clang -mllvm usage

I was interested in knowing which of the LLVM passes spends the most of the
time compiling the dns server BIND.
Do you have any suggestion on how to do that?

I have set: ./configure CC="clang" CFLAGS="-mllvm -time-passes"
The compilation gave me no problem but it seems that the -mllvm -time-passes
option does not work.
I also tried to do something easier as: clang -mllvm -time-passes -O3
test.c -o /dev/null
But I am not getting any report (as usually happens when you run opt with
the -time-passes option).
Am I doing something wrong?
Thank you in advance,