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Date: Thu, 2 Oct 2014 09:17:55 -0500
From: Segher Boessenkool <segher@kernel.crashing.org>
To: Anton Blanchard <anton@samba.org>
Subject: Re: [PATCH v2] powerpc: Speed up clear_page by unrolling it
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On Thu, Oct 02, 2014 at 03:44:21PM +1000, Anton Blanchard wrote:
> This assumes cacheline sizes won't grow beyond 512 bytes or
> page sizes wont drop below 1kB,

Or a combination of those.

> Michael found that some versions of gcc produce quite bad code
> (all multiplies), so we give gcc a hand by using shifts and adds.

You can make the code a lot less cluttered as well as making the
generated code independent of compiler version by writing the setup
of twox..eightx in the asm block itself.


Segher