Re: Arm ldaxr / stxr loop question

aph@littlepinkcloud.invalid wrote:

Terje Mathisen <terje.mathisen@tmsw.no> wrote:

aph@littlepinkcloud.invalid wrote:

Chris M. Thomasson <chris.m.thomasson.1@gmail.com> wrote:

>

>
That's right, but my point about LDAR on AArch64 is that you can get
sequential consistency without needing a StoreLoad. LDAR can peek
inside the store buffer and, much of the time, determine that it isn't
necessary to do a flush. I don't know if Arm were the first to do
this, but I don't recall seeing it before. It is a brilliant idea.

>
Isn't this just reusing the normal forwarding network?
>
If not found, you do as usual and start a regular load operation, but
now you also know that you can skip the flushing of the same?

>
Yes. As long as the data in the store buffer doesn't overlap with what
you're about to write, you can ship the flushing.
>

PS. I do agree that it is a good idea (even patent-worthy?), but not
brilliant since it is so very obvious in hindsight.

>
LOL!  :-)
>

>
To me brilliant is something that still isn't obvious after larning
about it.

>
You have very high standards.

 That is one of the reasons I never started a PhD track, I could never find an area of study that I thought would be sufficiently ground-breaking.
 The other reason is/was that my friend Andy "Crazy" Glew did try the PhD route for several years and hit the same stumbling block vs his advisors, and I know that Andy is an idea machine well beyond myself.