lib/CodeGen/CriticalAntiDepBreaker.h

   1 //=- llvm/CodeGen/CriticalAntiDepBreaker.h - Anti-Dep Support -*- 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 implements the CriticalAntiDepBreaker class, which
  11 // implements register anti-dependence breaking along a blocks
  12 // critical path during post-RA scheduler.
  13 //
  14 //===----------------------------------------------------------------------===//
  15
  16 #ifndef LLVM_CODEGEN_CRITICALANTIDEPBREAKER_H
  17 #define LLVM_CODEGEN_CRITICALANTIDEPBREAKER_H
  18
  19 #include "AntiDepBreaker.h"
  20 #include "llvm/CodeGen/MachineBasicBlock.h"
  21 #include "llvm/CodeGen/MachineFrameInfo.h"
  22 #include "llvm/CodeGen/MachineFunction.h"
  23 #include "llvm/CodeGen/MachineRegisterInfo.h"
  24 #include "llvm/CodeGen/ScheduleDAG.h"
  25 #include "llvm/ADT/BitVector.h"
  26 #include "llvm/ADT/SmallSet.h"
  27 #include <map>
  28
  29 namespace llvm {
  30 class TargetInstrInfo;
  31 class TargetRegisterInfo;
  32
  33   class CriticalAntiDepBreaker : public AntiDepBreaker {
  34     MachineFunction& MF;
  35     MachineRegisterInfo &MRI;
  36     const TargetInstrInfo *TII;
  37     const TargetRegisterInfo *TRI;
  38
  39     /// AllocatableSet - The set of allocatable registers.
  40     /// We'll be ignoring anti-dependencies on non-allocatable registers,
  41     /// because they may not be safe to break.
  42     const BitVector AllocatableSet;
  43
  44     /// Classes - For live regs that are only used in one register class in a
  45     /// live range, the register class. If the register is not live, the
  46     /// corresponding value is null. If the register is live but used in
  47     /// multiple register classes, the corresponding value is -1 casted to a
  48     /// pointer.
  49     std::vector<const TargetRegisterClass*> Classes;
  50
  51     /// RegRegs - Map registers to all their references within a live range.
  52     std::multimap<unsigned, MachineOperand *> RegRefs;
  53     typedef std::multimap<unsigned, MachineOperand *>::const_iterator
  54       RegRefIter;
  55
  56     /// KillIndices - The index of the most recent kill (proceding bottom-up),
  57     /// or ~0u if the register is not live.
  58     std::vector<unsigned> KillIndices;
  59
  60     /// DefIndices - The index of the most recent complete def (proceding bottom
  61     /// up), or ~0u if the register is live.
  62     std::vector<unsigned> DefIndices;
  63
  64     /// KeepRegs - A set of registers which are live and cannot be changed to
  65     /// break anti-dependencies.
  66     SmallSet<unsigned, 4> KeepRegs;
  67
  68   public:
  69     CriticalAntiDepBreaker(MachineFunction& MFi);
  70     ~CriticalAntiDepBreaker();
  71
  72     /// Start - Initialize anti-dep breaking for a new basic block.
  73     void StartBlock(MachineBasicBlock *BB);
  74
  75     /// BreakAntiDependencies - Identifiy anti-dependencies along the critical
  76     /// path
  77     /// of the ScheduleDAG and break them by renaming registers.
  78     ///
  79     unsigned BreakAntiDependencies(const std::vector<SUnit>& SUnits,
  80                                    MachineBasicBlock::iterator Begin,
  81                                    MachineBasicBlock::iterator End,
  82                                    unsigned InsertPosIndex);
  83
  84     /// Observe - Update liveness information to account for the current
  85     /// instruction, which will not be scheduled.
  86     ///
  87     void Observe(MachineInstr *MI, unsigned Count, unsigned InsertPosIndex);
  88
  89     /// Finish - Finish anti-dep breaking for a basic block.
  90     void FinishBlock();
  91
  92   private:
  93     void PrescanInstruction(MachineInstr *MI);
  94     void ScanInstruction(MachineInstr *MI, unsigned Count);
  95     bool isNewRegModifiedByRefs(RegRefIter RegRefBegin,
  96                                 RegRefIter RegRefEnd,
  97                                 unsigned NewReg);
  98     unsigned findSuitableFreeRegister(RegRefIter RegRefBegin,
  99                                       RegRefIter RegRefEnd,
 100                                       unsigned AntiDepReg,
 101                                       unsigned LastNewReg,
 102                                       const TargetRegisterClass *RC);
 103   };
 104 }
 105
 106 #endif