diff --git a/.dart_tool/package_config.json b/.dart_tool/package_config.json
index 57799b3..ca0bcfc 100644
--- a/.dart_tool/package_config.json
+++ b/.dart_tool/package_config.json
@@ -794,4 +794,4 @@
       "languageVersion": "2.12"
     }
   ]
-}
\ No newline at end of file
+}
diff --git a/DEPS b/DEPS
index aa76f78..5955ccb 100644
--- a/DEPS
+++ b/DEPS
@@ -149,7 +149,7 @@
   "source_maps-0.9.4_rev": "38524",
   "source_maps_rev": "53eb92ccfe6e64924054f83038a534b959b12b3e",
   "source_span_rev": "1be3c44045a06dff840d2ed3a13e6082d7a03a23",
-  "sse_tag": "17b52bbdeee53fc54e5bdf9b80934460a9d63ba6",
+  "sse_tag": "8add37c0ec0419ce28153a03f299d44ce006a975",
   "stack_trace_tag": "6788afc61875079b71b3d1c3e65aeaa6a25cbc2f",
   "stagehand_rev": "e64ac90cac508981011299c4ceb819149e71f1bd",
   "stream_channel_tag": "d7251e61253ec389ee6e045ee1042311bced8f1d",
diff --git a/pkg/dev_compiler/lib/src/kernel/command.dart b/pkg/dev_compiler/lib/src/kernel/command.dart
index 4a7f62a..958d410 100644
--- a/pkg/dev_compiler/lib/src/kernel/command.dart
+++ b/pkg/dev_compiler/lib/src/kernel/command.dart
@@ -16,7 +16,6 @@
 import 'package:kernel/class_hierarchy.dart';
 import 'package:kernel/core_types.dart';
 import 'package:kernel/kernel.dart' hide MapEntry;
-import 'package:kernel/ast.dart' show NonNullableByDefaultCompiledMode;
 import 'package:kernel/target/targets.dart';
 import 'package:kernel/text/ast_to_text.dart' as kernel show Printer;
 import 'package:path/path.dart' as p;
diff --git a/pkg/dev_compiler/lib/src/kernel/expression_compiler_worker.dart b/pkg/dev_compiler/lib/src/kernel/expression_compiler_worker.dart
index 020a579..9956b4f 100644
--- a/pkg/dev_compiler/lib/src/kernel/expression_compiler_worker.dart
+++ b/pkg/dev_compiler/lib/src/kernel/expression_compiler_worker.dart
@@ -463,8 +463,8 @@
 
   Future<Component> _loadComponent(Uri uri) async {
     var file = _processedOptions.fileSystem.entityForUri(uri);
-    if (await file.exists()) {
-      var bytes = await file.readAsBytes();
+    if (await file.existsAsyncIfPossible()) {
+      var bytes = await file.readAsBytesAsyncIfPossible();
       var component = _processedOptions.loadComponent(bytes, _sdkComponent.root,
           alwaysCreateNewNamedNodes: true);
       return component;
diff --git a/runtime/lib/stacktrace.cc b/runtime/lib/stacktrace.cc
index 2c75f02..545a3d3 100644
--- a/runtime/lib/stacktrace.cc
+++ b/runtime/lib/stacktrace.cc
@@ -18,25 +18,35 @@
 
 static const intptr_t kDefaultStackAllocation = 8;
 
+static StackTracePtr CreateStackTraceObject(
+    Zone* zone,
+    const GrowableObjectArray& code_list,
+    const GrowableArray<uword>& pc_offset_list) {
+  const auto& code_array =
+      Array::Handle(zone, Array::MakeFixedLength(code_list));
+  const auto& pc_offset_array = TypedData::Handle(
+      zone, TypedData::New(kUintPtrCid, pc_offset_list.length()));
+  {
+    NoSafepointScope no_safepoint;
+    memmove(pc_offset_array.DataAddr(0), pc_offset_list.data(),
+            pc_offset_list.length() * kWordSize);
+  }
+  return StackTrace::New(code_array, pc_offset_array);
+}
+
 static StackTracePtr CurrentSyncStackTraceLazy(Thread* thread,
                                                intptr_t skip_frames = 1) {
   Zone* zone = thread->zone();
 
   const auto& code_array = GrowableObjectArray::ZoneHandle(
       zone, GrowableObjectArray::New(kDefaultStackAllocation));
-  const auto& pc_offset_array = GrowableObjectArray::ZoneHandle(
-      zone, GrowableObjectArray::New(kDefaultStackAllocation));
+  GrowableArray<uword> pc_offset_array;
 
   // Collect the frames.
-  StackTraceUtils::CollectFramesLazy(thread, code_array, pc_offset_array,
+  StackTraceUtils::CollectFramesLazy(thread, code_array, &pc_offset_array,
                                      skip_frames);
 
-  const auto& code_array_fixed =
-      Array::Handle(zone, Array::MakeFixedLength(code_array));
-  const auto& pc_offset_array_fixed =
-      Array::Handle(zone, Array::MakeFixedLength(pc_offset_array));
-
-  return StackTrace::New(code_array_fixed, pc_offset_array_fixed);
+  return CreateStackTraceObject(zone, code_array, pc_offset_array);
 }
 
 static StackTracePtr CurrentSyncStackTrace(Thread* thread,
@@ -51,8 +61,8 @@
   // Allocate once.
   const Array& code_array =
       Array::ZoneHandle(zone, Array::New(stack_trace_length));
-  const Array& pc_offset_array =
-      Array::ZoneHandle(zone, Array::New(stack_trace_length));
+  const TypedData& pc_offset_array = TypedData::ZoneHandle(
+      zone, TypedData::New(kUintPtrCid, stack_trace_length));
 
   // Collect the frames.
   const intptr_t collected_frames_count = StackTraceUtils::CollectFrames(
@@ -89,7 +99,7 @@
 }
 
 static void AppendFrames(const GrowableObjectArray& code_list,
-                         const GrowableObjectArray& pc_offset_list,
+                         GrowableArray<uword>* pc_offset_list,
                          int skip_frames) {
   Thread* thread = Thread::Current();
   Zone* zone = thread->zone();
@@ -98,7 +108,6 @@
   StackFrame* frame = frames.NextFrame();
   ASSERT(frame != NULL);  // We expect to find a dart invocation frame.
   Code& code = Code::Handle(zone);
-  Smi& offset = Smi::Handle(zone);
   for (; frame != NULL; frame = frames.NextFrame()) {
     if (!frame->IsDartFrame()) {
       continue;
@@ -109,9 +118,9 @@
     }
 
     code = frame->LookupDartCode();
-    offset = Smi::New(frame->pc() - code.PayloadStart());
+    const intptr_t pc_offset = frame->pc() - code.PayloadStart();
     code_list.Add(code);
-    pc_offset_list.Add(offset);
+    pc_offset_list->Add(pc_offset);
   }
 }
 
@@ -119,16 +128,14 @@
 //
 // Skips the first skip_frames Dart frames.
 const StackTrace& GetCurrentStackTrace(int skip_frames) {
+  Zone* zone = Thread::Current()->zone();
   const GrowableObjectArray& code_list =
-      GrowableObjectArray::Handle(GrowableObjectArray::New());
-  const GrowableObjectArray& pc_offset_list =
-      GrowableObjectArray::Handle(GrowableObjectArray::New());
-  AppendFrames(code_list, pc_offset_list, skip_frames);
-  const Array& code_array = Array::Handle(Array::MakeFixedLength(code_list));
-  const Array& pc_offset_array =
-      Array::Handle(Array::MakeFixedLength(pc_offset_list));
-  const StackTrace& stacktrace =
-      StackTrace::Handle(StackTrace::New(code_array, pc_offset_array));
+      GrowableObjectArray::Handle(zone, GrowableObjectArray::New());
+  GrowableArray<uword> pc_offset_list;
+  AppendFrames(code_list, &pc_offset_list, skip_frames);
+
+  const StackTrace& stacktrace = StackTrace::Handle(
+      zone, CreateStackTraceObject(zone, code_list, pc_offset_list));
   return stacktrace;
 }
 
diff --git a/runtime/vm/code_patcher_arm.cc b/runtime/vm/code_patcher_arm.cc
index 0947b58..2fc5361 100644
--- a/runtime/vm/code_patcher_arm.cc
+++ b/runtime/vm/code_patcher_arm.cc
@@ -96,9 +96,8 @@
     const Code& caller_code,
     const Object& data,
     const Code& target) {
-  ASSERT(caller_code.ContainsInstructionAt(return_address));
   if (FLAG_precompiled_mode && FLAG_use_bare_instructions) {
-    BareSwitchableCallPattern call(return_address, caller_code);
+    BareSwitchableCallPattern call(return_address);
     call.SetData(data);
     call.SetTarget(target);
   } else {
@@ -110,9 +109,8 @@
 
 uword CodePatcher::GetSwitchableCallTargetEntryAt(uword return_address,
                                                   const Code& caller_code) {
-  ASSERT(caller_code.ContainsInstructionAt(return_address));
   if (FLAG_precompiled_mode && FLAG_use_bare_instructions) {
-    BareSwitchableCallPattern call(return_address, caller_code);
+    BareSwitchableCallPattern call(return_address);
     return call.target_entry();
   } else {
     SwitchableCallPattern call(return_address, caller_code);
@@ -122,9 +120,8 @@
 
 ObjectPtr CodePatcher::GetSwitchableCallDataAt(uword return_address,
                                                const Code& caller_code) {
-  ASSERT(caller_code.ContainsInstructionAt(return_address));
   if (FLAG_precompiled_mode && FLAG_use_bare_instructions) {
-    BareSwitchableCallPattern call(return_address, caller_code);
+    BareSwitchableCallPattern call(return_address);
     return call.data();
   } else {
     SwitchableCallPattern call(return_address, caller_code);
diff --git a/runtime/vm/code_patcher_arm64.cc b/runtime/vm/code_patcher_arm64.cc
index b7590db..c399fd1 100644
--- a/runtime/vm/code_patcher_arm64.cc
+++ b/runtime/vm/code_patcher_arm64.cc
@@ -132,9 +132,8 @@
     const Code& caller_code,
     const Object& data,
     const Code& target) {
-  ASSERT(caller_code.ContainsInstructionAt(return_address));
   if (FLAG_precompiled_mode && FLAG_use_bare_instructions) {
-    BareSwitchableCallPattern call(return_address, caller_code);
+    BareSwitchableCallPattern call(return_address);
     call.SetData(data);
     call.SetTarget(target);
   } else {
@@ -146,9 +145,8 @@
 
 uword CodePatcher::GetSwitchableCallTargetEntryAt(uword return_address,
                                                   const Code& caller_code) {
-  ASSERT(caller_code.ContainsInstructionAt(return_address));
   if (FLAG_precompiled_mode && FLAG_use_bare_instructions) {
-    BareSwitchableCallPattern call(return_address, caller_code);
+    BareSwitchableCallPattern call(return_address);
     return call.target_entry();
   } else {
     SwitchableCallPattern call(return_address, caller_code);
@@ -158,9 +156,8 @@
 
 ObjectPtr CodePatcher::GetSwitchableCallDataAt(uword return_address,
                                                const Code& caller_code) {
-  ASSERT(caller_code.ContainsInstructionAt(return_address));
   if (FLAG_precompiled_mode && FLAG_use_bare_instructions) {
-    BareSwitchableCallPattern call(return_address, caller_code);
+    BareSwitchableCallPattern call(return_address);
     return call.data();
   } else {
     SwitchableCallPattern call(return_address, caller_code);
diff --git a/runtime/vm/code_patcher_x64.cc b/runtime/vm/code_patcher_x64.cc
index 1ba005f..ce1d9f2 100644
--- a/runtime/vm/code_patcher_x64.cc
+++ b/runtime/vm/code_patcher_x64.cc
@@ -220,10 +220,8 @@
 //   call target.entry           call stub.entry         call stub.entry
 class SwitchableCallBase : public ValueObject {
  public:
-  explicit SwitchableCallBase(const Code& code)
-      : object_pool_(ObjectPool::Handle(code.GetObjectPool())),
-        target_index_(-1),
-        data_index_(-1) {}
+  explicit SwitchableCallBase(const ObjectPool& object_pool)
+      : object_pool_(object_pool), target_index_(-1), data_index_(-1) {}
 
   intptr_t data_index() const { return data_index_; }
   intptr_t target_index() const { return target_index_; }
@@ -237,7 +235,7 @@
   }
 
  protected:
-  ObjectPool& object_pool_;
+  const ObjectPool& object_pool_;
   intptr_t target_index_;
   intptr_t data_index_;
 
@@ -251,8 +249,9 @@
 // monomorphic function or a stub code.
 class SwitchableCall : public SwitchableCallBase {
  public:
-  SwitchableCall(uword return_address, const Code& code)
-      : SwitchableCallBase(code) {
+  SwitchableCall(uword return_address, const Code& caller_code)
+      : SwitchableCallBase(ObjectPool::Handle(caller_code.GetObjectPool())) {
+    ASSERT(caller_code.ContainsInstructionAt(return_address));
     uword pc = return_address;
 
     // callq RCX
@@ -333,11 +332,9 @@
 // of the monomorphic function or a stub entry point.
 class BareSwitchableCall : public SwitchableCallBase {
  public:
-  BareSwitchableCall(uword return_address, const Code& code)
-      : SwitchableCallBase(code) {
-    object_pool_ = ObjectPool::RawCast(
-        IsolateGroup::Current()->object_store()->global_object_pool());
-
+  explicit BareSwitchableCall(uword return_address)
+      : SwitchableCallBase(ObjectPool::Handle(
+            IsolateGroup::Current()->object_store()->global_object_pool())) {
     uword pc = return_address;
 
     // callq RCX
@@ -489,9 +486,8 @@
     const Code& caller_code,
     const Object& data,
     const Code& target) {
-  ASSERT(caller_code.ContainsInstructionAt(return_address));
   if (FLAG_precompiled_mode && FLAG_use_bare_instructions) {
-    BareSwitchableCall call(return_address, caller_code);
+    BareSwitchableCall call(return_address);
     call.SetData(data);
     call.SetTarget(target);
   } else {
@@ -503,9 +499,8 @@
 
 uword CodePatcher::GetSwitchableCallTargetEntryAt(uword return_address,
                                                   const Code& caller_code) {
-  ASSERT(caller_code.ContainsInstructionAt(return_address));
   if (FLAG_precompiled_mode && FLAG_use_bare_instructions) {
-    BareSwitchableCall call(return_address, caller_code);
+    BareSwitchableCall call(return_address);
     return call.target_entry();
   } else {
     SwitchableCall call(return_address, caller_code);
@@ -515,9 +510,8 @@
 
 ObjectPtr CodePatcher::GetSwitchableCallDataAt(uword return_address,
                                                const Code& caller_code) {
-  ASSERT(caller_code.ContainsInstructionAt(return_address));
   if (FLAG_precompiled_mode && FLAG_use_bare_instructions) {
-    BareSwitchableCall call(return_address, caller_code);
+    BareSwitchableCall call(return_address);
     return call.data();
   } else {
     SwitchableCall call(return_address, caller_code);
diff --git a/runtime/vm/compiler/assembler/disassembler.cc b/runtime/vm/compiler/assembler/disassembler.cc
index 78ae30b..9e19290 100644
--- a/runtime/vm/compiler/assembler/disassembler.cc
+++ b/runtime/vm/compiler/assembler/disassembler.cc
@@ -457,6 +457,9 @@
 void Disassembler::DisassembleCode(const Function& function,
                                    const Code& code,
                                    bool optimized) {
+  if (code.IsUnknownDartCode()) {
+    return;
+  }
   TextBuffer buffer(128);
   const char* function_fullname = function.ToFullyQualifiedCString();
   buffer.Printf("%s", Function::KindToCString(function.kind()));
diff --git a/runtime/vm/compiler/stub_code_compiler.cc b/runtime/vm/compiler/stub_code_compiler.cc
index e08b548..c4ed124 100644
--- a/runtime/vm/compiler/stub_code_compiler.cc
+++ b/runtime/vm/compiler/stub_code_compiler.cc
@@ -796,6 +796,19 @@
   GenerateRangeError(assembler, /*with_fpu_regs=*/true);
 }
 
+void StubCodeCompiler::GenerateFrameAwaitingMaterializationStub(
+    Assembler* assembler) {
+  __ Breakpoint();  // Marker stub.
+}
+
+void StubCodeCompiler::GenerateAsynchronousGapMarkerStub(Assembler* assembler) {
+  __ Breakpoint();  // Marker stub.
+}
+
+void StubCodeCompiler::GenerateUnknownDartCodeStub(Assembler* assembler) {
+  __ Breakpoint();  // Marker stub.
+}
+
 }  // namespace compiler
 
 }  // namespace dart
diff --git a/runtime/vm/compiler/stub_code_compiler_arm.cc b/runtime/vm/compiler/stub_code_compiler_arm.cc
index 0dfaa61..db3bb60 100644
--- a/runtime/vm/compiler/stub_code_compiler_arm.cc
+++ b/runtime/vm/compiler/stub_code_compiler_arm.cc
@@ -3291,15 +3291,6 @@
       CODE_REG, target::Code::entry_point_offset(CodeEntryKind::kMonomorphic)));
 }
 
-void StubCodeCompiler::GenerateFrameAwaitingMaterializationStub(
-    Assembler* assembler) {
-  __ bkpt(0);
-}
-
-void StubCodeCompiler::GenerateAsynchronousGapMarkerStub(Assembler* assembler) {
-  __ bkpt(0);
-}
-
 void StubCodeCompiler::GenerateNotLoadedStub(Assembler* assembler) {
   __ EnterStubFrame();
   __ CallRuntime(kNotLoadedRuntimeEntry, 0);
diff --git a/runtime/vm/compiler/stub_code_compiler_arm64.cc b/runtime/vm/compiler/stub_code_compiler_arm64.cc
index 2bbe95e..e5f2d4e 100644
--- a/runtime/vm/compiler/stub_code_compiler_arm64.cc
+++ b/runtime/vm/compiler/stub_code_compiler_arm64.cc
@@ -3435,15 +3435,6 @@
   __ br(R1);
 }
 
-void StubCodeCompiler::GenerateFrameAwaitingMaterializationStub(
-    Assembler* assembler) {
-  __ brk(0);
-}
-
-void StubCodeCompiler::GenerateAsynchronousGapMarkerStub(Assembler* assembler) {
-  __ brk(0);
-}
-
 void StubCodeCompiler::GenerateNotLoadedStub(Assembler* assembler) {
   __ EnterStubFrame();
   __ CallRuntime(kNotLoadedRuntimeEntry, 0);
diff --git a/runtime/vm/compiler/stub_code_compiler_ia32.cc b/runtime/vm/compiler/stub_code_compiler_ia32.cc
index 229be66..d96a18b 100644
--- a/runtime/vm/compiler/stub_code_compiler_ia32.cc
+++ b/runtime/vm/compiler/stub_code_compiler_ia32.cc
@@ -2788,15 +2788,6 @@
   __ int3();  // AOT only.
 }
 
-void StubCodeCompiler::GenerateFrameAwaitingMaterializationStub(
-    Assembler* assembler) {
-  __ int3();  // Marker stub.
-}
-
-void StubCodeCompiler::GenerateAsynchronousGapMarkerStub(Assembler* assembler) {
-  __ int3();  // Marker stub.
-}
-
 void StubCodeCompiler::GenerateNotLoadedStub(Assembler* assembler) {
   __ EnterStubFrame();
   __ CallRuntime(kNotLoadedRuntimeEntry, 0);
diff --git a/runtime/vm/compiler/stub_code_compiler_x64.cc b/runtime/vm/compiler/stub_code_compiler_x64.cc
index 175ed5d..8c4bb23 100644
--- a/runtime/vm/compiler/stub_code_compiler_x64.cc
+++ b/runtime/vm/compiler/stub_code_compiler_x64.cc
@@ -3365,15 +3365,6 @@
   __ jmp(RCX);
 }
 
-void StubCodeCompiler::GenerateFrameAwaitingMaterializationStub(
-    Assembler* assembler) {
-  __ int3();
-}
-
-void StubCodeCompiler::GenerateAsynchronousGapMarkerStub(Assembler* assembler) {
-  __ int3();
-}
-
 void StubCodeCompiler::GenerateNotLoadedStub(Assembler* assembler) {
   __ EnterStubFrame();
   __ CallRuntime(kNotLoadedRuntimeEntry, 0);
diff --git a/runtime/vm/debugger.cc b/runtime/vm/debugger.cc
index acf1abd..16cc361 100644
--- a/runtime/vm/debugger.cc
+++ b/runtime/vm/debugger.cc
@@ -1846,7 +1846,6 @@
   Code& code = Code::Handle(zone);
   Code& inlined_code = Code::Handle(zone);
   Array& deopt_frame = Array::Handle(zone);
-  Smi& offset = Smi::Handle(zone);
   Function& function = Function::Handle(zone);
 
   constexpr intptr_t kDefaultStackAllocation = 8;
@@ -1854,8 +1853,7 @@
 
   const auto& code_array = GrowableObjectArray::ZoneHandle(
       zone, GrowableObjectArray::New(kDefaultStackAllocation));
-  const auto& pc_offset_array = GrowableObjectArray::ZoneHandle(
-      zone, GrowableObjectArray::New(kDefaultStackAllocation));
+  GrowableArray<uword> pc_offset_array(kDefaultStackAllocation);
   bool has_async = false;
 
   std::function<void(StackFrame*)> on_sync_frame = [&](StackFrame* frame) {
@@ -1864,7 +1862,7 @@
                      &inlined_code, &deopt_frame);
   };
 
-  StackTraceUtils::CollectFramesLazy(thread, code_array, pc_offset_array,
+  StackTraceUtils::CollectFramesLazy(thread, code_array, &pc_offset_array,
                                      /*skip_frames=*/0, &on_sync_frame,
                                      &has_async);
 
@@ -1900,8 +1898,8 @@
       continue;
     }
 
-    offset ^= pc_offset_array.At(i);
-    const uword absolute_pc = code.PayloadStart() + offset.Value();
+    const uword pc_offset = pc_offset_array[i];
+    const uword absolute_pc = code.PayloadStart() + pc_offset;
     stack_trace->AddAsyncCausalFrame(absolute_pc, code);
   }
 
@@ -2136,8 +2134,7 @@
       function = code.function();
       if (function.is_visible()) {
         ASSERT(function.ptr() == code.function());
-        uword pc =
-            code.PayloadStart() + Smi::Value(ex_trace.PcOffsetAtFrame(i));
+        uword pc = code.PayloadStart() + ex_trace.PcOffsetAtFrame(i);
         if (code.is_optimized() && ex_trace.expand_inlined()) {
           // Traverse inlined frames.
           for (InlinedFunctionsIterator it(code, pc); !it.Done();
diff --git a/runtime/vm/dwarf.cc b/runtime/vm/dwarf.cc
index a818df9..35df763 100644
--- a/runtime/vm/dwarf.cc
+++ b/runtime/vm/dwarf.cc
@@ -146,7 +146,7 @@
   // Dwarf object (which is currently true).  Otherwise, need to copy.
   code_to_name_.Insert({&code, name});
 
-  if (code.IsFunctionCode()) {
+  if (code.IsFunctionCode() && !code.IsUnknownDartCode()) {
     const Function& function = Function::Handle(zone_, code.function());
     AddFunction(function);
   }
@@ -364,7 +364,7 @@
   for (intptr_t i = 0; i < codes_.length(); i++) {
     const Code& code = *(codes_[i]);
     RELEASE_ASSERT(!code.IsNull());
-    if (!code.IsFunctionCode()) {
+    if (!code.IsFunctionCode() || code.IsUnknownDartCode()) {
       continue;
     }
 
diff --git a/runtime/vm/exceptions.cc b/runtime/vm/exceptions.cc
index e9464e3..1d76750 100644
--- a/runtime/vm/exceptions.cc
+++ b/runtime/vm/exceptions.cc
@@ -35,7 +35,7 @@
   StackTraceBuilder() {}
   virtual ~StackTraceBuilder() {}
 
-  virtual void AddFrame(const Object& code, const Smi& offset) = 0;
+  virtual void AddFrame(const Object& code, uword pc_offset) = 0;
 };
 
 class PreallocatedStackTraceBuilder : public StackTraceBuilder {
@@ -50,7 +50,7 @@
   }
   ~PreallocatedStackTraceBuilder() {}
 
-  virtual void AddFrame(const Object& code, const Smi& offset);
+  void AddFrame(const Object& code, uword pc_offset) override;
 
  private:
   static const int kNumTopframes = StackTrace::kPreallocatedStackdepth / 2;
@@ -63,11 +63,10 @@
 };
 
 void PreallocatedStackTraceBuilder::AddFrame(const Object& code,
-                                             const Smi& offset) {
+                                             uword pc_offset) {
   if (cur_index_ >= StackTrace::kPreallocatedStackdepth) {
     // The number of frames is overflowing the preallocated stack trace object.
     Object& frame_code = Object::Handle();
-    Smi& frame_offset = Smi::Handle();
     intptr_t start = StackTrace::kPreallocatedStackdepth - (kNumTopframes - 1);
     intptr_t null_slot = start - 2;
     // We are going to drop one frame.
@@ -80,20 +79,19 @@
       dropped_frames_++;
     }
     // Encode the number of dropped frames into the pc offset.
-    frame_offset = Smi::New(dropped_frames_);
-    stacktrace_.SetPcOffsetAtFrame(null_slot, frame_offset);
+    stacktrace_.SetPcOffsetAtFrame(null_slot, dropped_frames_);
     // Move frames one slot down so that we can accommodate the new frame.
     for (intptr_t i = start; i < StackTrace::kPreallocatedStackdepth; i++) {
       intptr_t prev = (i - 1);
       frame_code = stacktrace_.CodeAtFrame(i);
-      frame_offset = stacktrace_.PcOffsetAtFrame(i);
+      const uword frame_offset = stacktrace_.PcOffsetAtFrame(i);
       stacktrace_.SetCodeAtFrame(prev, frame_code);
       stacktrace_.SetPcOffsetAtFrame(prev, frame_offset);
     }
     cur_index_ = (StackTrace::kPreallocatedStackdepth - 1);
   }
   stacktrace_.SetCodeAtFrame(cur_index_, code);
-  stacktrace_.SetPcOffsetAtFrame(cur_index_, offset);
+  stacktrace_.SetPcOffsetAtFrame(cur_index_, pc_offset);
   cur_index_ += 1;
 }
 
@@ -104,15 +102,14 @@
   StackFrame* frame = frames.NextFrame();
   ASSERT(frame != NULL);  // We expect to find a dart invocation frame.
   Code& code = Code::Handle();
-  Smi& offset = Smi::Handle();
   for (; frame != NULL; frame = frames.NextFrame()) {
     if (!frame->IsDartFrame()) {
       continue;
     }
     code = frame->LookupDartCode();
     ASSERT(code.ContainsInstructionAt(frame->pc()));
-    offset = Smi::New(frame->pc() - code.PayloadStart());
-    builder->AddFrame(code, offset);
+    const uword pc_offset = frame->pc() - code.PayloadStart();
+    builder->AddFrame(code, pc_offset);
   }
 }
 
diff --git a/runtime/vm/instructions_arm.cc b/runtime/vm/instructions_arm.cc
index c2b7014..1c45ff9 100644
--- a/runtime/vm/instructions_arm.cc
+++ b/runtime/vm/instructions_arm.cc
@@ -263,10 +263,9 @@
   object_pool_.SetObjectAt(target_pool_index_, target_code);
 }
 
-SwitchableCallPatternBase::SwitchableCallPatternBase(const Code& code)
-    : object_pool_(ObjectPool::Handle(code.GetObjectPool())),
-      data_pool_index_(-1),
-      target_pool_index_(-1) {}
+SwitchableCallPatternBase::SwitchableCallPatternBase(
+    const ObjectPool& object_pool)
+    : object_pool_(object_pool), data_pool_index_(-1), target_pool_index_(-1) {}
 
 ObjectPtr SwitchableCallPatternBase::data() const {
   return object_pool_.ObjectAt(data_pool_index_);
@@ -278,7 +277,7 @@
 }
 
 SwitchableCallPattern::SwitchableCallPattern(uword pc, const Code& code)
-    : SwitchableCallPatternBase(code) {
+    : SwitchableCallPatternBase(ObjectPool::Handle(code.GetObjectPool())) {
   ASSERT(code.ContainsInstructionAt(pc));
   // Last instruction: blx lr.
   ASSERT(*(reinterpret_cast<uint32_t*>(pc) - 1) == 0xe12fff3e);
@@ -302,9 +301,9 @@
   object_pool_.SetObjectAt(target_pool_index_, target);
 }
 
-BareSwitchableCallPattern::BareSwitchableCallPattern(uword pc, const Code& code)
-    : SwitchableCallPatternBase(code) {
-  ASSERT(code.ContainsInstructionAt(pc));
+BareSwitchableCallPattern::BareSwitchableCallPattern(uword pc)
+    : SwitchableCallPatternBase(ObjectPool::Handle(
+          IsolateGroup::Current()->object_store()->global_object_pool())) {
   // Last instruction: blx lr.
   ASSERT(*(reinterpret_cast<uint32_t*>(pc) - 1) == 0xe12fff3e);
 
diff --git a/runtime/vm/instructions_arm.h b/runtime/vm/instructions_arm.h
index 7b7b43b..a1e1f9b 100644
--- a/runtime/vm/instructions_arm.h
+++ b/runtime/vm/instructions_arm.h
@@ -131,7 +131,7 @@
 //   call target.entry           call stub.entry         call stub.entry
 class SwitchableCallPatternBase : public ValueObject {
  public:
-  explicit SwitchableCallPatternBase(const Code& code);
+  explicit SwitchableCallPatternBase(const ObjectPool& object_pool);
 
   ObjectPtr data() const;
   void SetData(const Object& data) const;
@@ -166,7 +166,7 @@
 // of the monomorphic function or a stub entry point.
 class BareSwitchableCallPattern : public SwitchableCallPatternBase {
  public:
-  BareSwitchableCallPattern(uword pc, const Code& code);
+  explicit BareSwitchableCallPattern(uword pc);
 
   uword target_entry() const;
   void SetTarget(const Code& target) const;
diff --git a/runtime/vm/instructions_arm64.cc b/runtime/vm/instructions_arm64.cc
index a38a07e..d193510 100644
--- a/runtime/vm/instructions_arm64.cc
+++ b/runtime/vm/instructions_arm64.cc
@@ -397,10 +397,9 @@
   // No need to flush the instruction cache, since the code is not modified.
 }
 
-SwitchableCallPatternBase::SwitchableCallPatternBase(const Code& code)
-    : object_pool_(ObjectPool::Handle(code.GetObjectPool())),
-      data_pool_index_(-1),
-      target_pool_index_(-1) {}
+SwitchableCallPatternBase::SwitchableCallPatternBase(
+    const ObjectPool& object_pool)
+    : object_pool_(object_pool), data_pool_index_(-1), target_pool_index_(-1) {}
 
 ObjectPtr SwitchableCallPatternBase::data() const {
   return object_pool_.ObjectAt(data_pool_index_);
@@ -412,7 +411,7 @@
 }
 
 SwitchableCallPattern::SwitchableCallPattern(uword pc, const Code& code)
-    : SwitchableCallPatternBase(code) {
+    : SwitchableCallPatternBase(ObjectPool::Handle(code.GetObjectPool())) {
   ASSERT(code.ContainsInstructionAt(pc));
   // Last instruction: blr lr.
   ASSERT(*(reinterpret_cast<uint32_t*>(pc) - 1) == 0xd63f03c0);
@@ -438,9 +437,9 @@
   object_pool_.SetObjectAt(target_pool_index_, target);
 }
 
-BareSwitchableCallPattern::BareSwitchableCallPattern(uword pc, const Code& code)
-    : SwitchableCallPatternBase(code) {
-  ASSERT(code.ContainsInstructionAt(pc));
+BareSwitchableCallPattern::BareSwitchableCallPattern(uword pc)
+    : SwitchableCallPatternBase(ObjectPool::Handle(
+          IsolateGroup::Current()->object_store()->global_object_pool())) {
   // Last instruction: blr lr.
   ASSERT(*(reinterpret_cast<uint32_t*>(pc) - 1) == 0xd63f03c0);
 
diff --git a/runtime/vm/instructions_arm64.h b/runtime/vm/instructions_arm64.h
index ae75539..b450522 100644
--- a/runtime/vm/instructions_arm64.h
+++ b/runtime/vm/instructions_arm64.h
@@ -141,7 +141,7 @@
 //   call target.entry           call stub.entry         call stub.entry
 class SwitchableCallPatternBase : public ValueObject {
  public:
-  explicit SwitchableCallPatternBase(const Code& code);
+  explicit SwitchableCallPatternBase(const ObjectPool& object_pool);
 
   ObjectPtr data() const;
   void SetData(const Object& data) const;
@@ -176,7 +176,7 @@
 // of the monomorphic function or a stub entry point.
 class BareSwitchableCallPattern : public SwitchableCallPatternBase {
  public:
-  BareSwitchableCallPattern(uword pc, const Code& code);
+  explicit BareSwitchableCallPattern(uword pc);
 
   uword target_entry() const;
   void SetTarget(const Code& target) const;
diff --git a/runtime/vm/object.cc b/runtime/vm/object.cc
index 1186974..286f4f1 100644
--- a/runtime/vm/object.cc
+++ b/runtime/vm/object.cc
@@ -75,7 +75,7 @@
 
 namespace dart {
 
-DEFINE_FLAG(int,
+DEFINE_FLAG(uint64_t,
             huge_method_cutoff_in_code_size,
             200000,
             "Huge method cutoff in unoptimized code size (in bytes).");
@@ -1059,6 +1059,11 @@
   cls.set_is_declaration_loaded();
   cls.set_is_type_finalized();
 
+  cls = Class::New<FunctionType, RTN::FunctionType>(isolate_group);
+  cls.set_is_allocate_finalized();
+  cls.set_is_declaration_loaded();
+  cls.set_is_type_finalized();
+
   cls = dynamic_class_;
   *dynamic_type_ =
       Type::New(cls, Object::null_type_arguments(), Nullability::kNullable);
@@ -1365,6 +1370,12 @@
   cls = isolate_group->class_table()->At(kForwardingCorpse);
   cls.set_name(Symbols::ForwardingCorpse());
 
+#if defined(DART_PRECOMPILER)
+  const auto& function =
+      Function::Handle(StubCode::UnknownDartCode().function());
+  function.set_name(Symbols::OptimizedOut());
+#endif  // defined(DART_PRECOMPILER)
+
   {
     ASSERT(isolate_group == Dart::vm_isolate_group());
     Thread* thread = Thread::Current();
@@ -16773,7 +16784,8 @@
 #endif  // !defined(DART_PRECOMPILED_RUNTIME)
 
 bool Code::SlowFindRawCodeVisitor::FindObject(ObjectPtr raw_obj) const {
-  return UntaggedCode::ContainsPC(raw_obj, pc_);
+  return UntaggedCode::ContainsPC(raw_obj, pc_) &&
+         !Code::IsUnknownDartCode(Code::RawCast(raw_obj));
 }
 
 CodePtr Code::LookupCodeInIsolateGroup(IsolateGroup* isolate_group, uword pc) {
@@ -16928,6 +16940,10 @@
   return OwnerClassId() == kFunctionCid;
 }
 
+bool Code::IsUnknownDartCode(CodePtr code) {
+  return code == StubCode::UnknownDartCode().ptr();
+}
+
 void Code::DisableDartCode() const {
   SafepointOperationScope safepoint(Thread::Current());
   ASSERT(IsFunctionCode());
@@ -17044,6 +17060,41 @@
   reader.DumpSourcePositions(relative_addresses ? 0 : PayloadStart());
 }
 
+bool Code::CanBeOmittedFromAOTSnapshot() const {
+  NoSafepointScope no_safepoint;
+
+  // Code objects are stored in stack frames if not use_bare_instructions.
+  // Code objects are used by stack traces if not dwarf_stack_traces.
+  if (!FLAG_precompiled_mode || !FLAG_use_bare_instructions ||
+      !FLAG_dwarf_stack_traces_mode) {
+    return false;
+  }
+  // Only omit Code objects corresponding to Dart functions.
+  if (!IsFunctionCode()) {
+    return false;
+  }
+  // Retain Code object if it has exception handlers or PC descriptors.
+  if ((exception_handlers() != Object::empty_exception_handlers().ptr()) ||
+      (pc_descriptors() != Object::empty_descriptors().ptr())) {
+    return false;
+  }
+  if (!owner()->IsHeapObject()) {
+    // Can drop Code if precompiler dropped the Function and only left Smi
+    // classId.
+    return true;
+  }
+  // Retain Code objects corresponding to:
+  // * invisible functions (to filter them from stack traces);
+  // * async/async* closures (to construct async stacks).
+  // * native functions (to find native implementation).
+  const auto& func = Function::Handle(function());
+  if (!func.is_visible() || func.is_native() || func.IsAsyncClosure() ||
+      func.IsAsyncGenClosure()) {
+    return false;
+  }
+  return true;
+}
+
 intptr_t Context::GetLevel() const {
   intptr_t level = 0;
   Context& parent_ctx = Context::Handle(parent());
@@ -24666,15 +24717,17 @@
   code_array.SetAt(frame_index, code);
 }
 
-SmiPtr StackTrace::PcOffsetAtFrame(intptr_t frame_index) const {
-  const Array& pc_offset_array = Array::Handle(untag()->pc_offset_array());
-  return static_cast<SmiPtr>(pc_offset_array.At(frame_index));
+uword StackTrace::PcOffsetAtFrame(intptr_t frame_index) const {
+  const TypedData& pc_offset_array =
+      TypedData::Handle(untag()->pc_offset_array());
+  return pc_offset_array.GetUintPtr(frame_index * kWordSize);
 }
 
 void StackTrace::SetPcOffsetAtFrame(intptr_t frame_index,
-                                    const Smi& pc_offset) const {
-  const Array& pc_offset_array = Array::Handle(untag()->pc_offset_array());
-  pc_offset_array.SetAt(frame_index, pc_offset);
+                                    uword pc_offset) const {
+  const TypedData& pc_offset_array =
+      TypedData::Handle(untag()->pc_offset_array());
+  pc_offset_array.SetUintPtr(frame_index * kWordSize, pc_offset);
 }
 
 void StackTrace::set_async_link(const StackTrace& async_link) const {
@@ -24685,7 +24738,7 @@
   untag()->set_code_array(code_array.ptr());
 }
 
-void StackTrace::set_pc_offset_array(const Array& pc_offset_array) const {
+void StackTrace::set_pc_offset_array(const TypedData& pc_offset_array) const {
   untag()->set_pc_offset_array(pc_offset_array.ptr());
 }
 
@@ -24698,7 +24751,7 @@
 }
 
 StackTracePtr StackTrace::New(const Array& code_array,
-                              const Array& pc_offset_array,
+                              const TypedData& pc_offset_array,
                               Heap::Space space) {
   StackTrace& result = StackTrace::Handle();
   {
@@ -24715,7 +24768,7 @@
 }
 
 StackTracePtr StackTrace::New(const Array& code_array,
-                              const Array& pc_offset_array,
+                              const TypedData& pc_offset_array,
                               const StackTrace& async_link,
                               bool skip_sync_start_in_parent_stack,
                               Heap::Space space) {
@@ -24902,9 +24955,8 @@
         if ((i < (stack_trace.Length() - 1)) &&
             (stack_trace.CodeAtFrame(i + 1) != Code::null())) {
           buffer.AddString("...\n...\n");
-          ASSERT(stack_trace.PcOffsetAtFrame(i) != Smi::null());
           // To account for gap frames.
-          frame_index += Smi::Value(stack_trace.PcOffsetAtFrame(i));
+          frame_index += stack_trace.PcOffsetAtFrame(i);
         }
         continue;
       }
@@ -24917,7 +24969,7 @@
         continue;
       }
 
-      intptr_t pc_offset = Smi::Value(stack_trace.PcOffsetAtFrame(i));
+      const uword pc_offset = stack_trace.PcOffsetAtFrame(i);
       ASSERT(code_object.IsCode());
       code ^= code_object.ptr();
       ASSERT(code.IsFunctionCode());
diff --git a/runtime/vm/object.h b/runtime/vm/object.h
index 5cf9f6c..33d8942 100644
--- a/runtime/vm/object.h
+++ b/runtime/vm/object.h
@@ -5970,6 +5970,7 @@
   uword PayloadStart() const { return PayloadStartOf(ptr()); }
   static uword PayloadStartOf(const CodePtr code) {
 #if defined(DART_PRECOMPILED_RUNTIME)
+    if (IsUnknownDartCode(code)) return 0;
     const uword entry_offset = HasMonomorphicEntry(code)
                                    ? Instructions::kPolymorphicEntryOffsetAOT
                                    : 0;
@@ -6015,9 +6016,10 @@
   }
 
   // Returns the size of [instructions()].
-  intptr_t Size() const { return PayloadSizeOf(ptr()); }
-  static intptr_t PayloadSizeOf(const CodePtr code) {
+  uword Size() const { return PayloadSizeOf(ptr()); }
+  static uword PayloadSizeOf(const CodePtr code) {
 #if defined(DART_PRECOMPILED_RUNTIME)
+    if (IsUnknownDartCode(code)) return kUwordMax;
     return code->untag()->instructions_length_;
 #else
     return Instructions::Size(InstructionsOf(code));
@@ -6347,6 +6349,11 @@
   bool IsTypeTestStubCode() const;
   bool IsFunctionCode() const;
 
+  // Returns true if this Code object represents
+  // Dart function code without any additional information.
+  bool IsUnknownDartCode() const { return IsUnknownDartCode(ptr()); }
+  static bool IsUnknownDartCode(CodePtr code);
+
   void DisableDartCode() const;
 
   void DisableStubCode() const;
@@ -6371,6 +6378,11 @@
     untag()->set_object_pool(object_pool);
   }
 
+  // Returns true if given Code object can be omitted from
+  // the AOT snapshot (when corresponding instructions are
+  // included).
+  bool CanBeOmittedFromAOTSnapshot() const;
+
  private:
   void set_state_bits(intptr_t bits) const;
 
@@ -10803,9 +10815,9 @@
   ObjectPtr CodeAtFrame(intptr_t frame_index) const;
   void SetCodeAtFrame(intptr_t frame_index, const Object& code) const;
 
-  ArrayPtr pc_offset_array() const { return untag()->pc_offset_array(); }
-  SmiPtr PcOffsetAtFrame(intptr_t frame_index) const;
-  void SetPcOffsetAtFrame(intptr_t frame_index, const Smi& pc_offset) const;
+  TypedDataPtr pc_offset_array() const { return untag()->pc_offset_array(); }
+  uword PcOffsetAtFrame(intptr_t frame_index) const;
+  void SetPcOffsetAtFrame(intptr_t frame_index, uword pc_offset) const;
 
   bool skip_sync_start_in_parent_stack() const;
   void set_skip_sync_start_in_parent_stack(bool value) const;
@@ -10828,18 +10840,18 @@
     return RoundedAllocationSize(sizeof(UntaggedStackTrace));
   }
   static StackTracePtr New(const Array& code_array,
-                           const Array& pc_offset_array,
+                           const TypedData& pc_offset_array,
                            Heap::Space space = Heap::kNew);
 
   static StackTracePtr New(const Array& code_array,
-                           const Array& pc_offset_array,
+                           const TypedData& pc_offset_array,
                            const StackTrace& async_link,
                            bool skip_sync_start_in_parent_stack,
                            Heap::Space space = Heap::kNew);
 
  private:
   void set_code_array(const Array& code_array) const;
-  void set_pc_offset_array(const Array& pc_offset_array) const;
+  void set_pc_offset_array(const TypedData& pc_offset_array) const;
   bool expand_inlined() const;
 
   FINAL_HEAP_OBJECT_IMPLEMENTATION(StackTrace, Instance);
diff --git a/runtime/vm/object_graph.cc b/runtime/vm/object_graph.cc
index 8fc322a..0b7cd00 100644
--- a/runtime/vm/object_graph.cc
+++ b/runtime/vm/object_graph.cc
@@ -963,7 +963,11 @@
       ScrubAndWriteUtf8(static_cast<FunctionPtr>(obj)->untag()->name_);
     } else if (cid == kCodeCid) {
       ObjectPtr owner = static_cast<CodePtr>(obj)->untag()->owner_;
-      if (owner->IsFunction()) {
+      if (!owner->IsHeapObject()) {
+        // Precompiler removed owner object from the snapshot,
+        // only leaving Smi classId.
+        writer_->WriteUnsigned(kNoData);
+      } else if (owner->IsFunction()) {
         writer_->WriteUnsigned(kNameData);
         ScrubAndWriteUtf8(static_cast<FunctionPtr>(owner)->untag()->name_);
       } else if (owner->IsClass()) {
diff --git a/runtime/vm/object_store.cc b/runtime/vm/object_store.cc
index feb4803..57343da 100644
--- a/runtime/vm/object_store.cc
+++ b/runtime/vm/object_store.cc
@@ -53,8 +53,9 @@
 static StackTracePtr CreatePreallocatedStackTrace(Zone* zone) {
   const Array& code_array = Array::Handle(
       zone, Array::New(StackTrace::kPreallocatedStackdepth, Heap::kOld));
-  const Array& pc_offset_array = Array::Handle(
-      zone, Array::New(StackTrace::kPreallocatedStackdepth, Heap::kOld));
+  const TypedData& pc_offset_array = TypedData::Handle(
+      zone, TypedData::New(kUintPtrCid, StackTrace::kPreallocatedStackdepth,
+                           Heap::kOld));
   const StackTrace& stack_trace =
       StackTrace::Handle(zone, StackTrace::New(code_array, pc_offset_array));
   // Expansion of inlined functions requires additional memory at run time,
diff --git a/runtime/vm/profiler.cc b/runtime/vm/profiler.cc
index f0d9d2c..684d7f3 100644
--- a/runtime/vm/profiler.cc
+++ b/runtime/vm/profiler.cc
@@ -1410,7 +1410,7 @@
   ~CodeLookupTableBuilder() {}
 
   void VisitObject(ObjectPtr raw_obj) {
-    if (raw_obj->IsCode()) {
+    if (raw_obj->IsCode() && !Code::IsUnknownDartCode(Code::RawCast(raw_obj))) {
       table_->Add(Code::Handle(Code::RawCast(raw_obj)));
     }
   }
diff --git a/runtime/vm/profiler_service.cc b/runtime/vm/profiler_service.cc
index 599885b..0ba5912 100644
--- a/runtime/vm/profiler_service.cc
+++ b/runtime/vm/profiler_service.cc
@@ -70,6 +70,9 @@
     return NULL;
   }
   const Script& script = Script::Handle(function_.script());
+  if (script.IsNull()) {
+    return NULL;
+  }
   const String& uri = String::Handle(script.resolved_url());
   if (uri.IsNull()) {
     return NULL;
diff --git a/runtime/vm/profiler_test.cc b/runtime/vm/profiler_test.cc
index d4e62d2..40f1a09 100644
--- a/runtime/vm/profiler_test.cc
+++ b/runtime/vm/profiler_test.cc
@@ -2288,7 +2288,7 @@
 static uword FindPCForTokenPosition(const Code& code, TokenPosition tp) {
   GrowableArray<const Function*> functions;
   GrowableArray<TokenPosition> token_positions;
-  for (intptr_t pc_offset = 0; pc_offset < code.Size(); pc_offset++) {
+  for (uword pc_offset = 0; pc_offset < code.Size(); pc_offset++) {
     code.GetInlinedFunctionsAtInstruction(pc_offset, &functions,
                                           &token_positions);
     if (token_positions[0] == tp) {
diff --git a/runtime/vm/raw_object.h b/runtime/vm/raw_object.h
index 1ac32d0..160185c 100644
--- a/runtime/vm/raw_object.h
+++ b/runtime/vm/raw_object.h
@@ -2835,10 +2835,18 @@
 // Define an aliases for intptr_t.
 #if defined(ARCH_IS_32_BIT)
 #define kIntPtrCid kTypedDataInt32ArrayCid
+#define GetIntPtr GetInt32
 #define SetIntPtr SetInt32
+#define kUintPtrCid kTypedDataUint32ArrayCid
+#define GetUintPtr GetUint32
+#define SetUintPtr SetUint32
 #elif defined(ARCH_IS_64_BIT)
 #define kIntPtrCid kTypedDataInt64ArrayCid
+#define GetIntPtr GetInt64
 #define SetIntPtr SetInt64
+#define kUintPtrCid kTypedDataUint64ArrayCid
+#define GetUintPtr GetUint64
+#define SetUintPtr SetUint64
 #else
 #error Architecture is not 32-bit or 64-bit.
 #endif  // ARCH_IS_32_BIT
@@ -2917,7 +2925,8 @@
                 async_link);  // Link to parent async stack trace.
   POINTER_FIELD(ArrayPtr,
                 code_array);  // Code object for each frame in the stack trace.
-  POINTER_FIELD(ArrayPtr, pc_offset_array);  // Offset of PC for each frame.
+  POINTER_FIELD(TypedDataPtr, pc_offset_array);  // Offset of PC for each frame.
+
   VISIT_TO(ObjectPtr, pc_offset_array)
   ObjectPtr* to_snapshot(Snapshot::Kind kind) { return to(); }
 
diff --git a/runtime/vm/reverse_pc_lookup_cache.cc b/runtime/vm/reverse_pc_lookup_cache.cc
index dad8849..70f06df 100644
--- a/runtime/vm/reverse_pc_lookup_cache.cc
+++ b/runtime/vm/reverse_pc_lookup_cache.cc
@@ -10,9 +10,9 @@
 
 namespace dart {
 
-CodePtr ReversePc::Lookup(IsolateGroup* group,
-                          uword pc,
-                          bool is_return_address) {
+CodePtr ReversePc::LookupInGroup(IsolateGroup* group,
+                                 uword pc,
+                                 bool is_return_address) {
 #if defined(DART_PRECOMPILED_RUNTIME)
   // This can run in the middle of GC and must not allocate handles.
   NoSafepointScope no_safepoint;
@@ -67,4 +67,35 @@
   return Code::null();
 }
 
+CodePtr ReversePc::Lookup(IsolateGroup* group,
+                          uword pc,
+                          bool is_return_address) {
+  ASSERT(FLAG_precompiled_mode && FLAG_use_bare_instructions);
+  NoSafepointScope no_safepoint;
+
+  CodePtr code = LookupInGroup(group, pc, is_return_address);
+  if (code == Code::null()) {
+    code = LookupInGroup(Dart::vm_isolate_group(), pc, is_return_address);
+  }
+  return code;
+}
+
+CompressedStackMapsPtr ReversePc::FindCompressedStackMaps(
+    IsolateGroup* group,
+    uword pc,
+    bool is_return_address,
+    uword* code_start) {
+  ASSERT(FLAG_precompiled_mode && FLAG_use_bare_instructions);
+  NoSafepointScope no_safepoint;
+
+  CodePtr code = Lookup(group, pc, is_return_address);
+  if (code != Code::null()) {
+    *code_start = Code::PayloadStartOf(code);
+    return code->untag()->compressed_stackmaps();
+  }
+
+  *code_start = 0;
+  return CompressedStackMaps::null();
+}
+
 }  // namespace dart
diff --git a/runtime/vm/reverse_pc_lookup_cache.h b/runtime/vm/reverse_pc_lookup_cache.h
index 8c45bb1..9eb0558 100644
--- a/runtime/vm/reverse_pc_lookup_cache.h
+++ b/runtime/vm/reverse_pc_lookup_cache.h
@@ -13,11 +13,28 @@
 
 class IsolateGroup;
 
+// This class provides mechanism to find Code and CompressedStackMaps
+// objects corresponding to the given PC.
+// Can only be used in AOT runtime with bare instructions.
 class ReversePc : public AllStatic {
  public:
-  static CodePtr Lookup(IsolateGroup* group,
-                        uword pc,
-                        bool is_return_address = false);
+  // Looks for Code object corresponding to |pc| in the
+  // given isolate |group| and vm isolate group.
+  static CodePtr Lookup(IsolateGroup* group, uword pc, bool is_return_address);
+
+  // Looks for CompressedStackMaps corresponding to |pc| in the
+  // given isolate |group| and vm isolate group.
+  // Sets |code_start| to the beginning of the instructions corresponding
+  // to |pc| (like Code::PayloadStart()).
+  static CompressedStackMapsPtr FindCompressedStackMaps(IsolateGroup* group,
+                                                        uword pc,
+                                                        bool is_return_address,
+                                                        uword* code_start);
+
+ private:
+  static CodePtr LookupInGroup(IsolateGroup* group,
+                               uword pc,
+                               bool is_return_address);
 };
 
 }  // namespace dart
diff --git a/runtime/vm/service_test.cc b/runtime/vm/service_test.cc
index c078398..7dec0a8 100644
--- a/runtime/vm/service_test.cc
+++ b/runtime/vm/service_test.cc
@@ -259,7 +259,7 @@
   // Use the entry of the code object as it's reference.
   uword entry = code_c.PayloadStart();
   int64_t compile_timestamp = code_c.compile_timestamp();
-  EXPECT_GT(code_c.Size(), 16);
+  EXPECT_GT(code_c.Size(), 16u);
   uword last = entry + code_c.Size();
 
   // Build a mock message handler and wrap it in a dart port.
diff --git a/runtime/vm/stack_frame.cc b/runtime/vm/stack_frame.cc
index 51c1722..037e70d 100644
--- a/runtime/vm/stack_frame.cc
+++ b/runtime/vm/stack_frame.cc
@@ -105,6 +105,9 @@
 }
 
 bool StackFrame::IsBareInstructionsDartFrame() const {
+  if (!(FLAG_precompiled_mode && FLAG_use_bare_instructions)) {
+    return false;
+  }
   NoSafepointScope no_safepoint;
 
   Code code;
@@ -115,18 +118,14 @@
     ASSERT(cid == kNullCid || cid == kClassCid || cid == kFunctionCid);
     return cid == kFunctionCid;
   }
-  code = ReversePc::Lookup(Dart::vm_isolate_group(), pc(),
-                           /*is_return_address=*/true);
-  if (!code.IsNull()) {
-    auto const cid = code.OwnerClassId();
-    ASSERT(cid == kNullCid || cid == kClassCid || cid == kFunctionCid);
-    return cid == kFunctionCid;
-  }
 
   return false;
 }
 
 bool StackFrame::IsBareInstructionsStubFrame() const {
+  if (!(FLAG_precompiled_mode && FLAG_use_bare_instructions)) {
+    return false;
+  }
   NoSafepointScope no_safepoint;
 
   Code code;
@@ -137,13 +136,6 @@
     ASSERT(cid == kNullCid || cid == kClassCid || cid == kFunctionCid);
     return cid == kNullCid || cid == kClassCid;
   }
-  code = ReversePc::Lookup(Dart::vm_isolate_group(), pc(),
-                           /*is_return_address=*/true);
-  if (!code.IsNull()) {
-    auto const cid = code.OwnerClassId();
-    ASSERT(cid == kNullCid || cid == kClassCid || cid == kFunctionCid);
-    return cid == kNullCid || cid == kClassCid;
-  }
 
   return false;
 }
@@ -225,9 +217,13 @@
   // helper functions to the raw object interface.
   NoSafepointScope no_safepoint;
   Code code;
+  CompressedStackMaps maps;
+  uword code_start;
 
   if (FLAG_precompiled_mode && FLAG_use_bare_instructions) {
-    code = GetCodeObject();
+    maps = ReversePc::FindCompressedStackMaps(isolate_group(), pc(),
+                                              /*is_return_address=*/true,
+                                              &code_start);
   } else {
     ObjectPtr pc_marker = *(reinterpret_cast<ObjectPtr*>(
         fp() + (runtime_frame_layout.code_from_fp * kWordSize)));
@@ -236,23 +232,23 @@
     visitor->VisitPointer(&pc_marker);
     if (pc_marker->IsHeapObject() && (pc_marker->GetClassId() == kCodeCid)) {
       code ^= pc_marker;
+      code_start = code.PayloadStart();
+      maps = code.compressed_stackmaps();
+      ASSERT(!maps.IsNull());
     } else {
       ASSERT(pc_marker == Object::null());
     }
   }
 
-  if (!code.IsNull()) {
+  if (!maps.IsNull()) {
     // Optimized frames have a stack map. We need to visit the frame based
     // on the stack map.
-    CompressedStackMaps maps;
-    maps = code.compressed_stackmaps();
     CompressedStackMaps global_table;
 
     global_table =
         isolate_group()->object_store()->canonicalized_stack_map_entries();
     CompressedStackMaps::Iterator it(maps, global_table);
-    const uword start = code.PayloadStart();
-    const uint32_t pc_offset = pc() - start;
+    const uint32_t pc_offset = pc() - code_start;
     if (it.Find(pc_offset)) {
       ObjectPtr* first = reinterpret_cast<ObjectPtr*>(sp());
       ObjectPtr* last = reinterpret_cast<ObjectPtr*>(
@@ -305,8 +301,14 @@
     // unoptimized code, code with no stack map information at all, or the entry
     // to an osr function. In each of these cases, all stack slots contain
     // tagged pointers, so fall through.
-    ASSERT(!code.is_optimized() || maps.IsNull() ||
-           (pc_offset == code.EntryPoint() - code.PayloadStart()));
+#if defined(DEBUG)
+    if (FLAG_precompiled_mode && FLAG_use_bare_instructions) {
+      ASSERT(IsStubFrame());
+    } else {
+      ASSERT(!code.is_optimized() ||
+             (pc_offset == code.EntryPoint() - code.PayloadStart()));
+    }
+#endif  // defined(DEBUG)
   }
 
   // For normal unoptimized Dart frames and Stub frames each slot
@@ -348,15 +350,23 @@
 CodePtr StackFrame::GetCodeObject() const {
 #if defined(DART_PRECOMPILED_RUNTIME)
   if (FLAG_precompiled_mode && FLAG_use_bare_instructions) {
-    CodePtr code = ReversePc::Lookup(isolate_group(), pc(),
-                                     /*is_return_address=*/true);
-    if (code != Code::null()) {
-      return code;
-    }
-    code = ReversePc::Lookup(Dart::vm_isolate_group(), pc(),
+    NoSafepointScope no_safepoint;
+    Code code;
+    code = ReversePc::Lookup(isolate_group(), pc(),
                              /*is_return_address=*/true);
-    if (code != Code::null()) {
-      return code;
+    if (!code.IsNull()) {
+      // This is needed in order to test stack traces with the future
+      // behavior of ReversePc::Lookup which will return
+      // StubCode::UnknownDartCode() if code object is omitted from
+      // the snapshot.
+      if (FLAG_dwarf_stack_traces_mode && code.CanBeOmittedFromAOTSnapshot()) {
+        ASSERT(StubCode::UnknownDartCode().PayloadStart() == 0);
+        ASSERT(StubCode::UnknownDartCode().Size() == kUwordMax);
+        ASSERT(StubCode::UnknownDartCode().IsFunctionCode());
+        ASSERT(StubCode::UnknownDartCode().IsUnknownDartCode());
+        return StubCode::UnknownDartCode().ptr();
+      }
+      return code.ptr();
     }
     UNREACHABLE();
   }
diff --git a/runtime/vm/stack_trace.cc b/runtime/vm/stack_trace.cc
index e392260..f200269 100644
--- a/runtime/vm/stack_trace.cc
+++ b/runtime/vm/stack_trace.cc
@@ -429,19 +429,17 @@
 void StackTraceUtils::UnwindAwaiterChain(
     Zone* zone,
     const GrowableObjectArray& code_array,
-    const GrowableObjectArray& pc_offset_array,
+    GrowableArray<uword>* pc_offset_array,
     CallerClosureFinder* caller_closure_finder,
     const Closure& leaf_closure) {
   auto& code = Code::Handle(zone);
   auto& function = Function::Handle(zone);
   auto& closure = Closure::Handle(zone, leaf_closure.ptr());
   auto& pc_descs = PcDescriptors::Handle(zone);
-  auto& offset = Smi::Handle(zone);
 
   // Inject async suspension marker.
   code_array.Add(StubCode::AsynchronousGapMarker());
-  offset = Smi::New(0);
-  pc_offset_array.Add(offset);
+  pc_offset_array->Add(0);
 
   // Traverse the trail of async futures all the way up.
   for (; !closure.IsNull();
@@ -455,23 +453,22 @@
     RELEASE_ASSERT(!code.IsNull());
     code_array.Add(code);
     pc_descs = code.pc_descriptors();
-    offset = Smi::New(FindPcOffset(pc_descs, GetYieldIndex(closure)));
+    const intptr_t pc_offset = FindPcOffset(pc_descs, GetYieldIndex(closure));
     // Unlike other sources of PC offsets, the offset may be 0 here if we
     // reach a non-async closure receiving the yielded value.
-    ASSERT(offset.Value() >= 0);
-    pc_offset_array.Add(offset);
+    ASSERT(pc_offset >= 0);
+    pc_offset_array->Add(pc_offset);
 
     // Inject async suspension marker.
     code_array.Add(StubCode::AsynchronousGapMarker());
-    offset = Smi::New(0);
-    pc_offset_array.Add(offset);
+    pc_offset_array->Add(0);
   }
 }
 
 void StackTraceUtils::CollectFramesLazy(
     Thread* thread,
     const GrowableObjectArray& code_array,
-    const GrowableObjectArray& pc_offset_array,
+    GrowableArray<uword>* pc_offset_array,
     int skip_frames,
     std::function<void(StackFrame*)>* on_sync_frames,
     bool* has_async) {
@@ -489,7 +486,6 @@
   }
 
   auto& code = Code::Handle(zone);
-  auto& offset = Smi::Handle(zone);
   auto& closure = Closure::Handle(zone);
 
   CallerClosureFinder caller_closure_finder(zone);
@@ -513,10 +509,9 @@
       // Add the current synchronous frame.
       code = frame->LookupDartCode();
       code_array.Add(code);
-      const intptr_t pc_offset = frame->pc() - code.PayloadStart();
+      const uword pc_offset = frame->pc() - code.PayloadStart();
       ASSERT(pc_offset > 0 && pc_offset <= code.Size());
-      offset = Smi::New(pc_offset);
-      pc_offset_array.Add(offset);
+      pc_offset_array->Add(pc_offset);
       // Callback for sync frame.
       if (on_sync_frames != nullptr) {
         (*on_sync_frames)(frame);
@@ -593,7 +588,7 @@
 
 intptr_t StackTraceUtils::CollectFrames(Thread* thread,
                                         const Array& code_array,
-                                        const Array& pc_offset_array,
+                                        const TypedData& pc_offset_array,
                                         intptr_t array_offset,
                                         intptr_t count,
                                         int skip_frames) {
@@ -602,7 +597,6 @@
   StackFrame* frame = frames.NextFrame();
   ASSERT(frame != NULL);  // We expect to find a dart invocation frame.
   Code& code = Code::Handle(zone);
-  Smi& offset = Smi::Handle(zone);
   intptr_t collected_frames_count = 0;
   for (; (frame != NULL) && (collected_frames_count < count);
        frame = frames.NextFrame()) {
@@ -611,9 +605,9 @@
       continue;
     }
     code = frame->LookupDartCode();
-    offset = Smi::New(frame->pc() - code.PayloadStart());
+    const intptr_t pc_offset = frame->pc() - code.PayloadStart();
     code_array.SetAt(array_offset, code);
-    pc_offset_array.SetAt(array_offset, offset);
+    pc_offset_array.SetUintPtr(array_offset * kWordSize, pc_offset);
     array_offset++;
     collected_frames_count++;
   }
diff --git a/runtime/vm/stack_trace.h b/runtime/vm/stack_trace.h
index a08221f..c2eb02a 100644
--- a/runtime/vm/stack_trace.h
+++ b/runtime/vm/stack_trace.h
@@ -107,7 +107,7 @@
 
   static void UnwindAwaiterChain(Zone* zone,
                                  const GrowableObjectArray& code_array,
-                                 const GrowableObjectArray& pc_offset_array,
+                                 GrowableArray<uword>* pc_offset_array,
                                  CallerClosureFinder* caller_closure_finder,
                                  const Closure& leaf_closure);
 
@@ -130,7 +130,7 @@
   static void CollectFramesLazy(
       Thread* thread,
       const GrowableObjectArray& code_array,
-      const GrowableObjectArray& pc_offset_array,
+      GrowableArray<uword>* pc_offset_array,
       int skip_frames,
       std::function<void(StackFrame*)>* on_sync_frames = nullptr,
       bool* has_async = nullptr);
@@ -151,7 +151,7 @@
   /// Returns the number of frames collected.
   static intptr_t CollectFrames(Thread* thread,
                                 const Array& code_array,
-                                const Array& pc_offset_array,
+                                const TypedData& pc_offset_array,
                                 intptr_t array_offset,
                                 intptr_t count,
                                 int skip_frames);
diff --git a/runtime/vm/stub_code.cc b/runtime/vm/stub_code.cc
index e41c642..a78d1b0 100644
--- a/runtime/vm/stub_code.cc
+++ b/runtime/vm/stub_code.cc
@@ -60,6 +60,30 @@
   for (size_t i = 0; i < ARRAY_SIZE(entries_); i++) {
     entries_[i].code->set_object_pool(object_pool.ptr());
   }
+
+#if defined(DART_PRECOMPILER)
+  {
+    // Set Function owner for UnknownDartCode stub so it pretends to
+    // be a Dart code.
+    Zone* zone = Thread::Current()->zone();
+    const auto& signature = FunctionType::Handle(zone, FunctionType::New());
+    auto& owner = Object::Handle(zone);
+    owner = Object::void_class();
+    ASSERT(!owner.IsNull());
+    owner = Function::New(signature, Object::null_string(),
+                          UntaggedFunction::kRegularFunction,
+                          /*is_static=*/true,
+                          /*is_const=*/false,
+                          /*is_abstract=*/false,
+                          /*is_external=*/false,
+                          /*is_native=*/false, owner, TokenPosition::kNoSource);
+    StubCode::UnknownDartCode().set_owner(owner);
+    StubCode::UnknownDartCode().set_exception_handlers(
+        Object::empty_exception_handlers());
+    StubCode::UnknownDartCode().set_pc_descriptors(Object::empty_descriptors());
+    ASSERT(StubCode::UnknownDartCode().IsFunctionCode());
+  }
+#endif  // defined(DART_PRECOMPILER)
 }
 
 #undef STUB_CODE_GENERATE
diff --git a/runtime/vm/stub_code_list.h b/runtime/vm/stub_code_list.h
index c08bfd6..d99a661 100644
--- a/runtime/vm/stub_code_list.h
+++ b/runtime/vm/stub_code_list.h
@@ -128,7 +128,8 @@
   V(InstantiateTypeArguments)                                                  \
   V(InstantiateTypeArgumentsMayShareInstantiatorTA)                            \
   V(InstantiateTypeArgumentsMayShareFunctionTA)                                \
-  V(NoSuchMethodDispatcher)
+  V(NoSuchMethodDispatcher)                                                    \
+  V(UnknownDartCode)
 
 }  // namespace dart
 
diff --git a/tools/VERSION b/tools/VERSION
index 88d050c..900cdf2 100644
--- a/tools/VERSION
+++ b/tools/VERSION
@@ -27,5 +27,5 @@
 MAJOR 2
 MINOR 13
 PATCH 0
-PRERELEASE 46
+PRERELEASE 47
 PRERELEASE_PATCH 0
\ No newline at end of file