1 //===-- RegAllocLocal.cpp - A BasicBlock generic register allocator -------===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the LLVM research group and is distributed under
6 // the University of Illinois Open Source 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/CodeGen/Passes.h"
17 #include "llvm/CodeGen/MachineFunctionPass.h"
18 #include "llvm/CodeGen/MachineInstr.h"
19 #include "llvm/CodeGen/SSARegMap.h"
20 #include "llvm/CodeGen/MachineFrameInfo.h"
21 #include "llvm/CodeGen/LiveVariables.h"
22 #include "llvm/Target/TargetInstrInfo.h"
23 #include "llvm/Target/TargetMachine.h"
24 #include "llvm/Support/CommandLine.h"
25 #include "llvm/Support/Debug.h"
26 #include "llvm/ADT/DenseMap.h"
27 #include "llvm/ADT/Statistic.h"
33 Statistic<> NumStores("ra-local", "Number of stores added");
34 Statistic<> NumLoads ("ra-local", "Number of loads added");
35 Statistic<> NumFolded("ra-local", "Number of loads/stores folded into "
37 class RA : public MachineFunctionPass {
38 const TargetMachine *TM;
40 const MRegisterInfo *RegInfo;
42 bool *PhysRegsEverUsed;
44 // StackSlotForVirtReg - Maps virtual regs to the frame index where these
45 // values are spilled.
46 std::map<unsigned, int> StackSlotForVirtReg;
48 // Virt2PhysRegMap - This map contains entries for each virtual register
49 // that is currently available in a physical register.
50 DenseMap<unsigned, VirtReg2IndexFunctor> Virt2PhysRegMap;
52 unsigned &getVirt2PhysRegMapSlot(unsigned VirtReg) {
53 return Virt2PhysRegMap[VirtReg];
56 // PhysRegsUsed - This array is effectively a map, containing entries for
57 // each physical register that currently has a value (ie, it is in
58 // Virt2PhysRegMap). The value mapped to is the virtual register
59 // corresponding to the physical register (the inverse of the
60 // Virt2PhysRegMap), or 0. The value is set to 0 if this register is pinned
61 // because it is used by a future instruction. If the entry for a physical
62 // register is -1, then the physical register is "not in the map".
64 std::vector<int> PhysRegsUsed;
66 // PhysRegsUseOrder - This contains a list of the physical registers that
67 // currently have a virtual register value in them. This list provides an
68 // ordering of registers, imposing a reallocation order. This list is only
69 // used if all registers are allocated and we have to spill one, in which
70 // case we spill the least recently used register. Entries at the front of
71 // the list are the least recently used registers, entries at the back are
72 // the most recently used.
74 std::vector<unsigned> PhysRegsUseOrder;
76 // VirtRegModified - This bitset contains information about which virtual
77 // registers need to be spilled back to memory when their registers are
78 // scavenged. If a virtual register has simply been rematerialized, there
79 // is no reason to spill it to memory when we need the register back.
81 std::vector<bool> VirtRegModified;
83 void markVirtRegModified(unsigned Reg, bool Val = true) {
84 assert(MRegisterInfo::isVirtualRegister(Reg) && "Illegal VirtReg!");
85 Reg -= MRegisterInfo::FirstVirtualRegister;
86 if (VirtRegModified.size() <= Reg) VirtRegModified.resize(Reg+1);
87 VirtRegModified[Reg] = Val;
90 bool isVirtRegModified(unsigned Reg) const {
91 assert(MRegisterInfo::isVirtualRegister(Reg) && "Illegal VirtReg!");
92 assert(Reg - MRegisterInfo::FirstVirtualRegister < VirtRegModified.size()
93 && "Illegal virtual register!");
94 return VirtRegModified[Reg - MRegisterInfo::FirstVirtualRegister];
97 void MarkPhysRegRecentlyUsed(unsigned Reg) {
98 if(PhysRegsUseOrder.empty() ||
99 PhysRegsUseOrder.back() == Reg) return; // Already most recently used
101 for (unsigned i = PhysRegsUseOrder.size(); i != 0; --i)
102 if (areRegsEqual(Reg, PhysRegsUseOrder[i-1])) {
103 unsigned RegMatch = PhysRegsUseOrder[i-1]; // remove from middle
104 PhysRegsUseOrder.erase(PhysRegsUseOrder.begin()+i-1);
105 // Add it to the end of the list
106 PhysRegsUseOrder.push_back(RegMatch);
108 return; // Found an exact match, exit early
113 virtual const char *getPassName() const {
114 return "Local Register Allocator";
117 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
118 AU.addRequired<LiveVariables>();
119 AU.addRequiredID(PHIEliminationID);
120 AU.addRequiredID(TwoAddressInstructionPassID);
121 MachineFunctionPass::getAnalysisUsage(AU);
125 /// runOnMachineFunction - Register allocate the whole function
126 bool runOnMachineFunction(MachineFunction &Fn);
128 /// AllocateBasicBlock - Register allocate the specified basic block.
129 void AllocateBasicBlock(MachineBasicBlock &MBB);
132 /// areRegsEqual - This method returns true if the specified registers are
133 /// related to each other. To do this, it checks to see if they are equal
134 /// or if the first register is in the alias set of the second register.
136 bool areRegsEqual(unsigned R1, unsigned R2) const {
137 if (R1 == R2) return true;
138 for (const unsigned *AliasSet = RegInfo->getAliasSet(R2);
139 *AliasSet; ++AliasSet) {
140 if (*AliasSet == R1) return true;
145 /// getStackSpaceFor - This returns the frame index of the specified virtual
146 /// register on the stack, allocating space if necessary.
147 int getStackSpaceFor(unsigned VirtReg, const TargetRegisterClass *RC);
149 /// removePhysReg - This method marks the specified physical register as no
150 /// longer being in use.
152 void removePhysReg(unsigned PhysReg);
154 /// spillVirtReg - This method spills the value specified by PhysReg into
155 /// the virtual register slot specified by VirtReg. It then updates the RA
156 /// data structures to indicate the fact that PhysReg is now available.
158 void spillVirtReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator MI,
159 unsigned VirtReg, unsigned PhysReg);
161 /// spillPhysReg - This method spills the specified physical register into
162 /// the virtual register slot associated with it. If OnlyVirtRegs is set to
163 /// true, then the request is ignored if the physical register does not
164 /// contain a virtual register.
166 void spillPhysReg(MachineBasicBlock &MBB, MachineInstr *I,
167 unsigned PhysReg, bool OnlyVirtRegs = false);
169 /// assignVirtToPhysReg - This method updates local state so that we know
170 /// that PhysReg is the proper container for VirtReg now. The physical
171 /// register must not be used for anything else when this is called.
173 void assignVirtToPhysReg(unsigned VirtReg, unsigned PhysReg);
175 /// liberatePhysReg - Make sure the specified physical register is available
176 /// for use. If there is currently a value in it, it is either moved out of
177 /// the way or spilled to memory.
179 void liberatePhysReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator &I,
182 /// isPhysRegAvailable - Return true if the specified physical register is
183 /// free and available for use. This also includes checking to see if
184 /// aliased registers are all free...
186 bool isPhysRegAvailable(unsigned PhysReg) const;
188 /// getFreeReg - Look to see if there is a free register available in the
189 /// specified register class. If not, return 0.
191 unsigned getFreeReg(const TargetRegisterClass *RC);
193 /// getReg - Find a physical register to hold the specified virtual
194 /// register. If all compatible physical registers are used, this method
195 /// spills the last used virtual register to the stack, and uses that
198 unsigned getReg(MachineBasicBlock &MBB, MachineInstr *MI,
201 /// reloadVirtReg - This method transforms the specified specified virtual
202 /// register use to refer to a physical register. This method may do this
203 /// in one of several ways: if the register is available in a physical
204 /// register already, it uses that physical register. If the value is not
205 /// in a physical register, and if there are physical registers available,
206 /// it loads it into a register. If register pressure is high, and it is
207 /// possible, it tries to fold the load of the virtual register into the
208 /// instruction itself. It avoids doing this if register pressure is low to
209 /// improve the chance that subsequent instructions can use the reloaded
210 /// value. This method returns the modified instruction.
212 MachineInstr *reloadVirtReg(MachineBasicBlock &MBB, MachineInstr *MI,
216 void reloadPhysReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator &I,
221 /// getStackSpaceFor - This allocates space for the specified virtual register
222 /// to be held on the stack.
223 int RA::getStackSpaceFor(unsigned VirtReg, const TargetRegisterClass *RC) {
224 // Find the location Reg would belong...
225 std::map<unsigned, int>::iterator I =StackSlotForVirtReg.lower_bound(VirtReg);
227 if (I != StackSlotForVirtReg.end() && I->first == VirtReg)
228 return I->second; // Already has space allocated?
230 // Allocate a new stack object for this spill location...
231 int FrameIdx = MF->getFrameInfo()->CreateStackObject(RC->getSize(),
234 // Assign the slot...
235 StackSlotForVirtReg.insert(I, std::make_pair(VirtReg, FrameIdx));
240 /// removePhysReg - This method marks the specified physical register as no
241 /// longer being in use.
243 void RA::removePhysReg(unsigned PhysReg) {
244 PhysRegsUsed[PhysReg] = -1; // PhyReg no longer used
246 std::vector<unsigned>::iterator It =
247 std::find(PhysRegsUseOrder.begin(), PhysRegsUseOrder.end(), PhysReg);
248 if (It != PhysRegsUseOrder.end())
249 PhysRegsUseOrder.erase(It);
253 /// spillVirtReg - This method spills the value specified by PhysReg into the
254 /// virtual register slot specified by VirtReg. It then updates the RA data
255 /// structures to indicate the fact that PhysReg is now available.
257 void RA::spillVirtReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator I,
258 unsigned VirtReg, unsigned PhysReg) {
259 assert(VirtReg && "Spilling a physical register is illegal!"
260 " Must not have appropriate kill for the register or use exists beyond"
261 " the intended one.");
262 DEBUG(std::cerr << " Spilling register " << RegInfo->getName(PhysReg);
263 std::cerr << " containing %reg" << VirtReg;
264 if (!isVirtRegModified(VirtReg))
265 std::cerr << " which has not been modified, so no store necessary!");
267 // Otherwise, there is a virtual register corresponding to this physical
268 // register. We only need to spill it into its stack slot if it has been
270 if (isVirtRegModified(VirtReg)) {
271 const TargetRegisterClass *RC = MF->getSSARegMap()->getRegClass(VirtReg);
272 int FrameIndex = getStackSpaceFor(VirtReg, RC);
273 DEBUG(std::cerr << " to stack slot #" << FrameIndex);
274 RegInfo->storeRegToStackSlot(MBB, I, PhysReg, FrameIndex, RC);
275 ++NumStores; // Update statistics
278 getVirt2PhysRegMapSlot(VirtReg) = 0; // VirtReg no longer available
280 DEBUG(std::cerr << "\n");
281 removePhysReg(PhysReg);
285 /// spillPhysReg - This method spills the specified physical register into the
286 /// virtual register slot associated with it. If OnlyVirtRegs is set to true,
287 /// then the request is ignored if the physical register does not contain a
288 /// virtual register.
290 void RA::spillPhysReg(MachineBasicBlock &MBB, MachineInstr *I,
291 unsigned PhysReg, bool OnlyVirtRegs) {
292 if (PhysRegsUsed[PhysReg] != -1) { // Only spill it if it's used!
293 if (PhysRegsUsed[PhysReg] || !OnlyVirtRegs)
294 spillVirtReg(MBB, I, PhysRegsUsed[PhysReg], PhysReg);
296 // If the selected register aliases any other registers, we must make
297 // sure that one of the aliases isn't alive...
298 for (const unsigned *AliasSet = RegInfo->getAliasSet(PhysReg);
299 *AliasSet; ++AliasSet)
300 if (PhysRegsUsed[*AliasSet] != -1) // Spill aliased register...
301 if (PhysRegsUsed[*AliasSet] || !OnlyVirtRegs)
302 spillVirtReg(MBB, I, PhysRegsUsed[*AliasSet], *AliasSet);
307 /// assignVirtToPhysReg - This method updates local state so that we know
308 /// that PhysReg is the proper container for VirtReg now. The physical
309 /// register must not be used for anything else when this is called.
311 void RA::assignVirtToPhysReg(unsigned VirtReg, unsigned PhysReg) {
312 assert(PhysRegsUsed[PhysReg] == -1 && "Phys reg already assigned!");
313 // Update information to note the fact that this register was just used, and
315 PhysRegsUsed[PhysReg] = VirtReg;
316 getVirt2PhysRegMapSlot(VirtReg) = PhysReg;
317 PhysRegsUseOrder.push_back(PhysReg); // New use of PhysReg
321 /// isPhysRegAvailable - Return true if the specified physical register is free
322 /// and available for use. This also includes checking to see if aliased
323 /// registers are all free...
325 bool RA::isPhysRegAvailable(unsigned PhysReg) const {
326 if (PhysRegsUsed[PhysReg] != -1) return false;
328 // If the selected register aliases any other allocated registers, it is
330 for (const unsigned *AliasSet = RegInfo->getAliasSet(PhysReg);
331 *AliasSet; ++AliasSet)
332 if (PhysRegsUsed[*AliasSet] != -1) // Aliased register in use?
333 return false; // Can't use this reg then.
338 /// getFreeReg - Look to see if there is a free register available in the
339 /// specified register class. If not, return 0.
341 unsigned RA::getFreeReg(const TargetRegisterClass *RC) {
342 // Get iterators defining the range of registers that are valid to allocate in
343 // this class, which also specifies the preferred allocation order.
344 TargetRegisterClass::iterator RI = RC->allocation_order_begin(*MF);
345 TargetRegisterClass::iterator RE = RC->allocation_order_end(*MF);
347 for (; RI != RE; ++RI)
348 if (isPhysRegAvailable(*RI)) { // Is reg unused?
349 assert(*RI != 0 && "Cannot use register!");
350 return *RI; // Found an unused register!
356 /// liberatePhysReg - Make sure the specified physical register is available for
357 /// use. If there is currently a value in it, it is either moved out of the way
358 /// or spilled to memory.
360 void RA::liberatePhysReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator &I,
362 spillPhysReg(MBB, I, PhysReg);
366 /// getReg - Find a physical register to hold the specified virtual
367 /// register. If all compatible physical registers are used, this method spills
368 /// the last used virtual register to the stack, and uses that register.
370 unsigned RA::getReg(MachineBasicBlock &MBB, MachineInstr *I,
372 const TargetRegisterClass *RC = MF->getSSARegMap()->getRegClass(VirtReg);
374 // First check to see if we have a free register of the requested type...
375 unsigned PhysReg = getFreeReg(RC);
377 // If we didn't find an unused register, scavenge one now!
379 assert(!PhysRegsUseOrder.empty() && "No allocated registers??");
381 // Loop over all of the preallocated registers from the least recently used
382 // to the most recently used. When we find one that is capable of holding
383 // our register, use it.
384 for (unsigned i = 0; PhysReg == 0; ++i) {
385 assert(i != PhysRegsUseOrder.size() &&
386 "Couldn't find a register of the appropriate class!");
388 unsigned R = PhysRegsUseOrder[i];
390 // We can only use this register if it holds a virtual register (ie, it
391 // can be spilled). Do not use it if it is an explicitly allocated
392 // physical register!
393 assert(PhysRegsUsed[R] != -1 &&
394 "PhysReg in PhysRegsUseOrder, but is not allocated?");
395 if (PhysRegsUsed[R]) {
396 // If the current register is compatible, use it.
397 if (RC->contains(R)) {
401 // If one of the registers aliased to the current register is
402 // compatible, use it.
403 for (const unsigned *AliasSet = RegInfo->getAliasSet(R);
404 *AliasSet; ++AliasSet) {
405 if (RC->contains(*AliasSet)) {
406 PhysReg = *AliasSet; // Take an aliased register
414 assert(PhysReg && "Physical register not assigned!?!?");
416 // At this point PhysRegsUseOrder[i] is the least recently used register of
417 // compatible register class. Spill it to memory and reap its remains.
418 spillPhysReg(MBB, I, PhysReg);
421 // Now that we know which register we need to assign this to, do it now!
422 assignVirtToPhysReg(VirtReg, PhysReg);
427 /// reloadVirtReg - This method transforms the specified specified virtual
428 /// register use to refer to a physical register. This method may do this in
429 /// one of several ways: if the register is available in a physical register
430 /// already, it uses that physical register. If the value is not in a physical
431 /// register, and if there are physical registers available, it loads it into a
432 /// register. If register pressure is high, and it is possible, it tries to
433 /// fold the load of the virtual register into the instruction itself. It
434 /// avoids doing this if register pressure is low to improve the chance that
435 /// subsequent instructions can use the reloaded value. This method returns the
436 /// modified instruction.
438 MachineInstr *RA::reloadVirtReg(MachineBasicBlock &MBB, MachineInstr *MI,
440 unsigned VirtReg = MI->getOperand(OpNum).getReg();
442 // If the virtual register is already available, just update the instruction
444 if (unsigned PR = getVirt2PhysRegMapSlot(VirtReg)) {
445 MarkPhysRegRecentlyUsed(PR); // Already have this value available!
446 MI->SetMachineOperandReg(OpNum, PR); // Assign the input register
450 // Otherwise, we need to fold it into the current instruction, or reload it.
451 // If we have registers available to hold the value, use them.
452 const TargetRegisterClass *RC = MF->getSSARegMap()->getRegClass(VirtReg);
453 unsigned PhysReg = getFreeReg(RC);
454 int FrameIndex = getStackSpaceFor(VirtReg, RC);
456 if (PhysReg) { // Register is available, allocate it!
457 assignVirtToPhysReg(VirtReg, PhysReg);
458 } else { // No registers available.
459 // If we can fold this spill into this instruction, do so now.
460 if (MachineInstr* FMI = RegInfo->foldMemoryOperand(MI, OpNum, FrameIndex)){
462 // Since we changed the address of MI, make sure to update live variables
463 // to know that the new instruction has the properties of the old one.
464 LV->instructionChanged(MI, FMI);
465 return MBB.insert(MBB.erase(MI), FMI);
468 // It looks like we can't fold this virtual register load into this
469 // instruction. Force some poor hapless value out of the register file to
470 // make room for the new register, and reload it.
471 PhysReg = getReg(MBB, MI, VirtReg);
474 markVirtRegModified(VirtReg, false); // Note that this reg was just reloaded
476 DEBUG(std::cerr << " Reloading %reg" << VirtReg << " into "
477 << RegInfo->getName(PhysReg) << "\n");
479 // Add move instruction(s)
480 RegInfo->loadRegFromStackSlot(MBB, MI, PhysReg, FrameIndex, RC);
481 ++NumLoads; // Update statistics
483 PhysRegsEverUsed[PhysReg] = true;
484 MI->SetMachineOperandReg(OpNum, PhysReg); // Assign the input register
490 void RA::AllocateBasicBlock(MachineBasicBlock &MBB) {
491 // loop over each instruction
492 MachineBasicBlock::iterator MII = MBB.begin();
493 const TargetInstrInfo &TII = *TM->getInstrInfo();
494 while (MII != MBB.end()) {
495 MachineInstr *MI = MII++;
496 const TargetInstrDescriptor &TID = TII.get(MI->getOpcode());
497 DEBUG(std::cerr << "\nStarting RegAlloc of: " << *MI;
498 std::cerr << " Regs have values: ";
499 for (unsigned i = 0; i != RegInfo->getNumRegs(); ++i)
500 if (PhysRegsUsed[i] != -1)
501 std::cerr << "[" << RegInfo->getName(i)
502 << ",%reg" << PhysRegsUsed[i] << "] ";
505 // Loop over the implicit uses, making sure that they are at the head of the
506 // use order list, so they don't get reallocated.
507 for (const unsigned *ImplicitUses = TID.ImplicitUses;
508 *ImplicitUses; ++ImplicitUses)
509 MarkPhysRegRecentlyUsed(*ImplicitUses);
511 // Get the used operands into registers. This has the potential to spill
512 // incoming values if we are out of registers. Note that we completely
513 // ignore physical register uses here. We assume that if an explicit
514 // physical register is referenced by the instruction, that it is guaranteed
515 // to be live-in, or the input is badly hosed.
517 for (unsigned i = 0; i != MI->getNumOperands(); ++i) {
518 MachineOperand& MO = MI->getOperand(i);
519 // here we are looking for only used operands (never def&use)
520 if (!MO.isDef() && MO.isRegister() && MO.getReg() &&
521 MRegisterInfo::isVirtualRegister(MO.getReg()))
522 MI = reloadVirtReg(MBB, MI, i);
525 // If this instruction is the last user of anything in registers, kill the
526 // value, freeing the register being used, so it doesn't need to be
527 // spilled to memory.
529 for (LiveVariables::killed_iterator KI = LV->killed_begin(MI),
530 KE = LV->killed_end(MI); KI != KE; ++KI) {
531 unsigned VirtReg = *KI;
532 unsigned PhysReg = VirtReg;
533 if (MRegisterInfo::isVirtualRegister(VirtReg)) {
534 // If the virtual register was never materialized into a register, it
535 // might not be in the map, but it won't hurt to zero it out anyway.
536 unsigned &PhysRegSlot = getVirt2PhysRegMapSlot(VirtReg);
537 PhysReg = PhysRegSlot;
542 DEBUG(std::cerr << " Last use of " << RegInfo->getName(PhysReg)
543 << "[%reg" << VirtReg <<"], removing it from live set\n");
544 removePhysReg(PhysReg);
548 // Loop over all of the operands of the instruction, spilling registers that
549 // are defined, and marking explicit destinations in the PhysRegsUsed map.
550 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
551 MachineOperand& MO = MI->getOperand(i);
552 if (MO.isDef() && MO.isRegister() && MO.getReg() &&
553 MRegisterInfo::isPhysicalRegister(MO.getReg())) {
554 unsigned Reg = MO.getReg();
555 PhysRegsEverUsed[Reg] = true;
556 spillPhysReg(MBB, MI, Reg, true); // Spill any existing value in the reg
557 PhysRegsUsed[Reg] = 0; // It is free and reserved now
558 PhysRegsUseOrder.push_back(Reg);
559 for (const unsigned *AliasSet = RegInfo->getAliasSet(Reg);
560 *AliasSet; ++AliasSet) {
561 PhysRegsUseOrder.push_back(*AliasSet);
562 PhysRegsUsed[*AliasSet] = 0; // It is free and reserved now
563 PhysRegsEverUsed[*AliasSet] = true;
568 // Loop over the implicit defs, spilling them as well.
569 for (const unsigned *ImplicitDefs = TID.ImplicitDefs;
570 *ImplicitDefs; ++ImplicitDefs) {
571 unsigned Reg = *ImplicitDefs;
572 spillPhysReg(MBB, MI, Reg, true);
573 PhysRegsUseOrder.push_back(Reg);
574 PhysRegsUsed[Reg] = 0; // It is free and reserved now
575 PhysRegsEverUsed[Reg] = true;
577 for (const unsigned *AliasSet = RegInfo->getAliasSet(Reg);
578 *AliasSet; ++AliasSet) {
579 PhysRegsUseOrder.push_back(*AliasSet);
580 PhysRegsUsed[*AliasSet] = 0; // It is free and reserved now
581 PhysRegsEverUsed[*AliasSet] = true;
585 // Okay, we have allocated all of the source operands and spilled any values
586 // that would be destroyed by defs of this instruction. Loop over the
587 // explicit defs and assign them to a register, spilling incoming values if
588 // we need to scavenge a register.
590 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
591 MachineOperand& MO = MI->getOperand(i);
592 if (MO.isDef() && MO.isRegister() && MO.getReg() &&
593 MRegisterInfo::isVirtualRegister(MO.getReg())) {
594 unsigned DestVirtReg = MO.getReg();
595 unsigned DestPhysReg;
597 // If DestVirtReg already has a value, use it.
598 if (!(DestPhysReg = getVirt2PhysRegMapSlot(DestVirtReg)))
599 DestPhysReg = getReg(MBB, MI, DestVirtReg);
600 PhysRegsEverUsed[DestPhysReg] = true;
601 markVirtRegModified(DestVirtReg);
602 MI->SetMachineOperandReg(i, DestPhysReg); // Assign the output register
606 // If this instruction defines any registers that are immediately dead,
609 for (LiveVariables::killed_iterator KI = LV->dead_begin(MI),
610 KE = LV->dead_end(MI); KI != KE; ++KI) {
611 unsigned VirtReg = *KI;
612 unsigned PhysReg = VirtReg;
613 if (MRegisterInfo::isVirtualRegister(VirtReg)) {
614 unsigned &PhysRegSlot = getVirt2PhysRegMapSlot(VirtReg);
615 PhysReg = PhysRegSlot;
616 assert(PhysReg != 0);
621 DEBUG(std::cerr << " Register " << RegInfo->getName(PhysReg)
622 << " [%reg" << VirtReg
623 << "] is never used, removing it frame live list\n");
624 removePhysReg(PhysReg);
628 // Finally, if this is a noop copy instruction, zap it.
629 unsigned SrcReg, DstReg;
630 if (TII.isMoveInstr(*MI, SrcReg, DstReg) && SrcReg == DstReg)
634 MachineBasicBlock::iterator MI = MBB.getFirstTerminator();
636 // Spill all physical registers holding virtual registers now.
637 for (unsigned i = 0, e = RegInfo->getNumRegs(); i != e; ++i)
638 if (PhysRegsUsed[i] != -1)
639 if (unsigned VirtReg = PhysRegsUsed[i])
640 spillVirtReg(MBB, MI, VirtReg, i);
645 // This checking code is very expensive.
647 for (unsigned i = MRegisterInfo::FirstVirtualRegister,
648 e = MF->getSSARegMap()->getLastVirtReg(); i <= e; ++i)
649 if (unsigned PR = Virt2PhysRegMap[i]) {
650 std::cerr << "Register still mapped: " << i << " -> " << PR << "\n";
653 assert(AllOk && "Virtual registers still in phys regs?");
656 // Clear any physical register which appear live at the end of the basic
657 // block, but which do not hold any virtual registers. e.g., the stack
659 PhysRegsUseOrder.clear();
663 /// runOnMachineFunction - Register allocate the whole function
665 bool RA::runOnMachineFunction(MachineFunction &Fn) {
666 DEBUG(std::cerr << "Machine Function " << "\n");
668 TM = &Fn.getTarget();
669 RegInfo = TM->getRegisterInfo();
670 LV = &getAnalysis<LiveVariables>();
672 PhysRegsEverUsed = new bool[RegInfo->getNumRegs()];
673 std::fill(PhysRegsEverUsed, PhysRegsEverUsed+RegInfo->getNumRegs(), false);
674 Fn.setUsedPhysRegs(PhysRegsEverUsed);
676 PhysRegsUsed.assign(RegInfo->getNumRegs(), -1);
678 // initialize the virtual->physical register map to have a 'null'
679 // mapping for all virtual registers
680 Virt2PhysRegMap.grow(MF->getSSARegMap()->getLastVirtReg());
682 // Loop over all of the basic blocks, eliminating virtual register references
683 for (MachineFunction::iterator MBB = Fn.begin(), MBBe = Fn.end();
685 AllocateBasicBlock(*MBB);
687 StackSlotForVirtReg.clear();
688 PhysRegsUsed.clear();
689 VirtRegModified.clear();
690 Virt2PhysRegMap.clear();
694 FunctionPass *llvm::createLocalRegisterAllocator() {