1 //===-- RegAllocLocal.cpp - A BasicBlock generic register allocator -------===//
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");
41 static RegisterRegAlloc
42 localRegAlloc("local", "local register allocator",
43 createLocalRegisterAllocator);
46 class RALocal : public MachineFunctionPass {
49 RALocal() : MachineFunctionPass(&ID), StackSlotForVirtReg(-1) {}
51 const TargetMachine *TM;
53 const TargetRegisterInfo *TRI;
54 const TargetInstrInfo *TII;
56 // StackSlotForVirtReg - Maps virtual regs to the frame index where these
57 // values are spilled.
58 IndexedMap<int, VirtReg2IndexFunctor> StackSlotForVirtReg;
60 // Virt2PhysRegMap - This map contains entries for each virtual register
61 // that is currently available in a physical register.
62 IndexedMap<unsigned, VirtReg2IndexFunctor> Virt2PhysRegMap;
64 unsigned &getVirt2PhysRegMapSlot(unsigned VirtReg) {
65 return Virt2PhysRegMap[VirtReg];
68 // PhysRegsUsed - This array is effectively a map, containing entries for
69 // each physical register that currently has a value (ie, it is in
70 // Virt2PhysRegMap). The value mapped to is the virtual register
71 // corresponding to the physical register (the inverse of the
72 // Virt2PhysRegMap), or 0. The value is set to 0 if this register is pinned
73 // because it is used by a future instruction, and to -2 if it is not
74 // allocatable. If the entry for a physical register is -1, then the
75 // physical register is "not in the map".
77 std::vector<int> PhysRegsUsed;
79 // PhysRegsUseOrder - This contains a list of the physical registers that
80 // currently have a virtual register value in them. This list provides an
81 // ordering of registers, imposing a reallocation order. This list is only
82 // used if all registers are allocated and we have to spill one, in which
83 // case we spill the least recently used register. Entries at the front of
84 // the list are the least recently used registers, entries at the back are
85 // the most recently used.
87 std::vector<unsigned> PhysRegsUseOrder;
89 // Virt2LastUseMap - This maps each virtual register to its last use
90 // (MachineInstr*, operand index pair).
91 IndexedMap<std::pair<MachineInstr*, unsigned>, VirtReg2IndexFunctor>
94 std::pair<MachineInstr*,unsigned>& getVirtRegLastUse(unsigned Reg) {
95 assert(TargetRegisterInfo::isVirtualRegister(Reg) && "Illegal VirtReg!");
96 return Virt2LastUseMap[Reg];
99 // VirtRegModified - This bitset contains information about which virtual
100 // registers need to be spilled back to memory when their registers are
101 // scavenged. If a virtual register has simply been rematerialized, there
102 // is no reason to spill it to memory when we need the register back.
104 BitVector VirtRegModified;
106 // UsedInMultipleBlocks - Tracks whether a particular register is used in
107 // more than one block.
108 BitVector UsedInMultipleBlocks;
110 void markVirtRegModified(unsigned Reg, bool Val = true) {
111 assert(TargetRegisterInfo::isVirtualRegister(Reg) && "Illegal VirtReg!");
112 Reg -= TargetRegisterInfo::FirstVirtualRegister;
114 VirtRegModified.set(Reg);
116 VirtRegModified.reset(Reg);
119 bool isVirtRegModified(unsigned Reg) const {
120 assert(TargetRegisterInfo::isVirtualRegister(Reg) && "Illegal VirtReg!");
121 assert(Reg - TargetRegisterInfo::FirstVirtualRegister <
122 VirtRegModified.size() && "Illegal virtual register!");
123 return VirtRegModified[Reg - TargetRegisterInfo::FirstVirtualRegister];
126 void AddToPhysRegsUseOrder(unsigned Reg) {
127 std::vector<unsigned>::iterator It =
128 std::find(PhysRegsUseOrder.begin(), PhysRegsUseOrder.end(), Reg);
129 if (It != PhysRegsUseOrder.end())
130 PhysRegsUseOrder.erase(It);
131 PhysRegsUseOrder.push_back(Reg);
134 void MarkPhysRegRecentlyUsed(unsigned Reg) {
135 if (PhysRegsUseOrder.empty() ||
136 PhysRegsUseOrder.back() == Reg) return; // Already most recently used
138 for (unsigned i = PhysRegsUseOrder.size(); i != 0; --i) {
139 unsigned RegMatch = PhysRegsUseOrder[i-1]; // remove from middle
140 if (!areRegsEqual(Reg, RegMatch)) continue;
142 PhysRegsUseOrder.erase(PhysRegsUseOrder.begin()+i-1);
143 // Add it to the end of the list
144 PhysRegsUseOrder.push_back(RegMatch);
146 return; // Found an exact match, exit early
151 virtual const char *getPassName() const {
152 return "Local Register Allocator";
155 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
156 AU.setPreservesCFG();
157 AU.addRequiredID(PHIEliminationID);
158 AU.addRequiredID(TwoAddressInstructionPassID);
159 MachineFunctionPass::getAnalysisUsage(AU);
163 /// runOnMachineFunction - Register allocate the whole function
164 bool runOnMachineFunction(MachineFunction &Fn);
166 /// AllocateBasicBlock - Register allocate the specified basic block.
167 void AllocateBasicBlock(MachineBasicBlock &MBB);
170 /// areRegsEqual - This method returns true if the specified registers are
171 /// related to each other. To do this, it checks to see if they are equal
172 /// or if the first register is in the alias set of the second register.
174 bool areRegsEqual(unsigned R1, unsigned R2) const {
175 if (R1 == R2) return true;
176 for (const unsigned *AliasSet = TRI->getAliasSet(R2);
177 *AliasSet; ++AliasSet) {
178 if (*AliasSet == R1) return true;
183 /// getStackSpaceFor - This returns the frame index of the specified virtual
184 /// register on the stack, allocating space if necessary.
185 int getStackSpaceFor(unsigned VirtReg, const TargetRegisterClass *RC);
187 /// removePhysReg - This method marks the specified physical register as no
188 /// longer being in use.
190 void removePhysReg(unsigned PhysReg);
192 void storeVirtReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator I,
193 unsigned VirtReg, unsigned PhysReg, bool isKill);
195 /// spillVirtReg - This method spills the value specified by PhysReg into
196 /// the virtual register slot specified by VirtReg. It then updates the RA
197 /// data structures to indicate the fact that PhysReg is now available.
199 void spillVirtReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator MI,
200 unsigned VirtReg, unsigned PhysReg);
202 /// spillPhysReg - This method spills the specified physical register into
203 /// the virtual register slot associated with it. If OnlyVirtRegs is set to
204 /// true, then the request is ignored if the physical register does not
205 /// contain a virtual register.
207 void spillPhysReg(MachineBasicBlock &MBB, MachineInstr *I,
208 unsigned PhysReg, bool OnlyVirtRegs = false);
210 /// assignVirtToPhysReg - This method updates local state so that we know
211 /// that PhysReg is the proper container for VirtReg now. The physical
212 /// register must not be used for anything else when this is called.
214 void assignVirtToPhysReg(unsigned VirtReg, unsigned PhysReg);
216 /// isPhysRegAvailable - Return true if the specified physical register is
217 /// free and available for use. This also includes checking to see if
218 /// aliased registers are all free...
220 bool isPhysRegAvailable(unsigned PhysReg) const;
222 /// getFreeReg - Look to see if there is a free register available in the
223 /// specified register class. If not, return 0.
225 unsigned getFreeReg(const TargetRegisterClass *RC);
227 /// getReg - Find a physical register to hold the specified virtual
228 /// register. If all compatible physical registers are used, this method
229 /// spills the last used virtual register to the stack, and uses that
230 /// register. If NoFree is true, that means the caller knows there isn't
231 /// a free register, do not call getFreeReg().
232 unsigned getReg(MachineBasicBlock &MBB, MachineInstr *MI,
233 unsigned VirtReg, bool NoFree = false);
235 /// reloadVirtReg - This method transforms the specified virtual
236 /// register use to refer to a physical register. This method may do this
237 /// in one of several ways: if the register is available in a physical
238 /// register already, it uses that physical register. If the value is not
239 /// in a physical register, and if there are physical registers available,
240 /// it loads it into a register: PhysReg if that is an available physical
241 /// register, otherwise any physical register of the right class.
242 /// If register pressure is high, and it is possible, it tries to fold the
243 /// load of the virtual register into the instruction itself. It avoids
244 /// doing this if register pressure is low to improve the chance that
245 /// subsequent instructions can use the reloaded value. This method
246 /// returns the modified instruction.
248 MachineInstr *reloadVirtReg(MachineBasicBlock &MBB, MachineInstr *MI,
249 unsigned OpNum, SmallSet<unsigned, 4> &RRegs,
252 /// ComputeLocalLiveness - Computes liveness of registers within a basic
253 /// block, setting the killed/dead flags as appropriate.
254 void ComputeLocalLiveness(MachineBasicBlock& MBB);
256 void reloadPhysReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator &I,
259 char RALocal::ID = 0;
262 /// getStackSpaceFor - This allocates space for the specified virtual register
263 /// to be held on the stack.
264 int RALocal::getStackSpaceFor(unsigned VirtReg, const TargetRegisterClass *RC) {
265 // Find the location Reg would belong...
266 int SS = StackSlotForVirtReg[VirtReg];
268 return SS; // Already has space allocated?
270 // Allocate a new stack object for this spill location...
271 int FrameIdx = MF->getFrameInfo()->CreateSpillStackObject(RC->getSize(),
275 StackSlotForVirtReg[VirtReg] = FrameIdx;
280 /// removePhysReg - This method marks the specified physical register as no
281 /// longer being in use.
283 void RALocal::removePhysReg(unsigned PhysReg) {
284 PhysRegsUsed[PhysReg] = -1; // PhyReg no longer used
286 std::vector<unsigned>::iterator It =
287 std::find(PhysRegsUseOrder.begin(), PhysRegsUseOrder.end(), PhysReg);
288 if (It != PhysRegsUseOrder.end())
289 PhysRegsUseOrder.erase(It);
292 /// storeVirtReg - Store a virtual register to its assigned stack slot.
293 void RALocal::storeVirtReg(MachineBasicBlock &MBB,
294 MachineBasicBlock::iterator I,
295 unsigned VirtReg, unsigned PhysReg,
297 const TargetRegisterClass *RC = MF->getRegInfo().getRegClass(VirtReg);
298 int FrameIndex = getStackSpaceFor(VirtReg, RC);
299 DEBUG(dbgs() << " to stack slot #" << FrameIndex);
300 TII->storeRegToStackSlot(MBB, I, PhysReg, isKill, FrameIndex, RC, TRI);
301 ++NumStores; // Update statistics
304 /// spillVirtReg - This method spills the value specified by PhysReg into the
305 /// virtual register slot specified by VirtReg. It then updates the RA data
306 /// structures to indicate the fact that PhysReg is now available.
308 void RALocal::spillVirtReg(MachineBasicBlock &MBB,
309 MachineBasicBlock::iterator I,
310 unsigned VirtReg, unsigned PhysReg) {
311 assert(VirtReg && "Spilling a physical register is illegal!"
312 " Must not have appropriate kill for the register or use exists beyond"
313 " the intended one.");
314 DEBUG(dbgs() << " Spilling register " << TRI->getName(PhysReg)
315 << " containing %reg" << VirtReg);
317 if (!isVirtRegModified(VirtReg)) {
318 DEBUG(dbgs() << " which has not been modified, so no store necessary!");
319 std::pair<MachineInstr*, unsigned> &LastUse = getVirtRegLastUse(VirtReg);
321 LastUse.first->getOperand(LastUse.second).setIsKill();
323 // Otherwise, there is a virtual register corresponding to this physical
324 // register. We only need to spill it into its stack slot if it has been
326 // If the instruction reads the register that's spilled, (e.g. this can
327 // happen if it is a move to a physical register), then the spill
328 // instruction is not a kill.
329 bool isKill = !(I != MBB.end() && I->readsRegister(PhysReg));
330 storeVirtReg(MBB, I, VirtReg, PhysReg, isKill);
333 getVirt2PhysRegMapSlot(VirtReg) = 0; // VirtReg no longer available
335 DEBUG(dbgs() << '\n');
336 removePhysReg(PhysReg);
340 /// spillPhysReg - This method spills the specified physical register into the
341 /// virtual register slot associated with it. If OnlyVirtRegs is set to true,
342 /// then the request is ignored if the physical register does not contain a
343 /// virtual register.
345 void RALocal::spillPhysReg(MachineBasicBlock &MBB, MachineInstr *I,
346 unsigned PhysReg, bool OnlyVirtRegs) {
347 if (PhysRegsUsed[PhysReg] != -1) { // Only spill it if it's used!
348 assert(PhysRegsUsed[PhysReg] != -2 && "Non allocable reg used!");
349 if (PhysRegsUsed[PhysReg] || !OnlyVirtRegs)
350 spillVirtReg(MBB, I, PhysRegsUsed[PhysReg], PhysReg);
354 // If the selected register aliases any other registers, we must make
355 // sure that one of the aliases isn't alive.
356 for (const unsigned *AliasSet = TRI->getAliasSet(PhysReg);
357 *AliasSet; ++AliasSet) {
358 if (PhysRegsUsed[*AliasSet] == -1 || // Spill aliased register.
359 PhysRegsUsed[*AliasSet] == -2) // If allocatable.
362 if (PhysRegsUsed[*AliasSet])
363 spillVirtReg(MBB, I, PhysRegsUsed[*AliasSet], *AliasSet);
368 /// assignVirtToPhysReg - This method updates local state so that we know
369 /// that PhysReg is the proper container for VirtReg now. The physical
370 /// register must not be used for anything else when this is called.
372 void RALocal::assignVirtToPhysReg(unsigned VirtReg, unsigned PhysReg) {
373 assert(PhysRegsUsed[PhysReg] == -1 && "Phys reg already assigned!");
374 // Update information to note the fact that this register was just used, and
376 PhysRegsUsed[PhysReg] = VirtReg;
377 getVirt2PhysRegMapSlot(VirtReg) = PhysReg;
378 AddToPhysRegsUseOrder(PhysReg); // New use of PhysReg
382 /// isPhysRegAvailable - Return true if the specified physical register is free
383 /// and available for use. This also includes checking to see if aliased
384 /// registers are all free...
386 bool RALocal::isPhysRegAvailable(unsigned PhysReg) const {
387 if (PhysRegsUsed[PhysReg] != -1) return false;
389 // If the selected register aliases any other allocated registers, it is
391 for (const unsigned *AliasSet = TRI->getAliasSet(PhysReg);
392 *AliasSet; ++AliasSet)
393 if (PhysRegsUsed[*AliasSet] >= 0) // Aliased register in use?
394 return false; // Can't use this reg then.
399 /// getFreeReg - Look to see if there is a free register available in the
400 /// specified register class. If not, return 0.
402 unsigned RALocal::getFreeReg(const TargetRegisterClass *RC) {
403 // Get iterators defining the range of registers that are valid to allocate in
404 // this class, which also specifies the preferred allocation order.
405 TargetRegisterClass::iterator RI = RC->allocation_order_begin(*MF);
406 TargetRegisterClass::iterator RE = RC->allocation_order_end(*MF);
408 for (; RI != RE; ++RI)
409 if (isPhysRegAvailable(*RI)) { // Is reg unused?
410 assert(*RI != 0 && "Cannot use register!");
411 return *RI; // Found an unused register!
417 /// getReg - Find a physical register to hold the specified virtual
418 /// register. If all compatible physical registers are used, this method spills
419 /// the last used virtual register to the stack, and uses that register.
421 unsigned RALocal::getReg(MachineBasicBlock &MBB, MachineInstr *I,
422 unsigned VirtReg, bool NoFree) {
423 const TargetRegisterClass *RC = MF->getRegInfo().getRegClass(VirtReg);
425 // First check to see if we have a free register of the requested type...
426 unsigned PhysReg = NoFree ? 0 : getFreeReg(RC);
429 // Assign the register.
430 assignVirtToPhysReg(VirtReg, PhysReg);
434 // If we didn't find an unused register, scavenge one now!
435 assert(!PhysRegsUseOrder.empty() && "No allocated registers??");
437 // Loop over all of the preallocated registers from the least recently used
438 // to the most recently used. When we find one that is capable of holding
439 // our register, use it.
440 for (unsigned i = 0; PhysReg == 0; ++i) {
441 assert(i != PhysRegsUseOrder.size() &&
442 "Couldn't find a register of the appropriate class!");
444 unsigned R = PhysRegsUseOrder[i];
446 // We can only use this register if it holds a virtual register (ie, it
447 // can be spilled). Do not use it if it is an explicitly allocated
448 // physical register!
449 assert(PhysRegsUsed[R] != -1 &&
450 "PhysReg in PhysRegsUseOrder, but is not allocated?");
451 if (PhysRegsUsed[R] && PhysRegsUsed[R] != -2) {
452 // If the current register is compatible, use it.
453 if (RC->contains(R)) {
458 // If one of the registers aliased to the current register is
459 // compatible, use it.
460 for (const unsigned *AliasIt = TRI->getAliasSet(R);
461 *AliasIt; ++AliasIt) {
462 if (!RC->contains(*AliasIt)) continue;
464 // If this is pinned down for some reason, don't use it. For
465 // example, if CL is pinned, and we run across CH, don't use
466 // CH as justification for using scavenging ECX (which will
468 if (PhysRegsUsed[*AliasIt] == 0) continue;
470 // Make sure the register is allocatable. Don't allocate SIL on
472 if (PhysRegsUsed[*AliasIt] == -2) continue;
474 PhysReg = *AliasIt; // Take an aliased register
480 assert(PhysReg && "Physical register not assigned!?!?");
482 // At this point PhysRegsUseOrder[i] is the least recently used register of
483 // compatible register class. Spill it to memory and reap its remains.
484 spillPhysReg(MBB, I, PhysReg);
486 // Now that we know which register we need to assign this to, do it now!
487 assignVirtToPhysReg(VirtReg, PhysReg);
492 /// reloadVirtReg - This method transforms the specified virtual
493 /// register use to refer to a physical register. This method may do this in
494 /// one of several ways: if the register is available in a physical register
495 /// already, it uses that physical register. If the value is not in a physical
496 /// register, and if there are physical registers available, it loads it into a
497 /// register: PhysReg if that is an available physical register, otherwise any
498 /// register. If register pressure is high, and it is possible, it tries to
499 /// fold the load of the virtual register into the instruction itself. It
500 /// avoids doing this if register pressure is low to improve the chance that
501 /// subsequent instructions can use the reloaded value. This method returns
502 /// the modified instruction.
504 MachineInstr *RALocal::reloadVirtReg(MachineBasicBlock &MBB, MachineInstr *MI,
506 SmallSet<unsigned, 4> &ReloadedRegs,
508 unsigned VirtReg = MI->getOperand(OpNum).getReg();
510 // If the virtual register is already available, just update the instruction
512 if (unsigned PR = getVirt2PhysRegMapSlot(VirtReg)) {
513 MI->getOperand(OpNum).setReg(PR); // Assign the input register
514 if (!MI->isDebugValue()) {
515 // Do not do these for DBG_VALUE as they can affect codegen.
516 MarkPhysRegRecentlyUsed(PR); // Already have this value available!
517 getVirtRegLastUse(VirtReg) = std::make_pair(MI, OpNum);
522 // Otherwise, we need to fold it into the current instruction, or reload it.
523 // If we have registers available to hold the value, use them.
524 const TargetRegisterClass *RC = MF->getRegInfo().getRegClass(VirtReg);
525 // If we already have a PhysReg (this happens when the instruction is a
526 // reg-to-reg copy with a PhysReg destination) use that.
527 if (!PhysReg || !TargetRegisterInfo::isPhysicalRegister(PhysReg) ||
528 !isPhysRegAvailable(PhysReg))
529 PhysReg = getFreeReg(RC);
530 int FrameIndex = getStackSpaceFor(VirtReg, RC);
532 if (PhysReg) { // Register is available, allocate it!
533 assignVirtToPhysReg(VirtReg, PhysReg);
534 } else { // No registers available.
535 // Force some poor hapless value out of the register file to
536 // make room for the new register, and reload it.
537 PhysReg = getReg(MBB, MI, VirtReg, true);
540 markVirtRegModified(VirtReg, false); // Note that this reg was just reloaded
542 DEBUG(dbgs() << " Reloading %reg" << VirtReg << " into "
543 << TRI->getName(PhysReg) << "\n");
545 // Add move instruction(s)
546 TII->loadRegFromStackSlot(MBB, MI, PhysReg, FrameIndex, RC, TRI);
547 ++NumLoads; // Update statistics
549 MF->getRegInfo().setPhysRegUsed(PhysReg);
550 MI->getOperand(OpNum).setReg(PhysReg); // Assign the input register
551 getVirtRegLastUse(VirtReg) = std::make_pair(MI, OpNum);
553 if (!ReloadedRegs.insert(PhysReg)) {
555 raw_string_ostream Msg(msg);
556 Msg << "Ran out of registers during register allocation!";
557 if (MI->isInlineAsm()) {
558 Msg << "\nPlease check your inline asm statement for invalid "
562 report_fatal_error(Msg.str());
564 for (const unsigned *SubRegs = TRI->getSubRegisters(PhysReg);
565 *SubRegs; ++SubRegs) {
566 if (ReloadedRegs.insert(*SubRegs)) continue;
569 raw_string_ostream Msg(msg);
570 Msg << "Ran out of registers during register allocation!";
571 if (MI->isInlineAsm()) {
572 Msg << "\nPlease check your inline asm statement for invalid "
576 report_fatal_error(Msg.str());
582 /// isReadModWriteImplicitKill - True if this is an implicit kill for a
583 /// read/mod/write register, i.e. update partial register.
584 static bool isReadModWriteImplicitKill(MachineInstr *MI, unsigned Reg) {
585 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
586 MachineOperand &MO = MI->getOperand(i);
587 if (MO.isReg() && MO.getReg() == Reg && MO.isImplicit() &&
588 MO.isDef() && !MO.isDead())
594 /// isReadModWriteImplicitDef - True if this is an implicit def for a
595 /// read/mod/write register, i.e. update partial register.
596 static bool isReadModWriteImplicitDef(MachineInstr *MI, unsigned Reg) {
597 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
598 MachineOperand &MO = MI->getOperand(i);
599 if (MO.isReg() && MO.getReg() == Reg && MO.isImplicit() &&
600 !MO.isDef() && MO.isKill())
606 // precedes - Helper function to determine with MachineInstr A
607 // precedes MachineInstr B within the same MBB.
608 static bool precedes(MachineBasicBlock::iterator A,
609 MachineBasicBlock::iterator B) {
613 MachineBasicBlock::iterator I = A->getParent()->begin();
614 while (I != A->getParent()->end()) {
626 /// ComputeLocalLiveness - Computes liveness of registers within a basic
627 /// block, setting the killed/dead flags as appropriate.
628 void RALocal::ComputeLocalLiveness(MachineBasicBlock& MBB) {
629 MachineRegisterInfo &MRI = MBB.getParent()->getRegInfo();
630 // Keep track of the most recently seen previous use or def of each reg,
631 // so that we can update them with dead/kill markers.
632 DenseMap<unsigned, std::pair<MachineInstr*, unsigned> > LastUseDef;
633 for (MachineBasicBlock::iterator I = MBB.begin(), E = MBB.end();
635 if (I->isDebugValue())
638 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
639 MachineOperand &MO = I->getOperand(i);
640 // Uses don't trigger any flags, but we need to save
641 // them for later. Also, we have to process these
642 // _before_ processing the defs, since an instr
643 // uses regs before it defs them.
644 if (!MO.isReg() || !MO.getReg() || !MO.isUse())
647 // Ignore helpful kill flags from earlier passes.
650 LastUseDef[MO.getReg()] = std::make_pair(I, i);
652 if (TargetRegisterInfo::isVirtualRegister(MO.getReg())) continue;
654 const unsigned *Aliases = TRI->getAliasSet(MO.getReg());
659 DenseMap<unsigned, std::pair<MachineInstr*, unsigned> >::iterator
660 alias = LastUseDef.find(*Aliases);
662 if (alias != LastUseDef.end() && alias->second.first != I)
663 LastUseDef[*Aliases] = std::make_pair(I, i);
669 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
670 MachineOperand &MO = I->getOperand(i);
671 // Defs others than 2-addr redefs _do_ trigger flag changes:
672 // - A def followed by a def is dead
673 // - A use followed by a def is a kill
674 if (!MO.isReg() || !MO.getReg() || !MO.isDef()) continue;
676 DenseMap<unsigned, std::pair<MachineInstr*, unsigned> >::iterator
677 last = LastUseDef.find(MO.getReg());
678 if (last != LastUseDef.end()) {
679 // Check if this is a two address instruction. If so, then
680 // the def does not kill the use.
681 if (last->second.first == I &&
682 I->isRegTiedToUseOperand(i))
685 MachineOperand &lastUD =
686 last->second.first->getOperand(last->second.second);
688 lastUD.setIsDead(true);
690 lastUD.setIsKill(true);
693 LastUseDef[MO.getReg()] = std::make_pair(I, i);
697 // Live-out (of the function) registers contain return values of the function,
698 // so we need to make sure they are alive at return time.
699 MachineBasicBlock::iterator Ret = MBB.getFirstTerminator();
700 bool BBEndsInReturn = (Ret != MBB.end() && Ret->getDesc().isReturn());
703 for (MachineRegisterInfo::liveout_iterator
704 I = MF->getRegInfo().liveout_begin(),
705 E = MF->getRegInfo().liveout_end(); I != E; ++I)
706 if (!Ret->readsRegister(*I)) {
707 Ret->addOperand(MachineOperand::CreateReg(*I, false, true));
708 LastUseDef[*I] = std::make_pair(Ret, Ret->getNumOperands()-1);
711 // Finally, loop over the final use/def of each reg
712 // in the block and determine if it is dead.
713 for (DenseMap<unsigned, std::pair<MachineInstr*, unsigned> >::iterator
714 I = LastUseDef.begin(), E = LastUseDef.end(); I != E; ++I) {
715 MachineInstr *MI = I->second.first;
716 unsigned idx = I->second.second;
717 MachineOperand &MO = MI->getOperand(idx);
719 bool isPhysReg = TargetRegisterInfo::isPhysicalRegister(MO.getReg());
721 // A crude approximation of "live-out" calculation
722 bool usedOutsideBlock = isPhysReg ? false :
723 UsedInMultipleBlocks.test(MO.getReg() -
724 TargetRegisterInfo::FirstVirtualRegister);
726 // If the machine BB ends in a return instruction, then the value isn't used
727 // outside of the BB.
728 if (!isPhysReg && (!usedOutsideBlock || BBEndsInReturn)) {
729 // DBG_VALUE complicates this: if the only refs of a register outside
730 // this block are DBG_VALUE, we can't keep the reg live just for that,
731 // as it will cause the reg to be spilled at the end of this block when
732 // it wouldn't have been otherwise. Nullify the DBG_VALUEs when that
734 bool UsedByDebugValueOnly = false;
735 for (MachineRegisterInfo::reg_iterator UI = MRI.reg_begin(MO.getReg()),
736 UE = MRI.reg_end(); UI != UE; ++UI) {
738 // - used in another block
739 // - used in the same block before it is defined (loop)
740 if (UI->getParent() == &MBB &&
741 !(MO.isDef() && UI.getOperand().isUse() && precedes(&*UI, MI)))
744 if (UI->isDebugValue()) {
745 UsedByDebugValueOnly = true;
749 // A non-DBG_VALUE use means we can leave DBG_VALUE uses alone.
750 UsedInMultipleBlocks.set(MO.getReg() -
751 TargetRegisterInfo::FirstVirtualRegister);
752 usedOutsideBlock = true;
753 UsedByDebugValueOnly = false;
757 if (UsedByDebugValueOnly)
758 for (MachineRegisterInfo::reg_iterator UI = MRI.reg_begin(MO.getReg()),
759 UE = MRI.reg_end(); UI != UE; ++UI)
760 if (UI->isDebugValue() &&
761 (UI->getParent() != &MBB ||
762 (MO.isDef() && precedes(&*UI, MI))))
763 UI.getOperand().setReg(0U);
766 // Physical registers and those that are not live-out of the block are
767 // killed/dead at their last use/def within this block.
768 if (isPhysReg || !usedOutsideBlock || BBEndsInReturn) {
770 // Don't mark uses that are tied to defs as kills.
771 if (!MI->isRegTiedToDefOperand(idx))
780 void RALocal::AllocateBasicBlock(MachineBasicBlock &MBB) {
781 // loop over each instruction
782 MachineBasicBlock::iterator MII = MBB.begin();
785 const BasicBlock *LBB = MBB.getBasicBlock();
787 dbgs() << "\nStarting RegAlloc of BB: " << LBB->getName();
790 // Add live-in registers as active.
791 for (MachineBasicBlock::livein_iterator I = MBB.livein_begin(),
792 E = MBB.livein_end(); I != E; ++I) {
794 MF->getRegInfo().setPhysRegUsed(Reg);
795 PhysRegsUsed[Reg] = 0; // It is free and reserved now
796 AddToPhysRegsUseOrder(Reg);
797 for (const unsigned *SubRegs = TRI->getSubRegisters(Reg);
798 *SubRegs; ++SubRegs) {
799 if (PhysRegsUsed[*SubRegs] == -2) continue;
801 AddToPhysRegsUseOrder(*SubRegs);
802 PhysRegsUsed[*SubRegs] = 0; // It is free and reserved now
803 MF->getRegInfo().setPhysRegUsed(*SubRegs);
807 ComputeLocalLiveness(MBB);
809 // Otherwise, sequentially allocate each instruction in the MBB.
810 while (MII != MBB.end()) {
811 MachineInstr *MI = MII++;
812 const TargetInstrDesc &TID = MI->getDesc();
814 dbgs() << "\nStarting RegAlloc of: " << *MI;
815 dbgs() << " Regs have values: ";
816 for (unsigned i = 0; i != TRI->getNumRegs(); ++i)
817 if (PhysRegsUsed[i] != -1 && PhysRegsUsed[i] != -2) {
818 if (PhysRegsUsed[i] && isVirtRegModified(PhysRegsUsed[i]))
820 dbgs() << "[" << TRI->getName(i)
821 << ",%reg" << PhysRegsUsed[i] << "] ";
826 // Determine whether this is a copy instruction. The cases where the
827 // source or destination are phys regs are handled specially.
828 unsigned SrcCopyReg, DstCopyReg, SrcCopySubReg, DstCopySubReg;
829 unsigned SrcCopyPhysReg = 0U;
830 bool isCopy = TII->isMoveInstr(*MI, SrcCopyReg, DstCopyReg,
831 SrcCopySubReg, DstCopySubReg);
832 if (isCopy && TargetRegisterInfo::isVirtualRegister(SrcCopyReg))
833 SrcCopyPhysReg = getVirt2PhysRegMapSlot(SrcCopyReg);
835 // Loop over the implicit uses, making sure that they are at the head of the
836 // use order list, so they don't get reallocated.
837 if (TID.ImplicitUses) {
838 for (const unsigned *ImplicitUses = TID.ImplicitUses;
839 *ImplicitUses; ++ImplicitUses)
840 MarkPhysRegRecentlyUsed(*ImplicitUses);
843 SmallVector<unsigned, 8> Kills;
844 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
845 MachineOperand &MO = MI->getOperand(i);
846 if (!MO.isReg() || !MO.isKill()) continue;
848 if (!MO.isImplicit())
849 Kills.push_back(MO.getReg());
850 else if (!isReadModWriteImplicitKill(MI, MO.getReg()))
851 // These are extra physical register kills when a sub-register
852 // is defined (def of a sub-register is a read/mod/write of the
853 // larger registers). Ignore.
854 Kills.push_back(MO.getReg());
857 // If any physical regs are earlyclobber, spill any value they might
858 // have in them, then mark them unallocatable.
859 // If any virtual regs are earlyclobber, allocate them now (before
860 // freeing inputs that are killed).
861 if (MI->isInlineAsm()) {
862 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
863 MachineOperand &MO = MI->getOperand(i);
864 if (!MO.isReg() || !MO.isDef() || !MO.isEarlyClobber() ||
868 if (TargetRegisterInfo::isVirtualRegister(MO.getReg())) {
869 unsigned DestVirtReg = MO.getReg();
870 unsigned DestPhysReg;
872 // If DestVirtReg already has a value, use it.
873 if (!(DestPhysReg = getVirt2PhysRegMapSlot(DestVirtReg)))
874 DestPhysReg = getReg(MBB, MI, DestVirtReg);
875 MF->getRegInfo().setPhysRegUsed(DestPhysReg);
876 markVirtRegModified(DestVirtReg);
877 getVirtRegLastUse(DestVirtReg) =
878 std::make_pair((MachineInstr*)0, 0);
879 DEBUG(dbgs() << " Assigning " << TRI->getName(DestPhysReg)
880 << " to %reg" << DestVirtReg << "\n");
881 MO.setReg(DestPhysReg); // Assign the earlyclobber register
883 unsigned Reg = MO.getReg();
884 if (PhysRegsUsed[Reg] == -2) continue; // Something like ESP.
885 // These are extra physical register defs when a sub-register
886 // is defined (def of a sub-register is a read/mod/write of the
887 // larger registers). Ignore.
888 if (isReadModWriteImplicitDef(MI, MO.getReg())) continue;
890 MF->getRegInfo().setPhysRegUsed(Reg);
891 spillPhysReg(MBB, MI, Reg, true); // Spill any existing value in reg
892 PhysRegsUsed[Reg] = 0; // It is free and reserved now
893 AddToPhysRegsUseOrder(Reg);
895 for (const unsigned *SubRegs = TRI->getSubRegisters(Reg);
896 *SubRegs; ++SubRegs) {
897 if (PhysRegsUsed[*SubRegs] == -2) continue;
898 MF->getRegInfo().setPhysRegUsed(*SubRegs);
899 PhysRegsUsed[*SubRegs] = 0; // It is free and reserved now
900 AddToPhysRegsUseOrder(*SubRegs);
906 // If a DBG_VALUE says something is located in a spilled register,
907 // change the DBG_VALUE to be undef, which prevents the register
908 // from being reloaded here. Doing that would change the generated
909 // code, unless another use immediately follows this instruction.
910 if (MI->isDebugValue() &&
911 MI->getNumOperands()==3 && MI->getOperand(0).isReg()) {
912 unsigned VirtReg = MI->getOperand(0).getReg();
913 if (VirtReg && TargetRegisterInfo::isVirtualRegister(VirtReg) &&
914 !getVirt2PhysRegMapSlot(VirtReg))
915 MI->getOperand(0).setReg(0U);
918 // Get the used operands into registers. This has the potential to spill
919 // incoming values if we are out of registers. Note that we completely
920 // ignore physical register uses here. We assume that if an explicit
921 // physical register is referenced by the instruction, that it is guaranteed
922 // to be live-in, or the input is badly hosed.
924 SmallSet<unsigned, 4> ReloadedRegs;
925 for (unsigned i = 0; i != MI->getNumOperands(); ++i) {
926 MachineOperand &MO = MI->getOperand(i);
927 // here we are looking for only used operands (never def&use)
928 if (MO.isReg() && !MO.isDef() && MO.getReg() && !MO.isImplicit() &&
929 TargetRegisterInfo::isVirtualRegister(MO.getReg()))
930 MI = reloadVirtReg(MBB, MI, i, ReloadedRegs,
931 isCopy ? DstCopyReg : 0);
934 // If this instruction is the last user of this register, kill the
935 // value, freeing the register being used, so it doesn't need to be
936 // spilled to memory.
938 for (unsigned i = 0, e = Kills.size(); i != e; ++i) {
939 unsigned VirtReg = Kills[i];
940 unsigned PhysReg = VirtReg;
941 if (TargetRegisterInfo::isVirtualRegister(VirtReg)) {
942 // If the virtual register was never materialized into a register, it
943 // might not be in the map, but it won't hurt to zero it out anyway.
944 unsigned &PhysRegSlot = getVirt2PhysRegMapSlot(VirtReg);
945 PhysReg = PhysRegSlot;
947 } else if (PhysRegsUsed[PhysReg] == -2) {
948 // Unallocatable register dead, ignore.
951 assert((!PhysRegsUsed[PhysReg] || PhysRegsUsed[PhysReg] == -1) &&
952 "Silently clearing a virtual register?");
955 if (!PhysReg) continue;
957 DEBUG(dbgs() << " Last use of " << TRI->getName(PhysReg)
958 << "[%reg" << VirtReg <<"], removing it from live set\n");
959 removePhysReg(PhysReg);
960 for (const unsigned *SubRegs = TRI->getSubRegisters(PhysReg);
961 *SubRegs; ++SubRegs) {
962 if (PhysRegsUsed[*SubRegs] != -2) {
963 DEBUG(dbgs() << " Last use of "
964 << TRI->getName(*SubRegs) << "[%reg" << VirtReg
965 <<"], removing it from live set\n");
966 removePhysReg(*SubRegs);
971 // Loop over all of the operands of the instruction, spilling registers that
972 // are defined, and marking explicit destinations in the PhysRegsUsed map.
973 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
974 MachineOperand &MO = MI->getOperand(i);
975 if (!MO.isReg() || !MO.isDef() || MO.isImplicit() || !MO.getReg() ||
976 MO.isEarlyClobber() ||
977 !TargetRegisterInfo::isPhysicalRegister(MO.getReg()))
980 unsigned Reg = MO.getReg();
981 if (PhysRegsUsed[Reg] == -2) continue; // Something like ESP.
982 // These are extra physical register defs when a sub-register
983 // is defined (def of a sub-register is a read/mod/write of the
984 // larger registers). Ignore.
985 if (isReadModWriteImplicitDef(MI, MO.getReg())) continue;
987 MF->getRegInfo().setPhysRegUsed(Reg);
988 spillPhysReg(MBB, MI, Reg, true); // Spill any existing value in reg
989 PhysRegsUsed[Reg] = 0; // It is free and reserved now
990 AddToPhysRegsUseOrder(Reg);
992 for (const unsigned *SubRegs = TRI->getSubRegisters(Reg);
993 *SubRegs; ++SubRegs) {
994 if (PhysRegsUsed[*SubRegs] == -2) continue;
996 MF->getRegInfo().setPhysRegUsed(*SubRegs);
997 PhysRegsUsed[*SubRegs] = 0; // It is free and reserved now
998 AddToPhysRegsUseOrder(*SubRegs);
1002 // Loop over the implicit defs, spilling them as well.
1003 if (TID.ImplicitDefs) {
1004 for (const unsigned *ImplicitDefs = TID.ImplicitDefs;
1005 *ImplicitDefs; ++ImplicitDefs) {
1006 unsigned Reg = *ImplicitDefs;
1007 if (PhysRegsUsed[Reg] != -2) {
1008 spillPhysReg(MBB, MI, Reg, true);
1009 AddToPhysRegsUseOrder(Reg);
1010 PhysRegsUsed[Reg] = 0; // It is free and reserved now
1012 MF->getRegInfo().setPhysRegUsed(Reg);
1013 for (const unsigned *SubRegs = TRI->getSubRegisters(Reg);
1014 *SubRegs; ++SubRegs) {
1015 if (PhysRegsUsed[*SubRegs] == -2) continue;
1017 AddToPhysRegsUseOrder(*SubRegs);
1018 PhysRegsUsed[*SubRegs] = 0; // It is free and reserved now
1019 MF->getRegInfo().setPhysRegUsed(*SubRegs);
1024 SmallVector<unsigned, 8> DeadDefs;
1025 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
1026 MachineOperand &MO = MI->getOperand(i);
1027 if (MO.isReg() && MO.isDead())
1028 DeadDefs.push_back(MO.getReg());
1031 // Okay, we have allocated all of the source operands and spilled any values
1032 // that would be destroyed by defs of this instruction. Loop over the
1033 // explicit defs and assign them to a register, spilling incoming values if
1034 // we need to scavenge a register.
1036 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
1037 MachineOperand &MO = MI->getOperand(i);
1038 if (!MO.isReg() || !MO.isDef() || !MO.getReg() ||
1039 MO.isEarlyClobber() ||
1040 !TargetRegisterInfo::isVirtualRegister(MO.getReg()))
1043 unsigned DestVirtReg = MO.getReg();
1044 unsigned DestPhysReg;
1046 // If DestVirtReg already has a value, use it.
1047 if (!(DestPhysReg = getVirt2PhysRegMapSlot(DestVirtReg))) {
1048 // If this is a copy try to reuse the input as the output;
1049 // that will make the copy go away.
1050 // If this is a copy, the source reg is a phys reg, and
1051 // that reg is available, use that phys reg for DestPhysReg.
1052 // If this is a copy, the source reg is a virtual reg, and
1053 // the phys reg that was assigned to that virtual reg is now
1054 // available, use that phys reg for DestPhysReg. (If it's now
1055 // available that means this was the last use of the source.)
1057 TargetRegisterInfo::isPhysicalRegister(SrcCopyReg) &&
1058 isPhysRegAvailable(SrcCopyReg)) {
1059 DestPhysReg = SrcCopyReg;
1060 assignVirtToPhysReg(DestVirtReg, DestPhysReg);
1061 } else if (isCopy &&
1062 TargetRegisterInfo::isVirtualRegister(SrcCopyReg) &&
1063 SrcCopyPhysReg && isPhysRegAvailable(SrcCopyPhysReg) &&
1064 MF->getRegInfo().getRegClass(DestVirtReg)->
1065 contains(SrcCopyPhysReg)) {
1066 DestPhysReg = SrcCopyPhysReg;
1067 assignVirtToPhysReg(DestVirtReg, DestPhysReg);
1069 DestPhysReg = getReg(MBB, MI, DestVirtReg);
1071 MF->getRegInfo().setPhysRegUsed(DestPhysReg);
1072 markVirtRegModified(DestVirtReg);
1073 getVirtRegLastUse(DestVirtReg) = std::make_pair((MachineInstr*)0, 0);
1074 DEBUG(dbgs() << " Assigning " << TRI->getName(DestPhysReg)
1075 << " to %reg" << DestVirtReg << "\n");
1076 MO.setReg(DestPhysReg); // Assign the output register
1079 // If this instruction defines any registers that are immediately dead,
1082 for (unsigned i = 0, e = DeadDefs.size(); i != e; ++i) {
1083 unsigned VirtReg = DeadDefs[i];
1084 unsigned PhysReg = VirtReg;
1085 if (TargetRegisterInfo::isVirtualRegister(VirtReg)) {
1086 unsigned &PhysRegSlot = getVirt2PhysRegMapSlot(VirtReg);
1087 PhysReg = PhysRegSlot;
1088 assert(PhysReg != 0);
1090 } else if (PhysRegsUsed[PhysReg] == -2) {
1091 // Unallocatable register dead, ignore.
1093 } else if (!PhysReg)
1096 DEBUG(dbgs() << " Register " << TRI->getName(PhysReg)
1097 << " [%reg" << VirtReg
1098 << "] is never used, removing it from live set\n");
1099 removePhysReg(PhysReg);
1100 for (const unsigned *AliasSet = TRI->getAliasSet(PhysReg);
1101 *AliasSet; ++AliasSet) {
1102 if (PhysRegsUsed[*AliasSet] != -2) {
1103 DEBUG(dbgs() << " Register " << TRI->getName(*AliasSet)
1104 << " [%reg" << *AliasSet
1105 << "] is never used, removing it from live set\n");
1106 removePhysReg(*AliasSet);
1111 // If this instruction is a call, make sure there are no dirty registers. The
1112 // call might throw an exception, and the landing pad expects to find all
1113 // registers in stack slots.
1115 for (unsigned i = 0, e = TRI->getNumRegs(); i != e; ++i) {
1116 if (PhysRegsUsed[i] <= 0) continue;
1117 unsigned VirtReg = PhysRegsUsed[i];
1118 if (!isVirtRegModified(VirtReg)) continue;
1119 DEBUG(dbgs() << " Storing dirty %reg" << VirtReg);
1120 storeVirtReg(MBB, MI, VirtReg, i, false);
1121 markVirtRegModified(VirtReg, false);
1122 DEBUG(dbgs() << " because the call might throw\n");
1125 // Finally, if this is a noop copy instruction, zap it. (Except that if
1126 // the copy is dead, it must be kept to avoid messing up liveness info for
1127 // the register scavenger. See pr4100.)
1128 if (TII->isMoveInstr(*MI, SrcCopyReg, DstCopyReg,
1129 SrcCopySubReg, DstCopySubReg) &&
1130 SrcCopyReg == DstCopyReg && DeadDefs.empty())
1134 MachineBasicBlock::iterator MI = MBB.getFirstTerminator();
1136 // Spill all physical registers holding virtual registers now.
1137 for (unsigned i = 0, e = TRI->getNumRegs(); i != e; ++i)
1138 if (PhysRegsUsed[i] != -1 && PhysRegsUsed[i] != -2) {
1139 if (unsigned VirtReg = PhysRegsUsed[i])
1140 spillVirtReg(MBB, MI, VirtReg, i);
1146 // This checking code is very expensive.
1148 for (unsigned i = TargetRegisterInfo::FirstVirtualRegister,
1149 e = MF->getRegInfo().getLastVirtReg(); i <= e; ++i)
1150 if (unsigned PR = Virt2PhysRegMap[i]) {
1151 cerr << "Register still mapped: " << i << " -> " << PR << "\n";
1154 assert(AllOk && "Virtual registers still in phys regs?");
1157 // Clear any physical register which appear live at the end of the basic
1158 // block, but which do not hold any virtual registers. e.g., the stack
1160 PhysRegsUseOrder.clear();
1163 /// runOnMachineFunction - Register allocate the whole function
1165 bool RALocal::runOnMachineFunction(MachineFunction &Fn) {
1166 DEBUG(dbgs() << "Machine Function\n");
1168 TM = &Fn.getTarget();
1169 TRI = TM->getRegisterInfo();
1170 TII = TM->getInstrInfo();
1172 PhysRegsUsed.assign(TRI->getNumRegs(), -1);
1174 // At various places we want to efficiently check to see whether a register
1175 // is allocatable. To handle this, we mark all unallocatable registers as
1176 // being pinned down, permanently.
1178 BitVector Allocable = TRI->getAllocatableSet(Fn);
1179 for (unsigned i = 0, e = Allocable.size(); i != e; ++i)
1181 PhysRegsUsed[i] = -2; // Mark the reg unallocable.
1184 // initialize the virtual->physical register map to have a 'null'
1185 // mapping for all virtual registers
1186 unsigned LastVirtReg = MF->getRegInfo().getLastVirtReg();
1187 StackSlotForVirtReg.grow(LastVirtReg);
1188 Virt2PhysRegMap.grow(LastVirtReg);
1189 Virt2LastUseMap.grow(LastVirtReg);
1190 VirtRegModified.resize(LastVirtReg+1 -
1191 TargetRegisterInfo::FirstVirtualRegister);
1192 UsedInMultipleBlocks.resize(LastVirtReg+1 -
1193 TargetRegisterInfo::FirstVirtualRegister);
1195 // Loop over all of the basic blocks, eliminating virtual register references
1196 for (MachineFunction::iterator MBB = Fn.begin(), MBBe = Fn.end();
1198 AllocateBasicBlock(*MBB);
1200 StackSlotForVirtReg.clear();
1201 PhysRegsUsed.clear();
1202 VirtRegModified.clear();
1203 UsedInMultipleBlocks.clear();
1204 Virt2PhysRegMap.clear();
1205 Virt2LastUseMap.clear();
1209 FunctionPass *llvm::createLocalRegisterAllocator() {
1210 return new RALocal();