Fix allocation stub switching

runtime/vm/object.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/object.h"
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "vm/assembler.h"
 #include "vm/cpu.h"
@@ skipping 2718 matching lines @@
   CHACodeArray a(*this);
   a.DisableCode();
 }
 
 
 void Class::SetTraceAllocation(bool trace_allocation) const {
   const bool changed = trace_allocation != this->trace_allocation();
   set_state_bits(
       TraceAllocationBit::update(trace_allocation, raw_ptr()->state_bits_));
   if (changed) {
-    // TODO(johnmccutchan): Deoptimize the world?
+    DisableAllocationStub();
   }
 }
 
 
 void Class::set_cha_codes(const Array& cache) const {
   StorePointer(&raw_ptr()->cha_codes_, cache.raw());
 }
 
 
 // Apply the members from the patch class to the original class.
@@ skipping 876 matching lines @@
 void Class::set_allocation_stub(const Code& value) const {
   // Never clear the stub as it may still be a target, but will be GC-d if
   // not referenced.
   ASSERT(!value.IsNull());
   ASSERT(raw_ptr()->allocation_stub_ == Code::null());
   StorePointer(&raw_ptr()->allocation_stub_, value.raw());
 }
 
 
 void Class::DisableAllocationStub() const {
+  const Code& existing_stub = Code::Handle(allocation_stub());
+  if (existing_stub.IsNull()) {
+    return;
+  }
+  ASSERT(!CodePatcher::IsEntryPatched(existing_stub));
+  // Patch the stub so that the next caller will regenerate the stub.
+  CodePatcher::PatchEntry(existing_stub);
+  // Disassociate the existing stub from class.
   StorePointer(&raw_ptr()->allocation_stub_, Code::null());
 }
 
 
 bool Class::IsFunctionClass() const {
   return raw() == Type::Handle(Type::Function()).type_class();
 }
 
 
 bool Class::IsCanonicalSignatureClass() const {
@@ skipping 17455 matching lines @@
   return tag_label.ToCString();
 }
 
 
 void UserTag::PrintJSONImpl(JSONStream* stream, bool ref) const {
   Instance::PrintJSONImpl(stream, ref);
 }
 
 
 }  // namespace dart