1//===- llvm/CodeGen/VirtRegMap.cpp - Virtual Register Map -----------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file implements the VirtRegMap class.
10//
11// It also contains implementations of the Spiller interface, which, given a
12// virtual register map and a machine function, eliminates all virtual
13// references by replacing them with physical register references - adding spill
14// code as necessary.
15//
16//===----------------------------------------------------------------------===//
17
18#include "llvm/CodeGen/VirtRegMap.h"
19#include "LiveDebugVariables.h"
20#include "llvm/ADT/SmallVector.h"
21#include "llvm/ADT/Statistic.h"
22#include "llvm/CodeGen/LiveInterval.h"
23#include "llvm/CodeGen/LiveIntervals.h"
24#include "llvm/CodeGen/LiveStacks.h"
25#include "llvm/CodeGen/MachineBasicBlock.h"
26#include "llvm/CodeGen/MachineFrameInfo.h"
27#include "llvm/CodeGen/MachineFunction.h"
28#include "llvm/CodeGen/MachineFunctionPass.h"
29#include "llvm/CodeGen/MachineInstr.h"
30#include "llvm/CodeGen/MachineOperand.h"
31#include "llvm/CodeGen/MachineRegisterInfo.h"
32#include "llvm/CodeGen/SlotIndexes.h"
33#include "llvm/CodeGen/TargetFrameLowering.h"
34#include "llvm/CodeGen/TargetInstrInfo.h"
35#include "llvm/CodeGen/TargetOpcodes.h"
36#include "llvm/CodeGen/TargetRegisterInfo.h"
37#include "llvm/CodeGen/TargetSubtargetInfo.h"
38#include "llvm/Config/llvm-config.h"
39#include "llvm/MC/LaneBitmask.h"
40#include "llvm/Pass.h"
41#include "llvm/Support/Compiler.h"
42#include "llvm/Support/Debug.h"
43#include "llvm/Support/raw_ostream.h"
44#include <cassert>
45#include <iterator>
46#include <utility>
47
48using namespace llvm;
49
50#define DEBUG_TYPE "regalloc"
51
52STATISTIC(NumSpillSlots, "Number of spill slots allocated");
53STATISTIC(NumIdCopies, "Number of identity moves eliminated after rewriting");
54
55//===----------------------------------------------------------------------===//
56// VirtRegMap implementation
57//===----------------------------------------------------------------------===//
58
59char VirtRegMap::ID = 0;
60
61INITIALIZE_PASS(VirtRegMap, "virtregmap", "Virtual Register Map", false, false)
62
63bool VirtRegMap::runOnMachineFunction(MachineFunction &mf) {
64 MRI = &mf.getRegInfo();
65 TII = mf.getSubtarget().getInstrInfo();
66 TRI = mf.getSubtarget().getRegisterInfo();
67 MF = &mf;
68
69 Virt2PhysMap.clear();
70 Virt2StackSlotMap.clear();
71 Virt2SplitMap.clear();
72 Virt2ShapeMap.clear();
73
74 grow();
75 return false;
76}
77
78void VirtRegMap::grow() {
79 unsigned NumRegs = MF->getRegInfo().getNumVirtRegs();
80 Virt2PhysMap.resize(s: NumRegs);
81 Virt2StackSlotMap.resize(s: NumRegs);
82 Virt2SplitMap.resize(s: NumRegs);
83}
84
85void VirtRegMap::assignVirt2Phys(Register virtReg, MCPhysReg physReg) {
86 assert(virtReg.isVirtual() && Register::isPhysicalRegister(physReg));
87 assert(Virt2PhysMap[virtReg.id()] == NO_PHYS_REG &&
88 "attempt to assign physical register to already mapped "
89 "virtual register");
90 assert(!getRegInfo().isReserved(physReg) &&
91 "Attempt to map virtReg to a reserved physReg");
92 Virt2PhysMap[virtReg.id()] = physReg;
93}
94
95unsigned VirtRegMap::createSpillSlot(const TargetRegisterClass *RC) {
96 unsigned Size = TRI->getSpillSize(RC: *RC);
97 Align Alignment = TRI->getSpillAlign(RC: *RC);
98 // Set preferred alignment if we are still able to realign the stack
99 auto &ST = MF->getSubtarget();
100 Align CurrentAlign = ST.getFrameLowering()->getStackAlign();
101 if (Alignment > CurrentAlign && !ST.getRegisterInfo()->canRealignStack(MF: *MF)) {
102 Alignment = CurrentAlign;
103 }
104 int SS = MF->getFrameInfo().CreateSpillStackObject(Size, Alignment);
105 ++NumSpillSlots;
106 return SS;
107}
108
109bool VirtRegMap::hasPreferredPhys(Register VirtReg) const {
110 Register Hint = MRI->getSimpleHint(VReg: VirtReg);
111 if (!Hint.isValid())
112 return false;
113 if (Hint.isVirtual())
114 Hint = getPhys(virtReg: Hint);
115 return Register(getPhys(virtReg: VirtReg)) == Hint;
116}
117
118bool VirtRegMap::hasKnownPreference(Register VirtReg) const {
119 std::pair<unsigned, Register> Hint = MRI->getRegAllocationHint(VReg: VirtReg);
120 if (Hint.second.isPhysical())
121 return true;
122 if (Hint.second.isVirtual())
123 return hasPhys(virtReg: Hint.second);
124 return false;
125}
126
127int VirtRegMap::assignVirt2StackSlot(Register virtReg) {
128 assert(virtReg.isVirtual());
129 assert(Virt2StackSlotMap[virtReg.id()] == NO_STACK_SLOT &&
130 "attempt to assign stack slot to already spilled register");
131 const TargetRegisterClass* RC = MF->getRegInfo().getRegClass(Reg: virtReg);
132 return Virt2StackSlotMap[virtReg.id()] = createSpillSlot(RC);
133}
134
135void VirtRegMap::assignVirt2StackSlot(Register virtReg, int SS) {
136 assert(virtReg.isVirtual());
137 assert(Virt2StackSlotMap[virtReg.id()] == NO_STACK_SLOT &&
138 "attempt to assign stack slot to already spilled register");
139 assert((SS >= 0 ||
140 (SS >= MF->getFrameInfo().getObjectIndexBegin())) &&
141 "illegal fixed frame index");
142 Virt2StackSlotMap[virtReg.id()] = SS;
143}
144
145void VirtRegMap::print(raw_ostream &OS, const Module*) const {
146 OS << "********** REGISTER MAP **********\n";
147 for (unsigned i = 0, e = MRI->getNumVirtRegs(); i != e; ++i) {
148 Register Reg = Register::index2VirtReg(Index: i);
149 if (Virt2PhysMap[Reg] != (unsigned)VirtRegMap::NO_PHYS_REG) {
150 OS << '[' << printReg(Reg, TRI) << " -> "
151 << printReg(Reg: Virt2PhysMap[Reg], TRI) << "] "
152 << TRI->getRegClassName(Class: MRI->getRegClass(Reg)) << "\n";
153 }
154 }
155
156 for (unsigned i = 0, e = MRI->getNumVirtRegs(); i != e; ++i) {
157 Register Reg = Register::index2VirtReg(Index: i);
158 if (Virt2StackSlotMap[Reg] != VirtRegMap::NO_STACK_SLOT) {
159 OS << '[' << printReg(Reg, TRI) << " -> fi#" << Virt2StackSlotMap[Reg]
160 << "] " << TRI->getRegClassName(Class: MRI->getRegClass(Reg)) << "\n";
161 }
162 }
163 OS << '\n';
164}
165
166#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
167LLVM_DUMP_METHOD void VirtRegMap::dump() const {
168 print(OS&: dbgs());
169}
170#endif
171
172//===----------------------------------------------------------------------===//
173// VirtRegRewriter
174//===----------------------------------------------------------------------===//
175//
176// The VirtRegRewriter is the last of the register allocator passes.
177// It rewrites virtual registers to physical registers as specified in the
178// VirtRegMap analysis. It also updates live-in information on basic blocks
179// according to LiveIntervals.
180//
181namespace {
182
183class VirtRegRewriter : public MachineFunctionPass {
184 MachineFunction *MF = nullptr;
185 const TargetRegisterInfo *TRI = nullptr;
186 const TargetInstrInfo *TII = nullptr;
187 MachineRegisterInfo *MRI = nullptr;
188 SlotIndexes *Indexes = nullptr;
189 LiveIntervals *LIS = nullptr;
190 VirtRegMap *VRM = nullptr;
191 LiveDebugVariables *DebugVars = nullptr;
192 DenseSet<Register> RewriteRegs;
193 bool ClearVirtRegs;
194
195 void rewrite();
196 void addMBBLiveIns();
197 bool readsUndefSubreg(const MachineOperand &MO) const;
198 void addLiveInsForSubRanges(const LiveInterval &LI, MCRegister PhysReg) const;
199 void handleIdentityCopy(MachineInstr &MI);
200 void expandCopyBundle(MachineInstr &MI) const;
201 bool subRegLiveThrough(const MachineInstr &MI, MCRegister SuperPhysReg) const;
202
203public:
204 static char ID;
205 VirtRegRewriter(bool ClearVirtRegs_ = true) :
206 MachineFunctionPass(ID),
207 ClearVirtRegs(ClearVirtRegs_) {}
208
209 void getAnalysisUsage(AnalysisUsage &AU) const override;
210
211 bool runOnMachineFunction(MachineFunction&) override;
212
213 MachineFunctionProperties getSetProperties() const override {
214 if (ClearVirtRegs) {
215 return MachineFunctionProperties().set(
216 MachineFunctionProperties::Property::NoVRegs);
217 }
218
219 return MachineFunctionProperties();
220 }
221};
222
223} // end anonymous namespace
224
225char VirtRegRewriter::ID = 0;
226
227char &llvm::VirtRegRewriterID = VirtRegRewriter::ID;
228
229INITIALIZE_PASS_BEGIN(VirtRegRewriter, "virtregrewriter",
230 "Virtual Register Rewriter", false, false)
231INITIALIZE_PASS_DEPENDENCY(SlotIndexes)
232INITIALIZE_PASS_DEPENDENCY(LiveIntervals)
233INITIALIZE_PASS_DEPENDENCY(LiveDebugVariables)
234INITIALIZE_PASS_DEPENDENCY(LiveStacks)
235INITIALIZE_PASS_DEPENDENCY(VirtRegMap)
236INITIALIZE_PASS_END(VirtRegRewriter, "virtregrewriter",
237 "Virtual Register Rewriter", false, false)
238
239void VirtRegRewriter::getAnalysisUsage(AnalysisUsage &AU) const {
240 AU.setPreservesCFG();
241 AU.addRequired<LiveIntervals>();
242 AU.addPreserved<LiveIntervals>();
243 AU.addRequired<SlotIndexes>();
244 AU.addPreserved<SlotIndexes>();
245 AU.addRequired<LiveDebugVariables>();
246 AU.addRequired<LiveStacks>();
247 AU.addPreserved<LiveStacks>();
248 AU.addRequired<VirtRegMap>();
249
250 if (!ClearVirtRegs)
251 AU.addPreserved<LiveDebugVariables>();
252
253 MachineFunctionPass::getAnalysisUsage(AU);
254}
255
256bool VirtRegRewriter::runOnMachineFunction(MachineFunction &fn) {
257 MF = &fn;
258 TRI = MF->getSubtarget().getRegisterInfo();
259 TII = MF->getSubtarget().getInstrInfo();
260 MRI = &MF->getRegInfo();
261 Indexes = &getAnalysis<SlotIndexes>();
262 LIS = &getAnalysis<LiveIntervals>();
263 VRM = &getAnalysis<VirtRegMap>();
264 DebugVars = &getAnalysis<LiveDebugVariables>();
265 LLVM_DEBUG(dbgs() << "********** REWRITE VIRTUAL REGISTERS **********\n"
266 << "********** Function: " << MF->getName() << '\n');
267 LLVM_DEBUG(VRM->dump());
268
269 // Add kill flags while we still have virtual registers.
270 LIS->addKillFlags(VRM);
271
272 // Live-in lists on basic blocks are required for physregs.
273 addMBBLiveIns();
274
275 // Rewrite virtual registers.
276 rewrite();
277
278 if (ClearVirtRegs) {
279 // Write out new DBG_VALUE instructions.
280
281 // We only do this if ClearVirtRegs is specified since this should be the
282 // final run of the pass and we don't want to emit them multiple times.
283 DebugVars->emitDebugValues(VRM);
284
285 // All machine operands and other references to virtual registers have been
286 // replaced. Remove the virtual registers and release all the transient data.
287 VRM->clearAllVirt();
288 MRI->clearVirtRegs();
289 }
290
291 return true;
292}
293
294void VirtRegRewriter::addLiveInsForSubRanges(const LiveInterval &LI,
295 MCRegister PhysReg) const {
296 assert(!LI.empty());
297 assert(LI.hasSubRanges());
298
299 using SubRangeIteratorPair =
300 std::pair<const LiveInterval::SubRange *, LiveInterval::const_iterator>;
301
302 SmallVector<SubRangeIteratorPair, 4> SubRanges;
303 SlotIndex First;
304 SlotIndex Last;
305 for (const LiveInterval::SubRange &SR : LI.subranges()) {
306 SubRanges.push_back(Elt: std::make_pair(x: &SR, y: SR.begin()));
307 if (!First.isValid() || SR.segments.front().start < First)
308 First = SR.segments.front().start;
309 if (!Last.isValid() || SR.segments.back().end > Last)
310 Last = SR.segments.back().end;
311 }
312
313 // Check all mbb start positions between First and Last while
314 // simultaneously advancing an iterator for each subrange.
315 for (SlotIndexes::MBBIndexIterator MBBI = Indexes->getMBBLowerBound(Idx: First);
316 MBBI != Indexes->MBBIndexEnd() && MBBI->first <= Last; ++MBBI) {
317 SlotIndex MBBBegin = MBBI->first;
318 // Advance all subrange iterators so that their end position is just
319 // behind MBBBegin (or the iterator is at the end).
320 LaneBitmask LaneMask;
321 for (auto &RangeIterPair : SubRanges) {
322 const LiveInterval::SubRange *SR = RangeIterPair.first;
323 LiveInterval::const_iterator &SRI = RangeIterPair.second;
324 while (SRI != SR->end() && SRI->end <= MBBBegin)
325 ++SRI;
326 if (SRI == SR->end())
327 continue;
328 if (SRI->start <= MBBBegin)
329 LaneMask |= SR->LaneMask;
330 }
331 if (LaneMask.none())
332 continue;
333 MachineBasicBlock *MBB = MBBI->second;
334 MBB->addLiveIn(PhysReg, LaneMask);
335 }
336}
337
338// Compute MBB live-in lists from virtual register live ranges and their
339// assignments.
340void VirtRegRewriter::addMBBLiveIns() {
341 for (unsigned Idx = 0, IdxE = MRI->getNumVirtRegs(); Idx != IdxE; ++Idx) {
342 Register VirtReg = Register::index2VirtReg(Index: Idx);
343 if (MRI->reg_nodbg_empty(RegNo: VirtReg))
344 continue;
345 LiveInterval &LI = LIS->getInterval(Reg: VirtReg);
346 if (LI.empty() || LIS->intervalIsInOneMBB(LI))
347 continue;
348 // This is a virtual register that is live across basic blocks. Its
349 // assigned PhysReg must be marked as live-in to those blocks.
350 Register PhysReg = VRM->getPhys(virtReg: VirtReg);
351 if (PhysReg == VirtRegMap::NO_PHYS_REG) {
352 // There may be no physical register assigned if only some register
353 // classes were already allocated.
354 assert(!ClearVirtRegs && "Unmapped virtual register");
355 continue;
356 }
357
358 if (LI.hasSubRanges()) {
359 addLiveInsForSubRanges(LI, PhysReg);
360 } else {
361 // Go over MBB begin positions and see if we have segments covering them.
362 // The following works because segments and the MBBIndex list are both
363 // sorted by slot indexes.
364 SlotIndexes::MBBIndexIterator I = Indexes->MBBIndexBegin();
365 for (const auto &Seg : LI) {
366 I = Indexes->getMBBLowerBound(Start: I, Idx: Seg.start);
367 for (; I != Indexes->MBBIndexEnd() && I->first < Seg.end; ++I) {
368 MachineBasicBlock *MBB = I->second;
369 MBB->addLiveIn(PhysReg);
370 }
371 }
372 }
373 }
374
375 // Sort and unique MBB LiveIns as we've not checked if SubReg/PhysReg were in
376 // each MBB's LiveIns set before calling addLiveIn on them.
377 for (MachineBasicBlock &MBB : *MF)
378 MBB.sortUniqueLiveIns();
379}
380
381/// Returns true if the given machine operand \p MO only reads undefined lanes.
382/// The function only works for use operands with a subregister set.
383bool VirtRegRewriter::readsUndefSubreg(const MachineOperand &MO) const {
384 // Shortcut if the operand is already marked undef.
385 if (MO.isUndef())
386 return true;
387
388 Register Reg = MO.getReg();
389 const LiveInterval &LI = LIS->getInterval(Reg);
390 const MachineInstr &MI = *MO.getParent();
391 SlotIndex BaseIndex = LIS->getInstructionIndex(Instr: MI);
392 // This code is only meant to handle reading undefined subregisters which
393 // we couldn't properly detect before.
394 assert(LI.liveAt(BaseIndex) &&
395 "Reads of completely dead register should be marked undef already");
396 unsigned SubRegIdx = MO.getSubReg();
397 assert(SubRegIdx != 0 && LI.hasSubRanges());
398 LaneBitmask UseMask = TRI->getSubRegIndexLaneMask(SubIdx: SubRegIdx);
399 // See if any of the relevant subregister liveranges is defined at this point.
400 for (const LiveInterval::SubRange &SR : LI.subranges()) {
401 if ((SR.LaneMask & UseMask).any() && SR.liveAt(index: BaseIndex))
402 return false;
403 }
404 return true;
405}
406
407void VirtRegRewriter::handleIdentityCopy(MachineInstr &MI) {
408 if (!MI.isIdentityCopy())
409 return;
410 LLVM_DEBUG(dbgs() << "Identity copy: " << MI);
411 ++NumIdCopies;
412
413 Register DstReg = MI.getOperand(i: 0).getReg();
414
415 // We may have deferred allocation of the virtual register, and the rewrite
416 // regs code doesn't handle the liveness update.
417 if (DstReg.isVirtual())
418 return;
419
420 RewriteRegs.insert(V: DstReg);
421
422 // Copies like:
423 // %r0 = COPY undef %r0
424 // %al = COPY %al, implicit-def %eax
425 // give us additional liveness information: The target (super-)register
426 // must not be valid before this point. Replace the COPY with a KILL
427 // instruction to maintain this information.
428 if (MI.getOperand(i: 1).isUndef() || MI.getNumOperands() > 2) {
429 MI.setDesc(TII->get(Opcode: TargetOpcode::KILL));
430 LLVM_DEBUG(dbgs() << " replace by: " << MI);
431 return;
432 }
433
434 if (Indexes)
435 Indexes->removeSingleMachineInstrFromMaps(MI);
436 MI.eraseFromBundle();
437 LLVM_DEBUG(dbgs() << " deleted.\n");
438}
439
440/// The liverange splitting logic sometimes produces bundles of copies when
441/// subregisters are involved. Expand these into a sequence of copy instructions
442/// after processing the last in the bundle. Does not update LiveIntervals
443/// which we shouldn't need for this instruction anymore.
444void VirtRegRewriter::expandCopyBundle(MachineInstr &MI) const {
445 if (!MI.isCopy() && !MI.isKill())
446 return;
447
448 if (MI.isBundledWithPred() && !MI.isBundledWithSucc()) {
449 SmallVector<MachineInstr *, 2> MIs({&MI});
450
451 // Only do this when the complete bundle is made out of COPYs and KILLs.
452 MachineBasicBlock &MBB = *MI.getParent();
453 for (MachineBasicBlock::reverse_instr_iterator I =
454 std::next(x: MI.getReverseIterator()), E = MBB.instr_rend();
455 I != E && I->isBundledWithSucc(); ++I) {
456 if (!I->isCopy() && !I->isKill())
457 return;
458 MIs.push_back(Elt: &*I);
459 }
460 MachineInstr *FirstMI = MIs.back();
461
462 auto anyRegsAlias = [](const MachineInstr *Dst,
463 ArrayRef<MachineInstr *> Srcs,
464 const TargetRegisterInfo *TRI) {
465 for (const MachineInstr *Src : Srcs)
466 if (Src != Dst)
467 if (TRI->regsOverlap(RegA: Dst->getOperand(i: 0).getReg(),
468 RegB: Src->getOperand(i: 1).getReg()))
469 return true;
470 return false;
471 };
472
473 // If any of the destination registers in the bundle of copies alias any of
474 // the source registers, try to schedule the instructions to avoid any
475 // clobbering.
476 for (int E = MIs.size(), PrevE = E; E > 1; PrevE = E) {
477 for (int I = E; I--; )
478 if (!anyRegsAlias(MIs[I], ArrayRef(MIs).take_front(N: E), TRI)) {
479 if (I + 1 != E)
480 std::swap(a&: MIs[I], b&: MIs[E - 1]);
481 --E;
482 }
483 if (PrevE == E) {
484 MF->getFunction().getContext().emitError(
485 ErrorStr: "register rewriting failed: cycle in copy bundle");
486 break;
487 }
488 }
489
490 MachineInstr *BundleStart = FirstMI;
491 for (MachineInstr *BundledMI : llvm::reverse(C&: MIs)) {
492 // If instruction is in the middle of the bundle, move it before the
493 // bundle starts, otherwise, just unbundle it. When we get to the last
494 // instruction, the bundle will have been completely undone.
495 if (BundledMI != BundleStart) {
496 BundledMI->removeFromBundle();
497 MBB.insert(I: BundleStart, MI: BundledMI);
498 } else if (BundledMI->isBundledWithSucc()) {
499 BundledMI->unbundleFromSucc();
500 BundleStart = &*std::next(x: BundledMI->getIterator());
501 }
502
503 if (Indexes && BundledMI != FirstMI)
504 Indexes->insertMachineInstrInMaps(MI&: *BundledMI);
505 }
506 }
507}
508
509/// Check whether (part of) \p SuperPhysReg is live through \p MI.
510/// \pre \p MI defines a subregister of a virtual register that
511/// has been assigned to \p SuperPhysReg.
512bool VirtRegRewriter::subRegLiveThrough(const MachineInstr &MI,
513 MCRegister SuperPhysReg) const {
514 SlotIndex MIIndex = LIS->getInstructionIndex(Instr: MI);
515 SlotIndex BeforeMIUses = MIIndex.getBaseIndex();
516 SlotIndex AfterMIDefs = MIIndex.getBoundaryIndex();
517 for (MCRegUnit Unit : TRI->regunits(Reg: SuperPhysReg)) {
518 const LiveRange &UnitRange = LIS->getRegUnit(Unit);
519 // If the regunit is live both before and after MI,
520 // we assume it is live through.
521 // Generally speaking, this is not true, because something like
522 // "RU = op RU" would match that description.
523 // However, we know that we are trying to assess whether
524 // a def of a virtual reg, vreg, is live at the same time of RU.
525 // If we are in the "RU = op RU" situation, that means that vreg
526 // is defined at the same time as RU (i.e., "vreg, RU = op RU").
527 // Thus, vreg and RU interferes and vreg cannot be assigned to
528 // SuperPhysReg. Therefore, this situation cannot happen.
529 if (UnitRange.liveAt(index: AfterMIDefs) && UnitRange.liveAt(index: BeforeMIUses))
530 return true;
531 }
532 return false;
533}
534
535void VirtRegRewriter::rewrite() {
536 bool NoSubRegLiveness = !MRI->subRegLivenessEnabled();
537 SmallVector<Register, 8> SuperDeads;
538 SmallVector<Register, 8> SuperDefs;
539 SmallVector<Register, 8> SuperKills;
540
541 for (MachineFunction::iterator MBBI = MF->begin(), MBBE = MF->end();
542 MBBI != MBBE; ++MBBI) {
543 LLVM_DEBUG(MBBI->print(dbgs(), Indexes));
544 for (MachineInstr &MI : llvm::make_early_inc_range(Range: MBBI->instrs())) {
545 for (MachineOperand &MO : MI.operands()) {
546 // Make sure MRI knows about registers clobbered by regmasks.
547 if (MO.isRegMask())
548 MRI->addPhysRegsUsedFromRegMask(RegMask: MO.getRegMask());
549
550 if (!MO.isReg() || !MO.getReg().isVirtual())
551 continue;
552 Register VirtReg = MO.getReg();
553 MCRegister PhysReg = VRM->getPhys(virtReg: VirtReg);
554 if (PhysReg == VirtRegMap::NO_PHYS_REG)
555 continue;
556
557 assert(Register(PhysReg).isPhysical());
558
559 RewriteRegs.insert(V: PhysReg);
560 assert(!MRI->isReserved(PhysReg) && "Reserved register assignment");
561
562 // Preserve semantics of sub-register operands.
563 unsigned SubReg = MO.getSubReg();
564 if (SubReg != 0) {
565 if (NoSubRegLiveness || !MRI->shouldTrackSubRegLiveness(VReg: VirtReg)) {
566 // A virtual register kill refers to the whole register, so we may
567 // have to add implicit killed operands for the super-register. A
568 // partial redef always kills and redefines the super-register.
569 if ((MO.readsReg() && (MO.isDef() || MO.isKill())) ||
570 (MO.isDef() && subRegLiveThrough(MI, SuperPhysReg: PhysReg)))
571 SuperKills.push_back(Elt: PhysReg);
572
573 if (MO.isDef()) {
574 // Also add implicit defs for the super-register.
575 if (MO.isDead())
576 SuperDeads.push_back(Elt: PhysReg);
577 else
578 SuperDefs.push_back(Elt: PhysReg);
579 }
580 } else {
581 if (MO.isUse()) {
582 if (readsUndefSubreg(MO))
583 // We need to add an <undef> flag if the subregister is
584 // completely undefined (and we are not adding super-register
585 // defs).
586 MO.setIsUndef(true);
587 } else if (!MO.isDead()) {
588 assert(MO.isDef());
589 }
590 }
591
592 // The def undef and def internal flags only make sense for
593 // sub-register defs, and we are substituting a full physreg. An
594 // implicit killed operand from the SuperKills list will represent the
595 // partial read of the super-register.
596 if (MO.isDef()) {
597 MO.setIsUndef(false);
598 MO.setIsInternalRead(false);
599 }
600
601 // PhysReg operands cannot have subregister indexes.
602 PhysReg = TRI->getSubReg(Reg: PhysReg, Idx: SubReg);
603 assert(PhysReg.isValid() && "Invalid SubReg for physical register");
604 MO.setSubReg(0);
605 }
606 // Rewrite. Note we could have used MachineOperand::substPhysReg(), but
607 // we need the inlining here.
608 MO.setReg(PhysReg);
609 MO.setIsRenamable(true);
610 }
611
612 // Add any missing super-register kills after rewriting the whole
613 // instruction.
614 while (!SuperKills.empty())
615 MI.addRegisterKilled(IncomingReg: SuperKills.pop_back_val(), RegInfo: TRI, AddIfNotFound: true);
616
617 while (!SuperDeads.empty())
618 MI.addRegisterDead(Reg: SuperDeads.pop_back_val(), RegInfo: TRI, AddIfNotFound: true);
619
620 while (!SuperDefs.empty())
621 MI.addRegisterDefined(Reg: SuperDefs.pop_back_val(), RegInfo: TRI);
622
623 LLVM_DEBUG(dbgs() << "> " << MI);
624
625 expandCopyBundle(MI);
626
627 // We can remove identity copies right now.
628 handleIdentityCopy(MI);
629 }
630 }
631
632 if (LIS) {
633 // Don't bother maintaining accurate LiveIntervals for registers which were
634 // already allocated.
635 for (Register PhysReg : RewriteRegs) {
636 for (MCRegUnit Unit : TRI->regunits(Reg: PhysReg)) {
637 LIS->removeRegUnit(Unit);
638 }
639 }
640 }
641
642 RewriteRegs.clear();
643}
644
645FunctionPass *llvm::createVirtRegRewriter(bool ClearVirtRegs) {
646 return new VirtRegRewriter(ClearVirtRegs);
647}
648

source code of llvm/lib/CodeGen/VirtRegMap.cpp