Re: [PATCH 1/7] riscv: bitmanip: add orc.b as an unspec

[Philipp Tomsich <philipp.tomsich@vrull.eu>]

On Mon, 14 Nov 2022 at 17:51, Jeff Law <jeffreyalaw@gmail.com> wrote:
>
>
> On 11/13/22 16:05, Christoph Muellner wrote:
> > From: Philipp Tomsich <philipp.tomsich@vrull.eu>
> >
> > As a basis for optimized string functions (e.g., the by-pieces
> > implementations), we need orc.b available.  This adds orc.b as an
> > unspec, so we can expand to it.
> >
> > gcc/ChangeLog:
> >
> >          * config/riscv/bitmanip.md (orcb<mode>2): Add orc.b as an
> >         unspec.
> >          * config/riscv/riscv.md: Add UNSPEC_ORC_B.
> In general, we should prefer to express things as "real" RTL rather than
> UNSPECS.  In this particular case expressing the orc could be done with
> a handful of IOR expressions, though they'd probably need to reference
> byte SUBREGs of the input and I dislike explicit SUBREGs in the md file
> even more than UNSPECs.  So....
>
> OK.

Applied to master. Thanks!
(After using emacs' whitespace-cleanup to fix the damage that
Christoph's vim did to the ChangeLog...)

Philipp.

>
>
> Jeff
>
>
> ps.  We could consider this a reduc_ior_scal insn, but that may be
> actively harmful.  Having vector ops on the general and vector registers
> is a wart I hope we can avoid.
>
>