Date: Sun, 8 Sep 2013 02:15:25 +0400 From: Solar Designer <solar@...nwall.com> To: john-dev@...ts.openwall.com Subject: Re: Parallella: Litecoin mining Rafael, I took a look at epiphany-salsa20_8.S as currently committed. What's the purpose of the approach you've taken so far - writing asm code without use of macros, and without an attempt at instruction scheduling either (or so it looks)? I suggest that you start by using macros as much as you can (commit this first), and only then expand some of them manually if you absolutely have to in order to achieve decent instruction scheduling. I guess that you'll find that rather than avoid use of macros, you'd need to use different macros - such as a macro doing several things at once (just enough for proper instruction scheduling inside it), and you'll be able to invoke that macro several times as appropriate. Please take a look at Katja's parallella_e_bcrypt.S. Also, please keep the pure C version of the code around, and please make it possible and easy to build cgminer with either code version (pure C or C+asm). This is needed e.g. to experiment with algorithm level changes, which would be more time-consuming to have to make to the asm version right away. It is also needed to troubleshoot problems (e.g. "is this problem we're having possibly with the asm code being incompatible with the new platform? let's try disabling asm to find out" - for whatever problems we or the users might run into at a later time). Regarding the likely/unlikely stuff in epiphany-scrypt.c - did it result in any speedup, in your testing? It might, if it results in a reduction in total number of taken branches. (On Epiphany, any taken branch costs 3 cycles. This applies to unconditional branches, too.) Alexander
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