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Date: Mon, 10 Dec 2012 03:49:35 +0400
From: Solar Designer <solar@...nwall.com>
To: john-dev@...ts.openwall.com
Subject: Re: GCN: indexed access to VGPRs

On Sun, Dec 09, 2012 at 02:24:32PM +0530, Sayantan Datta wrote:
> Yes I would. But I think 1024 integers in private array would eventually
> end up in global memory. I think the private arrays  will/could stay in
> VGPRs given that their size is small enough

Yes, that's what I think too.

> so that it doesn't span across
> multiple VGPRs. Which means arrays less than or equal to 512/32=16
> elements.

No, the different vector components correspond to different work-items,
so VGPR width is irrelevant to how many elements you can have in a
private array with it staying in registers.

Apparently, for GCN the maximum private array size that will stay in
registers is somewhere in the "up to 256" range.  Maybe 128 will work.

Alexander

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