llvm/lib/CodeGen/GlobalISel/Combiner.cpp

   1 //===-- lib/CodeGen/GlobalISel/Combiner.cpp -------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This file constains common code to combine machine functions at generic
  10 // level.
  11 //===----------------------------------------------------------------------===//
  12
  13 #include "llvm/CodeGen/GlobalISel/Combiner.h"
  14 #include "llvm/ADT/PostOrderIterator.h"
  15 #include "llvm/ADT/SetVector.h"
  16 #include "llvm/CodeGen/GlobalISel/CSEInfo.h"
  17 #include "llvm/CodeGen/GlobalISel/CSEMIRBuilder.h"
  18 #include "llvm/CodeGen/GlobalISel/CombinerInfo.h"
  19 #include "llvm/CodeGen/GlobalISel/GISelChangeObserver.h"
  20 #include "llvm/CodeGen/GlobalISel/GISelWorkList.h"
  21 #include "llvm/CodeGen/GlobalISel/MachineIRBuilder.h"
  22 #include "llvm/CodeGen/GlobalISel/Utils.h"
  23 #include "llvm/CodeGen/MachineOptimizationRemarkEmitter.h"
  24 #include "llvm/Support/Debug.h"
  25
  26 #define DEBUG_TYPE "gi-combiner"
  27
  28 using namespace llvm;
  29
  30 namespace llvm {
  31 cl::OptionCategory GICombinerOptionCategory(
  32     "GlobalISel Combiner",
  33     "Control the rules which are enabled. These options all take a comma "
  34     "separated list of rules to disable and may be specified by number "
  35     "or number range (e.g. 1-10)."
  36 #ifndef NDEBUG
  37     " They may also be specified by name."
  38 #endif
  39 );
  40 } // end namespace llvm
  41
  42 /// This class acts as the glue the joins the CombinerHelper to the overall
  43 /// Combine algorithm. The CombinerHelper is intended to report the
  44 /// modifications it makes to the MIR to the GISelChangeObserver and the
  45 /// observer subclass will act on these events. In this case, instruction
  46 /// erasure will cancel any future visits to the erased instruction and
  47 /// instruction creation will schedule that instruction for a future visit.
  48 /// Other Combiner implementations may require more complex behaviour from
  49 /// their GISelChangeObserver subclass.
  50 class Combiner::WorkListMaintainer : public GISelChangeObserver {
  51   using WorkListTy = GISelWorkList<512>;
  52   WorkListTy &WorkList;
  53   /// The instructions that have been created but we want to report once they
  54   /// have their operands. This is only maintained if debug output is requested.
  55 #ifndef NDEBUG
  56   SetVector<const MachineInstr *> CreatedInstrs;
  57 #endif
  58
  59 public:
  60   WorkListMaintainer(WorkListTy &WorkList) : WorkList(WorkList) {}
  61   virtual ~WorkListMaintainer() = default;
  62
  63   void erasingInstr(MachineInstr &MI) override {
  64     LLVM_DEBUG(dbgs() << "Erasing: " << MI << "\n");
  65     WorkList.remove(&MI);
  66   }
  67   void createdInstr(MachineInstr &MI) override {
  68     LLVM_DEBUG(dbgs() << "Creating: " << MI << "\n");
  69     WorkList.insert(&MI);
  70     LLVM_DEBUG(CreatedInstrs.insert(&MI));
  71   }
  72   void changingInstr(MachineInstr &MI) override {
  73     LLVM_DEBUG(dbgs() << "Changing: " << MI << "\n");
  74     WorkList.insert(&MI);
  75   }
  76   void changedInstr(MachineInstr &MI) override {
  77     LLVM_DEBUG(dbgs() << "Changed: " << MI << "\n");
  78     WorkList.insert(&MI);
  79   }
  80
  81   void reportFullyCreatedInstrs() {
  82     LLVM_DEBUG(for (const auto *MI
  83                     : CreatedInstrs) {
  84       dbgs() << "Created: ";
  85       MI->print(dbgs());
  86     });
  87     LLVM_DEBUG(CreatedInstrs.clear());
  88   }
  89 };
  90
  91 Combiner::Combiner(MachineFunction &MF, CombinerInfo &CInfo,
  92                    const TargetPassConfig *TPC, GISelKnownBits *KB,
  93                    GISelCSEInfo *CSEInfo)
  94     : Builder(CSEInfo ? std::make_unique<CSEMIRBuilder>()
  95                       : std::make_unique<MachineIRBuilder>()),
  96       WLObserver(std::make_unique<WorkListMaintainer>(WorkList)),
  97       ObserverWrapper(std::make_unique<GISelObserverWrapper>()), CInfo(CInfo),
  98       Observer(*ObserverWrapper), B(*Builder), MF(MF), MRI(MF.getRegInfo()),
  99       KB(KB), TPC(TPC), CSEInfo(CSEInfo) {
 100   (void)this->TPC; // FIXME: Remove when used.
 101
 102   // Setup builder.
 103   B.setMF(MF);
 104   if (CSEInfo)
 105     B.setCSEInfo(CSEInfo);
 106
 107   // Setup observer.
 108   ObserverWrapper->addObserver(WLObserver.get());
 109   if (CSEInfo)
 110     ObserverWrapper->addObserver(CSEInfo);
 111
 112   B.setChangeObserver(*ObserverWrapper);
 113 }
 114
 115 Combiner::~Combiner() = default;
 116
 117 bool Combiner::combineMachineInstrs() {
 118   // If the ISel pipeline failed, do not bother running this pass.
 119   // FIXME: Should this be here or in individual combiner passes.
 120   if (MF.getProperties().hasProperty(
 121           MachineFunctionProperties::Property::FailedISel))
 122     return false;
 123
 124   // We can't call this in the constructor because the derived class is
 125   // uninitialized at that time.
 126   if (!HasSetupMF) {
 127     HasSetupMF = true;
 128     setupMF(MF, KB);
 129   }
 130
 131   LLVM_DEBUG(dbgs() << "Generic MI Combiner for: " << MF.getName() << '\n');
 132
 133   MachineOptimizationRemarkEmitter MORE(MF, /*MBFI=*/nullptr);
 134
 135   bool MFChanged = false;
 136   bool Changed;
 137
 138   do {
 139     WorkList.clear();
 140
 141     // Collect all instructions. Do a post order traversal for basic blocks and
 142     // insert with list bottom up, so while we pop_back_val, we'll traverse top
 143     // down RPOT.
 144     Changed = false;
 145
 146     RAIIDelegateInstaller DelInstall(MF, ObserverWrapper.get());
 147     for (MachineBasicBlock *MBB : post_order(&MF)) {
 148       for (MachineInstr &CurMI :
 149            llvm::make_early_inc_range(llvm::reverse(*MBB))) {
 150         // Erase dead insts before even adding to the list.
 151         if (isTriviallyDead(CurMI, MRI)) {
 152           LLVM_DEBUG(dbgs() << CurMI << "Is dead; erasing.\n");
 153           llvm::salvageDebugInfo(MRI, CurMI);
 154           CurMI.eraseFromParent();
 155           continue;
 156         }
 157         WorkList.deferred_insert(&CurMI);
 158       }
 159     }
 160     WorkList.finalize();
 161     // Main Loop. Process the instructions here.
 162     while (!WorkList.empty()) {
 163       MachineInstr *CurrInst = WorkList.pop_back_val();
 164       LLVM_DEBUG(dbgs() << "\nTry combining " << *CurrInst;);
 165       Changed |= tryCombineAll(*CurrInst);
 166       WLObserver->reportFullyCreatedInstrs();
 167     }
 168     MFChanged |= Changed;
 169   } while (Changed);
 170
 171 #ifndef NDEBUG
 172   if (CSEInfo) {
 173     if (auto E = CSEInfo->verify()) {
 174       errs() << E << '\n';
 175       assert(false && "CSEInfo is not consistent. Likely missing calls to "
 176                       "observer on mutations.");
 177     }
 178   }
 179 #endif
 180   return MFChanged;
 181 }