Re: [-mm patch] i386: enable REGPARM by default

[Andi Kleen]

On Sun, May 15, 2005 at 02:37:31PM +0200, Adrian Bunk wrote:
> On Sun, May 15, 2005 at 02:22:34PM +0200, Andi Kleen wrote:
> > Adrian Bunk <bunk@xxxxxxxxx> writes:
> > 
> > > This patch should _not_ go into Linus' tree.
> > >
> > > At some time in the future, we want to unconditionally enable REGPARM on 
> > > i386.
> > >
> > > Let's give it a bit broader testing coverage among -mm users.
> > 
> > iirc problem is that gcc 2.95 and possibly 3.0.x have some known
> > miscompilations with regparams. That is why it was only used
> > with fastcall for a long time. One 3.1.x+ it should be safe.
> > But you cannot express dependencies on the compiler version
> > in Kconfig right now.
> > 
> > Of course getting rid of gcc 2.95 and 3.0.x support would be a good idea,
> > that would allow many other nice things.
> 
> If you'd read either arch/i386/Makefile or the help text for 
> CONFIG_REGPARM, you'd have noticed that we do never use regparm with
> gcc < 3.0 .

Yes, this means you cannot have binary compatible kernels compiled
with different compilers. Which might be a bad thing.  For that
reason alone I would keep the config.

-Andi
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