linux-kernel - Re: [PATCH] powerpc/32: Use r2 in wrtspr() instead of r0

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Message-Id: <161901050347.1961279.12121626398624044029.b4-ty@ellerman.id.au>
Date:   Wed, 21 Apr 2021 23:08:23 +1000
From:   Michael Ellerman <patch-notifications@...erman.id.au>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Paul Mackerras <paulus@...ba.org>
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] powerpc/32: Use r2 in wrtspr() instead of r0

On Fri, 22 Jan 2021 07:15:03 +0000 (UTC), Christophe Leroy wrote:
> wrtspr() is a function to write an arbitrary value in a special
> register. It is used on 8xx to write to SPRN_NRI, SPRN_EID and
> SPRN_EIE. Writing any value to one of those will play with MSR EE
> and MSR RI regardless of that value.
> 
> r0 is used many places in the generated code and using r0 for
> that creates an unnecessary dependency of this instruction with
> preceding ones using r0 in a few places in vmlinux.
> 
> [...]

Applied to powerpc/next.

[1/1] powerpc/32: Use r2 in wrtspr() instead of r0
      https://git.kernel.org/powerpc/c/867e762480f4ad4106b16299a373fa23eccf5b4b

cheers