clang -emit-llvm -c /Users/haidragon/Desktop/llvm_note/class5/test.m -o/Users/haidragon/Desktop/llvm_note/class5/test.bc
./opt -load /Users/haidragon/Desktop/llvm_note/class5/LLVMHello.dylib -hello -time-passes -disable-output /Users/haidragon/Desktop/llvm_note/class5/test.bc
