VM: Reland Inline instance object hash code into object header on 64bit.

runtime/vm/intrinsifier_x64.cc

Index: runtime/vm/intrinsifier_x64.cc
diff --git a/runtime/vm/intrinsifier_x64.cc b/runtime/vm/intrinsifier_x64.cc
index f0ca5913f9164fb4d092aecb7eee663df629afac..3b97a1bf80b551b928e90e98d4abb018a306f006 100644
--- a/runtime/vm/intrinsifier_x64.cc
+++ b/runtime/vm/intrinsifier_x64.cc
@@ -1754,6 +1754,23 @@ void Intrinsifier::String_getHashCode(Assembler* assembler) {
 }
 
 
+void Intrinsifier::Object_getHash(Assembler* assembler) {
+  __ movq(RAX, Address(RSP, +1 * kWordSize));  // Object.
+  __ movl(RAX, FieldAddress(RAX, String::hash_offset()));
+  __ SmiTag(RAX);
+  __ ret();
+}
+
+
+void Intrinsifier::Object_setHash(Assembler* assembler) {
+  __ movq(RAX, Address(RSP, +2 * kWordSize));  // Object.
+  __ movq(RDX, Address(RSP, +1 * kWordSize));  // Value.
+  __ SmiUntag(RDX);
+  __ movl(FieldAddress(RAX, String::hash_offset()), RDX);
+  __ ret();
+}
+
+
 void GenerateSubstringMatchesSpecialization(Assembler* assembler,
                                             intptr_t receiver_cid,
                                             intptr_t other_cid,