1 //===-- LiveVariables.cpp - Live Variable Analysis for Machine Code -------===//
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 // This file implements the LiveVariable analysis pass. For each machine
11 // instruction in the function, this pass calculates the set of registers that
12 // are immediately dead after the instruction (i.e., the instruction calculates
13 // the value, but it is never used) and the set of registers that are used by
14 // the instruction, but are never used after the instruction (i.e., they are
17 // This class computes live variables using are sparse implementation based on
18 // the machine code SSA form. This class computes live variable information for
19 // each virtual and _register allocatable_ physical register in a function. It
20 // uses the dominance properties of SSA form to efficiently compute live
21 // variables for virtual registers, and assumes that physical registers are only
22 // live within a single basic block (allowing it to do a single local analysis
23 // to resolve physical register lifetimes in each basic block). If a physical
24 // register is not register allocatable, it is not tracked. This is useful for
25 // things like the stack pointer and condition codes.
27 //===----------------------------------------------------------------------===//
29 #include "llvm/CodeGen/LiveVariables.h"
30 #include "llvm/CodeGen/MachineInstr.h"
31 #include "llvm/CodeGen/MachineRegisterInfo.h"
32 #include "llvm/CodeGen/Passes.h"
33 #include "llvm/Target/TargetRegisterInfo.h"
34 #include "llvm/Target/TargetInstrInfo.h"
35 #include "llvm/Target/TargetMachine.h"
36 #include "llvm/ADT/DepthFirstIterator.h"
37 #include "llvm/ADT/SmallPtrSet.h"
38 #include "llvm/ADT/SmallSet.h"
39 #include "llvm/ADT/STLExtras.h"
40 #include "llvm/Config/alloca.h"
44 char LiveVariables::ID = 0;
45 static RegisterPass<LiveVariables> X("livevars", "Live Variable Analysis");
48 void LiveVariables::getAnalysisUsage(AnalysisUsage &AU) const {
49 AU.addRequiredID(UnreachableMachineBlockElimID);
53 void LiveVariables::VarInfo::dump() const {
54 cerr << " Alive in blocks: ";
55 for (unsigned i = 0, e = AliveBlocks.size(); i != e; ++i)
56 if (AliveBlocks[i]) cerr << i << ", ";
57 cerr << " Used in blocks: ";
58 for (unsigned i = 0, e = UsedBlocks.size(); i != e; ++i)
59 if (UsedBlocks[i]) cerr << i << ", ";
60 cerr << "\n Killed by:";
62 cerr << " No instructions.\n";
64 for (unsigned i = 0, e = Kills.size(); i != e; ++i)
65 cerr << "\n #" << i << ": " << *Kills[i];
70 /// getVarInfo - Get (possibly creating) a VarInfo object for the given vreg.
71 LiveVariables::VarInfo &LiveVariables::getVarInfo(unsigned RegIdx) {
72 assert(TargetRegisterInfo::isVirtualRegister(RegIdx) &&
73 "getVarInfo: not a virtual register!");
74 RegIdx -= TargetRegisterInfo::FirstVirtualRegister;
75 if (RegIdx >= VirtRegInfo.size()) {
76 if (RegIdx >= 2*VirtRegInfo.size())
77 VirtRegInfo.resize(RegIdx*2);
79 VirtRegInfo.resize(2*VirtRegInfo.size());
81 VarInfo &VI = VirtRegInfo[RegIdx];
82 VI.AliveBlocks.resize(MF->getNumBlockIDs());
83 VI.UsedBlocks.resize(MF->getNumBlockIDs());
87 void LiveVariables::MarkVirtRegAliveInBlock(VarInfo& VRInfo,
88 MachineBasicBlock *DefBlock,
89 MachineBasicBlock *MBB,
90 std::vector<MachineBasicBlock*> &WorkList) {
91 unsigned BBNum = MBB->getNumber();
93 // Check to see if this basic block is one of the killing blocks. If so,
95 for (unsigned i = 0, e = VRInfo.Kills.size(); i != e; ++i)
96 if (VRInfo.Kills[i]->getParent() == MBB) {
97 VRInfo.Kills.erase(VRInfo.Kills.begin()+i); // Erase entry
101 if (MBB == DefBlock) return; // Terminate recursion
103 if (VRInfo.AliveBlocks[BBNum])
104 return; // We already know the block is live
106 // Mark the variable known alive in this bb
107 VRInfo.AliveBlocks[BBNum] = true;
109 for (MachineBasicBlock::const_pred_reverse_iterator PI = MBB->pred_rbegin(),
110 E = MBB->pred_rend(); PI != E; ++PI)
111 WorkList.push_back(*PI);
114 void LiveVariables::MarkVirtRegAliveInBlock(VarInfo &VRInfo,
115 MachineBasicBlock *DefBlock,
116 MachineBasicBlock *MBB) {
117 std::vector<MachineBasicBlock*> WorkList;
118 MarkVirtRegAliveInBlock(VRInfo, DefBlock, MBB, WorkList);
120 while (!WorkList.empty()) {
121 MachineBasicBlock *Pred = WorkList.back();
123 MarkVirtRegAliveInBlock(VRInfo, DefBlock, Pred, WorkList);
127 void LiveVariables::HandleVirtRegUse(unsigned reg, MachineBasicBlock *MBB,
129 assert(MRI->getVRegDef(reg) && "Register use before def!");
131 unsigned BBNum = MBB->getNumber();
133 VarInfo& VRInfo = getVarInfo(reg);
134 VRInfo.UsedBlocks[BBNum] = true;
137 // Check to see if this basic block is already a kill block.
138 if (!VRInfo.Kills.empty() && VRInfo.Kills.back()->getParent() == MBB) {
139 // Yes, this register is killed in this basic block already. Increase the
140 // live range by updating the kill instruction.
141 VRInfo.Kills.back() = MI;
146 for (unsigned i = 0, e = VRInfo.Kills.size(); i != e; ++i)
147 assert(VRInfo.Kills[i]->getParent() != MBB && "entry should be at end!");
150 // This situation can occur:
155 // | t2 = phi ... t1 ...
159 // | ... = ... t1 ...
163 // where there is a use in a PHI node that's a predecessor to the defining
164 // block. We don't want to mark all predecessors as having the value "alive"
166 if (MBB == MRI->getVRegDef(reg)->getParent()) return;
168 // Add a new kill entry for this basic block. If this virtual register is
169 // already marked as alive in this basic block, that means it is alive in at
170 // least one of the successor blocks, it's not a kill.
171 if (!VRInfo.AliveBlocks[BBNum])
172 VRInfo.Kills.push_back(MI);
174 // Update all dominating blocks to mark them as "known live".
175 for (MachineBasicBlock::const_pred_iterator PI = MBB->pred_begin(),
176 E = MBB->pred_end(); PI != E; ++PI)
177 MarkVirtRegAliveInBlock(VRInfo, MRI->getVRegDef(reg)->getParent(), *PI);
180 void LiveVariables::HandleVirtRegDef(unsigned Reg, MachineInstr *MI) {
181 VarInfo &VRInfo = getVarInfo(Reg);
183 if (VRInfo.AliveBlocks.none())
184 // If vr is not alive in any block, then defaults to dead.
185 VRInfo.Kills.push_back(MI);
188 /// FindLastPartialDef - Return the last partial def of the specified register.
189 /// Also returns the sub-register that's defined.
190 MachineInstr *LiveVariables::FindLastPartialDef(unsigned Reg,
191 unsigned &PartDefReg) {
192 unsigned LastDefReg = 0;
193 unsigned LastDefDist = 0;
194 MachineInstr *LastDef = NULL;
195 for (const unsigned *SubRegs = TRI->getSubRegisters(Reg);
196 unsigned SubReg = *SubRegs; ++SubRegs) {
197 MachineInstr *Def = PhysRegDef[SubReg];
200 unsigned Dist = DistanceMap[Def];
201 if (Dist > LastDefDist) {
207 PartDefReg = LastDefReg;
211 /// HandlePhysRegUse - Turn previous partial def's into read/mod/writes. Add
212 /// implicit defs to a machine instruction if there was an earlier def of its
214 void LiveVariables::HandlePhysRegUse(unsigned Reg, MachineInstr *MI) {
215 // If there was a previous use or a "full" def all is well.
216 if (!PhysRegDef[Reg] && !PhysRegUse[Reg]) {
217 // Otherwise, the last sub-register def implicitly defines this register.
220 // AL = ... <imp-def EAX>, <imp-kill AH>
224 // All of the sub-registers must have been defined before the use of Reg!
225 unsigned PartDefReg = 0;
226 MachineInstr *LastPartialDef = FindLastPartialDef(Reg, PartDefReg);
227 // If LastPartialDef is NULL, it must be using a livein register.
228 if (LastPartialDef) {
229 LastPartialDef->addOperand(MachineOperand::CreateReg(Reg, true/*IsDef*/,
231 PhysRegDef[Reg] = LastPartialDef;
232 SmallSet<unsigned, 8> Processed;
233 for (const unsigned *SubRegs = TRI->getSubRegisters(Reg);
234 unsigned SubReg = *SubRegs; ++SubRegs) {
235 if (Processed.count(SubReg))
237 if (SubReg == PartDefReg || TRI->isSubRegister(PartDefReg, SubReg))
239 // This part of Reg was defined before the last partial def. It's killed
241 LastPartialDef->addOperand(MachineOperand::CreateReg(SubReg,
244 PhysRegDef[SubReg] = LastPartialDef;
245 for (const unsigned *SS = TRI->getSubRegisters(SubReg); *SS; ++SS)
246 Processed.insert(*SS);
251 // There was an earlier def of a super-register. Add implicit def to that MI.
256 // Add implicit def to A if there isn't a use of AX (or EAX) before B.
257 if (!PhysRegUse[Reg]) {
258 MachineInstr *Def = PhysRegDef[Reg];
259 if (Def && !Def->modifiesRegister(Reg))
260 Def->addOperand(MachineOperand::CreateReg(Reg,
265 // Remember this use.
266 PhysRegUse[Reg] = MI;
267 for (const unsigned *SubRegs = TRI->getSubRegisters(Reg);
268 unsigned SubReg = *SubRegs; ++SubRegs)
269 PhysRegUse[SubReg] = MI;
272 /// hasRegisterUseBelow - Return true if the specified register is used after
273 /// the current instruction and before it's next definition.
274 bool LiveVariables::hasRegisterUseBelow(unsigned Reg,
275 MachineBasicBlock::iterator I,
276 MachineBasicBlock *MBB) {
280 // First find out if there are any uses / defs below.
281 bool hasDistInfo = true;
282 unsigned CurDist = DistanceMap[I];
283 SmallVector<MachineInstr*, 4> Uses;
284 SmallVector<MachineInstr*, 4> Defs;
285 for (MachineRegisterInfo::reg_iterator RI = MRI->reg_begin(Reg),
286 RE = MRI->reg_end(); RI != RE; ++RI) {
287 MachineOperand &UDO = RI.getOperand();
288 MachineInstr *UDMI = &*RI;
289 if (UDMI->getParent() != MBB)
291 DenseMap<MachineInstr*, unsigned>::iterator DI = DistanceMap.find(UDMI);
292 bool isBelow = false;
293 if (DI == DistanceMap.end()) {
294 // Must be below if it hasn't been assigned a distance yet.
297 } else if (DI->second > CurDist)
301 Uses.push_back(UDMI);
303 Defs.push_back(UDMI);
310 else if (!Uses.empty() && Defs.empty())
311 // There are uses below but no defs below.
313 // There are both uses and defs below. We need to know which comes first.
315 // Complete DistanceMap for this MBB. This information is computed only
319 for (MachineBasicBlock::iterator E = MBB->end(); I != E; ++I, ++CurDist)
320 DistanceMap.insert(std::make_pair(I, CurDist));
323 unsigned EarliestUse = DistanceMap[Uses[0]];
324 for (unsigned i = 1, e = Uses.size(); i != e; ++i) {
325 unsigned Dist = DistanceMap[Uses[i]];
326 if (Dist < EarliestUse)
329 for (unsigned i = 0, e = Defs.size(); i != e; ++i) {
330 unsigned Dist = DistanceMap[Defs[i]];
331 if (Dist < EarliestUse)
332 // The register is defined before its first use below.
338 bool LiveVariables::HandlePhysRegKill(unsigned Reg) {
339 if (!PhysRegUse[Reg] && !PhysRegDef[Reg])
342 MachineInstr *LastRefOrPartRef = PhysRegUse[Reg]
343 ? PhysRegUse[Reg] : PhysRegDef[Reg];
344 unsigned LastRefOrPartRefDist = DistanceMap[LastRefOrPartRef];
345 // The whole register is used.
350 // = AL, AX<imp-use, kill>
353 // Or whole register is defined, but not used at all.
358 // Or whole register is defined, but only partly used.
359 // AX<dead> = AL<imp-def>
362 SmallSet<unsigned, 8> PartUses;
363 for (const unsigned *SubRegs = TRI->getSubRegisters(Reg);
364 unsigned SubReg = *SubRegs; ++SubRegs) {
365 if (MachineInstr *Use = PhysRegUse[SubReg]) {
366 PartUses.insert(SubReg);
367 for (const unsigned *SS = TRI->getSubRegisters(SubReg); *SS; ++SS)
368 PartUses.insert(*SS);
369 unsigned Dist = DistanceMap[Use];
370 if (Dist > LastRefOrPartRefDist) {
371 LastRefOrPartRefDist = Dist;
372 LastRefOrPartRef = Use;
376 if (LastRefOrPartRef == PhysRegDef[Reg])
378 LastRefOrPartRef->addRegisterDead(Reg, TRI, true);
380 /* Partial uses. Mark register def dead and add implicit def of
381 sub-registers which are used.
382 FIXME: LiveIntervalAnalysis can't handle this yet!
383 EAX<dead> = op AL<imp-def>
384 That is, EAX def is dead but AL def extends pass it.
385 Enable this after live interval analysis is fixed to improve codegen!
386 else if (!PhysRegUse[Reg]) {
387 PhysRegDef[Reg]->addRegisterDead(Reg, TRI, true);
388 for (const unsigned *SubRegs = TRI->getSubRegisters(Reg);
389 unsigned SubReg = *SubRegs; ++SubRegs) {
390 if (PartUses.count(SubReg)) {
391 PhysRegDef[Reg]->addOperand(MachineOperand::CreateReg(SubReg,
393 LastRefOrPartRef->addRegisterKilled(SubReg, TRI, true);
394 for (const unsigned *SS = TRI->getSubRegisters(SubReg); *SS; ++SS)
400 LastRefOrPartRef->addRegisterKilled(Reg, TRI, true);
404 void LiveVariables::HandlePhysRegDef(unsigned Reg, MachineInstr *MI) {
405 // What parts of the register are previously defined?
406 SmallSet<unsigned, 32> Live;
407 if (PhysRegDef[Reg] || PhysRegUse[Reg]) {
409 for (const unsigned *SS = TRI->getSubRegisters(Reg); *SS; ++SS)
412 for (const unsigned *SubRegs = TRI->getSubRegisters(Reg);
413 unsigned SubReg = *SubRegs; ++SubRegs) {
414 // If a register isn't itself defined, but all parts that make up of it
415 // are defined, then consider it also defined.
420 if (PhysRegDef[SubReg] || PhysRegUse[SubReg]) {
422 for (const unsigned *SS = TRI->getSubRegisters(SubReg); *SS; ++SS)
428 // Start from the largest piece, find the last time any part of the register
430 if (!HandlePhysRegKill(Reg)) {
431 // Only some of the sub-registers are used.
432 for (const unsigned *SubRegs = TRI->getSubRegisters(Reg);
433 unsigned SubReg = *SubRegs; ++SubRegs) {
434 if (!Live.count(SubReg))
435 // Skip if this sub-register isn't defined.
437 if (HandlePhysRegKill(SubReg)) {
439 for (const unsigned *SS = TRI->getSubRegisters(SubReg); *SS; ++SS)
443 assert(Live.empty() && "Not all defined registers are killed / dead?");
447 // Does this extend the live range of a super-register?
448 SmallSet<unsigned, 8> Processed;
449 for (const unsigned *SuperRegs = TRI->getSuperRegisters(Reg);
450 unsigned SuperReg = *SuperRegs; ++SuperRegs) {
451 if (Processed.count(SuperReg))
453 MachineInstr *LastRef = PhysRegUse[SuperReg]
454 ? PhysRegUse[SuperReg] : PhysRegDef[SuperReg];
455 if (LastRef && LastRef != MI) {
456 // The larger register is previously defined. Now a smaller part is
457 // being re-defined. Treat it as read/mod/write if there are uses
460 // AX = EAX<imp-use,kill>, EAX<imp-def>
463 if (hasRegisterUseBelow(SuperReg, MI, MI->getParent())) {
464 MI->addOperand(MachineOperand::CreateReg(SuperReg, false/*IsDef*/,
465 true/*IsImp*/,true/*IsKill*/));
466 MI->addOperand(MachineOperand::CreateReg(SuperReg, true/*IsDef*/,
468 PhysRegDef[SuperReg] = MI;
469 PhysRegUse[SuperReg] = NULL;
470 Processed.insert(SuperReg);
471 for (const unsigned *SS = TRI->getSubRegisters(SuperReg); *SS; ++SS) {
472 PhysRegDef[*SS] = MI;
473 PhysRegUse[*SS] = NULL;
474 Processed.insert(*SS);
477 // Otherwise, the super register is killed.
478 if (HandlePhysRegKill(SuperReg)) {
479 PhysRegDef[SuperReg] = NULL;
480 PhysRegUse[SuperReg] = NULL;
481 for (const unsigned *SS = TRI->getSubRegisters(SuperReg); *SS; ++SS) {
482 PhysRegDef[*SS] = NULL;
483 PhysRegUse[*SS] = NULL;
484 Processed.insert(*SS);
491 // Remember this def.
492 PhysRegDef[Reg] = MI;
493 PhysRegUse[Reg] = NULL;
494 for (const unsigned *SubRegs = TRI->getSubRegisters(Reg);
495 unsigned SubReg = *SubRegs; ++SubRegs) {
496 PhysRegDef[SubReg] = MI;
497 PhysRegUse[SubReg] = NULL;
502 bool LiveVariables::runOnMachineFunction(MachineFunction &mf) {
504 MRI = &mf.getRegInfo();
505 TRI = MF->getTarget().getRegisterInfo();
507 ReservedRegisters = TRI->getReservedRegs(mf);
509 unsigned NumRegs = TRI->getNumRegs();
510 PhysRegDef = new MachineInstr*[NumRegs];
511 PhysRegUse = new MachineInstr*[NumRegs];
512 PHIVarInfo = new SmallVector<unsigned, 4>[MF->getNumBlockIDs()];
513 std::fill(PhysRegDef, PhysRegDef + NumRegs, (MachineInstr*)0);
514 std::fill(PhysRegUse, PhysRegUse + NumRegs, (MachineInstr*)0);
516 /// Get some space for a respectable number of registers.
517 VirtRegInfo.resize(64);
521 // Calculate live variable information in depth first order on the CFG of the
522 // function. This guarantees that we will see the definition of a virtual
523 // register before its uses due to dominance properties of SSA (except for PHI
524 // nodes, which are treated as a special case).
525 MachineBasicBlock *Entry = MF->begin();
526 SmallPtrSet<MachineBasicBlock*,16> Visited;
528 for (df_ext_iterator<MachineBasicBlock*, SmallPtrSet<MachineBasicBlock*,16> >
529 DFI = df_ext_begin(Entry, Visited), E = df_ext_end(Entry, Visited);
531 MachineBasicBlock *MBB = *DFI;
533 // Mark live-in registers as live-in.
534 for (MachineBasicBlock::const_livein_iterator II = MBB->livein_begin(),
535 EE = MBB->livein_end(); II != EE; ++II) {
536 assert(TargetRegisterInfo::isPhysicalRegister(*II) &&
537 "Cannot have a live-in virtual register!");
538 HandlePhysRegDef(*II, 0);
541 // Loop over all of the instructions, processing them.
544 for (MachineBasicBlock::iterator I = MBB->begin(), E = MBB->end();
546 MachineInstr *MI = I;
547 DistanceMap.insert(std::make_pair(MI, Dist++));
549 // Process all of the operands of the instruction...
550 unsigned NumOperandsToProcess = MI->getNumOperands();
552 // Unless it is a PHI node. In this case, ONLY process the DEF, not any
553 // of the uses. They will be handled in other basic blocks.
554 if (MI->getOpcode() == TargetInstrInfo::PHI)
555 NumOperandsToProcess = 1;
557 SmallVector<unsigned, 4> UseRegs;
558 SmallVector<unsigned, 4> DefRegs;
559 for (unsigned i = 0; i != NumOperandsToProcess; ++i) {
560 const MachineOperand &MO = MI->getOperand(i);
561 if (MO.isReg() && MO.getReg()) {
562 unsigned MOReg = MO.getReg();
564 UseRegs.push_back(MOReg);
566 DefRegs.push_back(MOReg);
571 for (unsigned i = 0, e = UseRegs.size(); i != e; ++i) {
572 unsigned MOReg = UseRegs[i];
573 if (TargetRegisterInfo::isVirtualRegister(MOReg))
574 HandleVirtRegUse(MOReg, MBB, MI);
575 else if (!ReservedRegisters[MOReg])
576 HandlePhysRegUse(MOReg, MI);
580 for (unsigned i = 0, e = DefRegs.size(); i != e; ++i) {
581 unsigned MOReg = DefRegs[i];
582 if (TargetRegisterInfo::isVirtualRegister(MOReg))
583 HandleVirtRegDef(MOReg, MI);
584 else if (!ReservedRegisters[MOReg])
585 HandlePhysRegDef(MOReg, MI);
589 // Handle any virtual assignments from PHI nodes which might be at the
590 // bottom of this basic block. We check all of our successor blocks to see
591 // if they have PHI nodes, and if so, we simulate an assignment at the end
592 // of the current block.
593 if (!PHIVarInfo[MBB->getNumber()].empty()) {
594 SmallVector<unsigned, 4>& VarInfoVec = PHIVarInfo[MBB->getNumber()];
596 for (SmallVector<unsigned, 4>::iterator I = VarInfoVec.begin(),
597 E = VarInfoVec.end(); I != E; ++I)
598 // Mark it alive only in the block we are representing.
599 MarkVirtRegAliveInBlock(getVarInfo(*I),MRI->getVRegDef(*I)->getParent(),
603 // Finally, if the last instruction in the block is a return, make sure to
604 // mark it as using all of the live-out values in the function.
605 if (!MBB->empty() && MBB->back().getDesc().isReturn()) {
606 MachineInstr *Ret = &MBB->back();
608 for (MachineRegisterInfo::liveout_iterator
609 I = MF->getRegInfo().liveout_begin(),
610 E = MF->getRegInfo().liveout_end(); I != E; ++I) {
611 assert(TargetRegisterInfo::isPhysicalRegister(*I) &&
612 "Cannot have a live-out virtual register!");
613 HandlePhysRegUse(*I, Ret);
615 // Add live-out registers as implicit uses.
616 if (!Ret->readsRegister(*I))
617 Ret->addOperand(MachineOperand::CreateReg(*I, false, true));
621 // Loop over PhysRegDef / PhysRegUse, killing any registers that are
622 // available at the end of the basic block.
623 for (unsigned i = 0; i != NumRegs; ++i)
624 if (PhysRegDef[i] || PhysRegUse[i])
625 HandlePhysRegDef(i, 0);
627 std::fill(PhysRegDef, PhysRegDef + NumRegs, (MachineInstr*)0);
628 std::fill(PhysRegUse, PhysRegUse + NumRegs, (MachineInstr*)0);
631 // Convert and transfer the dead / killed information we have gathered into
632 // VirtRegInfo onto MI's.
633 for (unsigned i = 0, e1 = VirtRegInfo.size(); i != e1; ++i)
634 for (unsigned j = 0, e2 = VirtRegInfo[i].Kills.size(); j != e2; ++j)
635 if (VirtRegInfo[i].Kills[j] ==
636 MRI->getVRegDef(i + TargetRegisterInfo::FirstVirtualRegister))
638 .Kills[j]->addRegisterDead(i +
639 TargetRegisterInfo::FirstVirtualRegister,
643 .Kills[j]->addRegisterKilled(i +
644 TargetRegisterInfo::FirstVirtualRegister,
647 // Check to make sure there are no unreachable blocks in the MC CFG for the
648 // function. If so, it is due to a bug in the instruction selector or some
649 // other part of the code generator if this happens.
651 for(MachineFunction::iterator i = MF->begin(), e = MF->end(); i != e; ++i)
652 assert(Visited.count(&*i) != 0 && "unreachable basic block found");
662 /// replaceKillInstruction - Update register kill info by replacing a kill
663 /// instruction with a new one.
664 void LiveVariables::replaceKillInstruction(unsigned Reg, MachineInstr *OldMI,
665 MachineInstr *NewMI) {
666 VarInfo &VI = getVarInfo(Reg);
667 std::replace(VI.Kills.begin(), VI.Kills.end(), OldMI, NewMI);
670 /// removeVirtualRegistersKilled - Remove all killed info for the specified
672 void LiveVariables::removeVirtualRegistersKilled(MachineInstr *MI) {
673 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
674 MachineOperand &MO = MI->getOperand(i);
675 if (MO.isReg() && MO.isKill()) {
677 unsigned Reg = MO.getReg();
678 if (TargetRegisterInfo::isVirtualRegister(Reg)) {
679 bool removed = getVarInfo(Reg).removeKill(MI);
680 assert(removed && "kill not in register's VarInfo?");
686 /// analyzePHINodes - Gather information about the PHI nodes in here. In
687 /// particular, we want to map the variable information of a virtual register
688 /// which is used in a PHI node. We map that to the BB the vreg is coming from.
690 void LiveVariables::analyzePHINodes(const MachineFunction& Fn) {
691 for (MachineFunction::const_iterator I = Fn.begin(), E = Fn.end();
693 for (MachineBasicBlock::const_iterator BBI = I->begin(), BBE = I->end();
694 BBI != BBE && BBI->getOpcode() == TargetInstrInfo::PHI; ++BBI)
695 for (unsigned i = 1, e = BBI->getNumOperands(); i != e; i += 2)
696 PHIVarInfo[BBI->getOperand(i + 1).getMBB()->getNumber()]
697 .push_back(BBI->getOperand(i).getReg());