For background compilation we copy ICData so that it is immutable during comnpilation. However, we …

runtime/vm/assembler_x64.cc

Index: runtime/vm/assembler_x64.cc
diff --git a/runtime/vm/assembler_x64.cc b/runtime/vm/assembler_x64.cc
index b3a1d09638ab931f579d0e3dfe5dd4fab5d1d95a..85b83a9c9cc99b88b5f677545eaa9a82916a3e5f 100644
--- a/runtime/vm/assembler_x64.cc
+++ b/runtime/vm/assembler_x64.cc
@@ -2737,6 +2737,7 @@ void Assembler::Drop(intptr_t stack_elements, Register tmp) {
 
 
 bool Assembler::CanLoadFromObjectPool(const Object& object) const {
+  ASSERT(!object.IsICData() || ICData::Cast(object).IsOriginal());
   ASSERT(!Thread::CanLoadFromThread(object));
   if (!constant_pool_allowed()) {
     return false;
@@ -2772,6 +2773,7 @@ void Assembler::LoadIsolate(Register dst) {
 void Assembler::LoadObjectHelper(Register dst,
                                  const Object& object,
                                  bool is_unique) {
+  ASSERT(!object.IsICData() || ICData::Cast(object).IsOriginal());
   if (Thread::CanLoadFromThread(object)) {
     movq(dst, Address(THR, Thread::OffsetFromThread(object)));
   } else if (CanLoadFromObjectPool(object)) {
@@ -2809,6 +2811,7 @@ void Assembler::LoadUniqueObject(Register dst, const Object& object) {
 
 
 void Assembler::StoreObject(const Address& dst, const Object& object) {
+  ASSERT(!object.IsICData() || ICData::Cast(object).IsOriginal());
   if (Thread::CanLoadFromThread(object)) {
     movq(TMP, Address(THR, Thread::OffsetFromThread(object)));
     movq(dst, TMP);
@@ -2823,6 +2826,7 @@ void Assembler::StoreObject(const Address& dst, const Object& object) {
 
 
 void Assembler::PushObject(const Object& object) {
+  ASSERT(!object.IsICData() || ICData::Cast(object).IsOriginal());
   if (Thread::CanLoadFromThread(object)) {
     pushq(Address(THR, Thread::OffsetFromThread(object)));
   } else if (CanLoadFromObjectPool(object)) {
@@ -2836,6 +2840,7 @@ void Assembler::PushObject(const Object& object) {
 
 
 void Assembler::CompareObject(Register reg, const Object& object) {
+  ASSERT(!object.IsICData() || ICData::Cast(object).IsOriginal());
   if (Thread::CanLoadFromThread(object)) {
     cmpq(reg, Address(THR, Thread::OffsetFromThread(object)));
   } else if (CanLoadFromObjectPool(object)) {
@@ -3062,6 +3067,7 @@ void Assembler::StoreIntoObjectNoBarrier(Register object,
                                          const Address& dest,
                                          const Object& value,
                                          FieldContent old_content) {
+  ASSERT(!value.IsICData() || ICData::Cast(value).IsOriginal());
   VerifyHeapWord(dest, old_content);
   if (VerifiedMemory::enabled()) {
     const Register temp = RCX;