lib/CodeGen/LiveRangeEdit.h

   1 //===---- LiveRangeEdit.h - Basic tools for split and spill -----*- 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 // The LiveRangeEdit class represents changes done to a virtual register when it
  11 // is spilled or split.
  12 //
  13 // The parent register is never changed. Instead, a number of new virtual
  14 // registers are created and added to the newRegs vector.
  15 //
  16 //===----------------------------------------------------------------------===//
  17
  18 #ifndef LLVM_CODEGEN_LIVERANGEEDIT_H
  19 #define LLVM_CODEGEN_LIVERANGEEDIT_H
  20
  21 #include "llvm/CodeGen/LiveInterval.h"
  22 #include "llvm/ADT/SmallPtrSet.h"
  23
  24 namespace llvm {
  25
  26 class AliasAnalysis;
  27 class LiveIntervals;
  28 class MachineRegisterInfo;
  29 class VirtRegMap;
  30
  31 class LiveRangeEdit {
  32   LiveInterval &parent_;
  33   SmallVectorImpl<LiveInterval*> &newRegs_;
  34   const SmallVectorImpl<LiveInterval*> &uselessRegs_;
  35
  36   /// firstNew_ - Index of the first register added to newRegs_.
  37   const unsigned firstNew_;
  38
  39   /// scannedRemattable_ - true when remattable values have been identified.
  40   bool scannedRemattable_;
  41
  42   /// remattable_ - Values defined by remattable instructions as identified by
  43   /// tii.isTriviallyReMaterializable().
  44   SmallPtrSet<VNInfo*,4> remattable_;
  45
  46   /// rematted_ - Values that were actually rematted, and so need to have their
  47   /// live range trimmed or entirely removed.
  48   SmallPtrSet<VNInfo*,4> rematted_;
  49
  50   /// scanRemattable - Identify the parent_ values that may rematerialize.
  51   void scanRemattable(LiveIntervals &lis,
  52                       const TargetInstrInfo &tii,
  53                       AliasAnalysis *aa);
  54
  55   /// allUsesAvailableAt - Return true if all registers used by OrigMI at
  56   /// OrigIdx are also available with the same value at UseIdx.
  57   bool allUsesAvailableAt(const MachineInstr *OrigMI, SlotIndex OrigIdx,
  58                           SlotIndex UseIdx, LiveIntervals &lis);
  59
  60 public:
  61   /// Create a LiveRangeEdit for breaking down parent into smaller pieces.
  62   /// @param parent The register being spilled or split.
  63   /// @param newRegs List to receive any new registers created. This needn't be
  64   ///                empty initially, any existing registers are ignored.
  65   /// @param uselessRegs List of registers that can't be used when
  66   ///        rematerializing values because they are about to be removed.
  67   LiveRangeEdit(LiveInterval &parent,
  68                 SmallVectorImpl<LiveInterval*> &newRegs,
  69                 const SmallVectorImpl<LiveInterval*> &uselessRegs)
  70     : parent_(parent), newRegs_(newRegs), uselessRegs_(uselessRegs),
  71       firstNew_(newRegs.size()), scannedRemattable_(false) {}
  72
  73   LiveInterval &getParent() const { return parent_; }
  74   unsigned getReg() const { return parent_.reg; }
  75
  76   /// Iterator for accessing the new registers added by this edit.
  77   typedef SmallVectorImpl<LiveInterval*>::const_iterator iterator;
  78   iterator begin() const { return newRegs_.begin()+firstNew_; }
  79   iterator end() const { return newRegs_.end(); }
  80   unsigned size() const { return newRegs_.size()-firstNew_; }
  81   LiveInterval *get(unsigned idx) const { return newRegs_[idx+firstNew_]; }
  82
  83   /// create - Create a new register with the same class and stack slot as
  84   /// parent.
  85   LiveInterval &create(MachineRegisterInfo&, LiveIntervals&, VirtRegMap&);
  86
  87   /// anyRematerializable - Return true if any parent values may be
  88   /// rematerializable.
  89   /// This function must be called before ny rematerialization is attempted.
  90   bool anyRematerializable(LiveIntervals&, const TargetInstrInfo&,
  91                            AliasAnalysis*);
  92
  93   /// Remat - Information needed to rematerialize at a specific location.
  94   struct Remat {
  95     VNInfo *ParentVNI;      // parent_'s value at the remat location.
  96     MachineInstr *OrigMI;   // Instruction defining ParentVNI.
  97     operator bool() const { return OrigMI; }
  98   };
  99
 100   /// canRematerializeAt - Determine if ParentVNI can be rematerialized at
 101   /// UseIdx. It is assumed that parent_.getVNINfoAt(UseIdx) == ParentVNI.
 102   /// When cheapAsAMove is set, only cheap remats are allowed.
 103   Remat canRematerializeAt(VNInfo *ParentVNI,
 104                            SlotIndex UseIdx,
 105                            bool cheapAsAMove,
 106                            LiveIntervals &lis);
 107
 108   /// rematerializeAt - Rematerialize RM.ParentVNI into DestReg by inserting an
 109   /// instruction into MBB before MI. The new instruction is mapped, but
 110   /// liveness is not updated.
 111   /// Return the SlotIndex of the new instruction.
 112   SlotIndex rematerializeAt(MachineBasicBlock &MBB,
 113                             MachineBasicBlock::iterator MI,
 114                             unsigned DestReg,
 115                             const Remat &RM,
 116                             LiveIntervals&,
 117                             const TargetInstrInfo&,
 118                             const TargetRegisterInfo&);
 119
 120   /// didRematerialize - Return true if ParentVNI was rematerialized anywhere.
 121   bool didRematerialize(VNInfo *ParentVNI) const {
 122     return rematted_.count(ParentVNI);
 123   }
 124 };
 125
 126 }
 127
 128 #endif