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Date: Mon, 24 Jun 2013 16:54:45 +0200
From: Katja Malvoni <>
Subject: Re: Parallella: bcrypt


On Tue, May 28, 2013 at 1:58 AM, Solar Designer <> wrote:

> Katja, Yaniv -
> On Sun, May 26, 2013 at 07:37:55PM -0400, Yaniv Sapir wrote:
> > Here's a couple command line options you can try when compiling the code.
> > Please look at the manual for further details.
> >
> > -mfp-mode=int        # this sets the FPU mode to integer. However, please
> > make sure that the generated code does not re-program the CONFIG register
> > before every integer operation
> Let's definitely try this.  I was afraid we'd have to resort to assembly
> code to use the FPU in integer mode - it's great news to me that we seem
> not to have to.

Unfortunately, this doesn't help a lot... Execution speed with -02 is
45.969000 ms and with -mfp-mode=int is 45.951000 ms. I checked generated
assembly code it seems that CONFIG register isn't re-programmed before
every integer operation.

> > -O3
> > -Ofast               # e-gcc supports this level too
> We can try these too, but I don't expect much/any advantage over -O2.

Actually these two made it even slower,  50.725000 ms with -O3 and
50.688000 ms with -Ofast

> -falign-loops=8 and -falign-functions=8 are worth trying.  (The latter
> should only make a measurable difference with the size-optimized
> implementation, where a portion of code has been moved into a separate
> function that is called from several places.)
These also didn't help - 46.504000 ms with -falign-loops=8 and 46.542000 ms
with -falign-functions=8

I attached output for every used command line option with code sizes.


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