Intermediate representation

clang --help

  -emit-llvm  Use the LLVM representation for assembler and object files
  -S          Only run preprocess and compilation steps

clang -S -emit-llvm ex.c generates a text file ex.ll.
clang -c -emit-llvm ex.c generates a binary file ex.bc.
llvm-dis ex.bc generates a file ex.ll, which is identical with the file generated using ``clang -S -emit-llvm ex.c`.
llvm-as ex.ll generates a file ex.bc, which is identical with the file generated using clang -c -emit-llvm ex.c.
llc ex.ll generates the assembly file ex.s
lli ex.ll can run this file. Use echo $? to see the return value.