[swift-dev] Renaming SILSuccessor -> SILCFGEdge

[Michael Gottesman]

> On Apr 26, 2017, at 1:44 PM, John McCall <rjmccall at apple.com> wrote:
> 
>> On Apr 26, 2017, at 4:24 PM, Michael Gottesman via swift-dev <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.

> 
> "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?

> 
> John.