1 //===-- RegAllocFast.cpp - A fast register allocator for debug 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 register allocator allocates registers to a basic block at a time,
11 // attempting to keep values in registers and reusing registers as appropriate.
13 //===----------------------------------------------------------------------===//
15 #define DEBUG_TYPE "regalloc"
16 #include "llvm/BasicBlock.h"
17 #include "llvm/CodeGen/MachineFunctionPass.h"
18 #include "llvm/CodeGen/MachineInstr.h"
19 #include "llvm/CodeGen/MachineFrameInfo.h"
20 #include "llvm/CodeGen/MachineRegisterInfo.h"
21 #include "llvm/CodeGen/Passes.h"
22 #include "llvm/CodeGen/RegAllocRegistry.h"
23 #include "llvm/Target/TargetInstrInfo.h"
24 #include "llvm/Target/TargetMachine.h"
25 #include "llvm/Support/CommandLine.h"
26 #include "llvm/Support/Debug.h"
27 #include "llvm/Support/ErrorHandling.h"
28 #include "llvm/Support/raw_ostream.h"
29 #include "llvm/ADT/DenseMap.h"
30 #include "llvm/ADT/IndexedMap.h"
31 #include "llvm/ADT/SmallSet.h"
32 #include "llvm/ADT/SmallVector.h"
33 #include "llvm/ADT/Statistic.h"
34 #include "llvm/ADT/STLExtras.h"
38 STATISTIC(NumStores, "Number of stores added");
39 STATISTIC(NumLoads , "Number of loads added");
40 STATISTIC(NumCopies, "Number of copies coalesced");
42 static RegisterRegAlloc
43 fastRegAlloc("fast", "fast register allocator", createFastRegisterAllocator);
46 class RAFast : public MachineFunctionPass {
49 RAFast() : MachineFunctionPass(&ID), StackSlotForVirtReg(-1),
50 isBulkSpilling(false) {}
52 const TargetMachine *TM;
54 MachineRegisterInfo *MRI;
55 const TargetRegisterInfo *TRI;
56 const TargetInstrInfo *TII;
58 // Basic block currently being allocated.
59 MachineBasicBlock *MBB;
61 // StackSlotForVirtReg - Maps virtual regs to the frame index where these
62 // values are spilled.
63 IndexedMap<int, VirtReg2IndexFunctor> StackSlotForVirtReg;
65 // Everything we know about a live virtual register.
67 MachineInstr *LastUse; // Last instr to use reg.
68 unsigned PhysReg; // Currently held here.
69 unsigned short LastOpNum; // OpNum on LastUse.
70 bool Dirty; // Register needs spill.
72 LiveReg(unsigned p=0) : LastUse(0), PhysReg(p), LastOpNum(0),
76 typedef DenseMap<unsigned, LiveReg> LiveRegMap;
77 typedef LiveRegMap::value_type LiveRegEntry;
79 // LiveVirtRegs - This map contains entries for each virtual register
80 // that is currently available in a physical register.
81 LiveRegMap LiveVirtRegs;
83 // RegState - Track the state of a physical register.
85 // A disabled register is not available for allocation, but an alias may
86 // be in use. A register can only be moved out of the disabled state if
87 // all aliases are disabled.
90 // A free register is not currently in use and can be allocated
91 // immediately without checking aliases.
94 // A reserved register has been assigned expolicitly (e.g., setting up a
95 // call parameter), and it remains reserved until it is used.
98 // A register state may also be a virtual register number, indication that
99 // the physical register is currently allocated to a virtual register. In
100 // that case, LiveVirtRegs contains the inverse mapping.
103 // PhysRegState - One of the RegState enums, or a virtreg.
104 std::vector<unsigned> PhysRegState;
106 // UsedInInstr - BitVector of physregs that are used in the current
107 // instruction, and so cannot be allocated.
108 BitVector UsedInInstr;
110 // Allocatable - vector of allocatable physical registers.
111 BitVector Allocatable;
113 // SkippedInstrs - Descriptors of instructions whose clobber list was ignored
114 // because all registers were spilled. It is still necessary to mark all the
115 // clobbered registers as used by the function.
116 SmallPtrSet<const TargetInstrDesc*, 4> SkippedInstrs;
118 // isBulkSpilling - This flag is set when LiveRegMap will be cleared
119 // completely after spilling all live registers. LiveRegMap entries should
126 spillImpossible = ~0u
129 virtual const char *getPassName() const {
130 return "Fast Register Allocator";
133 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
134 AU.setPreservesCFG();
135 AU.addRequiredID(PHIEliminationID);
136 AU.addRequiredID(TwoAddressInstructionPassID);
137 MachineFunctionPass::getAnalysisUsage(AU);
141 bool runOnMachineFunction(MachineFunction &Fn);
142 void AllocateBasicBlock();
143 void handleThroughOperands(MachineInstr *MI,
144 SmallVectorImpl<unsigned> &VirtDead);
145 int getStackSpaceFor(unsigned VirtReg, const TargetRegisterClass *RC);
146 bool isLastUseOfLocalReg(MachineOperand&);
148 void addKillFlag(const LiveReg&);
149 void killVirtReg(LiveRegMap::iterator);
150 void killVirtReg(unsigned VirtReg);
151 void spillVirtReg(MachineBasicBlock::iterator MI, LiveRegMap::iterator);
152 void spillVirtReg(MachineBasicBlock::iterator MI, unsigned VirtReg);
154 void usePhysReg(MachineOperand&);
155 void definePhysReg(MachineInstr *MI, unsigned PhysReg, RegState NewState);
156 unsigned calcSpillCost(unsigned PhysReg) const;
157 void assignVirtToPhysReg(LiveRegEntry &LRE, unsigned PhysReg);
158 void allocVirtReg(MachineInstr *MI, LiveRegEntry &LRE, unsigned Hint);
159 LiveRegMap::iterator defineVirtReg(MachineInstr *MI, unsigned OpNum,
160 unsigned VirtReg, unsigned Hint);
161 LiveRegMap::iterator reloadVirtReg(MachineInstr *MI, unsigned OpNum,
162 unsigned VirtReg, unsigned Hint);
163 void spillAll(MachineInstr *MI);
164 bool setPhysReg(MachineInstr *MI, unsigned OpNum, unsigned PhysReg);
169 /// getStackSpaceFor - This allocates space for the specified virtual register
170 /// to be held on the stack.
171 int RAFast::getStackSpaceFor(unsigned VirtReg, const TargetRegisterClass *RC) {
172 // Find the location Reg would belong...
173 int SS = StackSlotForVirtReg[VirtReg];
175 return SS; // Already has space allocated?
177 // Allocate a new stack object for this spill location...
178 int FrameIdx = MF->getFrameInfo()->CreateSpillStackObject(RC->getSize(),
182 StackSlotForVirtReg[VirtReg] = FrameIdx;
186 /// isLastUseOfLocalReg - Return true if MO is the only remaining reference to
187 /// its virtual register, and it is guaranteed to be a block-local register.
189 bool RAFast::isLastUseOfLocalReg(MachineOperand &MO) {
190 // Check for non-debug uses or defs following MO.
191 // This is the most likely way to fail - fast path it.
192 MachineOperand *Next = &MO;
193 while ((Next = Next->getNextOperandForReg()))
194 if (!Next->isDebug())
197 // If the register has ever been spilled or reloaded, we conservatively assume
198 // it is a global register used in multiple blocks.
199 if (StackSlotForVirtReg[MO.getReg()] != -1)
202 // Check that the use/def chain has exactly one operand - MO.
203 return &MRI->reg_nodbg_begin(MO.getReg()).getOperand() == &MO;
206 /// addKillFlag - Set kill flags on last use of a virtual register.
207 void RAFast::addKillFlag(const LiveReg &LR) {
208 if (!LR.LastUse) return;
209 MachineOperand &MO = LR.LastUse->getOperand(LR.LastOpNum);
210 if (MO.isUse() && !LR.LastUse->isRegTiedToDefOperand(LR.LastOpNum)) {
211 if (MO.getReg() == LR.PhysReg)
214 LR.LastUse->addRegisterKilled(LR.PhysReg, TRI, true);
218 /// killVirtReg - Mark virtreg as no longer available.
219 void RAFast::killVirtReg(LiveRegMap::iterator LRI) {
220 addKillFlag(LRI->second);
221 const LiveReg &LR = LRI->second;
222 assert(PhysRegState[LR.PhysReg] == LRI->first && "Broken RegState mapping");
223 PhysRegState[LR.PhysReg] = regFree;
224 // Erase from LiveVirtRegs unless we're spilling in bulk.
226 LiveVirtRegs.erase(LRI);
229 /// killVirtReg - Mark virtreg as no longer available.
230 void RAFast::killVirtReg(unsigned VirtReg) {
231 assert(TargetRegisterInfo::isVirtualRegister(VirtReg) &&
232 "killVirtReg needs a virtual register");
233 LiveRegMap::iterator LRI = LiveVirtRegs.find(VirtReg);
234 if (LRI != LiveVirtRegs.end())
238 /// spillVirtReg - This method spills the value specified by VirtReg into the
239 /// corresponding stack slot if needed. If isKill is set, the register is also
241 void RAFast::spillVirtReg(MachineBasicBlock::iterator MI, unsigned VirtReg) {
242 assert(TargetRegisterInfo::isVirtualRegister(VirtReg) &&
243 "Spilling a physical register is illegal!");
244 LiveRegMap::iterator LRI = LiveVirtRegs.find(VirtReg);
245 assert(LRI != LiveVirtRegs.end() && "Spilling unmapped virtual register");
246 spillVirtReg(MI, LRI);
249 /// spillVirtReg - Do the actual work of spilling.
250 void RAFast::spillVirtReg(MachineBasicBlock::iterator MI,
251 LiveRegMap::iterator LRI) {
252 LiveReg &LR = LRI->second;
253 assert(PhysRegState[LR.PhysReg] == LRI->first && "Broken RegState mapping");
256 // If this physreg is used by the instruction, we want to kill it on the
257 // instruction, not on the spill.
258 bool SpillKill = LR.LastUse != MI;
260 DEBUG(dbgs() << "Spilling %reg" << LRI->first
261 << " in " << TRI->getName(LR.PhysReg));
262 const TargetRegisterClass *RC = MRI->getRegClass(LRI->first);
263 int FI = getStackSpaceFor(LRI->first, RC);
264 DEBUG(dbgs() << " to stack slot #" << FI << "\n");
265 TII->storeRegToStackSlot(*MBB, MI, LR.PhysReg, SpillKill, FI, RC, TRI);
266 ++NumStores; // Update statistics
269 LR.LastUse = 0; // Don't kill register again
274 /// spillAll - Spill all dirty virtregs without killing them.
275 void RAFast::spillAll(MachineInstr *MI) {
276 if (LiveVirtRegs.empty()) return;
277 isBulkSpilling = true;
278 // The LiveRegMap is keyed by an unsigned (the virtreg number), so the order
279 // of spilling here is deterministic, if arbitrary.
280 for (LiveRegMap::iterator i = LiveVirtRegs.begin(), e = LiveVirtRegs.end();
283 LiveVirtRegs.clear();
284 isBulkSpilling = false;
287 /// usePhysReg - Handle the direct use of a physical register.
288 /// Check that the register is not used by a virtreg.
289 /// Kill the physreg, marking it free.
290 /// This may add implicit kills to MO->getParent() and invalidate MO.
291 void RAFast::usePhysReg(MachineOperand &MO) {
292 unsigned PhysReg = MO.getReg();
293 assert(TargetRegisterInfo::isPhysicalRegister(PhysReg) &&
294 "Bad usePhysReg operand");
296 switch (PhysRegState[PhysReg]) {
300 PhysRegState[PhysReg] = regFree;
303 UsedInInstr.set(PhysReg);
307 // The physreg was allocated to a virtual register. That means to value we
308 // wanted has been clobbered.
309 llvm_unreachable("Instruction uses an allocated register");
312 // Maybe a superregister is reserved?
313 for (const unsigned *AS = TRI->getAliasSet(PhysReg);
314 unsigned Alias = *AS; ++AS) {
315 switch (PhysRegState[Alias]) {
319 assert(TRI->isSuperRegister(PhysReg, Alias) &&
320 "Instruction is not using a subregister of a reserved register");
321 // Leave the superregister in the working set.
322 PhysRegState[Alias] = regFree;
323 UsedInInstr.set(Alias);
324 MO.getParent()->addRegisterKilled(Alias, TRI, true);
327 if (TRI->isSuperRegister(PhysReg, Alias)) {
328 // Leave the superregister in the working set.
329 UsedInInstr.set(Alias);
330 MO.getParent()->addRegisterKilled(Alias, TRI, true);
333 // Some other alias was in the working set - clear it.
334 PhysRegState[Alias] = regDisabled;
337 llvm_unreachable("Instruction uses an alias of an allocated register");
341 // All aliases are disabled, bring register into working set.
342 PhysRegState[PhysReg] = regFree;
343 UsedInInstr.set(PhysReg);
347 /// definePhysReg - Mark PhysReg as reserved or free after spilling any
348 /// virtregs. This is very similar to defineVirtReg except the physreg is
349 /// reserved instead of allocated.
350 void RAFast::definePhysReg(MachineInstr *MI, unsigned PhysReg,
352 UsedInInstr.set(PhysReg);
353 switch (unsigned VirtReg = PhysRegState[PhysReg]) {
357 spillVirtReg(MI, VirtReg);
361 PhysRegState[PhysReg] = NewState;
365 // This is a disabled register, disable all aliases.
366 PhysRegState[PhysReg] = NewState;
367 for (const unsigned *AS = TRI->getAliasSet(PhysReg);
368 unsigned Alias = *AS; ++AS) {
369 UsedInInstr.set(Alias);
370 switch (unsigned VirtReg = PhysRegState[Alias]) {
374 spillVirtReg(MI, VirtReg);
378 PhysRegState[Alias] = regDisabled;
379 if (TRI->isSuperRegister(PhysReg, Alias))
387 // calcSpillCost - Return the cost of spilling clearing out PhysReg and
388 // aliases so it is free for allocation.
389 // Returns 0 when PhysReg is free or disabled with all aliases disabled - it
390 // can be allocated directly.
391 // Returns spillImpossible when PhysReg or an alias can't be spilled.
392 unsigned RAFast::calcSpillCost(unsigned PhysReg) const {
393 if (UsedInInstr.test(PhysReg))
394 return spillImpossible;
395 switch (unsigned VirtReg = PhysRegState[PhysReg]) {
401 return spillImpossible;
403 return LiveVirtRegs.lookup(VirtReg).Dirty ? spillDirty : spillClean;
406 // This is a disabled register, add up const of aliases.
408 for (const unsigned *AS = TRI->getAliasSet(PhysReg);
409 unsigned Alias = *AS; ++AS) {
410 if (UsedInInstr.test(Alias))
411 return spillImpossible;
412 switch (unsigned VirtReg = PhysRegState[Alias]) {
419 return spillImpossible;
421 Cost += LiveVirtRegs.lookup(VirtReg).Dirty ? spillDirty : spillClean;
429 /// assignVirtToPhysReg - This method updates local state so that we know
430 /// that PhysReg is the proper container for VirtReg now. The physical
431 /// register must not be used for anything else when this is called.
433 void RAFast::assignVirtToPhysReg(LiveRegEntry &LRE, unsigned PhysReg) {
434 DEBUG(dbgs() << "Assigning %reg" << LRE.first << " to "
435 << TRI->getName(PhysReg) << "\n");
436 PhysRegState[PhysReg] = LRE.first;
437 assert(!LRE.second.PhysReg && "Already assigned a physreg");
438 LRE.second.PhysReg = PhysReg;
441 /// allocVirtReg - Allocate a physical register for VirtReg.
442 void RAFast::allocVirtReg(MachineInstr *MI, LiveRegEntry &LRE, unsigned Hint) {
443 const unsigned VirtReg = LRE.first;
445 assert(TargetRegisterInfo::isVirtualRegister(VirtReg) &&
446 "Can only allocate virtual registers");
448 const TargetRegisterClass *RC = MRI->getRegClass(VirtReg);
450 // Ignore invalid hints.
451 if (Hint && (!TargetRegisterInfo::isPhysicalRegister(Hint) ||
452 !RC->contains(Hint) || !Allocatable.test(Hint)))
455 // Take hint when possible.
457 switch(calcSpillCost(Hint)) {
459 definePhysReg(MI, Hint, regFree);
462 return assignVirtToPhysReg(LRE, Hint);
463 case spillImpossible:
468 TargetRegisterClass::iterator AOB = RC->allocation_order_begin(*MF);
469 TargetRegisterClass::iterator AOE = RC->allocation_order_end(*MF);
471 // First try to find a completely free register.
472 for (TargetRegisterClass::iterator I = AOB; I != AOE; ++I) {
473 unsigned PhysReg = *I;
474 if (PhysRegState[PhysReg] == regFree && !UsedInInstr.test(PhysReg))
475 return assignVirtToPhysReg(LRE, PhysReg);
478 DEBUG(dbgs() << "Allocating %reg" << VirtReg << " from " << RC->getName()
481 unsigned BestReg = 0, BestCost = spillImpossible;
482 for (TargetRegisterClass::iterator I = AOB; I != AOE; ++I) {
483 unsigned Cost = calcSpillCost(*I);
484 // Cost is 0 when all aliases are already disabled.
486 return assignVirtToPhysReg(LRE, *I);
488 BestReg = *I, BestCost = Cost;
492 definePhysReg(MI, BestReg, regFree);
493 return assignVirtToPhysReg(LRE, BestReg);
496 // Nothing we can do.
498 raw_string_ostream Msg(msg);
499 Msg << "Ran out of registers during register allocation!";
500 if (MI->isInlineAsm()) {
501 Msg << "\nPlease check your inline asm statement for "
502 << "invalid constraints:\n";
505 report_fatal_error(Msg.str());
508 /// defineVirtReg - Allocate a register for VirtReg and mark it as dirty.
509 RAFast::LiveRegMap::iterator
510 RAFast::defineVirtReg(MachineInstr *MI, unsigned OpNum,
511 unsigned VirtReg, unsigned Hint) {
512 assert(TargetRegisterInfo::isVirtualRegister(VirtReg) &&
513 "Not a virtual register");
514 LiveRegMap::iterator LRI;
516 tie(LRI, New) = LiveVirtRegs.insert(std::make_pair(VirtReg, LiveReg()));
517 LiveReg &LR = LRI->second;
519 // If there is no hint, peek at the only use of this register.
520 if ((!Hint || !TargetRegisterInfo::isPhysicalRegister(Hint)) &&
521 MRI->hasOneNonDBGUse(VirtReg)) {
522 unsigned SrcReg, DstReg, SrcSubReg, DstSubReg;
523 // It's a copy, use the destination register as a hint.
524 if (TII->isMoveInstr(*MRI->use_nodbg_begin(VirtReg),
525 SrcReg, DstReg, SrcSubReg, DstSubReg))
528 allocVirtReg(MI, *LRI, Hint);
529 } else if (LR.LastUse) {
530 // Redefining a live register - kill at the last use, unless it is this
531 // instruction defining VirtReg multiple times.
532 if (LR.LastUse != MI || LR.LastUse->getOperand(LR.LastOpNum).isUse())
535 assert(LR.PhysReg && "Register not assigned");
537 LR.LastOpNum = OpNum;
539 UsedInInstr.set(LR.PhysReg);
543 /// reloadVirtReg - Make sure VirtReg is available in a physreg and return it.
544 RAFast::LiveRegMap::iterator
545 RAFast::reloadVirtReg(MachineInstr *MI, unsigned OpNum,
546 unsigned VirtReg, unsigned Hint) {
547 assert(TargetRegisterInfo::isVirtualRegister(VirtReg) &&
548 "Not a virtual register");
549 LiveRegMap::iterator LRI;
551 tie(LRI, New) = LiveVirtRegs.insert(std::make_pair(VirtReg, LiveReg()));
552 LiveReg &LR = LRI->second;
553 MachineOperand &MO = MI->getOperand(OpNum);
555 allocVirtReg(MI, *LRI, Hint);
556 const TargetRegisterClass *RC = MRI->getRegClass(VirtReg);
557 int FrameIndex = getStackSpaceFor(VirtReg, RC);
558 DEBUG(dbgs() << "Reloading %reg" << VirtReg << " into "
559 << TRI->getName(LR.PhysReg) << "\n");
560 TII->loadRegFromStackSlot(*MBB, MI, LR.PhysReg, FrameIndex, RC, TRI);
562 } else if (LR.Dirty) {
563 if (isLastUseOfLocalReg(MO)) {
564 DEBUG(dbgs() << "Killing last use: " << MO << "\n");
569 } else if (MO.isKill()) {
570 DEBUG(dbgs() << "Clearing dubious kill: " << MO << "\n");
572 } else if (MO.isDead()) {
573 DEBUG(dbgs() << "Clearing dubious dead: " << MO << "\n");
576 } else if (MO.isKill()) {
577 // We must remove kill flags from uses of reloaded registers because the
578 // register would be killed immediately, and there might be a second use:
579 // %foo = OR %x<kill>, %x
580 // This would cause a second reload of %x into a different register.
581 DEBUG(dbgs() << "Clearing clean kill: " << MO << "\n");
583 } else if (MO.isDead()) {
584 DEBUG(dbgs() << "Clearing clean dead: " << MO << "\n");
587 assert(LR.PhysReg && "Register not assigned");
589 LR.LastOpNum = OpNum;
590 UsedInInstr.set(LR.PhysReg);
594 // setPhysReg - Change operand OpNum in MI the refer the PhysReg, considering
595 // subregs. This may invalidate any operand pointers.
596 // Return true if the operand kills its register.
597 bool RAFast::setPhysReg(MachineInstr *MI, unsigned OpNum, unsigned PhysReg) {
598 MachineOperand &MO = MI->getOperand(OpNum);
599 if (!MO.getSubReg()) {
601 return MO.isKill() || MO.isDead();
604 // Handle subregister index.
605 MO.setReg(PhysReg ? TRI->getSubReg(PhysReg, MO.getSubReg()) : 0);
608 // A kill flag implies killing the full register. Add corresponding super
611 MI->addRegisterKilled(PhysReg, TRI, true);
617 // Handle special instruction operand like early clobbers and tied ops when
618 // there are additional physreg defines.
619 void RAFast::handleThroughOperands(MachineInstr *MI,
620 SmallVectorImpl<unsigned> &VirtDead) {
621 DEBUG(dbgs() << "Scanning for through registers:");
622 SmallSet<unsigned, 8> ThroughRegs;
623 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
624 MachineOperand &MO = MI->getOperand(i);
625 if (!MO.isReg()) continue;
626 unsigned Reg = MO.getReg();
627 if (!Reg || TargetRegisterInfo::isPhysicalRegister(Reg)) continue;
628 if (MO.isEarlyClobber() || MI->isRegTiedToDefOperand(i) ||
629 (MO.getSubReg() && MI->readsVirtualRegister(Reg))) {
630 if (ThroughRegs.insert(Reg))
631 DEBUG(dbgs() << " %reg" << Reg);
635 // If any physreg defines collide with preallocated through registers,
636 // we must spill and reallocate.
637 DEBUG(dbgs() << "\nChecking for physdef collisions.\n");
638 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
639 MachineOperand &MO = MI->getOperand(i);
640 if (!MO.isReg() || !MO.isDef()) continue;
641 unsigned Reg = MO.getReg();
642 if (!Reg || !TargetRegisterInfo::isPhysicalRegister(Reg)) continue;
643 UsedInInstr.set(Reg);
644 if (ThroughRegs.count(PhysRegState[Reg]))
645 definePhysReg(MI, Reg, regFree);
646 for (const unsigned *AS = TRI->getAliasSet(Reg); *AS; ++AS) {
647 UsedInInstr.set(*AS);
648 if (ThroughRegs.count(PhysRegState[*AS]))
649 definePhysReg(MI, *AS, regFree);
653 SmallVector<unsigned, 8> PartialDefs;
654 DEBUG(dbgs() << "Allocating tied uses and early clobbers.\n");
655 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
656 MachineOperand &MO = MI->getOperand(i);
657 if (!MO.isReg()) continue;
658 unsigned Reg = MO.getReg();
659 if (!Reg || TargetRegisterInfo::isPhysicalRegister(Reg)) continue;
662 if (!MI->isRegTiedToDefOperand(i, &DefIdx)) continue;
663 DEBUG(dbgs() << "Operand " << i << "("<< MO << ") is tied to operand "
665 LiveRegMap::iterator LRI = reloadVirtReg(MI, i, Reg, 0);
666 unsigned PhysReg = LRI->second.PhysReg;
667 setPhysReg(MI, i, PhysReg);
668 // Note: we don't update the def operand yet. That would cause the normal
669 // def-scan to attempt spilling.
670 } else if (MO.getSubReg() && MI->readsVirtualRegister(Reg)) {
671 DEBUG(dbgs() << "Partial redefine: " << MO << "\n");
672 // Reload the register, but don't assign to the operand just yet.
673 // That would confuse the later phys-def processing pass.
674 LiveRegMap::iterator LRI = reloadVirtReg(MI, i, Reg, 0);
675 PartialDefs.push_back(LRI->second.PhysReg);
676 } else if (MO.isEarlyClobber()) {
677 // Note: defineVirtReg may invalidate MO.
678 LiveRegMap::iterator LRI = defineVirtReg(MI, i, Reg, 0);
679 unsigned PhysReg = LRI->second.PhysReg;
680 if (setPhysReg(MI, i, PhysReg))
681 VirtDead.push_back(Reg);
685 // Restore UsedInInstr to a state usable for allocating normal virtual uses.
687 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
688 MachineOperand &MO = MI->getOperand(i);
689 if (!MO.isReg() || (MO.isDef() && !MO.isEarlyClobber())) continue;
690 unsigned Reg = MO.getReg();
691 if (!Reg || !TargetRegisterInfo::isPhysicalRegister(Reg)) continue;
692 UsedInInstr.set(Reg);
693 for (const unsigned *AS = TRI->getAliasSet(Reg); *AS; ++AS)
694 UsedInInstr.set(*AS);
697 // Also mark PartialDefs as used to avoid reallocation.
698 for (unsigned i = 0, e = PartialDefs.size(); i != e; ++i)
699 UsedInInstr.set(PartialDefs[i]);
702 void RAFast::AllocateBasicBlock() {
703 DEBUG(dbgs() << "\nAllocating " << *MBB);
705 PhysRegState.assign(TRI->getNumRegs(), regDisabled);
706 assert(LiveVirtRegs.empty() && "Mapping not cleared form last block?");
708 MachineBasicBlock::iterator MII = MBB->begin();
710 // Add live-in registers as live.
711 for (MachineBasicBlock::livein_iterator I = MBB->livein_begin(),
712 E = MBB->livein_end(); I != E; ++I)
713 definePhysReg(MII, *I, regReserved);
715 SmallVector<unsigned, 8> VirtDead;
716 SmallVector<MachineInstr*, 32> Coalesced;
718 // Otherwise, sequentially allocate each instruction in the MBB.
719 while (MII != MBB->end()) {
720 MachineInstr *MI = MII++;
721 const TargetInstrDesc &TID = MI->getDesc();
723 dbgs() << "\n>> " << *MI << "Regs:";
724 for (unsigned Reg = 1, E = TRI->getNumRegs(); Reg != E; ++Reg) {
725 if (PhysRegState[Reg] == regDisabled) continue;
726 dbgs() << " " << TRI->getName(Reg);
727 switch(PhysRegState[Reg]) {
734 dbgs() << "=%reg" << PhysRegState[Reg];
735 if (LiveVirtRegs[PhysRegState[Reg]].Dirty)
737 assert(LiveVirtRegs[PhysRegState[Reg]].PhysReg == Reg &&
743 // Check that LiveVirtRegs is the inverse.
744 for (LiveRegMap::iterator i = LiveVirtRegs.begin(),
745 e = LiveVirtRegs.end(); i != e; ++i) {
746 assert(TargetRegisterInfo::isVirtualRegister(i->first) &&
748 assert(TargetRegisterInfo::isPhysicalRegister(i->second.PhysReg) &&
750 assert(PhysRegState[i->second.PhysReg] == i->first &&
755 // Debug values are not allowed to change codegen in any way.
756 if (MI->isDebugValue()) {
757 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
758 MachineOperand &MO = MI->getOperand(i);
759 if (!MO.isReg()) continue;
760 unsigned Reg = MO.getReg();
761 if (!Reg || TargetRegisterInfo::isPhysicalRegister(Reg)) continue;
762 LiveRegMap::iterator LRI = LiveVirtRegs.find(Reg);
763 if (LRI != LiveVirtRegs.end())
764 setPhysReg(MI, i, LRI->second.PhysReg);
766 MO.setReg(0); // We can't allocate a physreg for a DebugValue, sorry!
772 // If this is a copy, we may be able to coalesce.
773 unsigned CopySrc, CopyDst, CopySrcSub, CopyDstSub;
774 if (!TII->isMoveInstr(*MI, CopySrc, CopyDst, CopySrcSub, CopyDstSub))
775 CopySrc = CopyDst = 0;
777 // Track registers used by instruction.
781 // Mark physreg uses and early clobbers as used.
782 // Find the end of the virtreg operands
783 unsigned VirtOpEnd = 0;
784 bool hasTiedOps = false;
785 bool hasEarlyClobbers = false;
786 bool hasPartialRedefs = false;
787 bool hasPhysDefs = false;
788 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
789 MachineOperand &MO = MI->getOperand(i);
790 if (!MO.isReg()) continue;
791 unsigned Reg = MO.getReg();
793 if (TargetRegisterInfo::isVirtualRegister(Reg)) {
796 hasTiedOps = hasTiedOps ||
797 TID.getOperandConstraint(i, TOI::TIED_TO) != -1;
799 if (MO.isEarlyClobber())
800 hasEarlyClobbers = true;
801 if (MO.getSubReg() && MI->readsVirtualRegister(Reg))
802 hasPartialRedefs = true;
806 if (!Allocatable.test(Reg)) continue;
809 } else if (MO.isEarlyClobber()) {
810 definePhysReg(MI, Reg, (MO.isImplicit() || MO.isDead()) ?
811 regFree : regReserved);
812 hasEarlyClobbers = true;
817 // The instruction may have virtual register operands that must be allocated
818 // the same register at use-time and def-time: early clobbers and tied
819 // operands. If there are also physical defs, these registers must avoid
820 // both physical defs and uses, making them more constrained than normal
822 // We didn't detect inline asm tied operands above, so just make this extra
823 // pass for all inline asm.
824 if (MI->isInlineAsm() || hasEarlyClobbers || hasPartialRedefs ||
825 (hasTiedOps && hasPhysDefs)) {
826 handleThroughOperands(MI, VirtDead);
827 // Don't attempt coalescing when we have funny stuff going on.
832 // Allocate virtreg uses.
833 for (unsigned i = 0; i != VirtOpEnd; ++i) {
834 MachineOperand &MO = MI->getOperand(i);
835 if (!MO.isReg()) continue;
836 unsigned Reg = MO.getReg();
837 if (!Reg || TargetRegisterInfo::isPhysicalRegister(Reg)) continue;
839 LiveRegMap::iterator LRI = reloadVirtReg(MI, i, Reg, CopyDst);
840 unsigned PhysReg = LRI->second.PhysReg;
841 CopySrc = (CopySrc == Reg || CopySrc == PhysReg) ? PhysReg : 0;
842 if (setPhysReg(MI, i, PhysReg))
847 MRI->addPhysRegsUsed(UsedInInstr);
849 // Track registers defined by instruction - early clobbers at this point.
851 if (hasEarlyClobbers) {
852 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
853 MachineOperand &MO = MI->getOperand(i);
854 if (!MO.isReg() || !MO.isDef()) continue;
855 unsigned Reg = MO.getReg();
856 if (!Reg || !TargetRegisterInfo::isPhysicalRegister(Reg)) continue;
857 UsedInInstr.set(Reg);
858 for (const unsigned *AS = TRI->getAliasSet(Reg); *AS; ++AS)
859 UsedInInstr.set(*AS);
863 unsigned DefOpEnd = MI->getNumOperands();
865 // Spill all virtregs before a call. This serves two purposes: 1. If an
866 // exception is thrown, the landing pad is going to expect to find registers
867 // in their spill slots, and 2. we don't have to wade through all the
868 // <imp-def> operands on the call instruction.
869 DefOpEnd = VirtOpEnd;
870 DEBUG(dbgs() << " Spilling remaining registers before call.\n");
873 // The imp-defs are skipped below, but we still need to mark those
874 // registers as used by the function.
875 SkippedInstrs.insert(&TID);
879 // Allocate defs and collect dead defs.
880 for (unsigned i = 0; i != DefOpEnd; ++i) {
881 MachineOperand &MO = MI->getOperand(i);
882 if (!MO.isReg() || !MO.isDef() || !MO.getReg() || MO.isEarlyClobber())
884 unsigned Reg = MO.getReg();
886 if (TargetRegisterInfo::isPhysicalRegister(Reg)) {
887 if (!Allocatable.test(Reg)) continue;
888 definePhysReg(MI, Reg, (MO.isImplicit() || MO.isDead()) ?
889 regFree : regReserved);
892 LiveRegMap::iterator LRI = defineVirtReg(MI, i, Reg, CopySrc);
893 unsigned PhysReg = LRI->second.PhysReg;
894 if (setPhysReg(MI, i, PhysReg)) {
895 VirtDead.push_back(Reg);
896 CopyDst = 0; // cancel coalescing;
898 CopyDst = (CopyDst == Reg || CopyDst == PhysReg) ? PhysReg : 0;
901 // Kill dead defs after the scan to ensure that multiple defs of the same
902 // register are allocated identically. We didn't need to do this for uses
903 // because we are crerating our own kill flags, and they are always at the
905 for (unsigned i = 0, e = VirtDead.size(); i != e; ++i)
906 killVirtReg(VirtDead[i]);
909 MRI->addPhysRegsUsed(UsedInInstr);
911 if (CopyDst && CopyDst == CopySrc && CopyDstSub == CopySrcSub) {
912 DEBUG(dbgs() << "-- coalescing: " << *MI);
913 Coalesced.push_back(MI);
915 DEBUG(dbgs() << "<< " << *MI);
919 // Spill all physical registers holding virtual registers now.
920 DEBUG(dbgs() << "Spilling live registers at end of block.\n");
921 spillAll(MBB->getFirstTerminator());
923 // Erase all the coalesced copies. We are delaying it until now because
924 // LiveVirtRegs might refer to the instrs.
925 for (unsigned i = 0, e = Coalesced.size(); i != e; ++i)
926 MBB->erase(Coalesced[i]);
927 NumCopies += Coalesced.size();
932 /// runOnMachineFunction - Register allocate the whole function
934 bool RAFast::runOnMachineFunction(MachineFunction &Fn) {
935 DEBUG(dbgs() << "********** FAST REGISTER ALLOCATION **********\n"
936 << "********** Function: "
937 << ((Value*)Fn.getFunction())->getName() << '\n');
939 MRI = &MF->getRegInfo();
940 TM = &Fn.getTarget();
941 TRI = TM->getRegisterInfo();
942 TII = TM->getInstrInfo();
944 UsedInInstr.resize(TRI->getNumRegs());
945 Allocatable = TRI->getAllocatableSet(*MF);
947 // initialize the virtual->physical register map to have a 'null'
948 // mapping for all virtual registers
949 unsigned LastVirtReg = MRI->getLastVirtReg();
950 StackSlotForVirtReg.grow(LastVirtReg);
952 // Loop over all of the basic blocks, eliminating virtual register references
953 for (MachineFunction::iterator MBBi = Fn.begin(), MBBe = Fn.end();
954 MBBi != MBBe; ++MBBi) {
956 AllocateBasicBlock();
959 // Make sure the set of used physregs is closed under subreg operations.
960 MRI->closePhysRegsUsed(*TRI);
962 // Add the clobber lists for all the instructions we skipped earlier.
963 for (SmallPtrSet<const TargetInstrDesc*, 4>::const_iterator
964 I = SkippedInstrs.begin(), E = SkippedInstrs.end(); I != E; ++I)
965 if (const unsigned *Defs = (*I)->getImplicitDefs())
967 MRI->setPhysRegUsed(*Defs++);
969 SkippedInstrs.clear();
970 StackSlotForVirtReg.clear();
974 FunctionPass *llvm::createFastRegisterAllocator() {