forked from OSchip/llvm-project
95055d8f8b
infinite-inlining across multiple runs of the inliner by keeping a tiny history of internal-to-SCC inlining decisions. This is still a bit gross, but I don't yet have any fundamentally better ideas and numerous people are blocked on this to use new PM and ThinLTO together. The core of the idea is to detect when we are about to do an inline that has a chance of re-splitting an SCC which we have split before with a similar inlining step. That is a critical component in the inlining forming a cycle and so far detects all of the various cyclic patterns I can come up with as well as the original real-world test case (which comes from a ThinLTO build of libunwind). I've added some tests that I think really demonstrate what is going on here. They are essentially state machines that march the inliner through various steps of a cycle and check that we stop when the cycle is closed and that we actually did do inlining to form that cycle. A lot of thanks go to Eric Christopher and Sanjoy Das for the help understanding this issue and improving the test cases. The biggest "yuck" here is the layering issue -- the CGSCC pass manager is providing somewhat magical state to the inliner for it to use to make itself converge. This isn't great, but I don't honestly have a lot of better ideas yet and at least seems nicely isolated. I have tested this patch, and it doesn't block *any* inlining on the entire LLVM test suite and SPEC, so it seems sufficiently narrowly targeted to the issue at hand. We have come up with hypothetical issues that this patch doesn't cover, but so far none of them are practical and we don't have a viable solution yet that covers the hypothetical stuff, so proceeding here in the interim. Definitely an area that we will be back and revisiting in the future. Differential Revision: https://reviews.llvm.org/D36188 llvm-svn: 309784 |
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| .. | ||
| AlwaysInliner.cpp | ||
| ArgumentPromotion.cpp | ||
| BarrierNoopPass.cpp | ||
| CMakeLists.txt | ||
| ConstantMerge.cpp | ||
| CrossDSOCFI.cpp | ||
| DeadArgumentElimination.cpp | ||
| ElimAvailExtern.cpp | ||
| ExtractGV.cpp | ||
| ForceFunctionAttrs.cpp | ||
| FunctionAttrs.cpp | ||
| FunctionImport.cpp | ||
| GlobalDCE.cpp | ||
| GlobalOpt.cpp | ||
| GlobalSplit.cpp | ||
| IPConstantPropagation.cpp | ||
| IPO.cpp | ||
| InferFunctionAttrs.cpp | ||
| InlineSimple.cpp | ||
| Inliner.cpp | ||
| Internalize.cpp | ||
| LLVMBuild.txt | ||
| LoopExtractor.cpp | ||
| LowerTypeTests.cpp | ||
| MergeFunctions.cpp | ||
| PartialInlining.cpp | ||
| PassManagerBuilder.cpp | ||
| PruneEH.cpp | ||
| SampleProfile.cpp | ||
| StripDeadPrototypes.cpp | ||
| StripSymbols.cpp | ||
| ThinLTOBitcodeWriter.cpp | ||
| WholeProgramDevirt.cpp | ||