Re: Asm volatile causing performance regressions on ARM

[Yury Gribov <y dot gribov at samsung dot com>]

Richard Biener wrote:
> > > If this behavior is not intended, what would be the best way to fix
> > > performance? I could teach GCC to not remove constant RTXs in
> > > flush_hash_table() but this is probably very naive and won't cover some
> > > corner-cases.
> >
> > That could be a good starting point though.
>
> Though with modifying "machine state" you can modify constants as well, no?

Valid point but this would mean relying on compiler to always load all 
constants from memory (instead of, say, generating them via movhi/movlo) 
for a piece of code which looks extremely unstable.

What is the general attitude towards volatile asm? Are people interested 
in making it more defined/performant or should we just leave this can of 
worms as is? I can try to improve generated code but my patches will be 
doomed if there is no consensus on what volatile asm actually means...

-Y