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