[stubs] Introduce CSA::OptimalParameterMode(), TagParameter() and UntagParameter().

src/builtins/builtins-internal.cc

Index: src/builtins/builtins-internal.cc
diff --git a/src/builtins/builtins-internal.cc b/src/builtins/builtins-internal.cc
index 87c5dd549c3655f9de133b14660d65af9a68f01b..b5858c64927e9849809cad4ff77fe0b3407d7ca7 100644
--- a/src/builtins/builtins-internal.cc
+++ b/src/builtins/builtins-internal.cc
@@ -64,12 +64,9 @@ void Builtins::Generate_CopyFastSmiOrObjectElements(
   // Load the {object}s elements.
   Node* source = assembler->LoadObjectField(object, JSObject::kElementsOffset);
 
-  CodeStubAssembler::ParameterMode mode =
-      assembler->Is64() ? CodeStubAssembler::INTEGER_PARAMETERS
-                        : CodeStubAssembler::SMI_PARAMETERS;
-  Node* length = (mode == CodeStubAssembler::INTEGER_PARAMETERS)
-                     ? assembler->LoadAndUntagFixedArrayBaseLength(source)
-                     : assembler->LoadFixedArrayBaseLength(source);
+  CodeStubAssembler::ParameterMode mode = assembler->OptimalParameterMode();
+  Node* length = assembler->UntagParameter(
+      assembler->LoadFixedArrayBaseLength(source), mode);
 
   // Check if we can allocate in new space.
   ElementsKind kind = FAST_ELEMENTS;