Hi, Christoph,
The partial modules is very interesting. Was it used for a publication? If
so, could
you please tell me some reference(s).
If I see well partial does not use the deadcodeelim module, but, as
written in
CIL.pdf, it does if-statement simplification which goes in that direction. The
two modules
complement their functionality, but, clearly partial is more complex.
Christoph, please provide a link for the "Generalized Multi-Level Flow"
paper - I
wasn't able to find the paper (at
http://www.informatik.uni-trier.de/~ley/pers/hd/d/Das:Manuvir.html, etc). I'll
take a look
at CIL's pointer alias module and maybe I'll find some time to tweak it.
Best regards,
Alex
On 9/18/2013 10:33 AM, Christoph Spiel wrote:
> Alex -
>
> On Tue, Sep 17, 2013 at 04:21:43PM +0300, Alex Susu wrote:
>> Did anybody use Dead code elimination (DCE)?
>
> We used it, but that dates back almost a
> decade, when we analyzed several large projects
> in embedded environments.
>
> Let me summarize the problems I still remember.
>
> (1) CIL introduces "goto" statements even in
> "goto"-free source code. The `Partial'
> module is not smart enough to disentangle
> all kinds of cross-block jumps and thus
> opportunities for eliminating e.g. one
> branch of an "if" are missed even if the
> condition is known.
>
> (2) `Partial' does not respect the "volatile"
> attribute of constants. It might wrongly
> flag expressions as constant and in turn
> code as suitable for elimination. See my
> comment in "partial.ml" around line 1100.
>
> (3) Precise pointer analysis turned out to be
> crucial. The default `Olf' module is much
> to imprecise, but you can simply replace it
> with `Golf' at the top of "ptranal.ml".
> Golf returns _much_ smaller alias-sets,
> opening up further DCE opportunities.
>
> A more powerful pointer-analysis like the
> "Generalized Multi-Level Flow" as hinted in
> Manuvir Das' papers is still missing in
> CIL's code base, though highly desirable.
>
> HTH,
> Chris
>
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