From: Michael Ellerman <patch-notifications@ellerman.id.au>
To: Christophe Leroy <christophe.leroy@c-s.fr>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>,
segher@kernel.crashing.org
Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v4 1/3] powerpc: rewrite LOAD_REG_IMMEDIATE() as an intelligent macro
Date: Wed, 28 Aug 2019 14:24:49 +1000 (AEST) [thread overview]
Message-ID: <46JCM570Xkz9sP6@ozlabs.org> (raw)
In-Reply-To: <d60ce8dd3a383c7adbfc322bf1d53d81724a6000.1566311636.git.christophe.leroy@c-s.fr>
On Tue, 2019-08-20 at 14:34:12 UTC, Christophe Leroy wrote:
> Today LOAD_REG_IMMEDIATE() is a basic #define which loads all
> parts on a value into a register, including the parts that are NUL.
>
> This means always 2 instructions on PPC32 and always 5 instructions
> on PPC64. And those instructions cannot run in parallele as they are
> updating the same register.
>
> Ex: LOAD_REG_IMMEDIATE(r1,THREAD_SIZE) in head_64.S results in:
>
> 3c 20 00 00 lis r1,0
> 60 21 00 00 ori r1,r1,0
> 78 21 07 c6 rldicr r1,r1,32,31
> 64 21 00 00 oris r1,r1,0
> 60 21 40 00 ori r1,r1,16384
>
> Rewrite LOAD_REG_IMMEDIATE() with GAS macro in order to skip
> the parts that are NUL.
>
> Rename existing LOAD_REG_IMMEDIATE() as LOAD_REG_IMMEDIATE_SYM()
> and use that one for loading value of symbols which are not known
> at compile time.
>
> Now LOAD_REG_IMMEDIATE(r1,THREAD_SIZE) in head_64.S results in:
>
> 38 20 40 00 li r1,16384
>
> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Series applied to powerpc next, thanks.
https://git.kernel.org/powerpc/c/c691b4b83b6a348f7b9d13c36916e73c2e1d85e4
cheers
prev parent reply other threads:[~2019-08-28 4:41 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-20 14:34 [PATCH v4 1/3] powerpc: rewrite LOAD_REG_IMMEDIATE() as an intelligent macro Christophe Leroy
2019-08-20 14:34 ` [PATCH v4 2/3] powerpc/32: replace LOAD_MSR_KERNEL() by LOAD_REG_IMMEDIATE() Christophe Leroy
2019-08-20 14:34 ` [PATCH v4 3/3] powerpc/64: optimise LOAD_REG_IMMEDIATE_SYM() Christophe Leroy
2019-08-28 4:24 ` Michael Ellerman [this message]
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