Re: [boost] Boost SIMD beta release

Subject: Re: [boost] Boost SIMD beta release
From: Peter Dimov (lists_at_[hidden])
Date: 2012-12-25 10:28:23

Mathias Gaunard wrote:
> On 25/12/12 15:43, Peter Dimov wrote:
> > Mathias Gaunard wrote:
> >> The shifted iterator and the shifted load allow to do aligned loads if
> >> you statically know the misalignment of the memory.
> >
> > Does this have any performance advantage over just using an unaligned
> > load? I'd expect the microcode to do whatever the shifted load does, but
> > I haven't measured it.
>
> The shifted load statically knows the alignment, unaligned loads do not.
> Note that the switch is outside of the loop, not for each load.

Ah, you're probably talking AltiVec, which probably doesn't have an 
unaligned load instruction. I was thinking SSE, which does.