question about gcc assembly

[Coline Lelong-Pantel]

> Both gcc versions you quote are fairly old; if efficiency
interests you,
> you might try a current version.  Were you able to show a
significant
> difference in performance on a CPU which is important to you?

I have not checked that, my goal is to produce, if it is
possible, the same assembly code.

I would
> guess the most important reason for avoiding use of eax here
would be to
> keep that register available for other use.  The
optimization could be
> affected by compiler switches (-Os, -O2) or by selection of
-march
> option, and many other possibilities.

If I try using optimisation flags or -march, i get a
completely different code.

> Newer CPUs have hardware merging of operations, as well as
stalls on
> certain immediate data operations, so it is impossible to
know the
> performance implications from what you have presented.

What do you mean by "hardware merging of operations" ?


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