diff --git a/llvm/lib/CodeGen/MachineScheduler.cpp b/llvm/lib/CodeGen/MachineScheduler.cpp index 55b007533861..92fd3edf9236 100644 --- a/llvm/lib/CodeGen/MachineScheduler.cpp +++ b/llvm/lib/CodeGen/MachineScheduler.cpp @@ -1580,34 +1580,48 @@ void BaseMemOpClusterMutation::clusterNeighboringMemOps( return; llvm::sort(MemOpRecords); + + // At this point, `MemOpRecords` array must hold atleast two mem ops. Try to + // cluster mem ops collected within `MemOpRecords` array. unsigned ClusterLength = 1; for (unsigned Idx = 0, End = MemOpRecords.size(); Idx < (End - 1); ++Idx) { - SUnit *SUa = MemOpRecords[Idx].SU; - SUnit *SUb = MemOpRecords[Idx+1].SU; - if (TII->shouldClusterMemOps(MemOpRecords[Idx].BaseOps, - MemOpRecords[Idx + 1].BaseOps, - ClusterLength + 1)) { - if (SUa->NodeNum > SUb->NodeNum) - std::swap(SUa, SUb); - if (DAG->addEdge(SUb, SDep(SUa, SDep::Cluster))) { - LLVM_DEBUG(dbgs() << "Cluster ld/st SU(" << SUa->NodeNum << ") - SU(" - << SUb->NodeNum << ")\n"); - // Copy successor edges from SUa to SUb. Interleaving computation - // dependent on SUa can prevent load combining due to register reuse. - // Predecessor edges do not need to be copied from SUb to SUa since - // nearby loads should have effectively the same inputs. - for (const SDep &Succ : SUa->Succs) { - if (Succ.getSUnit() == SUb) - continue; - LLVM_DEBUG(dbgs() - << " Copy Succ SU(" << Succ.getSUnit()->NodeNum << ")\n"); - DAG->addEdge(Succ.getSUnit(), SDep(SUb, SDep::Artificial)); - } - ++ClusterLength; - } else - ClusterLength = 1; - } else + // Decision to cluster mem ops is taken based on target dependent logic + auto MemOpa = MemOpRecords[Idx]; + auto MemOpb = MemOpRecords[Idx + 1]; + ++ClusterLength; + if (!TII->shouldClusterMemOps(MemOpa.BaseOps, MemOpb.BaseOps, + ClusterLength)) { + // Current mem ops pair could not be clustered, reset cluster length, and + // go to next pair ClusterLength = 1; + continue; + } + + SUnit *SUa = MemOpa.SU; + SUnit *SUb = MemOpb.SU; + if (SUa->NodeNum > SUb->NodeNum) + std::swap(SUa, SUb); + + // FIXME: Is this check really required? + if (!DAG->addEdge(SUb, SDep(SUa, SDep::Cluster))) { + ClusterLength = 1; + continue; + } + + LLVM_DEBUG(dbgs() << "Cluster ld/st SU(" << SUa->NodeNum << ") - SU(" + << SUb->NodeNum << ")\n"); + + // Copy successor edges from SUa to SUb. Interleaving computation + // dependent on SUa can prevent load combining due to register reuse. + // Predecessor edges do not need to be copied from SUb to SUa since + // nearby loads should have effectively the same inputs. + for (const SDep &Succ : SUa->Succs) { + if (Succ.getSUnit() == SUb) + continue; + LLVM_DEBUG(dbgs() << " Copy Succ SU(" << Succ.getSUnit()->NodeNum + << ")\n"); + DAG->addEdge(Succ.getSUnit(), SDep(SUb, SDep::Artificial)); + } } }