Adding intrinsic in llvm

i am trying to add intrinsic to LLVM in LLVM project folder in llvm/include/IR folder i created a intrinsicsOWN .td file and i wrote one function with all the headers included

def int_own_smulbb : GCCBuiltin<"__builtin_own_smulbb">,
Intrinsic<[llvm_i32_ty], [llvm_i32_ty, llvm_i32_ty], [IntrNoMem]>;
and file i included in file
and after that in clang/include/basic folder i included builtinsown.def file and again i tried to rebuild the LLVMproject and i got the error like

__builtin_own_smulbb is not a member of llvm intrinsics

so i request the give some ideas how add our own intrinsics in llvm and any corrections has to be made which i have included.