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

[Richard Guenther]

On Sat, 26 Mar 2005 02:17:58 +0100, Steven Bosscher <stevenb@suse.de> wrote:
> 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_instructions): 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.

Why can't we just kill this beast on HEAD _now_ and this way force
people who experience regressions work on the new loop optimizer?
We're waiting for that happening since 3.4 now...

Richard.