Re: kernel: -mpreferred-stack-boundary=2 ??

[Bruce Evans]

On Tue, 30 Nov 1999, Marcel Moolenaar wrote:

> Matthew Dillon wrote:
> 
> >     All I can say to that is "bleh".  The real question is whether performance
> >     is actually improved significantly or not.  If not, I'd sent a nasty email
> >     to the gcc folks :-)
> 
> I guess only if you do have a PIII and are using the new instructions.
> In most cases this has no effect whatsoever. Not counting the
> significant code size increase.

It's also useful for properly aligning doubles on the stack.  I would have
expected the most generally efficient way to align doubles and the new PIII
obkects to be aligning the stack only in functions that have such objects
on the stack.  This requires at most one extra instruction:

        andl $~0xf,$esp         16-byte alignment

Bruce



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