This is the mail archive of the
mailing list for the GCC project.
Re: [PATCH] Don't truncate paradoxical subregs in store_bit_field_1
- From: Adam Nemet <anemet at caviumnetworks dot com>
- To: Paolo Bonzini <paolo dot bonzini at gmail dot com>
- Cc: gcc-patches at gcc dot gnu dot org
- Date: Wed, 24 Jun 2009 14:00:08 -0700
- Subject: Re: [PATCH] Don't truncate paradoxical subregs in store_bit_field_1
- References: <email@example.com> <4A428808.firstname.lastname@example.org>
Paolo Bonzini writes:
> Adam Nemet wrote:
> > My patch here:
> > http://gcc.gnu.org/ml/gcc-patches/2008-12/msg00766.html
> > was basically wrong. We create a truncation of a paradoxical subreg,
> > i.e. note the second insn from the link:
> > (set (reg:SI 193)
> > (truncate:SI (subreg:DI (reg:SI 193) 0)))
> > With more aggressive optization of truncate (I am working on a patch to handle
> > TRUNCATE in force_to_mode) the above is turned into a simple no-op copy, which
> > I think is a valid optimization.
> I think so. Anyway your patch does not affect code on
> non-TRULY_NOOP_TRUNCATION targets, which is of course a point in favor
> of it.
Thanks. You must mean "it does not affect TRULY_NOOP_TRUNCATION targets" :).