Execution speed

[Stefan Monnier <monnier@iro.umontreal.ca>]

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Someone on SO reported a surprising behavior where a recursive
implementation of `gcd` turned out faster than the iterative version:

    http://stackoverflow.com/questions/42792988/

The more surprising thing is that when I try it I get the
opposite result, even though it's basically on the same kind of system
(GNU/Linx x86).

I'm curious where the difference might come from.  Could you guys try
out the test?

Just do `emacs -Q --batch -l .../ir-test.el`.  Here's what I got:

    % emacs24 -Q --batch -l ~/tmp/ir-test.el
    Interpreted:  Iterative=1.770s; Recursive=1.937s
    Bytecompiled: Iterative=1.187s; Recursive=1.496s
    % .../src/emacs -Q --batch -l ~/tmp/ir-test.el
    Interpreted:  Iterative=4.496s; Recursive=4.595s
    Bytecompiled: Iterative=2.471s; Recursive=2.983s

where `emacs24` is Debian's whereas the other one is my locally
built&hacked version with debugging assertions and stuff.


        Stefan

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