Re: [rtl-optimization] Improve Data Prefetch for IA-64

[Canqun Yang]

The last ChangeLog of rtlopt-branch was written in 
2003. After more than one year, many impovements in 
this branch haven't been put into the GCC HEAD. Why? 

ÒýÑÔ Steven Bosscher <stevenb@suse.de>:

> On Saturday 26 March 2005 02:22, Canqun Yang wrote:
> >         * loop.c (PREFETCH_BLOCKS>
> _BEFORE_LOOP_MAX): Defined conditionally.
> >         (scan_loop): Change extra>
> _size from 16 to 128.
> >         (emit_prefetch_instructio>
> ns): Don't ignore all prefetches within
> > loop.
>
> OK, so I know this is not a popular subject, but can 
we *please* stop
> working on loop.c and focus on getting the new RTL 
and tree loop passes
> to do what we want?  All this loop.c patching is a 
typical example of
> why free software development does not always work: 
always going for
> the low-hanging fruit.  In this case, there have 
been several attempts
> to replace the prefetching stuff in loop.c with 
something better.  On
> the rtl-opt branch there is a new RTL loop-
prefetch.c, and on the LNO
> branch there is a re-use analysis based prefetching 
pass.  Why don't
> you try to finish and improve those passes, instead 
of making it yet
> again harder to remove loop.c.  This one file is a 
*huge* problem for
> just about the entire RTL optimizer path.  It is, 
for example, the
> reason why there is no profile information available 
before this old
> piece of, if I may say, junk runs, and it the only 
reason why a great
> many functions in for example jump.c and the various 
cfg*.c files can
> still not be removed.
>
> Gr.
> Steven
>
> 



Canqun Yang
Creative Compiler Research Group.
National University of Defense Technology, China.