::ObjectRef prototype);
+  bool TryBuildFastOrdinaryHasInstance(ValueNode* object,
+                                       compiler::JSObjectRef callable,
+                                       ValueNode* callable_node);
+  void BuildOrdinaryHasInstance(ValueNode* object,
+                                compiler::JSObjectRef callable,
+                                ValueNode* callable_node);
+  bool TryBuildFastInstanceOf(ValueNode* object,
+                              compiler::JSObjectRef callable_ref,
+                              ValueNode* callable_node);
+  bool TryBuildFastInstanceOfWithFeedback(
+      ValueNode* object, ValueNode* callable,
+      compiler::FeedbackSource feedback_source);
+
   template <Operation kOperation>
   void BuildGenericUnaryOperationNode();
   template <Operation kOperation>
diff --git a/src/maglev/maglev-graph-printer.cc b/src/maglev/maglev-graph-printer.cc
index 65032bf19d..e869707c53 100644
--- a/src/maglev/maglev-graph-printer.cc
+++ b/src/maglev/maglev-graph-printer.cc
@@ -365,6 +365,57 @@ void MaglevPrintingVisitor::PreProcessBasicBlock(BasicBlock* block) {
 
 namespace {
 
+void PrintSingleDeoptFrame(
+    std::ostream& os, MaglevGraphLabeller* graph_labeller,
+    const DeoptFrame& frame, InputLocation*& current_input_location,
+    LazyDeoptInfo* lazy_deopt_info_if_top_frame = nullptr) {
+  switch (frame.type()) {
+    case DeoptFrame::FrameType::kInterpretedFrame: {
+      os << "@" << frame.as_interpreted().bytecode_position() << " : {";
+      bool first = true;
+      frame.as_interpreted().frame_state()->ForEachValue(
+          frame.as_interpreted().unit(),
+          [&](ValueNode* node, interpreter::Register reg) {
+            if (first) {
+              first = false;
+            } else {
+              os << ", ";
+            }
+            os << reg.ToString() << ":";
+            if (lazy_deopt_info_if_top_frame &&
+                lazy_deopt_info_if_top_frame->IsResultRegister(reg)) {
+              os << "<result>";
+            } else {
+              os << PrintNodeLabel(graph_labeller, node) << ":"
+                 << current_input_location->operand();
+              current_input_location++;
+            }
+          });
+      os << "}";
+      break;
+    }
+    case DeoptFrame::FrameType::kBuiltinContinuationFrame: {
+      os << "@" << Builtins::name(frame.as_builtin_continuation().builtin_id())
+         << " : {";
+      int arg_index = 0;
+      for (ValueNode* node : frame.as_builtin_continuation().parameters()) {
+        os << "a" << arg_index << ":" << PrintNodeLabel(graph_labeller, node)
+           << ":" << current_input_location->operand();
+        arg_index++;
+        current_input_location++;
+        os << ", ";
+      }
+      os << "<context>:"
+         << PrintNodeLabel(graph_labeller,
+                           frame.as_builtin_continuation().context())
+         << ":" << current_input_location->operand();
+      current_input_location++;
+      os << "}";
+      break;
+    }
+  }
+}
+
 void RecursivePrintEagerDeopt(std::ostream& os,
                               std::vector<BasicBlock*> targets,
                               const DeoptFrame& frame,
@@ -379,26 +430,12 @@ void RecursivePrintEagerDeopt(std::ostream& os,
   PrintVerticalArrows(os, targets);
   PrintPadding(os, graph_labeller, max_node_id, 0);
   if (!frame.parent()) {
-    os << "  ↱ eager @" << frame.as_interpreted().bytecode_position() << " : {";
+    os << "  ↱ eager ";
   } else {
-    os << "  │       @" << frame.as_interpreted().bytecode_position().ToInt()
-       << " : {";
+    os << "  │       ";
   }
-
-  bool first = true;
-  frame.as_interpreted().frame_state()->ForEachValue(
-      frame.as_interpreted().unit(),
-      [&](ValueNode* node, interpreter::Register reg) {
-        if (first) {
-          first = false;
-        } else {
-          os << ", ";
-        }
-        os << reg.ToString() << ":" << PrintNodeLabel(graph_labeller, node)
-           << ":" << current_input_location->operand();
-        current_input_location++;
-      });
-  os << "}\n";
+  PrintSingleDeoptFrame(os, graph_labeller, frame, current_input_location);
+  os << "\n";
 }
 
 void PrintEagerDeopt(std::ostream& os, std::vector<BasicBlock*> targets,
@@ -430,23 +467,9 @@ void RecursivePrintLazyDeopt(std::ostream& os, std::vector<BasicBlock*> targets,
 
   PrintVerticalArrows(os, targets);
   PrintPadding(os, graph_labeller, max_node_id, 0);
-  os << "  │      @" << frame.as_interpreted().bytecode_position().ToInt()
-     << " : {";
-
-  bool first = true;
-  frame.as_interpreted().frame_state()->ForEachValue(
-      frame.as_interpreted().unit(),
-      [&](ValueNode* node, interpreter::Register reg) {
-        if (first) {
-          first = false;
-        } else {
-          os << ", ";
-        }
-        os << reg.ToString() << ":" << PrintNodeLabel(graph_labeller, node)
-           << ":" << current_input_location->operand();
-        current_input_location++;
-      });
-  os << "}\n";
+  os << "  │      ";
+  PrintSingleDeoptFrame(os, graph_labeller, frame, current_input_location);
+  os << "\n";
 }
 
 template <typename NodeT>
@@ -464,27 +487,10 @@ void PrintLazyDeopt(std::ostream& os, std::vector<BasicBlock*> targets,
   PrintVerticalArrows(os, targets);
   PrintPadding(os, graph_labeller, max_node_id, 0);
 
-  os << "  ↳ lazy @" << top_frame.as_interpreted().bytecode_position()
-     << " : {";
-  bool first = true;
-  top_frame.as_interpreted().frame_state()->ForEachValue(
-      top_frame.as_interpreted().unit(),
-      [&](ValueNode* node, interpreter::Register reg) {
-        if (first) {
-          first = false;
-        } else {
-          os << ", ";
-        }
-        os << reg.ToString() << ":";
-        if (deopt_info->IsResultRegister(reg)) {
-          os << "<result>";
-        } else {
-          os << PrintNodeLabel(graph_labeller, node) << ":"
-             << current_input_location->operand();
-          current_input_location++;
-        }
-      });
-  os << "}\n";
+  os << "  ↳ lazy ";
+  PrintSingleDeoptFrame(os, graph_labeller, top_frame, current_input_location,
+                        deopt_info);
+  os << "\n";
 }
 
 template <typename NodeT>
@@ -509,15 +515,20 @@ void PrintExceptionHandlerPoint(std::ostream& os,
   // The exception handler liveness should be a subset of lazy_deopt_info one.
   auto* liveness = block->state()->frame_state().liveness();
   LazyDeoptInfo* deopt_info = node->lazy_deopt_info();
-  const DeoptFrame& top_frame = deopt_info->top_frame();
+
+  const InterpretedDeoptFrame& lazy_frame =
+      deopt_info->top_frame().type() ==
+              DeoptFrame::FrameType::kBuiltinContinuationFrame
+          ? deopt_info->top_frame().parent()->as_interpreted()
+          : deopt_info->top_frame().as_interpreted();
 
   PrintVerticalArrows(os, targets);
   PrintPadding(os, graph_labeller, max_node_id, 0);
 
   os << "  ↳ throw @" << handler_offset << " : {";
   bool first = true;
-  top_frame.as_interpreted().frame_state()->ForEachValue(
-      top_frame.as_interpreted().unit(),
+  lazy_frame.as_interpreted().frame_state()->ForEachValue(
+      lazy_frame.as_interpreted().unit(),
       [&](ValueNode* node, interpreter::Register reg) {
         if (!reg.is_parameter() && !liveness->RegisterIsLive(reg.index())) {
           // Skip, since not live at the handler offset.
diff --git a/src/maglev/maglev-graph-verifier.h b/src/maglev/maglev-graph-verifier.h
index adb48c0e70..15b5ae14aa 100644
--- a/src/maglev/maglev-graph-verifier.h
+++ b/src/maglev/maglev-graph-verifier.h
@@ -28,21 +28,6 @@ std::ostream& operator<<(std::ostream& os, const ValueRepresentation& repr) {
   return os;
 }
 
-namespace {
-ValueRepresentation ToValueRepresentation(MachineType type) {
-  switch (type.representation()) {
-    case MachineRepresentation::kTagged:
-    case MachineRepresentation::kTaggedSigned:
-    case MachineRepresentation::kTaggedPointer:
-      return ValueRepresentation::kTagged;
-    case MachineRepresentation::kFloat64:
-      return ValueRepresentation::kFloat64;
-    default:
-      return ValueRepresentation::kInt32;
-  }
-}
-}  // namespace
-
 class Graph;
 
 // TODO(victorgomes): Currently it only verifies the inputs for all ValueNodes
@@ -59,6 +44,19 @@ class MaglevGraphVerifier {
   void PostProcessGraph(Graph* graph) {}
   void PreProcessBasicBlock(BasicBlock* block) {}
 
+  static ValueRepresentation ToValueRepresentation(MachineType type) {
+    switch (type.representation()) {
+      case MachineRepresentation::kTagged:
+      case MachineRepresentation::kTaggedSigned:
+      case MachineRepresentation::kTaggedPointer:
+        return ValueRepresentation::kTagged;
+      case MachineRepresentation::kFloat64:
+        return ValueRepresentation::kFloat64;
+      default:
+        return ValueRepresentation::kInt32;
+    }
+  }
+
   void CheckValueInputIs(NodeBase* node, int i, ValueRepresentation expected) {
     ValueNode* input = node->input(i).node();
     ValueRepresentation got = input->properties().value_representation();
@@ -142,6 +140,7 @@ class MaglevGraphVerifier {
       case Opcode::kSetPendingMessage:
       case Opcode::kStoreMap:
       case Opcode::kStringLength:
+      case Opcode::kToBoolean:
       case Opcode::kToBooleanLogicalNot:
       case Opcode::kTestUndetectable:
       case Opcode::kTestTypeOf:
diff --git a/src/maglev/maglev-ir-inl.h b/src/maglev/maglev-ir-inl.h
index 539db3246a..db58acaa25 100644
--- a/src/maglev/maglev-ir-inl.h
+++ b/src/maglev/maglev-ir-inl.h
@@ -26,9 +26,15 @@ void DeepForEachInputImpl(const DeoptFrame& frame,
       frame.as_interpreted().frame_state()->ForEachValue(
           frame.as_interpreted().unit(),
           [&](ValueNode* node, interpreter::Register reg) {
-            f(node, reg, &input_locations[index++]);
+            f(node, &input_locations[index++]);
           });
       break;
+    case DeoptFrame::FrameType::kBuiltinContinuationFrame:
+      for (ValueNode* node : frame.as_builtin_continuation().parameters()) {
+        f(node, &input_locations[index++]);
+      }
+      f(frame.as_builtin_continuation().context(), &input_locations[index++]);
+      UNREACHABLE();
   }
 }
 
@@ -42,10 +48,10 @@ void DeepForEachInput(const EagerDeoptInfo* deopt_info, Function&& f) {
 template <typename Function>
 void DeepForEachInput(const LazyDeoptInfo* deopt_info, Function&& f) {
   int index = 0;
+  InputLocation* input_locations = deopt_info->input_locations();
   const DeoptFrame& top_frame = deopt_info->top_frame();
   if (top_frame.parent()) {
-    DeepForEachInputImpl(*top_frame.parent(), deopt_info->input_locations(),
-                         index, f);
+    DeepForEachInputImpl(*top_frame.parent(), input_locations, index, f);
   }
   // Handle the top-of-frame info separately, since we have to skip the result
   // location.
@@ -57,9 +63,15 @@ void DeepForEachInput(const LazyDeoptInfo* deopt_info, Function&& f) {
             // Skip over the result location since it is irrelevant for lazy
             // deopts (unoptimized code will recreate the result).
             if (deopt_info->IsResultRegister(reg)) return;
-            f(node, reg, &deopt_info->input_locations()[index++]);
+            f(node, &input_locations[index++]);
           });
       break;
+    case DeoptFrame::FrameType::kBuiltinContinuationFrame:
+      for (ValueNode* node : top_frame.as_builtin_continuation().parameters()) {
+        f(node, &input_locations[index++]);
+      };
+      f(top_frame.as_builtin_continuation().context(),
+        &input_locations[index++]);
   }
 }
 
diff --git a/src/maglev/maglev-ir.cc b/src/maglev/maglev-ir.cc
index 3645bd020b..80414c36bb 100644
--- a/src/maglev/maglev-ir.cc
+++ b/src/maglev/maglev-ir.cc
@@ -145,8 +145,7 @@ class SaveRegisterStateForCall {
 RegList GetGeneralRegistersUsedAsInputs(const EagerDeoptInfo* deopt_info) {
   RegList regs;
   detail::DeepForEachInput(deopt_info,
-                           [&regs](ValueNode* value, interpreter::Register reg,
-                                   InputLocation* input) {
+                           [&regs](ValueNode* value, InputLocation* input) {
                              if (input->IsGeneralRegister()) {
                                regs.set(input->AssignedGeneralRegister());
                              }
@@ -221,8 +220,8 @@ void AllocateRaw(MaglevAssembler* masm, RegisterSnapshot& register_snapshot,
   __ bind(*done);
 }
 
-void ToBoolean(MaglevAssembler* masm, Register value, ZoneLabelRef is_true,
-               ZoneLabelRef is_false, bool fallthrough_when_true) {
+void EmitToBoolean(MaglevAssembler* masm, Register value, ZoneLabelRef is_true,
+                   ZoneLabelRef is_false, bool fallthrough_when_true) {
   Register map = kScratchRegister;
 
   // Check if {{value}} is Smi.
@@ -378,9 +377,16 @@ size_t GetInputLocationsArraySize(const DeoptFrame& top_frame) {
   size_t size = 0;
   const DeoptFrame* frame = &top_frame;
   do {
-    const InterpretedDeoptFrame& interpreted_frame = frame->as_interpreted();
-    size += interpreted_frame.frame_state()->size(interpreted_frame.unit());
-    frame = interpreted_frame.parent();
+    switch (frame->type()) {
+      case DeoptFrame::FrameType::kInterpretedFrame:
+        size += frame->as_interpreted().frame_state()->size(
+            frame->as_interpreted().unit());
+        break;
+      case DeoptFrame::FrameType::kBuiltinContinuationFrame:
+        size += frame->as_builtin_continuation().parameters().size() + 1;
+        break;
+    }
+    frame = frame->parent();
   } while (frame != nullptr);
   return size;
 }
@@ -3205,6 +3211,28 @@ void SetPendingMessage::GenerateCode(MaglevAssembler* masm,
   }
 }
 
+void ToBoolean::AllocateVreg(MaglevVregAllocationState* vreg_state) {
+  UseRegister(value());
+  DefineAsRegister(vreg_state, this);
+}
+void ToBoolean::GenerateCode(MaglevAssembler* masm,
+                             const ProcessingState& state) {
+  Register object = ToRegister(value());
+  Register return_value = ToRegister(result());
+  Label done;
+  Zone* zone = masm->compilation_info()->zone();
+  ZoneLabelRef object_is_true(zone), object_is_false(zone);
+  // TODO(leszeks): We're likely to be calling this on an existing boolean --
+  // maybe that's a case we should fast-path here and re-use that boolean value?
+  EmitToBoolean(masm, object, object_is_true, object_is_false, true);
+  __ bind(*object_is_true);
+  __ LoadRoot(return_value, RootIndex::kTrueValue);
+  __ jmp(&done, Label::kNear);
+  __ bind(*object_is_false);
+  __ LoadRoot(return_value, RootIndex::kFalseValue);
+  __ bind(&done);
+}
+
 void ToBooleanLogicalNot::AllocateVreg(MaglevVregAllocationState* vreg_state) {
   UseRegister(value());
   DefineAsRegister(vreg_state, this);
@@ -3216,7 +3244,7 @@ void ToBooleanLogicalNot::GenerateCode(MaglevAssembler* masm,
   Label done;
   Zone* zone = masm->compilation_info()->zone();
   ZoneLabelRef object_is_true(zone), object_is_false(zone);
-  ToBoolean(masm, object, object_is_true, object_is_false, true);
+  EmitToBoolean(masm, object, object_is_true, object_is_false, true);
   __ bind(*object_is_true);
   __ LoadRoot(return_value, RootIndex::kFalseValue);
   __ jmp(&done, Label::kNear);
@@ -4259,9 +4287,7 @@ void AttemptOnStackReplacement(MaglevAssembler* masm,
       // configurable.
       RegisterSnapshot snapshot = node->register_snapshot();
       detail::DeepForEachInput(
-          node->eager_deopt_info(),
-          [&](ValueNode* node, interpreter::Register reg,
-              InputLocation* input) {
+          node->eager_deopt_info(), [&](ValueNode* node, InputLocation* input) {
             if (!input->IsAnyRegister()) return;
             if (input->IsDoubleRegister()) {
               snapshot.live_double_registers.set(
@@ -4445,8 +4471,8 @@ void BranchIfToBooleanTrue::GenerateCode(MaglevAssembler* masm,
   ZoneLabelRef false_label =
       ZoneLabelRef::UnsafeFromLabelPointer(if_false()->label());
   bool fallthrough_when_true = (if_true() == state.next_block());
-  ToBoolean(masm, ToRegister(condition_input()), true_label, false_label,
-            fallthrough_when_true);
+  EmitToBoolean(masm, ToRegister(condition_input()), true_label, false_label,
+                fallthrough_when_true);
 }
 
 }  // namespace maglev
diff --git a/src/maglev/maglev-ir.h b/src/maglev/maglev-ir.h
index b2171cd932..c6697f3524 100644
--- a/src/maglev/maglev-ir.h
+++ b/src/maglev/maglev-ir.h
@@ -179,6 +179,7 @@ class CompactInterpreterFrameState;
   V(SetPendingMessage)             \
   V(StringAt)                      \
   V(StringLength)                  \
+  V(ToBoolean)                     \
   V(ToBooleanLogicalNot)           \
   V(TaggedEqual)                   \
   V(TaggedNotEqual)                \
@@ -665,17 +666,19 @@ class Input : public InputLocation {
 };
 
 class InterpretedDeoptFrame;
+class BuiltinContinuationDeoptFrame;
 class DeoptFrame {
  public:
   enum class FrameType {
     kInterpretedFrame,
-    // kBuiltinContinuationFrame,
+    kBuiltinContinuationFrame,
   };
 
   FrameType type() const { return type_; }
   const DeoptFrame* parent() const { return parent_; }
 
   inline const InterpretedDeoptFrame& as_interpreted() const;
+  inline const BuiltinContinuationDeoptFrame& as_builtin_continuation() const;
 
  protected:
   struct InterpretedFrameData {
@@ -684,14 +687,24 @@ class DeoptFrame {
     BytecodeOffset bytecode_position;
     SourcePosition source_position;
   };
+  struct BuiltinContinuationFrameData {
+    Builtin builtin_id;
+    base::Vector<ValueNode*> parameters;
+    ValueNode* context;
+  };
 
   DeoptFrame(InterpretedFrameData data, const DeoptFrame* parent)
       : interpreted_frame_data_(data),
         type_(FrameType::kInterpretedFrame),
         parent_(parent) {}
+  DeoptFrame(BuiltinContinuationFrameData data, const DeoptFrame* parent)
+      : builtin_continuation_frame_data_(data),
+        type_(FrameType::kBuiltinContinuationFrame),
+        parent_(parent) {}
 
   union {
     const InterpretedFrameData interpreted_frame_data_;
+    const BuiltinContinuationFrameData builtin_continuation_frame_data_;
   };
   FrameType type_;
   const DeoptFrame* parent_;
@@ -730,6 +743,35 @@ inline const InterpretedDeoptFrame& DeoptFrame::as_interpreted() const {
   return static_cast<const InterpretedDeoptFrame&>(*this);
 }
 
+class BuiltinContinuationDeoptFrame : public DeoptFrame {
+ public:
+  BuiltinContinuationDeoptFrame(Builtin builtin_id,
+                                base::Vector<ValueNode*> parameters,
+                                ValueNode* context, const DeoptFrame* parent)
+      : DeoptFrame(
+            BuiltinContinuationFrameData{builtin_id, parameters, context},
+            parent) {}
+
+  const Builtin& builtin_id() const {
+    return builtin_continuation_frame_data_.builtin_id;
+  }
+  base::Vector<ValueNode*> parameters() const {
+    return builtin_continuation_frame_data_.parameters;
+  }
+  ValueNode* context() const {
+    return builtin_continuation_frame_data_.context;
+  }
+};
+
+// Make sure storing/passing deopt frames by value doesn't truncate them.
+static_assert(sizeof(BuiltinContinuationDeoptFrame) == sizeof(DeoptFrame));
+
+inline const BuiltinContinuationDeoptFrame&
+DeoptFrame::as_builtin_continuation() const {
+  DCHECK_EQ(type(), FrameType::kBuiltinContinuationFrame);
+  return static_cast<const BuiltinContinuationDeoptFrame&>(*this);
+}
+
 class DeoptInfo {
  protected:
   DeoptInfo(Zone* zone, DeoptFrame top_frame);
@@ -1999,6 +2041,19 @@ class SetPendingMessage : public FixedInputValueNodeT<1, SetPendingMessage> {
   void PrintParams(std::ostream&, MaglevGraphLabeller*) const {}
 };
 
+class ToBoolean : public FixedInputValueNodeT<1, ToBoolean> {
+  using Base = FixedInputValueNodeT<1, ToBoolean>;
+
+ public:
+  explicit ToBoolean(uint64_t bitfield) : Base(bitfield) {}
+
+  Input& value() { return Node::input(0); }
+
+  void AllocateVreg(MaglevVregAllocationState*);
+  void GenerateCode(MaglevAssembler*, const ProcessingState&);
+  void PrintParams(std::ostream&, MaglevGraphLabeller*) const {}
+};
+
 class ToBooleanLogicalNot
     : public FixedInputValueNodeT<1, ToBooleanLogicalNot> {
   using Base = FixedInputValueNodeT<1, ToBooleanLogicalNot>;
diff --git a/src/maglev/maglev-regalloc.cc b/src/maglev/maglev-regalloc.cc
index b3ab2549bf..14ec1f5718 100644
--- a/src/maglev/maglev-regalloc.cc
+++ b/src/maglev/maglev-regalloc.cc
@@ -531,8 +531,7 @@ void StraightForwardRegisterAllocator::UpdateUse(
 void StraightForwardRegisterAllocator::UpdateUse(
     const EagerDeoptInfo& deopt_info) {
   detail::DeepForEachInput(
-      &deopt_info,
-      [&](ValueNode* node, interpreter::Register reg, InputLocation* input) {
+      &deopt_info, [&](ValueNode* node, InputLocation* input) {
         if (v8_flags.trace_maglev_regalloc) {
           printing_visitor_->os()
               << "- using " << PrintNodeLabel(graph_labeller(), node) << "\n";
@@ -549,8 +548,7 @@ void StraightForwardRegisterAllocator::UpdateUse(
 void StraightForwardRegisterAllocator::UpdateUse(
     const LazyDeoptInfo& deopt_info) {
   detail::DeepForEachInput(
-      &deopt_info,
-      [&](ValueNode* node, interpreter::Register reg, InputLocation* input) {
+      &deopt_info, [&](ValueNode* node, InputLocation* input) {
         if (v8_flags.trace_maglev_regalloc) {
           printing_visitor_->os()
               << "- using " << PrintNodeLabel(graph_labeller(), node) << "\n";
diff --git a/test/mjsunit/maglev/regress/regress-6373.js b/test/mjsunit/maglev/regress/regress-6373.js
new file mode 100644
index 0000000000..0209f786e6
--- /dev/null
+++ b/test/mjsunit/maglev/regress/regress-6373.js
@@ -0,0 +1,46 @@
+// Copyright 2022 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flags: --allow-natives-syntax --maglev
+
+(function() {
+var A = {};
+
+A[Symbol.hasInstance] = function(x) {
+  return 1;
+};
+
+var a = {};
+
+function foo(o) {
+  return o instanceof A;
+};
+%PrepareFunctionForOptimization(foo);
+foo(a);
+foo(a);
+assertSame(foo(a), true);
+%OptimizeMaglevOnNextCall(foo);
+assertSame(foo(a), true);
+})();
+
+(function() {
+var A = {};
+
+A[Symbol.hasInstance] = function(x) {
+  %DeoptimizeFunction(foo);
+  return 1;
+};
+
+var a = {};
+
+function foo(o) {
+  return o instanceof A;
+};
+%PrepareFunctionForOptimization(foo);
+foo(a);
+foo(a);
+assertSame(foo(a), true);
+%OptimizeMaglevOnNextCall(foo);
+assertSame(foo(a), true);
+})();