1 //===---- LiveRangeEdit.h - Basic tools for split and spill -----*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // The LiveRangeEdit class represents changes done to a virtual register when it
11 // is spilled or split.
13 // The parent register is never changed. Instead, a number of new virtual
14 // registers are created and added to the newRegs vector.
16 //===----------------------------------------------------------------------===//
18 #ifndef LLVM_CODEGEN_LIVERANGEEDIT_H
19 #define LLVM_CODEGEN_LIVERANGEEDIT_H
21 #include "llvm/CodeGen/LiveInterval.h"
22 #include "llvm/ADT/SmallPtrSet.h"
28 class MachineRegisterInfo;
33 /// Callback methods for LiveRangeEdit owners.
35 /// Called immediately before erasing a dead machine instruction.
36 virtual void LRE_WillEraseInstruction(MachineInstr *MI) {}
38 /// Called when a virtual register is no longer used. Return false to defer
39 /// its deletion from LiveIntervals.
40 virtual bool LRE_CanEraseVirtReg(unsigned) { return true; }
42 virtual ~Delegate() {}
46 LiveInterval &parent_;
47 SmallVectorImpl<LiveInterval*> &newRegs_;
48 Delegate *const delegate_;
49 const SmallVectorImpl<LiveInterval*> *uselessRegs_;
51 /// firstNew_ - Index of the first register added to newRegs_.
52 const unsigned firstNew_;
54 /// scannedRemattable_ - true when remattable values have been identified.
55 bool scannedRemattable_;
57 /// remattable_ - Values defined by remattable instructions as identified by
58 /// tii.isTriviallyReMaterializable().
59 SmallPtrSet<const VNInfo*,4> remattable_;
61 /// rematted_ - Values that were actually rematted, and so need to have their
62 /// live range trimmed or entirely removed.
63 SmallPtrSet<const VNInfo*,4> rematted_;
65 /// scanRemattable - Identify the parent_ values that may rematerialize.
66 void scanRemattable(LiveIntervals &lis,
67 const TargetInstrInfo &tii,
70 /// allUsesAvailableAt - Return true if all registers used by OrigMI at
71 /// OrigIdx are also available with the same value at UseIdx.
72 bool allUsesAvailableAt(const MachineInstr *OrigMI, SlotIndex OrigIdx,
73 SlotIndex UseIdx, LiveIntervals &lis);
76 /// Create a LiveRangeEdit for breaking down parent into smaller pieces.
77 /// @param parent The register being spilled or split.
78 /// @param newRegs List to receive any new registers created. This needn't be
79 /// empty initially, any existing registers are ignored.
80 /// @param uselessRegs List of registers that can't be used when
81 /// rematerializing values because they are about to be removed.
82 LiveRangeEdit(LiveInterval &parent,
83 SmallVectorImpl<LiveInterval*> &newRegs,
84 Delegate *delegate = 0,
85 const SmallVectorImpl<LiveInterval*> *uselessRegs = 0)
86 : parent_(parent), newRegs_(newRegs),
88 uselessRegs_(uselessRegs),
89 firstNew_(newRegs.size()),
90 scannedRemattable_(false) {}
92 LiveInterval &getParent() const { return parent_; }
93 unsigned getReg() const { return parent_.reg; }
95 /// Iterator for accessing the new registers added by this edit.
96 typedef SmallVectorImpl<LiveInterval*>::const_iterator iterator;
97 iterator begin() const { return newRegs_.begin()+firstNew_; }
98 iterator end() const { return newRegs_.end(); }
99 unsigned size() const { return newRegs_.size()-firstNew_; }
100 bool empty() const { return size() == 0; }
101 LiveInterval *get(unsigned idx) const { return newRegs_[idx+firstNew_]; }
103 /// FIXME: Temporary accessors until we can get rid of
104 /// LiveIntervals::AddIntervalsForSpills
105 SmallVectorImpl<LiveInterval*> *getNewVRegs() { return &newRegs_; }
106 const SmallVectorImpl<LiveInterval*> *getUselessVRegs() {
110 /// create - Create a new register with the same class and stack slot as
112 LiveInterval &create(MachineRegisterInfo&, LiveIntervals&, VirtRegMap&);
114 /// anyRematerializable - Return true if any parent values may be
115 /// rematerializable.
116 /// This function must be called before any rematerialization is attempted.
117 bool anyRematerializable(LiveIntervals&, const TargetInstrInfo&,
120 /// Remat - Information needed to rematerialize at a specific location.
122 VNInfo *ParentVNI; // parent_'s value at the remat location.
123 MachineInstr *OrigMI; // Instruction defining ParentVNI.
124 explicit Remat(VNInfo *ParentVNI) : ParentVNI(ParentVNI), OrigMI(0) {}
127 /// canRematerializeAt - Determine if ParentVNI can be rematerialized at
128 /// UseIdx. It is assumed that parent_.getVNINfoAt(UseIdx) == ParentVNI.
129 /// When cheapAsAMove is set, only cheap remats are allowed.
130 bool canRematerializeAt(Remat &RM,
135 /// rematerializeAt - Rematerialize RM.ParentVNI into DestReg by inserting an
136 /// instruction into MBB before MI. The new instruction is mapped, but
137 /// liveness is not updated.
138 /// Return the SlotIndex of the new instruction.
139 SlotIndex rematerializeAt(MachineBasicBlock &MBB,
140 MachineBasicBlock::iterator MI,
144 const TargetInstrInfo&,
145 const TargetRegisterInfo&);
147 /// markRematerialized - explicitly mark a value as rematerialized after doing
149 void markRematerialized(const VNInfo *ParentVNI) {
150 rematted_.insert(ParentVNI);
153 /// didRematerialize - Return true if ParentVNI was rematerialized anywhere.
154 bool didRematerialize(const VNInfo *ParentVNI) const {
155 return rematted_.count(ParentVNI);
158 /// eraseVirtReg - Notify the delegate that Reg is no longer in use, and try
159 /// to erase it from LIS.
160 void eraseVirtReg(unsigned Reg, LiveIntervals &LIS);
162 /// eliminateDeadDefs - Try to delete machine instructions that are now dead
163 /// (allDefsAreDead returns true). This may cause live intervals to be trimmed
164 /// and further dead efs to be eliminated.
165 void eliminateDeadDefs(SmallVectorImpl<MachineInstr*> &Dead,
167 const TargetInstrInfo&);