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 bool LiveRangeEdit::checkRematerializable(VNInfo *VNI,
40 const MachineInstr *DefMI,
41 const TargetInstrInfo &tii,
43 assert(DefMI && "Missing instruction");
44 scannedRemattable_ = true;
45 if (!tii.isTriviallyReMaterializable(DefMI, aa))
47 remattable_.insert(VNI);
51 void LiveRangeEdit::scanRemattable(LiveIntervals &lis,
52 const TargetInstrInfo &tii,
54 for (LiveInterval::vni_iterator I = parent_.vni_begin(),
55 E = parent_.vni_end(); I != E; ++I) {
59 MachineInstr *DefMI = lis.getInstructionFromIndex(VNI->def);
62 checkRematerializable(VNI, DefMI, tii, aa);
64 scannedRemattable_ = true;
67 bool LiveRangeEdit::anyRematerializable(LiveIntervals &lis,
68 const TargetInstrInfo &tii,
70 if (!scannedRemattable_)
71 scanRemattable(lis, tii, aa);
72 return !remattable_.empty();
75 /// allUsesAvailableAt - Return true if all registers used by OrigMI at
76 /// OrigIdx are also available with the same value at UseIdx.
77 bool LiveRangeEdit::allUsesAvailableAt(const MachineInstr *OrigMI,
81 OrigIdx = OrigIdx.getUseIndex();
82 UseIdx = UseIdx.getUseIndex();
83 for (unsigned i = 0, e = OrigMI->getNumOperands(); i != e; ++i) {
84 const MachineOperand &MO = OrigMI->getOperand(i);
85 if (!MO.isReg() || !MO.getReg() || MO.isDef())
87 // Reserved registers are OK.
88 if (MO.isUndef() || !lis.hasInterval(MO.getReg()))
90 // We cannot depend on virtual registers in uselessRegs_.
92 for (unsigned ui = 0, ue = uselessRegs_->size(); ui != ue; ++ui)
93 if ((*uselessRegs_)[ui]->reg == MO.getReg())
96 LiveInterval &li = lis.getInterval(MO.getReg());
97 const VNInfo *OVNI = li.getVNInfoAt(OrigIdx);
100 if (OVNI != li.getVNInfoAt(UseIdx))
106 bool LiveRangeEdit::canRematerializeAt(Remat &RM,
109 LiveIntervals &lis) {
110 assert(scannedRemattable_ && "Call anyRematerializable first");
112 // Use scanRemattable info.
113 if (!remattable_.count(RM.ParentVNI))
116 // No defining instruction provided.
119 DefIdx = lis.getInstructionIndex(RM.OrigMI);
121 DefIdx = RM.ParentVNI->def;
122 RM.OrigMI = lis.getInstructionFromIndex(DefIdx);
123 assert(RM.OrigMI && "No defining instruction for remattable value");
126 // If only cheap remats were requested, bail out early.
127 if (cheapAsAMove && !RM.OrigMI->getDesc().isAsCheapAsAMove())
130 // Verify that all used registers are available with the same values.
131 if (!allUsesAvailableAt(RM.OrigMI, DefIdx, UseIdx, lis))
137 SlotIndex LiveRangeEdit::rematerializeAt(MachineBasicBlock &MBB,
138 MachineBasicBlock::iterator MI,
142 const TargetInstrInfo &tii,
143 const TargetRegisterInfo &tri,
145 assert(RM.OrigMI && "Invalid remat");
146 tii.reMaterialize(MBB, MI, DestReg, 0, RM.OrigMI, tri);
147 rematted_.insert(RM.ParentVNI);
148 return lis.getSlotIndexes()->insertMachineInstrInMaps(--MI, Late)
152 void LiveRangeEdit::eraseVirtReg(unsigned Reg, LiveIntervals &LIS) {
153 if (delegate_ && delegate_->LRE_CanEraseVirtReg(Reg))
154 LIS.removeInterval(Reg);
157 bool LiveRangeEdit::foldAsLoad(LiveInterval *LI,
158 SmallVectorImpl<MachineInstr*> &Dead,
159 MachineRegisterInfo &MRI,
161 const TargetInstrInfo &TII) {
162 MachineInstr *DefMI = 0, *UseMI = 0;
164 // Check that there is a single def and a single use.
165 for (MachineRegisterInfo::reg_nodbg_iterator I = MRI.reg_nodbg_begin(LI->reg),
166 E = MRI.reg_nodbg_end(); I != E; ++I) {
167 MachineOperand &MO = I.getOperand();
168 MachineInstr *MI = MO.getParent();
170 if (DefMI && DefMI != MI)
172 if (!MI->getDesc().canFoldAsLoad())
175 } else if (!MO.isUndef()) {
176 if (UseMI && UseMI != MI)
178 // FIXME: Targets don't know how to fold subreg uses.
184 if (!DefMI || !UseMI)
187 DEBUG(dbgs() << "Try to fold single def: " << *DefMI
188 << " into single use: " << *UseMI);
190 SmallVector<unsigned, 8> Ops;
191 if (UseMI->readsWritesVirtualRegister(LI->reg, &Ops).second)
194 MachineInstr *FoldMI = TII.foldMemoryOperand(UseMI, Ops, DefMI);
197 DEBUG(dbgs() << " folded: " << *FoldMI);
198 LIS.ReplaceMachineInstrInMaps(UseMI, FoldMI);
199 UseMI->eraseFromParent();
200 DefMI->addRegisterDead(LI->reg, 0);
201 Dead.push_back(DefMI);
205 void LiveRangeEdit::eliminateDeadDefs(SmallVectorImpl<MachineInstr*> &Dead,
206 LiveIntervals &LIS, VirtRegMap &VRM,
207 const TargetInstrInfo &TII) {
208 SetVector<LiveInterval*,
209 SmallVector<LiveInterval*, 8>,
210 SmallPtrSet<LiveInterval*, 8> > ToShrink;
211 MachineRegisterInfo &MRI = VRM.getRegInfo();
214 // Erase all dead defs.
215 while (!Dead.empty()) {
216 MachineInstr *MI = Dead.pop_back_val();
217 assert(MI->allDefsAreDead() && "Def isn't really dead");
218 SlotIndex Idx = LIS.getInstructionIndex(MI).getDefIndex();
220 // Never delete inline asm.
221 if (MI->isInlineAsm()) {
222 DEBUG(dbgs() << "Won't delete: " << Idx << '\t' << *MI);
226 // Use the same criteria as DeadMachineInstructionElim.
227 bool SawStore = false;
228 if (!MI->isSafeToMove(&TII, 0, SawStore)) {
229 DEBUG(dbgs() << "Can't delete: " << Idx << '\t' << *MI);
233 DEBUG(dbgs() << "Deleting dead def " << Idx << '\t' << *MI);
235 // Check for live intervals that may shrink
236 for (MachineInstr::mop_iterator MOI = MI->operands_begin(),
237 MOE = MI->operands_end(); MOI != MOE; ++MOI) {
240 unsigned Reg = MOI->getReg();
241 if (!TargetRegisterInfo::isVirtualRegister(Reg))
243 LiveInterval &LI = LIS.getInterval(Reg);
245 // Shrink read registers, unless it is likely to be expensive and
246 // unlikely to change anything. We typically don't want to shrink the
247 // PIC base register that has lots of uses everywhere.
248 // Always shrink COPY uses that probably come from live range splitting.
249 if (MI->readsVirtualRegister(Reg) &&
250 (MI->isCopy() || MOI->isDef() || MRI.hasOneNonDBGUse(Reg) ||
252 ToShrink.insert(&LI);
254 // Remove defined value.
256 if (VNInfo *VNI = LI.getVNInfoAt(Idx)) {
258 delegate_->LRE_WillShrinkVirtReg(LI.reg);
261 ToShrink.remove(&LI);
262 eraseVirtReg(Reg, LIS);
269 delegate_->LRE_WillEraseInstruction(MI);
270 LIS.RemoveMachineInstrFromMaps(MI);
271 MI->eraseFromParent();
274 if (ToShrink.empty())
277 // Shrink just one live interval. Then delete new dead defs.
278 LiveInterval *LI = ToShrink.back();
280 if (foldAsLoad(LI, Dead, MRI, LIS, TII))
283 delegate_->LRE_WillShrinkVirtReg(LI->reg);
284 if (!LIS.shrinkToUses(LI, &Dead))
287 // LI may have been separated, create new intervals.
288 LI->RenumberValues(LIS);
289 ConnectedVNInfoEqClasses ConEQ(LIS);
290 unsigned NumComp = ConEQ.Classify(LI);
293 DEBUG(dbgs() << NumComp << " components: " << *LI << '\n');
294 SmallVector<LiveInterval*, 8> Dups(1, LI);
295 for (unsigned i = 1; i != NumComp; ++i) {
296 Dups.push_back(&createFrom(LI->reg, LIS, VRM));
298 delegate_->LRE_DidCloneVirtReg(Dups.back()->reg, LI->reg);
300 ConEQ.Distribute(&Dups[0], MRI);
304 void LiveRangeEdit::calculateRegClassAndHint(MachineFunction &MF,
306 const MachineLoopInfo &Loops) {
307 VirtRegAuxInfo VRAI(MF, LIS, Loops);
308 for (iterator I = begin(), E = end(); I != E; ++I) {
309 LiveInterval &LI = **I;
310 VRAI.CalculateRegClass(LI.reg);
311 VRAI.CalculateWeightAndHint(LI);