Thank you for the patience – indeed it took me some time to prepare the proper patch, which is now ready for review.
It comes without a regression test, as the only observable change is performance improvement of the analysis. From: Alexander Kornienko [mailto:[email protected]] Sent: 07 August 2014 23:35 To: Artyom Skrobov Cc: [email protected] Commits Subject: Re: r214064 - Factoring DataflowWorklist out of LiveVariables and UninitializedValues analyses Any news here? This keeps biting us. Maybe you can apply this patch first and work on a better solution after that? On Tue, Aug 5, 2014 at 6:23 PM, Artyom Skrobov <[email protected]> wrote: So, the simplest way to restore the original behaviour seems to be Index: lib/Analysis/LiveVariables.cpp =================================================================== --- lib/Analysis/LiveVariables.cpp (revision 214183) +++ lib/Analysis/LiveVariables.cpp (working copy) @@ -451,6 +451,7 @@ // Construct the dataflow worklist. Enqueue the exit block as the // start of the analysis. DataflowWorklist worklist(*cfg, AC); + worklist.quick_hack(); llvm::BitVector everAnalyzedBlock(cfg->getNumBlockIDs()); // FIXME: we should enqueue using post order. Index: include/clang/Analysis/Analyses/DataflowWorklist.h =================================================================== --- include/clang/Analysis/Analyses/DataflowWorklist.h (revision 214183) +++ include/clang/Analysis/Analyses/DataflowWorklist.h (working copy) @@ -53,6 +53,7 @@ const CFGBlock *dequeue(); void sortWorklist(); + void quick_hack() { enqueuedBlocks.reset(); PO_I = PO_E; } }; } // end clang namespace This has the effect of disabling the fallback post-order iteration. The reason for the performance regression, however, is related to the iteration order over the CFG: UninitializedValues expects to use the default (i.e. reverse) PostOrderCFGView iteration, whereas LiveVariables expects the opposite order, corresponding to using llvm::GraphTraits<llvm::Inverse<const CFG*> > > as the last parameter in typedef po_iterator. I’m currently thinking of a proper solution which would allow using PostOrderCFGView for iteration in either direction. From: Alexander Kornienko [mailto:[email protected]] Sent: 05 August 2014 12:30 To: Artyom Skrobov Cc: [email protected] Commits Subject: Re: r214064 - Factoring DataflowWorklist out of LiveVariables and UninitializedValues analyses On another file from the same project the difference in my setup is 2 minutes before the patch vs. 50+ hours (I terminated the analyzer before it finished) after the patch. So it's a rather bad performance regression.
DataflowWorklistInverse.patch
Description: Binary data
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