Re: Libatomic 16B

[Xi Ruoyao <xry111@mengyan1223.wang>]

On Wed, 2022-02-23 at 08:42 -0800, Satish Vasudeva via Gcc-help wrote:
> Hi Team,
> 
> I was looking at the hotspots in our software stack and interestingly I see
> libat_load_16_i1 seems to be one of the top in the list.
> 
> I am trying to understand why that is the case. My suspicion is some kind
> of lock usage for 16B atomic accesses.
> 
> I came across this discussion but frankly I am still confused.
> https://gcc.gnu.org/legacy-ml/gcc-patches/2017-01/msg02344.html
> 
> Do you think the overhead of libat_load_16_i1 is due to spinlock usage?
> Also reading some other Intel CPU docs, it seems like the CPU does support
> loading 16B in single access. In that case can we optimize this for
> performance?

Open a issue at https://gcc.gnu.org/bugzilla, with the reference to the
Intel CPU doc prove that some specific models supports loading 128-bit.

Don't use "it seems like", nobody wants to write some nasty SSE code and
then find it doesn't work on any CPU.
-- 
Xi Ruoyao <xry111@mengyan1223.wang>
School of Aerospace Science and Technology, Xidian University