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 MachineLoopInfo;
29 class MachineRegisterInfo;
34 /// Callback methods for LiveRangeEdit owners.
36 /// Called immediately before erasing a dead machine instruction.
37 virtual void LRE_WillEraseInstruction(MachineInstr *MI) {}
39 /// Called when a virtual register is no longer used. Return false to defer
40 /// its deletion from LiveIntervals.
41 virtual bool LRE_CanEraseVirtReg(unsigned) { return true; }
43 /// Called before shrinking the live range of a virtual register.
44 virtual void LRE_WillShrinkVirtReg(unsigned) {}
46 /// Called after cloning a virtual register.
47 /// This is used for new registers representing connected components of Old.
48 virtual void LRE_DidCloneVirtReg(unsigned New, unsigned Old) {}
50 virtual ~Delegate() {}
54 LiveInterval &parent_;
55 SmallVectorImpl<LiveInterval*> &newRegs_;
56 Delegate *const delegate_;
57 const SmallVectorImpl<LiveInterval*> *uselessRegs_;
59 /// firstNew_ - Index of the first register added to newRegs_.
60 const unsigned firstNew_;
62 /// scannedRemattable_ - true when remattable values have been identified.
63 bool scannedRemattable_;
65 /// remattable_ - Values defined by remattable instructions as identified by
66 /// tii.isTriviallyReMaterializable().
67 SmallPtrSet<const VNInfo*,4> remattable_;
69 /// rematted_ - Values that were actually rematted, and so need to have their
70 /// live range trimmed or entirely removed.
71 SmallPtrSet<const VNInfo*,4> rematted_;
73 /// scanRemattable - Identify the parent_ values that may rematerialize.
74 void scanRemattable(LiveIntervals &lis,
75 const TargetInstrInfo &tii,
78 /// allUsesAvailableAt - Return true if all registers used by OrigMI at
79 /// OrigIdx are also available with the same value at UseIdx.
80 bool allUsesAvailableAt(const MachineInstr *OrigMI, SlotIndex OrigIdx,
81 SlotIndex UseIdx, LiveIntervals &lis);
83 /// foldAsLoad - If LI has a single use and a single def that can be folded as
84 /// a load, eliminate the register by folding the def into the use.
85 bool foldAsLoad(LiveInterval *LI, SmallVectorImpl<MachineInstr*> &Dead,
86 MachineRegisterInfo&, LiveIntervals&, const TargetInstrInfo&);
89 /// Create a LiveRangeEdit for breaking down parent into smaller pieces.
90 /// @param parent The register being spilled or split.
91 /// @param newRegs List to receive any new registers created. This needn't be
92 /// empty initially, any existing registers are ignored.
93 /// @param uselessRegs List of registers that can't be used when
94 /// rematerializing values because they are about to be removed.
95 LiveRangeEdit(LiveInterval &parent,
96 SmallVectorImpl<LiveInterval*> &newRegs,
97 Delegate *delegate = 0,
98 const SmallVectorImpl<LiveInterval*> *uselessRegs = 0)
99 : parent_(parent), newRegs_(newRegs),
101 uselessRegs_(uselessRegs),
102 firstNew_(newRegs.size()),
103 scannedRemattable_(false) {}
105 LiveInterval &getParent() const { return parent_; }
106 unsigned getReg() const { return parent_.reg; }
108 /// Iterator for accessing the new registers added by this edit.
109 typedef SmallVectorImpl<LiveInterval*>::const_iterator iterator;
110 iterator begin() const { return newRegs_.begin()+firstNew_; }
111 iterator end() const { return newRegs_.end(); }
112 unsigned size() const { return newRegs_.size()-firstNew_; }
113 bool empty() const { return size() == 0; }
114 LiveInterval *get(unsigned idx) const { return newRegs_[idx+firstNew_]; }
116 /// FIXME: Temporary accessors until we can get rid of
117 /// LiveIntervals::AddIntervalsForSpills
118 SmallVectorImpl<LiveInterval*> *getNewVRegs() { return &newRegs_; }
119 const SmallVectorImpl<LiveInterval*> *getUselessVRegs() {
123 /// createFrom - Create a new virtual register based on OldReg.
124 LiveInterval &createFrom(unsigned OldReg, LiveIntervals&, VirtRegMap&);
126 /// create - Create a new register with the same class and original slot as
128 LiveInterval &create(LiveIntervals &LIS, VirtRegMap &VRM) {
129 return createFrom(getReg(), LIS, VRM);
132 /// anyRematerializable - Return true if any parent values may be
133 /// rematerializable.
134 /// This function must be called before any rematerialization is attempted.
135 bool anyRematerializable(LiveIntervals&, const TargetInstrInfo&,
138 /// checkRematerializable - Manually add VNI to the list of rematerializable
139 /// values if DefMI may be rematerializable.
140 void checkRematerializable(VNInfo *VNI, const MachineInstr *DefMI,
141 const TargetInstrInfo&, AliasAnalysis*);
143 /// Remat - Information needed to rematerialize at a specific location.
145 VNInfo *ParentVNI; // parent_'s value at the remat location.
146 MachineInstr *OrigMI; // Instruction defining ParentVNI.
147 explicit Remat(VNInfo *ParentVNI) : ParentVNI(ParentVNI), OrigMI(0) {}
150 /// canRematerializeAt - Determine if ParentVNI can be rematerialized at
151 /// UseIdx. It is assumed that parent_.getVNINfoAt(UseIdx) == ParentVNI.
152 /// When cheapAsAMove is set, only cheap remats are allowed.
153 bool canRematerializeAt(Remat &RM,
158 /// rematerializeAt - Rematerialize RM.ParentVNI into DestReg by inserting an
159 /// instruction into MBB before MI. The new instruction is mapped, but
160 /// liveness is not updated.
161 /// Return the SlotIndex of the new instruction.
162 SlotIndex rematerializeAt(MachineBasicBlock &MBB,
163 MachineBasicBlock::iterator MI,
167 const TargetInstrInfo&,
168 const TargetRegisterInfo&);
170 /// markRematerialized - explicitly mark a value as rematerialized after doing
172 void markRematerialized(const VNInfo *ParentVNI) {
173 rematted_.insert(ParentVNI);
176 /// didRematerialize - Return true if ParentVNI was rematerialized anywhere.
177 bool didRematerialize(const VNInfo *ParentVNI) const {
178 return rematted_.count(ParentVNI);
181 /// eraseVirtReg - Notify the delegate that Reg is no longer in use, and try
182 /// to erase it from LIS.
183 void eraseVirtReg(unsigned Reg, LiveIntervals &LIS);
185 /// eliminateDeadDefs - Try to delete machine instructions that are now dead
186 /// (allDefsAreDead returns true). This may cause live intervals to be trimmed
187 /// and further dead efs to be eliminated.
188 void eliminateDeadDefs(SmallVectorImpl<MachineInstr*> &Dead,
189 LiveIntervals&, VirtRegMap&,
190 const TargetInstrInfo&);
192 /// calculateRegClassAndHint - Recompute register class and hint for each new
194 void calculateRegClassAndHint(MachineFunction&, LiveIntervals&,
195 const MachineLoopInfo&);