Re: Intermediate report for AIX 5L port

...
> It can see the lock values don't have any effect on 'a'.  What actually
> does keep this stuff from moving around?

Lack of ambition?

I'm pretty sure that the only reasons *to* reorder instructions are:

1) there could be a performance gain, as in  a) loop unrolling b) pipeline fill considerations c) unnecessary
assignment(e.g. result is ignored, or only used on one
 
path)

2) the optimization level allows it (-O0 does not reorder at all)

I vaguely recall that the gcc docs discuss the kinds of optimizations
allowed at each level. Presumably IBM's AIX compiler was a bit more
aggressive in evaluating costs or pipeline fills than is gcc on other
processors.
                     - Thomas