Problem
-------

        In  this assignment  we  will  learn the  role  of Link  Time
        Optimization (LTO). LTO combines all compilation units that make
        up a  single executable and  enables optimization of  the entire
        program as a  single unit. LTO can only  combine the translation
        units  submitted to  GCC  and hence  library  functions are  not
        covered  by  LTO.  This  expands the  scope  of  interprocedural
        optimizations  to  encompass  the  whole  program  (or,  rather,
        everything that is visible at link time).

        A dynamic  plugin for interprocedural  pass is provided  to you.
        This  pass iterates  over the  call graph  generated by  GCC and
        prints the names  of the function and its  callers. Makefile and
        the input programs `test1.c' & `test2.c' are also provided.

          i.  Use the Makefile  and build the target with the option 

		"-flto -flto-partiton=none"

          ii. Use the Makefile and build the target with the option 

		"-flto"

        Observe the output  which is generated in the  dump file with
        the extension `.callers' for  the individual test programs. Also
        observe the output generated after merging the .o files.

          a.  What difference do you observe?
          b.  When  we  do  not specify  -flto-partition=none  as  an
              option, function names are not  printed in the merged dump
              file. Can you make suitable changes in the code to fix it?

Procedure
---------

        The  following steps  are to  followed to  execute the  given
        pass.  The Makefile  used  the name  `merged'  for the  combined
        translation unit.

        1. Execute the  plugin by giving the command  `make test' The
            option "-flto" has not been specified for this target.

        2.  Read  the  dump  file  with the  extension  `.callers'  for 
            individual  test   files.  Do   you  find  a   file  called 
            `merged.*.callers'?                                         

        3.  Execute   the   plugin   by   giving   the   command   `make
            test-none'  The  option  used  for  this  target  is  "-flto
            -flto-partition=none"

        4.  Read the  dump file `callers'  for individual test  files as
            also the file `merged.*.callers'.

        5.  Execute the plugin by giving the command `make test-default'
            The option that is used for this target is "-flto"

        6.  Read the  dump file `callers'  for individual test  files as
            also the file `merged.*.callers'.

        7.  Observe the difference in the output and explain.