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Hi Jakob, > Out of curiosity, how are you dealing with live range splitting and > coalescing in PBQP? I know you added the LoopSplitter pass. > > For linear scan in LLVM we are going in the direction of aggressive > coalescing before allocation, and on-demand splitting during allocation. > > I know that other allocators use no early coalescing, and coalesce during > allocation. The PBQP allocator uses the aggres...

...designed to make it easier to implement custom register allocation constraints. This is a quick summary of those changes, and of the status of the PBQP allocator in general. Thanks, Lang! Out of curiosity, how are you dealing with live range splitting and coalescing in PBQP? I know you added the LoopSplitter pass. For linear scan in LLVM we are going in the direction of aggressive coalescing before allocation, and on-demand splitting during allocation. I know that other allocators use no early coalescing, and coalesce during allocation. /jakob

...n properly take a second best hint, third best hint, etc as well. > Currently the PBQP allocator does not do any splitting, however I expect that it should be easy to add support for on-demand splitting, and I'll be looking into it soon-ish. > > I haven't had time to work on the LoopSplitter recently. It looks like SplitKit has subsumed LoopSplitter's functionality. If that's the case then I can go ahead and kill off LoopSplitter. SplitKit is currently pretty broken, but I am working on fixing it. It turns out you need a good deal of logic to correctly update LiveIntervals aft...

Hi All, I've just committed some changes to the PBQP allocator which are designed to make it easier to implement custom register allocation constraints. This is a quick summary of those changes, and of the status of the PBQP allocator in general. First a quick bit of background: The PBQP allocator is based on ideas described in [1]. I implemented this algorithm (with the improved heuristic