[aarch64-port-dev ] Help with SIMD for string_compare

[Andrew Haley]

On 05/18/2016 06:42 PM, Andrew Haley wrote:
> On 05/18/2016 06:25 PM, Pinski, Andrew wrote:
>> What about doing addv (adding across lanes) and then seeing if that result is zero.
>> Something like:
>> addv h0, v0.8h
>> mov w0, s0
>> cbnz w0, diff
> 
> Mmm, but that mov w0, so has a long latency.  How about
> 
> addv h0, v0.8h
> fcmp s0, #0.0
> bne ...

Ah hold on, wouldn't that be wrong because of carries?  We'd
need UMAXV rather than ADDV.

Andrew.