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Re: [PATCH] Don't truncate paradoxical subregs in store_bit_field_1


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" :).

Adam


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