Re: [PATCH] PR target/50038 fix: redundant zero extensions removal

[Eric Botcazou <ebotcazou at adacore dot com>]

> So, what about the patch? I think since we already have zee patch it
> would be great to use it as more general optimization. I tested it on
> EEMBC 2.0 on Atom and it showed 1% performance gain in geomean on 32
> bit which is really good for such simple optimization. For OOO archs
> patch is not so critical but still makes code cleaner

The patch cannot be accepted as-is since it doesn't update a single bit of the 
documentation present in implicit-zee.c.  The authors have made the effort of 
thoroughly documenting their code so it shouldn't be wasted.  Therefore, at a 
minimum, the documentation must be overhauled the same way the code will be.

I agree that the numbers are encouraging.  Moreover, the narrow specialization 
of the pass was critized when it was added so a generalization will probably 
be welcome.  So, unless other developers object, let's do it, but correctly, 
that is to say, let's rename the pass, eliminate all the hardcoded references 
to implicit zero-extensions in the code and turn it into a generic elimination 
of redundant extensions pass.

-- 
Eric Botcazou