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References: <20221113230521.712693-1-christoph.muellner@vrull.eu>
 <20221113230521.712693-2-christoph.muellner@vrull.eu> <15ccec02-5467-81aa-89b7-d75a7aa778c2@gmail.com>
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From: Philipp Tomsich <philipp.tomsich@vrull.eu>
Date: Mon, 14 Nov 2022 20:05:02 +0100
Message-ID: <CAAeLtUD0==jdBokjOZEUGDgz=BTao=BizODisYS-JHnjUhvwWg@mail.gmail.com>
Subject: Re: [PATCH 1/7] riscv: bitmanip: add orc.b as an unspec
To: Jeff Law <jeffreyalaw@gmail.com>
Cc: Christoph Muellner <christoph.muellner@vrull.eu>, gcc-patches@gcc.gnu.org, 
	Kito Cheng <kito.cheng@sifive.com>, Jim Wilson <jim.wilson.gcc@gmail.com>, 
	Palmer Dabbelt <palmer@dabbelt.com>, Andrew Waterman <andrew@sifive.com>, 
	Vineet Gupta <vineetg@rivosinc.com>
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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.
>
>