How to instrument an initcall?

["Haifeng He" <hehaifeng2nd@xxxxxxxxx>]

Hi,

I want to insert an initcall in a given program. The initcall should be executed
before any real computation starts. For example, given program as
main () {
  ...
}

I would like to transform to
main () {
  my_initcall();
}

I know how to add a call instruction in gimple tree but I am not sure
how to insert
the call inst into the right place. Any suggestion?

Thank

Haifeng