Track field types.

src/x64/stub-cache-x64.cc

Index: src/x64/stub-cache-x64.cc
diff --git a/src/x64/stub-cache-x64.cc b/src/x64/stub-cache-x64.cc
index f7836378e9b849d85c5c362ab5c885b38d9d82d0..c1129dc2a72a647a640c1a6807ee451a3203ba55 100644
--- a/src/x64/stub-cache-x64.cc
+++ b/src/x64/stub-cache-x64.cc
@@ -494,7 +494,12 @@ void StoreStubCompiler::GenerateStoreTransition(MacroAssembler* masm,
   } else if (representation.IsSmi()) {
     __ JumpIfNotSmi(value_reg, miss_label);
   } else if (representation.IsHeapObject()) {
-    __ JumpIfSmi(value_reg, miss_label);
+    HeapType* field_type = descriptors->GetFieldType(descriptor);
+    if (field_type->IsClass()) {
+      __ CheckMap(value_reg, field_type->AsClass(), miss_label, DO_SMI_CHECK);
+    } else {
+      __ JumpIfSmi(value_reg, miss_label);
+    }
   } else if (representation.IsDouble()) {
     Label do_store, heap_number;
     __ AllocateHeapNumber(storage_reg, scratch1, slow);
@@ -638,7 +643,12 @@ void StoreStubCompiler::GenerateStoreField(MacroAssembler* masm,
   if (representation.IsSmi()) {
     __ JumpIfNotSmi(value_reg, miss_label);
   } else if (representation.IsHeapObject()) {
-    __ JumpIfSmi(value_reg, miss_label);
+    HeapType* field_type = lookup->GetFieldType();
+    if (field_type->IsClass()) {
+      __ CheckMap(value_reg, field_type->AsClass(), miss_label, DO_SMI_CHECK);
+    } else {
+      __ JumpIfSmi(value_reg, miss_label);
+    }
   } else if (representation.IsDouble()) {
     // Load the double storage.
     if (index < 0) {