Re: Why not 03 ?
On Fri, May 30, 2014 at 11:10:29AM +1000, Russell Stuart wrote:
> In particular -O3 turns on auto-vectorisation. It can provide a big
> speed up to programs that can take advantage of it
[...]
> As others have pointed our -O3 turns on optimisations that help on some
> architectures and hinder on others. Vectorisation sort of falls into
> that category: hinder becomes "fail with a SIGILL".
On x86-64, AFAICS, you have at least SSE2 and 16 XMM registers, whatever the processor is. Yes, you can not enable AVX(2), but you still can do interesting vector optimizations with the most common x86-64 processor.
(*) http://en.wikipedia.org/wiki/X86-64
(*) http://en.wikipedia.org/wiki/Advanced_Vector_Extensions
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