[RFC] Fix PR28684

Revital1 Eres ERES@il.ibm.com
Thu Nov 16 15:42:00 GMT 2006




> I wasn't sure if general strength reduction was still controlled by the
> flag, but if it is, we need to mention it, and again the user can
> certify the code as being good in the face of it.  I worry a bit about
> strength reduction, as it often is unknown how extreme it can get, and
> in fp, sometimes it can mess with error (though in small ways).  For
instance,
> replacing 4*X --> X+X+X+X would increase the forward error slightly.  Can
> we bound the number of extra flops that strength reduction is allowed to
do?
> Is the strength reduction stuff necessary for vectorization?

I do not think we have cases of strength reduction in the list of
transformation
which are allowed by the flag; just reordering. I'll recheck that.



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