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Date: Sat, 27 Jul 2013 19:44:04 +0400
From: Solar Designer <>
Subject: Re: Parallella: bcrypt

Yaniv, Katja -

> On Thu, Jul 25, 2013 at 8:22 PM, Yaniv Sapir <> wrote:
> > NO! GP regs should never be accessed through their global address. This
> > can have unpredicted side-effects on the flow of the program.

Ouch.  That's a pity.  It would have been nice to have this supported,
and to have 1-cycle LDRB.  This would replace some other archs' "byte
extract" instructions (such as Alpha's EXTBL) without any opcode cost.
You could even have synthetic instructions (assembler mnemonics only)
like this (to avoid specifying GP registers' global addresses explicitly
in program source).

Another usage scenario would be having a tiny array also addressable via
registers.  It'd be used as array in loops, and via registers when
specific elements are referenced (such as in fully unrolled loops).
We could use this for P-box in bcrypt.

Since this is currently unsupported, perhaps the arch reference should
state so prominently?  Right now, it gives the opposite impression, at
least to me.

On Thu, Jul 25, 2013 at 10:29:27PM +0200, Katja Malvoni wrote:
>  Oops, this explain why I couldn't get correct results.

Oh, did you try?  Can you post a code excerpt, if you still have it?


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