[swift-dev] Renaming SILSuccessor -> SILCFGEdge

[John McCall]

> On Apr 27, 2017, at 12:01 AM, Bob Wilson <bob.wilson at apple.com> wrote:
>> On Apr 26, 2017, at 6:43 PM, John McCall via swift-dev <swift-dev at swift.org <mailto:swift-dev at swift.org>> wrote:
>> 
>>> On Apr 26, 2017, at 6:11 PM, Michael Gottesman <mgottesman at apple.com <mailto:mgottesman at apple.com>> wrote:
>>>> On Apr 26, 2017, at 1:44 PM, John McCall <rjmccall at apple.com <mailto:rjmccall at apple.com>> wrote:
>>>> 
>>>>> On Apr 26, 2017, at 4:24 PM, Michael Gottesman via swift-dev <swift-dev at swift.org <mailto:swift-dev at swift.org>> wrote:
>>>>> Hey everyone.
>>>>> 
>>>>> I am currently doing some small fixes to SILSuccessor (adding some comments and fixing some issues exposed by LLVM upstream). As I read the code it became pretty apparent that the name is a misnomer... SILSuccessor is not just representing a successor, rather it is representing a whole CFG edge. This can be seen in how SILSuccessor is used to iterate over the predecessors of the block.
>>>>> 
>>>>> With that in mind, I would like to rename SILSuccessor to SILCFGEdge. It will make it much clearer without knowing any context what this data structure is used for.
>>>>> 
>>>>> Any objections, disagreements, flames, etc?
>>>> 
>>>> It seems a little unnecessary to me.  The successor relationship is an edge, and all the edges of the local CFG are successor relationships.  I guess it looks a little funny that the edges into a block are represented by "successors", but I think when you think about it it makes sense.
>>> 
>>> IMO this is more of an issue than something "looking funny". Using code named "successor" to look up the "predecessors" of a block is misleading and results in unnecessary cognitive overhead for the reader who has to "think about it" for it to make sense.
>> 
>> Uh, sure, but this is also not something most people have to deal with a ton, and it's a learn-once-and-remember sort of thing.
>> 
>>>> "SILCFGEdge" is also not a very attractive name because of the two abbreviations.  If you had a nice alternative to "CFGEdge" that was less biased to the beginning/end (like Successor/Predecessor are), I probably wouldn't object.
>>> 
>>> Ok. Maybe SILControlFlowEdge?
>> 
>> A bit elaborate, but it could work.  Honestly, this is not a type I have to write out much.
> 
> How about just SILEdge?

SILEdge seems a little vague.  Also less obvious to someone who isn't thinking of the CFG as primarily a graph rather than a control-flow relationship.  But it could work.

I agree that I also don't mind just sticking with SILSuccessor.  In general, it would be good to see positive support from more than one person for this rename before agreeing to it.

John.

> 
> (Honestly I’d prefer to keep it as SILSuccessor and avoid the churn from this, but if it is important to you, I won’t object to changing it.)
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