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) {}
37 virtual ~Delegate() {}
41 LiveInterval &parent_;
42 SmallVectorImpl<LiveInterval*> &newRegs_;
43 Delegate *const delegate_;
44 const SmallVectorImpl<LiveInterval*> *uselessRegs_;
46 /// firstNew_ - Index of the first register added to newRegs_.
47 const unsigned firstNew_;
49 /// scannedRemattable_ - true when remattable values have been identified.
50 bool scannedRemattable_;
52 /// remattable_ - Values defined by remattable instructions as identified by
53 /// tii.isTriviallyReMaterializable().
54 SmallPtrSet<const VNInfo*,4> remattable_;
56 /// rematted_ - Values that were actually rematted, and so need to have their
57 /// live range trimmed or entirely removed.
58 SmallPtrSet<const VNInfo*,4> rematted_;
60 /// scanRemattable - Identify the parent_ values that may rematerialize.
61 void scanRemattable(LiveIntervals &lis,
62 const TargetInstrInfo &tii,
65 /// allUsesAvailableAt - Return true if all registers used by OrigMI at
66 /// OrigIdx are also available with the same value at UseIdx.
67 bool allUsesAvailableAt(const MachineInstr *OrigMI, SlotIndex OrigIdx,
68 SlotIndex UseIdx, LiveIntervals &lis);
71 /// Create a LiveRangeEdit for breaking down parent into smaller pieces.
72 /// @param parent The register being spilled or split.
73 /// @param newRegs List to receive any new registers created. This needn't be
74 /// empty initially, any existing registers are ignored.
75 /// @param uselessRegs List of registers that can't be used when
76 /// rematerializing values because they are about to be removed.
77 LiveRangeEdit(LiveInterval &parent,
78 SmallVectorImpl<LiveInterval*> &newRegs,
79 Delegate *delegate = 0,
80 const SmallVectorImpl<LiveInterval*> *uselessRegs = 0)
81 : parent_(parent), newRegs_(newRegs),
83 uselessRegs_(uselessRegs),
84 firstNew_(newRegs.size()),
85 scannedRemattable_(false) {}
87 LiveInterval &getParent() const { return parent_; }
88 unsigned getReg() const { return parent_.reg; }
90 /// Iterator for accessing the new registers added by this edit.
91 typedef SmallVectorImpl<LiveInterval*>::const_iterator iterator;
92 iterator begin() const { return newRegs_.begin()+firstNew_; }
93 iterator end() const { return newRegs_.end(); }
94 unsigned size() const { return newRegs_.size()-firstNew_; }
95 bool empty() const { return size() == 0; }
96 LiveInterval *get(unsigned idx) const { return newRegs_[idx+firstNew_]; }
98 /// FIXME: Temporary accessors until we can get rid of
99 /// LiveIntervals::AddIntervalsForSpills
100 SmallVectorImpl<LiveInterval*> *getNewVRegs() { return &newRegs_; }
101 const SmallVectorImpl<LiveInterval*> *getUselessVRegs() {
105 /// create - Create a new register with the same class and stack slot as
107 LiveInterval &create(MachineRegisterInfo&, LiveIntervals&, VirtRegMap&);
109 /// anyRematerializable - Return true if any parent values may be
110 /// rematerializable.
111 /// This function must be called before any rematerialization is attempted.
112 bool anyRematerializable(LiveIntervals&, const TargetInstrInfo&,
115 /// Remat - Information needed to rematerialize at a specific location.
117 VNInfo *ParentVNI; // parent_'s value at the remat location.
118 MachineInstr *OrigMI; // Instruction defining ParentVNI.
119 explicit Remat(VNInfo *ParentVNI) : ParentVNI(ParentVNI), OrigMI(0) {}
122 /// canRematerializeAt - Determine if ParentVNI can be rematerialized at
123 /// UseIdx. It is assumed that parent_.getVNINfoAt(UseIdx) == ParentVNI.
124 /// When cheapAsAMove is set, only cheap remats are allowed.
125 bool canRematerializeAt(Remat &RM,
130 /// rematerializeAt - Rematerialize RM.ParentVNI into DestReg by inserting an
131 /// instruction into MBB before MI. The new instruction is mapped, but
132 /// liveness is not updated.
133 /// Return the SlotIndex of the new instruction.
134 SlotIndex rematerializeAt(MachineBasicBlock &MBB,
135 MachineBasicBlock::iterator MI,
139 const TargetInstrInfo&,
140 const TargetRegisterInfo&);
142 /// markRematerialized - explicitly mark a value as rematerialized after doing
144 void markRematerialized(const VNInfo *ParentVNI) {
145 rematted_.insert(ParentVNI);
148 /// didRematerialize - Return true if ParentVNI was rematerialized anywhere.
149 bool didRematerialize(const VNInfo *ParentVNI) const {
150 return rematted_.count(ParentVNI);
153 /// eliminateDeadDefs - Try to delete machine instructions that are now dead
154 /// (allDefsAreDead returns true). This may cause live intervals to be trimmed
155 /// and further dead efs to be eliminated.
156 void eliminateDeadDefs(SmallVectorImpl<MachineInstr*> &Dead,
158 const TargetInstrInfo&);