RE: [PATCH] powerpc: Optimise the 64bit optimised __clear_user

=20

-----Original Message-----
From: Linuxppc-dev=20
[mailto:linuxppc-dev-bounces+david.laight=3Daculab.com@lists.ozl

abs.org] On Behalf Of Benjamin Herrenschmidt

Sent: 07 June 2012 07:40
To: Michael Neuling
Cc: michael@ellerman.id.au; paulus@samba.org; Anton=20
Blanchard; olof@lixom.net; linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH] powerpc: Optimise the 64bit optimised=20
__clear_user
=20
On Thu, 2012-06-07 at 16:05 +1000, Michael Neuling wrote:
=20

quoted

One problem with this is when we construct the=20

instructions, like using

quoted

anything from ppc-opcode.h.  eg. using PPC_POPCNTB would=20

need to go from:

quoted

    PPC_POPCNTB(r3,r3)=20
to:
    PPC_POPCNTB(3,3)=20
Which is less readable IMHO.

=20
Yes, I know. Not much to do about this, but it might still be=20
worth it,
how much time wasted due to mixing up or with ori in asm somewhere ?
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One option would be to #define R3 (or _r3) for use in those macros so
we still have something nicer than just "3"... oh well.

You then need to catch all the other bugs where a register
is being used instead of a constant.
Time to make the assembler require %r0 (etc)

	David