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Re: [PATCH] combine leaves superfluous mem subregs
- From: Roger Sayle <roger at eyesopen dot com>
- To: Andreas Krebbel <krebbel1 at de dot ibm dot com>
- Cc: gcc-patches at gcc dot gnu dot org
- Date: Fri, 17 Jun 2005 12:02:45 -0600 (MDT)
- Subject: Re: [PATCH] combine leaves superfluous mem subregs
On Fri, 17 Jun 2005, Andreas Krebbel wrote:
> 2005-06-17 Andreas Krebbel <krebbel1@de.ibm.com>
>
> * combine.c (make_compound_operation): Use simplify_subreg. Deleted
> a optimization already done by simplify_subreg.
This is OK for mainline. Thanks.
Normally, combine can generate a lot of junk patterns and it's the
role of recog to identify which are valid and which aren't. However
in this case, there's clearly an optimization opportunity by changing
the mode of the MEM (and it's not ideal to make the backends needlessly
strict).
My one concern that's outside of my area of expertise is that this could
potentially interact with aliasing at the RTL-level. Though I'm sure
if anyone more familiar with that aspect of the RTL optimizers spots a
potential problem, they'll let us know.
Thanks again.
Roger
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