dfa scheduler, bundling and packing

[林 彭]

>Richard Henderson wrote:
> > 
> > While looking at PR 11693, I noticed a bunch of schedules like
> > 
> >         .mlx
> >         nop 0
> >         movl r18 = -4611686018427387904
> >         .mmb
> >         nop 0
> >         addl r19 = 1632, r0
> >         nop 0
> > 
> > One immediately notices that this could have been
> > 
> >         .mlx
> >         addl r19 = 1632, r0
> >         movl r18 = -4611686018427387904
> > 
> > and used half the code space.
> > 
> > The issue, as far as I've been able to tell, is that *both* sequences
> >   can be executed in one cycle, and that the scheduler is given no 
other
> > metric by which to gauge the relative merits of these two sequences.
> > 
> > Have you any thoughts on what could be done here?

>   It can not be a pitfall of bundling because bundling never changes the
> insn order.  So it is a pitfall of insn scheduler.  The most probably
> movl has a bigger priority.  In this case we could add another hook (or
> well one more scheduler hook) to recognize such situation during the
> first cycle multipass insn scheduler.  There is a small probability that
> the first cycle multipass insn scheduler returns insns not in the
> original order when it could do this (I need to check).  Fixing the last
> possible problem still does not remove the 1st problem.  So I think
> there is no other way to fix it without introducing a new scheduler
> hook.

> I'll try to make a patch to fix the problem on this week.

> Vlad
I am intrested in this problem.
How to fix the problem ?
I want to know if we can use  two dfa together,et.,for Itanium2 "two" and 
"twob"
In the function max_issue() in haifa-sched.c,when "best==all" we find the 
max issued insns,we use dfa twob to reord the insns to get better template 
or code density.
But i am not sure dfa "tow" and "towb" can work synchronously ?
Or how i can make them work synchronously ?Specially for different insns 

                                                          Lin

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