Add 64-bit stubs to call into the runtime and to call native functions.

runtime/vm/runtime_entry_x64.cc

Index: runtime/vm/runtime_entry_x64.cc
===================================================================
--- runtime/vm/runtime_entry_x64.cc	(revision 2143)
+++ runtime/vm/runtime_entry_x64.cc	(working copy)
@@ -7,14 +7,35 @@
 
 #include "vm/runtime_entry.h"
 
+#include "vm/assembler.h"
+#include "vm/stub_code.h"
+
 namespace dart {
 
+#define __ assembler->
+
+
+// Generate code to call into the stub which will call the runtime
+// function. Input for the stub is as follows:
+//   RSP : points to the arguments and return value array.
+//   RBX : address of the runtime function to call.
+//   R10 : number of arguments to the call.
 void RuntimeEntry::CallFromDart(Assembler* assembler) const {
-  UNIMPLEMENTED();
+  __ movq(RBX, Immediate(GetEntryPoint()));
+  __ movq(R10, Immediate(argument_count()));
+  __ call(&StubCode::DartCallToRuntimeLabel());
 }
 
+
+// Generate code to call into the stub which will call the runtime
+// function. Input for the stub is as follows:
+//   RSP : points to the arguments and return value array.
+//   RBX : address of the runtime function to call.
+//   R10 : number of arguments to the call.
 void RuntimeEntry::CallFromStub(Assembler* assembler) const {
-  UNIMPLEMENTED();
+  __ movq(RBX, Immediate(GetEntryPoint()));
+  __ movq(R10, Immediate(argument_count()));
+  __ call(&StubCode::StubCallToRuntimeLabel());
 }
 
 }  // namespace dart