[wasm] Always provide a wasm instance object at runtime

src/frames.cc

 // Copyright 2012 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.
 
 #include "src/frames.h"
 
 #include <memory>
 #include <sstream>
 
 #include "src/base/bits.h"
@@ skipping 1540 matching lines @@
 Code* WasmFrame::unchecked_code() const {
   return static_cast<Code*>(isolate()->FindCodeObject(pc()));
 }
 
 void WasmFrame::Iterate(ObjectVisitor* v) const { IterateCompiledFrame(v); }
 
 Address WasmFrame::GetCallerStackPointer() const {
   return fp() + ExitFrameConstants::kCallerSPOffset;
 }
 
-Object* WasmFrame::wasm_instance() const {
+WasmInstanceObject* WasmFrame::wasm_instance() const {
   Object* ret = wasm::GetOwningWasmInstance(LookupCode());
-  if (ret == nullptr) ret = isolate()->heap()->undefined_value();
-  return ret;
+  // This is a live stack frame, there must be a live wasm instance available.
+  DCHECK_NOT_NULL(ret);
+  return WasmInstanceObject::cast(ret);
 }
 
 uint32_t WasmFrame::function_index() const {
   FixedArray* deopt_data = LookupCode()->deoptimization_data();
   DCHECK(deopt_data->length() == 2);
   return Smi::cast(deopt_data->get(1))->value();
 }
 
 Script* WasmFrame::script() const {
   Handle<JSObject> instance(JSObject::cast(wasm_instance()), isolate());
   return *wasm::GetScript(instance);
 }
 
 int WasmFrame::position() const {
   int position = StandardFrame::position();
-  if (wasm::WasmIsAsmJs(wasm_instance(), isolate())) {
+  if (wasm_instance()->get_compiled_module()->is_asm_js()) {
     Handle<WasmCompiledModule> compiled_module(
         WasmInstanceObject::cast(wasm_instance())->get_compiled_module(),
         isolate());
     DCHECK_LE(0, position);
     position = WasmCompiledModule::GetAsmJsSourcePosition(
         compiled_module, function_index(), static_cast<uint32_t>(position),
         at_to_number_conversion());
   }
   return position;
 }
@@ skipping 451 matching lines @@
   for (StackFrameIterator it(isolate); !it.done(); it.Advance()) {
     StackFrame* frame = AllocateFrameCopy(it.frame(), zone);
     list.Add(frame, zone);
   }
   return list.ToVector();
 }
 
 
 }  // namespace internal
 }  // namespace v8