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Both approaches are not exclusive. I would even think it makes sense to have a pre-split pass to prepare the graph, with a global view, and later on use use trySplit (or an equivalent) to handle the local coloring issues. From: Quentin Colombet [mailto:qcolombet at apple.com] Sent: 09 March 2015 23:08 To: Lang Hames Cc: Jonas Paulsson; llvmdev at cs.uiuc.edu; Arnaud De Grandmaison Subject: Re: PBQP spilling Hi Lang, Thanks for the clarifications....

...pdating it when splitting. As I see it, there are two logical places to integrate splitting into PBQP: 1) Split during spilling -- If a PBQP solution selects the spill option for a node, rather than spill immediately, split the interval first. This seems (superficially) like an opportunity to use trySplit, but I haven't looked at the code for it. If trySplit is looking at the existing allocation state to make those decisions we may have trouble: In RAGreedy some "current" colorings may be revisited, but during spilling in PBQP we're guaranteed that *all* colorings will be revisite...

...than optimal coloring...". I would then think that any register allocation algorithm should benefit from this, but find that only RegAllocGreedy is doing live range splitting, and that the code for doing this is local to that allocator. I would like to suggest a refactoring to make RAGreedy::trySplit() and its sub functions callable from any register allocator. Perhaps part of SplitEditor? What do you think about this? /Jonas From: Arnaud A. de Grandmaison [mailto:arnaud.degrandmaison at arm.com] Sent: den 4 mars 2015 15:43 To: Jonas Paulsson; Lang Hames Cc: llvmdev at cs.uiuc.edu Subject:...

Hi, I would like to ask about PBQPs use of InlineSpiller. The code output when using PBQP gets a lot bigger compared to when using RegAllocGreedy. PBQP does not split the live intervals, and a lot more (often redundant) reload instructions are emitted as a result, it seems. I wonder why this is, and if there are any plans to improve on this point? /Jonas Paulsson -------------- next part