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Re: Loop optimizer issues
- From: <tm_gccmail at mail dot kloo dot net>
- To: Diego Novillo <dnovillo at redhat dot com>
- Cc: Zdenek Dvorak <rakdver at atrey dot karlin dot mff dot cuni dot cz>,"gcc at gcc dot gnu dot org" <gcc at gcc dot gnu dot org>,Richard Henderson <rth at redhat dot com>, Jason Merrill <jason at redhat dot com>,pop at gauvain dot u-strasbg dot fr, Jan Hubicka <jh at suse dot cz>,Daniel Berlin <dberlin at dberlin dot org>
- Date: Tue, 29 Jul 2003 13:18:08 -0700 (PDT)
- Subject: Re: Loop optimizer issues
On 29 Jul 2003, Diego Novillo wrote:
> I've been thinking about this proposal and I am not convinced that it
> would be a good idea to merge the two branches.
> * The tree-ssa branch is primarily trying to replace RTL passes.
> This may include the loop optimizer. So far, it is not clear
> whether we will actually need to have a sophisticated loop
> optimizer at the RTL level (if at all). The only thing that
> comes to mind that may needed from RTL are:
> * instruction lengths/costs to guide the unroller
> * prefetching capabilities and memory costs to guide
> software pipelining and memory hierarchy optimizations.
We do BIV-to-GIV conversion and some addressing mode selection in the RTL
loop optimizer. This is critical for targets such as the SH.