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

Fri May 10 15:28:16 PDT 2019

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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