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Re: Any plan for rewriting loop.c using cfgloop.c
- From: Zdenek Dvorak <rakdver at atrey dot karlin dot mff dot cuni dot cz>
- To: Jie Zhang <zhangjie at magima dot com dot cn>
- Cc: gcc at gcc dot gnu dot org, Richard Kenner <kenner at vlsi1 dot ultra dot nyu dot edu>,hubicka at ucw dot cz
- Date: Thu, 23 Oct 2003 13:48:32 +0200
- Subject: Re: Any plan for rewriting loop.c using cfgloop.c
- References: <3F973DD9.3070509@magima.com.cn>
Hello,
> >Yes, this is understood problem. In particular expample, of strength
> >reduction, to do it strength reduction effectivly, one should know what
> >are the costs and addressing modes not available at tree-ssa level. To
> >do it correctly one should know about overflow semantics of input
> >language not available at RTL level.
> >
> >It is however not very well understood how to best deal with it. It is
> >probably best to experiment with both implmentations and
> >we will likely end up with loop optimizer split into multiple parts some
> >running at tree-ssa and some running at RTL level. THat is why I do
> >believe that Zdenek's work on RTL loop optimizer is important even after
> >merging tree-ssa.
> >
> >
> >
> Yes, I do think so. Most of the existing loop optimizations in loop.c
> are well suited at RTL level. What I want is rewriting these RTL level
> loop optimizations using the natural loop discovery code in cfgloop.c.
> The current loop optimization code in loop.c using the RTL codes, e.g.
> NOTE_INSN_LOOP_BEG and NOTE_INSN_LOOP_CONT, to find loops. It cannot
> find loop resulted from the code other than loop statements. Sometimes
> tt mistakes one-entry loop for multi-enty one and ignores it.
>
> Where can I find the information and status of Zdenek's work on RTL loop
> optimizer?
everything is in rtlopt-branch; I have no documentation except comments
in files (loop-*.c). I have sent some summary of what is implemented
and what needs to be done/improved to the mailing list when
we were discussing a possibility of merging with tree-ssa branch, it
should be easy to find.
Zdenek