LLVM Documentation: MergeFunctions pass

[Nick Lewycky]

On 15 September 2014 15:02, Sean Silva <chisophugis at gmail.com> wrote:

> Wow, this is a really detailed document. Great work!
>
> I wouldn't typically recommend a document to go into this much detail, but
> I think that in this particular case, it is fine to have this detail since
> the document can double as a "in-depth walkthrough of a specific LLVM
> pass", which I'm sure will be useful for newbies to get a feel for things.
>

Actually, I have questions on this point before I get into reviewing the
contents. This is the first piece of pass documentation. Who is the
intended audience? What is the desired level of detail and why? At what
point should implementation details be found by reading the code instead of
being in the documentation? Or is this supposed to be a higher-level
understanding of the algorithm like an academic paper but without the tone
(or impenetrable writing)? What is the burden for updating this document as
the implementation changes and why is that a good tradeoff?

Nick

In your first section please answer the three questions here:
> http://llvm.org/docs/SphinxQuickstartTemplate.html#guidelines
>
> I don't know that much about the pass (especially the new implementation),
> so Nick, could you skim over the content to make sure it is covering all
> the main bases?
>
> Some random comments:
>
> > Sometimes code contains functions that does exactly the same thing even
> though
> > they are non-equal on the binary level.
>
> This confuses me; do you mean non-equal on the source level, but equal on
> the binary level?
>
> > If we will track every numbers and flags to be compared we would be able
> to get
> > numbers chain and then create the hash number. So, once again,
> *total-ordering*
> > could be considered as a milestone for even faster (in theory)
> random-access
> > approach.
>
> I'm not sure this makes sense. I imagine that part of the benefit of the
> comparison-based approach is that the comparisons can return early once
> they find a difference. Hashing always has to look at everything. Does the
> current comparison routine look at the entire function before actually
> doing any comparisons?
>
> > #. For two trees *T1* and *T2* we perform *depth-first-trace* and have
> two
> >    chains as a product: "*T1Items*" and "*T2Items*".
>
> I think most readers would be more comfortable with the terms
> "depth-first-traversal" instead of "depth-first-trace" and "sequences"
> instead of "chains".
>
> > Consider modification of *cmpType* method.
>
> What does this paragraph mean?
>
> -- Sean Silva
>
>
>
> On Sun, Sep 14, 2014 at 11:02 PM, <llvm at dyatkovskiy.com> wrote:
>
>> ping
>>
>> 11.09.2014, 12:50, "Stepan Dyatkovskiy" <stpworld at narod.ru>:
>> > Reattached as patch.
>> >
>> > Stepan Dyatkovskiy wrote:
>> >>  Hello everyone,
>> >>  Please review the MergeFunctions pass documentation in attachment.
>> Hope
>> >>  doc is clear enough :-)
>> >>
>> >>  - Stepan
>> _______________________________________________
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>>
>
>
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