Line data    Source code

       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         157 :   WorkListMaintainer(WorkListTy &WorkList) : WorkList(WorkList) {}
      43         157 :   virtual ~WorkListMaintainer() {}
      44             : 
      45          33 :   void erasedInstr(MachineInstr &MI) override {
      46             :     LLVM_DEBUG(dbgs() << "Erased: "; MI.print(dbgs()); dbgs() << "\n");
      47          33 :     WorkList.remove(&MI);
      48          33 :   }
      49          15 :   void createdInstr(MachineInstr &MI) override {
      50             :     LLVM_DEBUG(dbgs() << "Created: "; MI.print(dbgs()); dbgs() << "\n");
      51          15 :     WorkList.insert(&MI);
      52          15 :   }
      53             : };
      54             : }
      55             : 
      56         128 : Combiner::Combiner(CombinerInfo &Info, const TargetPassConfig *TPC)
      57         128 :     : CInfo(Info), TPC(TPC) {
      58             :   (void)this->TPC; // FIXME: Remove when used.
      59         128 : }
      60             : 
      61         128 : 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         128 :   if (MF.getProperties().hasProperty(
      65             :           MachineFunctionProperties::Property::FailedISel))
      66             :     return false;
      67             : 
      68         128 :   MRI = &MF.getRegInfo();
      69         128 :   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         157 :   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         157 :     GISelWorkList<512> WorkList;
      84             :     WorkListMaintainer Observer(WorkList);
      85         551 :     for (MachineBasicBlock *MBB : post_order(&MF)) {
      86         237 :       if (MBB->empty())
      87             :         continue;
      88        2098 :       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        1863 :         if (isTriviallyDead(*CurMI, *MRI)) {
      93             :           LLVM_DEBUG(dbgs() << *CurMI << "Is dead; erasing.\n");
      94          24 :           CurMI->eraseFromParentAndMarkDBGValuesForRemoval();
      95          24 :           continue;
      96             :         }
      97        1839 :         WorkList.insert(CurMI);
      98             :       }
      99             :     }
     100             :     // Main Loop. Process the instructions here.
     101        1978 :     while (!WorkList.empty()) {
     102        1821 :       MachineInstr *CurrInst = WorkList.pop_back_val();
     103             :       LLVM_DEBUG(dbgs() << "Try combining " << *CurrInst << "\n";);
     104        1821 :       Changed |= CInfo.combine(Observer, *CurrInst, Builder);
     105             :     }
     106         157 :     MFChanged |= Changed;
     107             :   } while (Changed);
     108             : 
     109             :   return MFChanged;
     110             : }