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