Loop unrolling + fusion ?
simonpj at microsoft.com
Tue Mar 10 10:00:58 EDT 2009
| What I don't understand yet is the routemap for replacing -fvia-C
Good points, Claus. I think the story is as follows:
* -fvia-C does not produce much better code, except in exceptionally tight loops, because GHC gives gcc very little scope for optimisation. Simon mentioned something like 1% improvement.
* -fvia-C does not give substantially improved portability, because the Evil Mangler must have lots of new (Perl) code for each new platform. (And each new version of gcc changes the details.)
* -fvia-C does impose maintenance costs, as this thread has rehearsed.
* -fasm has the potential for producing *better* code than gcc, because we can temporarily re-use registers that we must nail down as far as gcc is concerned.
| In other words, what is the plan wrt to backends, especially wrt
| recovering the optimizations and portability issues previously left to
I think you may be over-optimistic about the portability and optimisation benefits. As to other back end plans, it's a fairly active place. Ben L is doing great stuff on refactoring the native code back end as part of his Sparc NCG. And John and Norman and I are actively (albeit diverted recently by ICFP submissions) working on getting the refactored STG...flat C-- story into mainstream.
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