Run several LLVM Passes automatically with clang

Hi,

I want to run several LLVM passes on the IR when clang compiles source code. I know the passes can run in this way “clang -Xclang -load -Xclang /path/to/LLVMpass.so src.c -o bin”. The time when the pass is executed can be determined through selecting a ExtensionPointTy. However, ExtensionPointTy does not allow me to specify the order of execution of my pass. My question is: If I want to run three passes, including LLVMMypass1.so, LLVMMypass2.so, inline (provided by LLVM), how should I specify the optimization flag of Clang?

Many thanks!
Gaoyao