[llvm] r360171 - [DAGCombiner] Avoid creating large tokenfactors in visitTokenFactor

Fri May 10 16:22:03 PDT 2019

Reverted in r360481. I have creduce going on the Machine InstCombiner
crash and down to "only" 7000 lines, so I think it will finish before I
leave today.

There were some crashes in other places (i.e. I don't think the bug is in
this patch, it's just revealing bugs in other places), so I'll have to see
if those reduce to the same thing -- I'll check that out next week.

Sorry for the inconvenience!

*From: *Jordan Rupprecht <rupprecht at google.com>
*Date: *Fri, May 10, 2019 at 3:28 PM
*To: *Florian Hahn
*Cc: *llvm-commits

Here's the full crash (minus the boiler plate) for the one in Machine
> InstCombiner:
>  #9 0x00007fb8d52cf5d2 (anonymous
> namespace)::DataDep::DataDep(llvm::MachineRegisterInfo const*, unsigned
> int, unsigned int)
> ${LLVM_SRC}/llvm/lib/CodeGen/MachineTraceMetrics.cpp:640:13
> #10 0x00007fb8d52cb644 getDataDeps(llvm::MachineInstr const&,
> llvm::SmallVectorImpl<(anonymous namespace)::DataDep>&,
> llvm::MachineRegisterInfo const*)
> ${LLVM_SRC}/llvm/lib/CodeGen/MachineTraceMetrics.cpp:672:22
> #11 0x00007fb8d52cb064
> llvm::MachineTraceMetrics::Ensemble::updateDepth(llvm::MachineTraceMetrics::TraceBlockInfo&,
> llvm::MachineInstr const&, llvm::SparseSet<llvm::LiveRegUnit,
> llvm::identity<unsigned int>, unsigned char>&)
> ${LLVM_SRC}/llvm/lib/CodeGen/MachineTraceMetrics.cpp:788:12
> #12 0x00007fb8d52cc300
> llvm::MachineTraceMetrics::Ensemble::computeInstrDepths(llvm::MachineBasicBlock
> const*) ${LLVM_SRC}/llvm/lib/CodeGen/MachineTraceMetrics.cpp:883:28
> #13 0x00007fb8d52cde9e
> llvm::MachineTraceMetrics::Ensemble::getTrace(llvm::MachineBasicBlock
> const*) ${LLVM_SRC}/llvm/lib/CodeGen/MachineTraceMetrics.cpp:1166:8
> #14 0x00007fb8d515ead4 (anonymous
> namespace)::MachineCombiner::combineInstructions(llvm::MachineBasicBlock*)
> ${LLVM_SRC}/llvm/lib/CodeGen/MachineCombiner.cpp:596:59
> #15 0x00007fb8d515e342 (anonymous
> namespace)::MachineCombiner::runOnMachineFunction(llvm::MachineFunction&)
> ${LLVM_SRC}/llvm/lib/CodeGen/MachineCombiner.cpp:654:16
> #16 0x00007fb8d51bf637
> llvm::MachineFunctionPass::runOnFunction(llvm::Function&)
> ${LLVM_SRC}/llvm/lib/CodeGen/MachineFunctionPass.cpp:73:8
> #17 0x00007fb8d47dd759 llvm::FPPassManager::runOnFunction(llvm::Function&)
> ${LLVM_SRC}/llvm/lib/IR/LegacyPassManager.cpp:1648:23
> #18 0x00007fb8d47ddb9f llvm::FPPassManager::runOnModule(llvm::Module&)
> ${LLVM_SRC}/llvm/lib/IR/LegacyPassManager.cpp:1685:16
> #19 0x00007fb8d47de305 (anonymous
> namespace)::MPPassManager::runOnModule(llvm::Module&)
> ${LLVM_SRC}/llvm/lib/IR/LegacyPassManager.cpp:1752:23
> #20 0x00007fb8d47dde45 llvm::legacy::PassManagerImpl::run(llvm::Module&)
> ${LLVM_SRC}/llvm/lib/IR/LegacyPassManager.cpp:1865:16
> #21 0x00007fb8d47de881 llvm::legacy::PassManager::run(llvm::Module&)
> ${LLVM_SRC}/llvm/lib/IR/LegacyPassManager.cpp:1896:3
> #22 0x00007fb8d117e15a (anonymous
> namespace)::EmitAssemblyHelper::EmitAssembly(clang::BackendAction,
> std::unique_ptr<llvm::raw_pwrite_stream,
> std::default_delete<llvm::raw_pwrite_stream> >)
> ${LLVM_SRC}/clang/lib/CodeGen/BackendUtil.cpp:894:3
>
>
> *From: *Jordan Rupprecht <rupprecht at google.com>
> *Date: *Fri, May 10, 2019 at 12:58 PM
> *To: *Florian Hahn
> *Cc: *llvm-commits
>
> Looks like this causes some asan/msan crashes (or in some cases, test
>> failure/miscompiles). I'll see if I can get a crash with debug+asserts
>> enabled. In release mode, it's crashing during Machine InstCombiner/Live
>> Variable Analysis for different repros.
>>
>>
>> *From: *Florian Hahn via llvm-commits <llvm-commits at lists.llvm.org>
>> *Date: *Tue, May 7, 2019 at 9:45 AM
>> *To: * <llvm-commits at lists.llvm.org>
>>
>> Author: fhahn
>>> Date: Tue May  7 09:47:27 2019
>>> New Revision: 360171
>>>
>>> URL: http://llvm.org/viewvc/llvm-project?rev=360171&view=rev
>>> Log:
>>> [DAGCombiner] Avoid creating large tokenfactors in visitTokenFactor
>>>
>>> When simplifying TokenFactors, we potentially iterate over all
>>> operands of a large number of TokenFactors. This causes quadratic
>>> compile times in some cases and the large token factors cause additional
>>> scalability problems elsewhere.
>>>
>>> This patch adds some limits to the number of nodes explored for the
>>> cases mentioned above.
>>>
>>> Reviewers: niravd, spatel, craig.topper
>>>
>>> Reviewed By: niravd
>>>
>>> Differential Revision: https://reviews.llvm.org/D61397
>>>
>>> Modified:
>>>     llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
>>>
>>> Modified: llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
>>> URL:
>>> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp?rev=360171&r1=360170&r2=360171&view=diff
>>>
>>> ==============================================================================
>>> --- llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp (original)
>>> +++ llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp Tue May  7
>>> 09:47:27 2019
>>> @@ -1792,8 +1792,9 @@ SDValue DAGCombiner::visitTokenFactor(SD
>>>    TFs.push_back(N);
>>>
>>>    // Iterate through token factors.  The TFs grows when new token
>>> factors are
>>> -  // encountered.
>>> -  for (unsigned i = 0; i < TFs.size(); ++i) {
>>> +  // encountered. Limit number of nodes to inline, to avoid quadratic
>>> compile
>>> +  // times.
>>> +  for (unsigned i = 0; i < TFs.size() && Ops.size() <= 2048; ++i) {
>>>      SDNode *TF = TFs[i];
>>>
>>>      // Check each of the operands.
>>>
>>>
>>> _______________________________________________
>>> llvm-commits mailing list
>>> llvm-commits at lists.llvm.org
>>> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits
>>>
>>
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