Source Code for Profile Guided Code Positioning

[vivek pandya]

Thanks Yury for
https://gcc.gnu.org/ml/gcc-patches/2011-09/msg01440.html this link.
It implements procedure reordering as linker plugin.
I have some questions :
1 ) Can you point me to some documentation for "how to write plugin
for linkers " I am I have not seen doc for structs with 'ld_' prefix
(i.e defined in plugin-api.h )
 2 ) There is one more algorithm for Basic Block ordering with
execution frequency count in PH paper . Is there any implementation
available for it ?

Sincerely,
Vivek