[PATCH] D49519: [RegisterCoalescer] Delay live interval update work until the rematerialization for all the uses from the same def is done

[Wei Mi via llvm-commits]

Hi Serguei,

I cannot think of what could possibly go wrong by looking at the
stacktrace. One thing may be worthy to try is to set
-late-remat-update-threshold=0 and then try the fuzzing test, that may
expose the problem on trunk or make creating the reproducer easier.

Thanks,
Wei.

On Tue, Dec 11, 2018 at 8:23 PM Serguei Katkov via Phabricator
<reviews at reviews.llvm.org> wrote:
>
> skatkov added a comment.
>
> Hello @wmi, in our local fuzzing testing we've got the following assert:
> src/include/llvm/ADT/IntervalMap.h:630: unsigned int llvm::IntervalMapImpl::LeafNode<KeyT, ValT, N, Traits>::insertFrom(unsigned int&, unsigned int, KeyT, KeyT, ValT) [with KeyT = llvm::SlotIndex; ValT = unsigned int; unsigned int N = 9u; Traits = llvm::IntervalMapInfo<llvm::SlotIndex>]: Assertion `!Traits::stopLess(b, a) && "Invalid interval"' failed.
>
> Triage points to this patch. Revert of this patch eliminates an assert. Also if I specify -late-remat-update-threshold=100000 test also passes.
> Unfortunately at this moment I cannot create a LLVM reproducer for this bug. Also This bug is not reproducible on the current trunk however I have a suspicion that it is just hided not fixed.
> I continue investigation.
>
> However if you have some insides or suggestion what it could be or what other commits could fix that bug, could you please share it, it would probably save me a lot of time to narrowing it down.
>
> The stack trace of the crash looks like:
> #0  0x00007ffff700c5d7 in raise () from /lib64/libc.so.6
> #1  0x00007ffff700dcc8 in abort () from /lib64/libc.so.6
> #2  0x00007ffff7005546 in __assert_fail_base () from /lib64/libc.so.6
> #3  0x00007ffff70055f2 in __assert_fail () from /lib64/libc.so.6
> #4  0x00007ffff13b334f in llvm::IntervalMapImpl::LeafNode<llvm::SlotIndex, unsigned int, 9u, llvm::IntervalMapInfo<llvm::SlotIndex> >::insertFrom (this=this at entry=0x7fff4811c0b8, Pos=@0x7fff5d8d4920: 2,
>
>   Size=2, a=..., a at entry=..., b=..., y=<optimized out>) at include/llvm/ADT/IntervalMap.h:630
>
> #5  0x00007ffff13bd56d in llvm::IntervalMap<llvm::SlotIndex, unsigned int, 9u, llvm::IntervalMapInfo<llvm::SlotIndex> >::insert (this=this at entry=0x7fff4811c0b8, a=a at entry=..., b=..., b at entry=...,
>
>   y=<optimized out>) at include/llvm/ADT/IntervalMap.h:1092
>
> #6  0x00007ffff13bd8ef in llvm::SplitEditor::useIntv (this=this at entry=0x7fff4811bff0, Start=Start at entry=..., End=...)
>
>   at lib/CodeGen/SplitKit.cpp:754
>
> #7  0x00007ffff13beeee in llvm::SplitEditor::splitSingleBlock (this=0x7fff4811bff0, BI=...) at lib/CodeGen/SplitKit.cpp:1580
> #8  0x00007ffff13297c7 in splitAroundRegion (UsedCands=..., LREdit=..., this=0x7fff482fd010)
>
>   at lib/CodeGen/RegAllocGreedy.cpp:1685
>
> #9  (anonymous namespace)::RAGreedy::doRegionSplit (this=0x7fff482fd010, VirtReg=..., BestCand=6, HasCompact=<optimized out>, NewVRegs=...)
>
>   at lib/CodeGen/RegAllocGreedy.cpp:1968
>
> #10 0x00007ffff1335b49 in tryRegionSplit (NewVRegs=..., Order=..., VirtReg=..., this=<optimized out>)
>
>   at lib/CodeGen/RegAllocGreedy.cpp:1832
>
> #11 trySplit (NewVRegs=..., Order=..., VirtReg=..., this=<optimized out>) at lib/CodeGen/RegAllocGreedy.cpp:2453
> #12 (anonymous namespace)::RAGreedy::selectOrSplitImpl (this=0x7fff482fd010, VirtReg=..., NewVRegs=..., FixedRegisters=..., Depth=1, Depth at entry=0)
>
>   at lib/CodeGen/RegAllocGreedy.cpp:3052
>
> #13 0x00007ffff1335f77 in (anonymous namespace)::RAGreedy::selectOrSplit (this=0x7fff482fd010, VirtReg=..., NewVRegs=...)
>
>   at lib/CodeGen/RegAllocGreedy.cpp:2732
>
> #14 0x00007ffff131905e in llvm::RegAllocBase::allocatePhysRegs (this=0x7fff482fd078, this at entry=0x7ffff3e19006 <llvm::MachineModuleInfo::ID>)
>
>   at lib/CodeGen/RegAllocBase.cpp:113
>
> #15 0x00007ffff132f7b1 in (anonymous namespace)::RAGreedy::runOnMachineFunction (this=0x7fff482fd010, mf=...)
>
>   at lib/CodeGen/RegAllocGreedy.cpp:3207
>
> #16 0x00007ffff123b6a5 in llvm::MachineFunctionPass::runOnFunction (this=0x7fff482fd010, F=...)
>
>   at lib/CodeGen/MachineFunctionPass.cpp:61
>
> #17 0x00007ffff1061957 in llvm::FPPassManager::runOnFunction (this=0x7fff480bd530, F=...) at lib/IR/LegacyPassManager.cpp:1586
>
>
> Repository:
>   rL LLVM
>
> CHANGES SINCE LAST ACTION
>   https://reviews.llvm.org/D49519/new/
>
> https://reviews.llvm.org/D49519
>
>
>