Re: [patch] Detect cache size with -mtune=native

[Zdenek Dvorak <rakdver at atrey dot karlin dot mff dot cuni dot cz>]

Hello,

> >this patch extends -mtune=native to detect the size of the l1 cache and
> >of the cache line, and to pass it to the compiler by params.  I have
> >tested this on several machines to that I have access, and the results
> >seem to be correct (but especially the intel way of describing the cache
> >sizes is quite ugly.
> 
> >Bootstrapped & regtested on i686.
> 
> Did you bootstrap gcc with BOOT_CFLAGS="... -mtune/-march=native ..."
> ?

not originally, I will try it now (although I do not expect any changes,
for the reasons below).

> There were some interesting bugs that blocked this for certain
> targets, but they should all be fixed in recent SVN.
> 
> Is there any measurable gain on bootstrap time using this patch?

No; at the moment, the information about cache size is unused.  It is
used in reuse analysis pass that I am going to submit soon.  Later, it
also should be used in the heuristics to determine usefulness of
high-level loop transformations, although I think nobody works on that
just now.

Zdenek

> Otherwise, I think this is a nice addition to have for i386 targets.
> But let's give Jan the last word, as it also affects x86_64.