RE: Information about LTO

["Sjodin, Jan" <Jan dot Sjodin at amd dot com>]

> -----Original Message-----
> From: Steven Bosscher [mailto:stevenb.gcc@gmail.com]
> Sent: Tuesday, May 01, 2007 4:09 PM
> To: Sjodin, Jan
> Cc: Diego Novillo; Joseph S. Myers; Ian Lance Taylor; gcc@gcc.gnu.org
> Subject: Re: Information about LTO
> 
> On 5/1/07, Sjodin, Jan <Jan.Sjodin@amd.com> wrote:
> > Can someone give similar information about LTO? How many people
> > (full/part time) and how long time it will take? How much work is
LTO
> > compared to the tuple representation?
> 
> A vast amount more if we're going to work on LTO with the current
> GIMPLE representation, because we'll end up rewriting almost all of it
> when the tuples representation is merged.
> 
> ;-)
> 
> More seriously: LTO is, by my uneducated guess, about the same amount
> of work as the tuples work.  I'm assuming single-language LTO here,
> because cross-language LTO is far harder (by the time we get there,
> we'll be talking about fixing the Fortran front end to play nice with
> the call graph, defining some kind of type system, etc.).
> 
> Personally, I think the most useful thing you could do at this point,
> is helping with the tuples repesentation, or helping with the
> preparations for LTO such as removing lang_hooks and perhaps some
> intermediate representation oddities like early uses of DECL_RTL (for
> e.g. register variables).  I think Kenny has shown that an IL
> reader/writer is not an awful lot of work, but IMHO it will be corner
> cases like the ones I just mention that will take a little while to
> resolve.  So, better start early, to make work easier later on.
> 
> But as I said, that's just my uneducated guess.  I haven't done any
> LTO work myself yet ;-)
> 
> Gr.
> Stevem
> 

Thanks for all the responses. It seems like LTO will have to wait for
the tuples or there will be a lot of throw-away code.

- Jan