[lld] r288409 - Updates file comments and variable names.

[Rui Ueyama via llvm-commits]

On Fri, Dec 2, 2016 at 9:24 PM, Sean Silva <chisophugis at gmail.com> wrote:

>
>
> On Fri, Dec 2, 2016 at 3:52 PM, Rui Ueyama <ruiu at google.com> wrote:
>
>> I'm not familiar with GVN, but even if it is similar to it, I don' think
>> I *should* use the same term used there. I originally chose GroupId
>> because it was a group id (and the term "group" is used in gold's safe ICF
>> paper to describe the concept http://static.googleuserconten
>> t.com/media/research.google.com/en//pubs/archive/36912.pdf), and then
>> changed it to Color because it's one word and easy to digest than GroupId
>> to me (e.g. we'll just color them in different colors!). Congruence class
>> is, well, it sounds too technical and doesn't improve readability at least
>> to me.
>>
>
> Personally, I'm pretty opposed to the term "color" here. In all the cases
> I can think of, algorithms that refer to "colors" the number of different
> colors is a constant (one talks about "k-colorability" etc.; the "k" is
> always a constant). That is not the case in this context and it is really
> confusing. This is *not* a coloring algorithm; coloring algorithms are
> about local constraints where adjacent things can't be colored the same.
>

If you feel strongly about that, I'm fine to change the term, but how do
you describe it?

I think congruence class is defined as this: if two sections are in the
same congruence class, they are identical.

That refers the result of the algorithm. We cannot say that we split
congruence class into smaller congruence classes on each iteration, because
if a congruence class can be split, it wasn't a congruence class.

GVN/CSE and the term "congruence" (or even "equivalence class") is
> technically correct. GroupId is consistent with the paper at least. But
> "coloring" is just wrong.
>
> -- Sean Silva
>
>
>>
>> On Fri, Dec 2, 2016 at 12:46 AM, Sean Silva <chisophugis at gmail.com>
>> wrote:
>>
>>>
>>>
>>> On Fri, Dec 2, 2016 at 12:35 AM, Davide Italiano <davide at freebsd.org>
>>> wrote:
>>>
>>>> On Fri, Dec 2, 2016 at 12:34 AM, Sean Silva via llvm-commits
>>>> <llvm-commits at lists.llvm.org> wrote:
>>>> >
>>>> >
>>>> > On Thu, Dec 1, 2016 at 11:45 AM, Rui Ueyama via llvm-commits
>>>> > <llvm-commits at lists.llvm.org> wrote:
>>>> >>
>>>> >> Author: ruiu
>>>> >> Date: Thu Dec  1 13:45:22 2016
>>>> >> New Revision: 288409
>>>> >>
>>>> >> URL: http://llvm.org/viewvc/llvm-project?rev=288409&view=rev
>>>> >> Log:
>>>> >> Updates file comments and variable names.
>>>> >>
>>>> >> Use "color" instead of "group id" to describe the ICF algorithm.
>>>> >
>>>> >
>>>> > The right term is "congruence class"; I think you should use it. This
>>>> ICF
>>>> > algorithm is basically a simple "optimistic" GVN/CSE algorithm; all
>>>> values
>>>> > are initially assumed to be in the same congruence class and then that
>>>> > equivalence class is iteratively split as contradictions are found
>>>> until
>>>> > there are no contradictions.
>>>> >
>>>>
>>>> +1, I think the proper term is congruence here.
>>>>
>>>
>>> I think you've been working on NewGVN for long enough to know better
>>> than "I think" ;)
>>>
>>> -- Sean Silva
>>>
>>>
>>>>
>>>> --
>>>> Davide
>>>>
>>>
>>>
>>
>
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