1 //===-- lib/CodeGen/GlobalISel/GICombiner.cpp -----------------------===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 // 10 // This file constains common code to combine machine functions at generic 11 // level. 12 //===----------------------------------------------------------------------===// 13 14 #include "llvm/CodeGen/GlobalISel/Combiner.h" 15 #include "llvm/CodeGen/GlobalISel/CombinerInfo.h" 16 #include "llvm/CodeGen/GlobalISel/MachineIRBuilder.h" 17 #include "llvm/CodeGen/MachineOptimizationRemarkEmitter.h" 18 #include "llvm/CodeGen/GlobalISel/GISelWorkList.h" 19 #include "llvm/ADT/PostOrderIterator.h" 20 #include "llvm/CodeGen/GlobalISel/Utils.h" 21 #include "llvm/CodeGen/MachineRegisterInfo.h" 22 #include "llvm/Support/Debug.h" 23 24 #define DEBUG_TYPE "gi-combiner" 25 26 using namespace llvm; 27 28 namespace { 29 /// This class acts as the glue the joins the CombinerHelper to the overall 30 /// Combine algorithm. The CombinerHelper is intended to report the 31 /// modifications it makes to the MIR to the CombinerChangeObserver and the 32 /// observer subclass will act on these events. In this case, instruction 33 /// erasure will cancel any future visits to the erased instruction and 34 /// instruction creation will schedule that instruction for a future visit. 35 /// Other Combiner implementations may require more complex behaviour from 36 /// their CombinerChangeObserver subclass. 37 class WorkListMaintainer : public CombinerChangeObserver { 38 using WorkListTy = GISelWorkList<512>; 39 WorkListTy &WorkList; 40 41 public: 42 WorkListMaintainer(WorkListTy &WorkList) : WorkList(WorkList) {} 43 virtual ~WorkListMaintainer() {} 44 45 void erasedInstr(MachineInstr &MI) override { 46 LLVM_DEBUG(dbgs() << "Erased: "; MI.print(dbgs()); dbgs() << "\n"); 47 WorkList.remove(&MI); 48 } 49 void createdInstr(MachineInstr &MI) override { 50 LLVM_DEBUG(dbgs() << "Created: "; MI.print(dbgs()); dbgs() << "\n"); 51 WorkList.insert(&MI); 52 } 53 }; 54 } 55 56 Combiner::Combiner(CombinerInfo &Info, const TargetPassConfig *TPC) 57 : CInfo(Info), TPC(TPC) { 58 (void)this->TPC; // FIXME: Remove when used. 59 } 60 61 bool Combiner::combineMachineInstrs(MachineFunction &MF) { 62 // If the ISel pipeline failed, do not bother running this pass. 63 // FIXME: Should this be here or in individual combiner passes. 64 if (MF.getProperties().hasProperty( 65 MachineFunctionProperties::Property::FailedISel)) 66 return false; 67 68 MRI = &MF.getRegInfo(); 69 Builder.setMF(MF); 70 71 LLVM_DEBUG(dbgs() << "Generic MI Combiner for: " << MF.getName() << '\n'); 72 73 MachineOptimizationRemarkEmitter MORE(MF, /*MBFI=*/nullptr); 74 75 bool MFChanged = false; 76 bool Changed; 77 78 do { 79 // Collect all instructions. Do a post order traversal for basic blocks and 80 // insert with list bottom up, so while we pop_back_val, we'll traverse top 81 // down RPOT. 82 Changed = false; 83 GISelWorkList<512> WorkList; 84 WorkListMaintainer Observer(WorkList); 85 for (MachineBasicBlock *MBB : post_order(&MF)) { 86 if (MBB->empty()) 87 continue; 88 for (auto MII = MBB->rbegin(), MIE = MBB->rend(); MII != MIE;) { 89 MachineInstr *CurMI = &*MII; 90 ++MII; 91 // Erase dead insts before even adding to the list. 92 if (isTriviallyDead(*CurMI, *MRI)) { 93 LLVM_DEBUG(dbgs() << *CurMI << "Is dead; erasing.\n"); 94 CurMI->eraseFromParentAndMarkDBGValuesForRemoval(); 95 continue; 96 } 97 WorkList.insert(CurMI); 98 } 99 } 100 // Main Loop. Process the instructions here. 101 while (!WorkList.empty()) { 102 MachineInstr *CurrInst = WorkList.pop_back_val(); 103 LLVM_DEBUG(dbgs() << "Try combining " << *CurrInst << "\n";); 104 Changed |= CInfo.combine(Observer, *CurrInst, Builder); 105 } 106 MFChanged |= Changed; 107 } while (Changed); 108 109 return MFChanged; 110 } 111