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b19a7319a9
LCSSA from it caused a crasher with the LoopUnroll pass. This crasher is really nasty. We destroy LCSSA form in a suprising way. When unrolling a loop into an outer loop, we not only need to restore LCSSA form for the outer loop, but for all children of the outer loop. This is somewhat obvious in retrospect, but hey! While this seems pretty heavy-handed, it's not that bad. Fundamentally, we only do this when we unroll a loop, which is already a heavyweight operation. We're unrolling all of these hypothetical inner loops as well, so their size and complexity is already on the critical path. This is just adding another pass over them to re-canonicalize. I have a test case from PR18616 that is great for reproducing this, but pretty useless to check in as it relies on many 10s of nested empty loops that get unrolled and deleted in just the right order. =/ What's worse is that investigating this has exposed another source of failure that is likely to be even harder to test. I'll try to come up with test cases for these fixes, but I want to get the fixes into the tree first as they're causing crashes in the wild. llvm-svn: 200273 |
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| .. | ||
| ASanStackFrameLayout.h | ||
| BasicBlockUtils.h | ||
| BuildLibCalls.h | ||
| BypassSlowDivision.h | ||
| Cloning.h | ||
| CmpInstAnalysis.h | ||
| CodeExtractor.h | ||
| GlobalStatus.h | ||
| IntegerDivision.h | ||
| Local.h | ||
| LoopUtils.h | ||
| ModuleUtils.h | ||
| PromoteMemToReg.h | ||
| SimplifyIndVar.h | ||
| SimplifyLibCalls.h | ||
| SpecialCaseList.h | ||
| SSAUpdater.h | ||
| SSAUpdaterImpl.h | ||
| UnifyFunctionExitNodes.h | ||
| UnrollLoop.h | ||
| ValueMapper.h | ||