[LLVMdev] Heads up! Planning to remove old vector shuffle lowering this week...

[Simon Pilgrim]

On 5 Jan 2015, at 22:30, Quentin Colombet <qcolombet at apple.com> wrote:

>> On Jan 4, 2015, at 4:25 PM, Simon Pilgrim <llvm-dev at redking.me.uk> wrote:
>> 
>> On 4 Jan 2015, at 23:30, Chandler Carruth <chandlerc at gmail.com> wrote:
>> 
>>> One question -- do you see any regressions that need fixing first? I don't see any, but I'm curious about others. The silence on this thread didn't inspire confidence, but perhaps its just that nothing is broken with the new stuff?
>> 
>> No notable regressions, I’m seeing different code but mostly for the better - although there are a number of vec256 shuffles (mostly lower/upper crossings) that are rather poor (I think Quentin raised bugs on a couple of these) - but the old system could be a lot worse.
> 
> I think Simon talks about PR21943, but this should not hold for moving forward.

PR21138 was the one that I was thinking of but PR21943 is a regression too.

PR21137 covers examples of the domain crossing issues I mentioned. If people are open to putting in specific logic for shuffles in the get/set ExecutionDomain code (and not just the basic matching tables) then a fix would be relatively trivial.

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