[Bug target/124336] different (noop) memory access size generated for -masm=intel/att with -fstack-check

[zsojka at seznam dot cz]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=124336

--- Comment #5 from Zdenek Sojka <zsojka at seznam dot cz> ---
(In reply to Uroš Bizjak from comment #4)
> (In reply to Zdenek Sojka from comment #3)
> > I think, from the performance point of view, generally the size of the
> > memory access should be the same as other accesses to the same memory
> > location [rsp+0], in order to allow store-to-load forwarding. (if there are
> > such accesses)
> This is only a probe insn that accesses the stack at the end of the page:
> 
>     c:  48 81 ec 00 10 00 00    sub    $0x1000,%rsp
>    13:  83 0c 24 00             orl    $0x0,(%rsp)
> 
> There is "nothing" at this location, so any kind of STL is not effective.

Thank you for the explanation!