Re: RCSP and modulo scheduling

[Vladimir Makarov <vmakarov at redhat dot com>]

David Edelsohn wrote:
> 
>         Is RCSP suppose to be a complete solution for software pipelining
> or used in conjunction with modulo scheduling?  The GCC IA-64 Wish List
> and GCC IA-64 Summit both seem to imply that RCSP is a fallback when
> modulo scheduling cannot be applied.  Should both be implemented and work
> together for a complete solution?

  I can not decide it alone.  I'd prefer to have only RCSP because
existing RCSP and modulo scheduling in one compiler is not reasonable
because of the code duplication.  I don't know industrial compilers
which implement several software pipelining (or insn scheduling)
methods.   It is too complicated optimization whose effect for the most
programs is negligible.

  I think about possibility to force RCSP work as modulo scheduling for
loops without if-constructions.  But I am not sure I'll be successful
(especial problem is usage of implementation of register rotation).  In
any case it will be not soon.  RCSP also works slower than modulo
scheduling.

  So may be there is a sense to use modulo scheduling for loops without
internal branches and RCSP for loops with them as a temporary solution
(although all temporary solutions aim to be permanent ones).  It would
be definitely worth to do it if we already had modulo scheduling.

Vlad