phc-discussions - Re: [PHC] yescrypt AVX2

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Date: Thu, 30 Apr 2015 17:32:48 +0100
From: Samuel Neves <sneves@....uc.pt>
To: discussions@...sword-hashing.net
Subject: Re: [PHC] yescrypt AVX2

On 04/30/2015 03:14 PM, Solar Designer wrote:
> Yes, the cast macros are not usable on the left-hand side, at least not
> with gcc.  Trying to do it with inline asm:
>
> #define LOAD2X128(hi, lo) ({ \
> 	register __m256i out asm("ymm0"); \
> 	__asm__("\n\tvbroadcasti128 %1,%%ymm0" \
> 		"\n\tmovdqa %2,%%xmm0" \
> 		: "=xm" (out) \
> 		: "xm" (hi), "xm" (lo)); \
> 	out; \
> })
>
> I got ridiculous speeds - like 30 times lower.

Is it me, or are you mixing VEX-encoded instructions with regular ones in the above snippet? That is bound to generate a
large number of stalls transitioning between YMM register states.