Re: [Qemu-devel] [PATCH] tcg/ppc: Add vector opcodes

[Mark Cave-Ayland]

On 22/02/2019 05:59, Richard Henderson wrote:

> This requires VSX, not just Altivec, so Power7 or later.
> 
> Signed-off-by: Richard Henderson <address@hidden>
> ---
> 
> At present there are no tunables that can avoid the 64-bit element
> load/store requirement.  As with requiring AVX1 for x86 hosts, I'm
> not sure it's worth inventing such a tunable for pre-power7 hosts.
> 
> Tested vs aarch64 risu test cases.  It's probably worth testing
> this vs Mark's target/ppc conversion.

Oooh this looks really exciting! However... I only have a G4 Mac Mini around 
that I
use for testing which is Altivec-only :(  Is it much work to support non-VSX 
hosts?

This leads me to a related point that came up when Howard and I were testing 
the PPC
vector patches - how do we know at runtime which optimisations were being used, 
e.g.
what is the value of have_avx2 on a particular CPU running QEMU?

Under Linux this isn't too bad since you can just do "cat /proc/cpuinfo | grep 
avx2"
but it becomes more tricky when getting bug reports from Windows users who 
aren't
particularly technical...


ATB,

Mark.