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RE: [PATCH] PR/17860: wrong code generated by loop optimizer up to 3.4
- From: "Dave Korn" <dk at artimi dot com>
- To: "'Paolo Bonzini'" <paolo dot bonzini at polimi dot it>
- Cc: "'Paolo Bonzini'" <bonzini at gnu dot org>,"'GCC Patches'" <gcc-patches at gcc dot gnu dot org>,<gcc at gcc dot gnu dot org>
- Date: Tue, 12 Oct 2004 15:23:27 +0100
- Subject: RE: [PATCH] PR/17860: wrong code generated by loop optimizer up to 3.4
> -----Original Message-----
> From: Paolo Bonzini
> Sent: 12 October 2004 13:25
> property may not be true anymore after CSE. Uses of vtop
> like the one I
> removed need to be either fixed or removed; and I suspect
> that *all of
> the uses of vtop* need to.
>
> Basically, I think that removing a not-very-often-used
> transformation in
> an almost dead optimization pass is feasible. Remember 3.4
> has Zdenek's
> dominator-based loop optimizer as well.
Mmm. Alas I'm supporting a 3.3 based compiler here, so I won't benefit
from that (but it might be a good reason to jump up a series), but as you
say....
> So removing them can only give pessimization (and less bugs), leaving
> them in can only give more optimization (and more bugs).
...which is really the sort of tradeoff I need to accept. When you're
working with experimental hardware, it can become difficult to tell what's
going wrong if you can't trust the hardware _and_ you can't trust the
software. I'm gonna just chop out the code that emits them. Thanks for
your advice :)
cheers,
DaveK
--
Can't think of a witty .sigline today....