1 //===--- LiveRangeEdit.cpp - Basic tools for editing a register live range --===//
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.
12 //===----------------------------------------------------------------------===//
14 #define DEBUG_TYPE "regalloc"
15 #include "LiveRangeEdit.h"
16 #include "VirtRegMap.h"
17 #include "llvm/ADT/SetVector.h"
18 #include "llvm/CodeGen/CalcSpillWeights.h"
19 #include "llvm/CodeGen/LiveIntervalAnalysis.h"
20 #include "llvm/CodeGen/MachineRegisterInfo.h"
21 #include "llvm/Target/TargetInstrInfo.h"
22 #include "llvm/Support/Debug.h"
23 #include "llvm/Support/raw_ostream.h"
27 LiveInterval &LiveRangeEdit::createFrom(unsigned OldReg,
30 MachineRegisterInfo &MRI = VRM.getRegInfo();
31 unsigned VReg = MRI.createVirtualRegister(MRI.getRegClass(OldReg));
33 VRM.setIsSplitFromReg(VReg, VRM.getOriginal(OldReg));
34 LiveInterval &LI = LIS.getOrCreateInterval(VReg);
35 newRegs_.push_back(&LI);
39 void LiveRangeEdit::checkRematerializable(VNInfo *VNI,
40 const MachineInstr *DefMI,
41 const TargetInstrInfo &tii,
43 assert(DefMI && "Missing instruction");
44 if (tii.isTriviallyReMaterializable(DefMI, aa))
45 remattable_.insert(VNI);
46 scannedRemattable_ = true;
49 void LiveRangeEdit::scanRemattable(LiveIntervals &lis,
50 const TargetInstrInfo &tii,
52 for (LiveInterval::vni_iterator I = parent_.vni_begin(),
53 E = parent_.vni_end(); I != E; ++I) {
57 MachineInstr *DefMI = lis.getInstructionFromIndex(VNI->def);
60 checkRematerializable(VNI, DefMI, tii, aa);
64 bool LiveRangeEdit::anyRematerializable(LiveIntervals &lis,
65 const TargetInstrInfo &tii,
67 if (!scannedRemattable_)
68 scanRemattable(lis, tii, aa);
69 return !remattable_.empty();
72 /// allUsesAvailableAt - Return true if all registers used by OrigMI at
73 /// OrigIdx are also available with the same value at UseIdx.
74 bool LiveRangeEdit::allUsesAvailableAt(const MachineInstr *OrigMI,
78 OrigIdx = OrigIdx.getUseIndex();
79 UseIdx = UseIdx.getUseIndex();
80 for (unsigned i = 0, e = OrigMI->getNumOperands(); i != e; ++i) {
81 const MachineOperand &MO = OrigMI->getOperand(i);
82 if (!MO.isReg() || !MO.getReg() || MO.isDef())
84 // Reserved registers are OK.
85 if (MO.isUndef() || !lis.hasInterval(MO.getReg()))
87 // We cannot depend on virtual registers in uselessRegs_.
89 for (unsigned ui = 0, ue = uselessRegs_->size(); ui != ue; ++ui)
90 if ((*uselessRegs_)[ui]->reg == MO.getReg())
93 LiveInterval &li = lis.getInterval(MO.getReg());
94 const VNInfo *OVNI = li.getVNInfoAt(OrigIdx);
97 if (OVNI != li.getVNInfoAt(UseIdx))
103 bool LiveRangeEdit::canRematerializeAt(Remat &RM,
106 LiveIntervals &lis) {
107 assert(scannedRemattable_ && "Call anyRematerializable first");
109 // Use scanRemattable info.
110 if (!remattable_.count(RM.ParentVNI))
113 // No defining instruction provided.
116 DefIdx = lis.getInstructionIndex(RM.OrigMI);
118 DefIdx = RM.ParentVNI->def;
119 RM.OrigMI = lis.getInstructionFromIndex(DefIdx);
120 assert(RM.OrigMI && "No defining instruction for remattable value");
123 // If only cheap remats were requested, bail out early.
124 if (cheapAsAMove && !RM.OrigMI->getDesc().isAsCheapAsAMove())
127 // Verify that all used registers are available with the same values.
128 if (!allUsesAvailableAt(RM.OrigMI, DefIdx, UseIdx, lis))
134 SlotIndex LiveRangeEdit::rematerializeAt(MachineBasicBlock &MBB,
135 MachineBasicBlock::iterator MI,
139 const TargetInstrInfo &tii,
140 const TargetRegisterInfo &tri) {
141 assert(RM.OrigMI && "Invalid remat");
142 tii.reMaterialize(MBB, MI, DestReg, 0, RM.OrigMI, tri);
143 rematted_.insert(RM.ParentVNI);
144 return lis.InsertMachineInstrInMaps(--MI).getDefIndex();
147 void LiveRangeEdit::eraseVirtReg(unsigned Reg, LiveIntervals &LIS) {
148 if (delegate_ && delegate_->LRE_CanEraseVirtReg(Reg))
149 LIS.removeInterval(Reg);
152 void LiveRangeEdit::eliminateDeadDefs(SmallVectorImpl<MachineInstr*> &Dead,
153 LiveIntervals &LIS, VirtRegMap &VRM,
154 const TargetInstrInfo &TII) {
155 SetVector<LiveInterval*,
156 SmallVector<LiveInterval*, 8>,
157 SmallPtrSet<LiveInterval*, 8> > ToShrink;
160 // Erase all dead defs.
161 while (!Dead.empty()) {
162 MachineInstr *MI = Dead.pop_back_val();
163 assert(MI->allDefsAreDead() && "Def isn't really dead");
164 SlotIndex Idx = LIS.getInstructionIndex(MI).getDefIndex();
166 // Never delete inline asm.
167 if (MI->isInlineAsm()) {
168 DEBUG(dbgs() << "Won't delete: " << Idx << '\t' << *MI);
172 // Use the same criteria as DeadMachineInstructionElim.
173 bool SawStore = false;
174 if (!MI->isSafeToMove(&TII, 0, SawStore)) {
175 DEBUG(dbgs() << "Can't delete: " << Idx << '\t' << *MI);
179 DEBUG(dbgs() << "Deleting dead def " << Idx << '\t' << *MI);
181 // Check for live intervals that may shrink
182 for (MachineInstr::mop_iterator MOI = MI->operands_begin(),
183 MOE = MI->operands_end(); MOI != MOE; ++MOI) {
186 unsigned Reg = MOI->getReg();
187 if (!TargetRegisterInfo::isVirtualRegister(Reg))
189 LiveInterval &LI = LIS.getInterval(Reg);
191 // Shrink read registers.
192 if (MI->readsVirtualRegister(Reg))
193 ToShrink.insert(&LI);
195 // Remove defined value.
197 if (VNInfo *VNI = LI.getVNInfoAt(Idx)) {
199 delegate_->LRE_WillShrinkVirtReg(LI.reg);
202 ToShrink.remove(&LI);
203 eraseVirtReg(Reg, LIS);
210 delegate_->LRE_WillEraseInstruction(MI);
211 LIS.RemoveMachineInstrFromMaps(MI);
212 MI->eraseFromParent();
215 if (ToShrink.empty())
218 // Shrink just one live interval. Then delete new dead defs.
219 LiveInterval *LI = ToShrink.back();
222 delegate_->LRE_WillShrinkVirtReg(LI->reg);
223 if (!LIS.shrinkToUses(LI, &Dead))
226 // LI may have been separated, create new intervals.
227 LI->RenumberValues(LIS);
228 ConnectedVNInfoEqClasses ConEQ(LIS);
229 unsigned NumComp = ConEQ.Classify(LI);
232 DEBUG(dbgs() << NumComp << " components: " << *LI << '\n');
233 SmallVector<LiveInterval*, 8> Dups(1, LI);
234 for (unsigned i = 1; i != NumComp; ++i)
235 Dups.push_back(&createFrom(LI->reg, LIS, VRM));
236 ConEQ.Distribute(&Dups[0], VRM.getRegInfo());
240 void LiveRangeEdit::calculateRegClassAndHint(MachineFunction &MF,
242 const MachineLoopInfo &Loops) {
243 VirtRegAuxInfo VRAI(MF, LIS, Loops);
244 for (iterator I = begin(), E = end(); I != E; ++I) {
245 LiveInterval &LI = **I;
246 VRAI.CalculateRegClass(LI.reg);
247 VRAI.CalculateWeightAndHint(LI);