Faster checks in polymorphic instance calls if Smi-s are involved

runtime/vm/intermediate_language_x64.cc

Index: runtime/vm/intermediate_language_x64.cc
diff --git a/runtime/vm/intermediate_language_x64.cc b/runtime/vm/intermediate_language_x64.cc
index 78b9a3f5117a40062782f88fb359b64869c1b375..8345f6f6ec88bf90a449ff4c105a5dfa06a6d573 100644
--- a/runtime/vm/intermediate_language_x64.cc
+++ b/runtime/vm/intermediate_language_x64.cc
@@ -5456,23 +5456,18 @@ void PolymorphicInstanceCallInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
     return;
   }
 
-  // Load receiver into RAX.
-  __ movq(RAX,
-      Address(RSP, (instance_call()->ArgumentCount() - 1) * kWordSize));
-
   Label* deopt = compiler->AddDeoptStub(
       deopt_id(), ICData::kDeoptPolymorphicInstanceCallTestFail);
-  LoadValueCid(compiler, RDI, RAX,
-               (ic_data().GetReceiverClassIdAt(0) == kSmiCid) ? NULL : deopt);
-
+  Label ok;
   compiler->EmitTestAndCall(ic_data(),
-                            RDI,  // Class id register.
                             instance_call()->ArgumentCount(),
                             instance_call()->argument_names(),
                             deopt,
+                            &ok,
                             deopt_id(),
                             instance_call()->token_pos(),
                             locs());
+  __ Bind(&ok);
 }