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Re: subreg rtl documentation
- From: Jim Wilson <wilson at tuliptree dot org>
- To: Kenneth Zadeck <zadeck at naturalbridge dot com>
- Cc: Jeff Law <law at redhat dot com>, Kenneth dot Zadeck at naturalbridge dot com, gcc-patches at gcc dot gnu dot org, "Bonzini, Paolo" <bonzini at gnu dot org>, Richard Kenner <kenner at vlsi1 dot ultra dot nyu dot edu>, Bernd Schmidt <bernds_cb1 at t-online dot de>, "Joseph S. Myers" <joseph at codesourcery dot com>, Joern Rennecke <joernr at arc dot com>, rsandifo at nildram dot co dot uk
- Date: Fri, 11 Apr 2008 09:58:29 -0700
- Subject: Re: subreg rtl documentation
- References: <87wsnda8bu.fsf@moria.site> <87ej9l8tad.fsf@firetop.home> <47FA40CC.5070503@naturalbridge.com> <87skxxabop.fsf@firetop.home> <47FA61D3.70504@tuliptree.org> <47FA6A4E.4090208@naturalbridge.com> <47FA6D0F.10703@redhat.com> <47FADCDB.90506@naturalbridge.com> <87ej9gzs13.fsf@firetop.home> <47FB970D.1080706@redhat.com> <1207672710.3224.11.camel@localhost.localdomain> <47FBA1C0.7060605@redhat.com> <47FBAE46.5040304@naturalbridge.com> <47FBB901.4040606@redhat.com> <47FBCD71.9090103@naturalbridge.com>
On Tue, 2008-04-08 at 15:54 -0400, Kenneth Zadeck wrote:
> It sounds like you (plural) are tentatively saying that if we made the
> same statements about subregs of mem after reload, we would be on ground
> that the community would be willing to support. That does not mean that
> anyone plans to submit patches to break this, but it gives us a basis to
> review things going forward.
I would go further and say that there should never be a subreg of mem
outside combine. It is OK for combine to create them, and simplify
them, but they should never escape out of combine. There is no need for
this. It is a good general principle that we should never accept RTL
that we know will require a reload later.
Jim