how to compile several files at ipa level using LLVM?

I download the 2.0 source and compile the llvm-gcc and llvm source code successfully. now try to compile the following two files using linking time optimization:
#include <stdio.h>
extern foo(int *x);
int main()
int x = 5;
printf(“x = %d\n”,x);

void foo(int *x)
*x = 8;

now after reading some tutorial and documents, I use the following steps to get the result:

  1. llvm-gcc -O3 -emit-llvm a.c -c -o a.bc
    2.llvm-gcc -O3 -emit-llvm b.c -c -o b.bc
  2. llvm-link -o final.bc a.bc b.bc
    4.lli final.bc
    x = 8

I want to know what’s the standard process to compile programs at inter-procedural level? for example, how can I write the config file in SPEC CPU2000 if I want to
compile them at “-O3 -ipo”, is there any way as intel compiler did? or is there any document for this?

thanks very much.