public static RegisterSpec makeLocalOptional(int reg, TypeBearer type, LocalItem local) {

    return intern(reg, type, local);
  }
Returns an instance for the given register number, type, and variable info. This method is
allowed to return shared instances (but doesn't necessarily do so).

@param reg {@code >= 0;} the register number
@param type {@code non-null;} the type (or possibly actual value) which is loaded from or
    stored to the indicated register
@param local {@code null-ok;} the associated variable info or null for none
@return {@code non-null;} an appropriately-constructed instance
android/android_framework/dex-maker/src/main/java/com/android/dx/rop/code/RegisterSpec.java