Re: [patch] entry.S asm improvement (removed some ugly jmp)

Kurt Garloff (garloff@kg1.ping.de)
Sat, 28 Nov 1998 00:45:29 +0100

On Fri, Nov 27, 1998 at 08:27:55PM +0100, Andrea Arcangeli wrote:
> The time of 2.1.130 simulation is 2.603s, the timings of 2.1.130 + my
> patch simulation is 2.601s. This is true on P5MMX I don' t know on other
> CPUs (any volunteers?). My patch produce also smaller code and looks like
> more nice to me ;)

What you might be missing is that we might be deep inside some calls. The
return optimization works by counting calls and rets. And it will be off by
one after your patch applied and all following ret predictions will fail.
This might cause pipeline stalls. And it will be worse the higher the
nesting level of the calls is.

-- 
Kurt Garloff <K.Garloff@ping.de>  (Dortmund, FRG)
PGP key on http://student.physik.uni-dortmund.de/homepages/garloff


Microsoft is not the answer. Microsoft is the question. The answer is no.


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