Simplify invocation sequence at monomorphic function invocation sites.

src/x64/lithium-codegen-x64.h

Index: src/x64/lithium-codegen-x64.h
diff --git a/src/x64/lithium-codegen-x64.h b/src/x64/lithium-codegen-x64.h
index f5045b66a2d589a4197ca53dd523051df64a0ae4..1331fba5556003296009bc8d7cb6c770a5c6e00c 100644
--- a/src/x64/lithium-codegen-x64.h
+++ b/src/x64/lithium-codegen-x64.h
@@ -196,12 +196,18 @@ class LCodeGen BASE_EMBEDDED {
                                int argc,
                                LInstruction* instr);
 
+  enum RDIState {
+    RDI_UNINITIALIZED,
+    RDI_CONTAINS_TARGET
+  };
+
   // Generate a direct call to a known function.  Expects the function
   // to be in rdi.
   void CallKnownFunction(Handle<JSFunction> function,
                          int arity,
                          LInstruction* instr,
-                         CallKind call_kind);
+                         CallKind call_kind,
+                         RDIState rdi_state);
 
 
   void RecordSafepointWithLazyDeopt(LInstruction* instr,