On Thu, Sep 16, 2021 at 02:49:23PM +0000, Qing Zhao wrote:
> > Testing for many instructions is always very fragile and dependent on exact
> > compiler flags etc.
>
> Yes, It’s indeed very fragile.
> > So, either the test should have a particular
> > -march=/-mtune= options
>
> I might add specific -march to the testing cases.
Even -mtune= is needed if you want to stay safe, otherwise people testing
with --target_board=unix/-mtune=cascadelake (or whatever else) might get
failures.
> > and ideally also -fno-stack-protector
> > -fno-stack-clash-protection etc.
>
> Could you explain a little bit on this why?
In case people test e.g. with --target_board=unix/\{,-fstack-protector-all\}
etc. (e.g. in Fedora/RHEL we do).
For the RTL scanning checks if they are done fairly early, those options
might not change anything, but with the ones scanning in the assembly,
one needs to watch if those options don't add e.g. in the prologue or
epilogue further copies of the instructions you scan for.
Jakub
