contrib/llvm/include/llvm/CodeGen/TailDuplicator.h

   1 //===- llvm/CodeGen/TailDuplicator.h ----------------------------*- C++ -*-===//
   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 defines the TailDuplicator class. Used by the
  11 // TailDuplication pass, and MachineBlockPlacement.
  12 //
  13 //===----------------------------------------------------------------------===//
  14
  15 #ifndef LLVM_CODEGEN_TAILDUPLICATOR_H
  16 #define LLVM_CODEGEN_TAILDUPLICATOR_H
  17
  18 #include "llvm/ADT/DenseMap.h"
  19 #include "llvm/ADT/DenseSet.h"
  20 #include "llvm/ADT/SetVector.h"
  21 #include "llvm/ADT/SmallVector.h"
  22 #include "llvm/ADT/STLExtras.h"
  23 #include "llvm/CodeGen/RegisterScavenging.h"
  24 #include "llvm/Support/CommandLine.h"
  25 #include "llvm/Target/TargetInstrInfo.h"
  26 #include "llvm/Target/TargetSubtargetInfo.h"
  27 #include <utility>
  28 #include <vector>
  29
  30 namespace llvm {
  31
  32 class MachineBasicBlock;
  33 class MachineBranchProbabilityInfo;
  34 class MachineFunction;
  35 class MachineInstr;
  36 class MachineModuleInfo;
  37 class MachineRegisterInfo;
  38 class TargetRegisterInfo;
  39
  40 /// Utility class to perform tail duplication.
  41 class TailDuplicator {
  42   const TargetInstrInfo *TII;
  43   const TargetRegisterInfo *TRI;
  44   const MachineBranchProbabilityInfo *MBPI;
  45   const MachineModuleInfo *MMI;
  46   MachineRegisterInfo *MRI;
  47   MachineFunction *MF;
  48   bool PreRegAlloc;
  49   bool LayoutMode;
  50   unsigned TailDupSize;
  51
  52   // A list of virtual registers for which to update SSA form.
  53   SmallVector<unsigned, 16> SSAUpdateVRs;
  54
  55   // For each virtual register in SSAUpdateVals keep a list of source virtual
  56   // registers.
  57   using AvailableValsTy = std::vector<std::pair<MachineBasicBlock *, unsigned>>;
  58
  59   DenseMap<unsigned, AvailableValsTy> SSAUpdateVals;
  60
  61 public:
  62   /// Prepare to run on a specific machine function.
  63   /// @param MF - Function that will be processed
  64   /// @param MBPI - Branch Probability Info. Used to propagate correct
  65   ///     probabilities when modifying the CFG.
  66   /// @param LayoutMode - When true, don't use the existing layout to make
  67   ///     decisions.
  68   /// @param TailDupSize - Maxmimum size of blocks to tail-duplicate. Zero
  69   ///     default implies using the command line value TailDupSize.
  70   void initMF(MachineFunction &MF,
  71               const MachineBranchProbabilityInfo *MBPI,
  72               bool LayoutMode, unsigned TailDupSize = 0);
  73
  74   bool tailDuplicateBlocks();
  75   static bool isSimpleBB(MachineBasicBlock *TailBB);
  76   bool shouldTailDuplicate(bool IsSimple, MachineBasicBlock &TailBB);
  77
  78   /// Returns true if TailBB can successfully be duplicated into PredBB
  79   bool canTailDuplicate(MachineBasicBlock *TailBB, MachineBasicBlock *PredBB);
  80
  81   /// Tail duplicate a single basic block into its predecessors, and then clean
  82   /// up.
  83   /// If \p DuplicatePreds is not null, it will be updated to contain the list
  84   /// of predecessors that received a copy of \p MBB.
  85   /// If \p RemovalCallback is non-null. It will be called before MBB is
  86   /// deleted.
  87   bool tailDuplicateAndUpdate(
  88       bool IsSimple, MachineBasicBlock *MBB,
  89       MachineBasicBlock *ForcedLayoutPred,
  90       SmallVectorImpl<MachineBasicBlock*> *DuplicatedPreds = nullptr,
  91       function_ref<void(MachineBasicBlock *)> *RemovalCallback = nullptr);
  92
  93 private:
  94   using RegSubRegPair = TargetInstrInfo::RegSubRegPair;
  95
  96   void addSSAUpdateEntry(unsigned OrigReg, unsigned NewReg,
  97                          MachineBasicBlock *BB);
  98   void processPHI(MachineInstr *MI, MachineBasicBlock *TailBB,
  99                   MachineBasicBlock *PredBB,
 100                   DenseMap<unsigned, RegSubRegPair> &LocalVRMap,
 101                   SmallVectorImpl<std::pair<unsigned, RegSubRegPair>> &Copies,
 102                   const DenseSet<unsigned> &UsedByPhi, bool Remove);
 103   void duplicateInstruction(MachineInstr *MI, MachineBasicBlock *TailBB,
 104                             MachineBasicBlock *PredBB,
 105                             DenseMap<unsigned, RegSubRegPair> &LocalVRMap,
 106                             const DenseSet<unsigned> &UsedByPhi);
 107   void updateSuccessorsPHIs(MachineBasicBlock *FromBB, bool isDead,
 108                             SmallVectorImpl<MachineBasicBlock *> &TDBBs,
 109                             SmallSetVector<MachineBasicBlock *, 8> &Succs);
 110   bool canCompletelyDuplicateBB(MachineBasicBlock &BB);
 111   bool duplicateSimpleBB(MachineBasicBlock *TailBB,
 112                          SmallVectorImpl<MachineBasicBlock *> &TDBBs,
 113                          const DenseSet<unsigned> &RegsUsedByPhi,
 114                          SmallVectorImpl<MachineInstr *> &Copies);
 115   bool tailDuplicate(bool IsSimple,
 116                      MachineBasicBlock *TailBB,
 117                      MachineBasicBlock *ForcedLayoutPred,
 118                      SmallVectorImpl<MachineBasicBlock *> &TDBBs,
 119                      SmallVectorImpl<MachineInstr *> &Copies);
 120   void appendCopies(MachineBasicBlock *MBB,
 121                  SmallVectorImpl<std::pair<unsigned,RegSubRegPair>> &CopyInfos,
 122                  SmallVectorImpl<MachineInstr *> &Copies);
 123
 124   void removeDeadBlock(
 125       MachineBasicBlock *MBB,
 126       function_ref<void(MachineBasicBlock *)> *RemovalCallback = nullptr);
 127 };
 128
 129 } // end namespace llvm
 130
 131 #endif // LLVM_CODEGEN_TAILDUPLICATOR_H