1 //===-- RegAllocLocal.cpp - A BasicBlock generic register allocator -------===//
3 // This register allocator allocates registers to a basic block at a time,
4 // attempting to keep values in registers and reusing registers as appropriate.
6 //===----------------------------------------------------------------------===//
8 #define DEBUG_TYPE "regalloc"
9 #include "llvm/CodeGen/Passes.h"
10 #include "llvm/CodeGen/MachineFunctionPass.h"
11 #include "llvm/CodeGen/MachineInstr.h"
12 #include "llvm/CodeGen/SSARegMap.h"
13 #include "llvm/CodeGen/MachineFrameInfo.h"
14 #include "llvm/CodeGen/LiveVariables.h"
15 #include "llvm/Target/TargetInstrInfo.h"
16 #include "llvm/Target/TargetMachine.h"
17 #include "Support/CommandLine.h"
18 #include "Support/Debug.h"
19 #include "Support/Statistic.h"
23 Statistic<> NumSpilled ("ra-local", "Number of registers spilled");
24 Statistic<> NumReloaded("ra-local", "Number of registers reloaded");
25 cl::opt<bool> DisableKill("no-kill", cl::Hidden,
26 cl::desc("Disable register kill in local-ra"));
28 class RA : public MachineFunctionPass {
29 const TargetMachine *TM;
31 const MRegisterInfo *RegInfo;
34 // StackSlotForVirtReg - Maps virtual regs to the frame index where these
35 // values are spilled.
36 std::map<unsigned, int> StackSlotForVirtReg;
38 // Virt2PhysRegMap - This map contains entries for each virtual register
39 // that is currently available in a physical register.
41 std::map<unsigned, unsigned> Virt2PhysRegMap;
43 // PhysRegsUsed - This map contains entries for each physical register that
44 // currently has a value (ie, it is in Virt2PhysRegMap). The value mapped
45 // to is the virtual register corresponding to the physical register (the
46 // inverse of the Virt2PhysRegMap), or 0. The value is set to 0 if this
47 // register is pinned because it is used by a future instruction.
49 std::map<unsigned, unsigned> PhysRegsUsed;
51 // PhysRegsUseOrder - This contains a list of the physical registers that
52 // currently have a virtual register value in them. This list provides an
53 // ordering of registers, imposing a reallocation order. This list is only
54 // used if all registers are allocated and we have to spill one, in which
55 // case we spill the least recently used register. Entries at the front of
56 // the list are the least recently used registers, entries at the back are
57 // the most recently used.
59 std::vector<unsigned> PhysRegsUseOrder;
61 // VirtRegModified - This bitset contains information about which virtual
62 // registers need to be spilled back to memory when their registers are
63 // scavenged. If a virtual register has simply been rematerialized, there
64 // is no reason to spill it to memory when we need the register back.
66 std::vector<bool> VirtRegModified;
68 void markVirtRegModified(unsigned Reg, bool Val = true) {
69 assert(Reg >= MRegisterInfo::FirstVirtualRegister && "Illegal VirtReg!");
70 Reg -= MRegisterInfo::FirstVirtualRegister;
71 if (VirtRegModified.size() <= Reg) VirtRegModified.resize(Reg+1);
72 VirtRegModified[Reg] = Val;
75 bool isVirtRegModified(unsigned Reg) const {
76 assert(Reg >= MRegisterInfo::FirstVirtualRegister && "Illegal VirtReg!");
77 assert(Reg - MRegisterInfo::FirstVirtualRegister < VirtRegModified.size()
78 && "Illegal virtual register!");
79 return VirtRegModified[Reg - MRegisterInfo::FirstVirtualRegister];
82 void MarkPhysRegRecentlyUsed(unsigned Reg) {
83 assert(!PhysRegsUseOrder.empty() && "No registers used!");
84 if (PhysRegsUseOrder.back() == Reg) return; // Already most recently used
86 for (unsigned i = PhysRegsUseOrder.size(); i != 0; --i)
87 if (areRegsEqual(Reg, PhysRegsUseOrder[i-1])) {
88 unsigned RegMatch = PhysRegsUseOrder[i-1]; // remove from middle
89 PhysRegsUseOrder.erase(PhysRegsUseOrder.begin()+i-1);
90 // Add it to the end of the list
91 PhysRegsUseOrder.push_back(RegMatch);
93 return; // Found an exact match, exit early
98 virtual const char *getPassName() const {
99 return "Local Register Allocator";
102 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
104 AU.addRequired<LiveVariables>();
105 AU.addRequiredID(PHIEliminationID);
106 MachineFunctionPass::getAnalysisUsage(AU);
110 /// runOnMachineFunction - Register allocate the whole function
111 bool runOnMachineFunction(MachineFunction &Fn);
113 /// AllocateBasicBlock - Register allocate the specified basic block.
114 void AllocateBasicBlock(MachineBasicBlock &MBB);
117 /// areRegsEqual - This method returns true if the specified registers are
118 /// related to each other. To do this, it checks to see if they are equal
119 /// or if the first register is in the alias set of the second register.
121 bool areRegsEqual(unsigned R1, unsigned R2) const {
122 if (R1 == R2) return true;
123 if (const unsigned *AliasSet = RegInfo->getAliasSet(R2))
124 for (unsigned i = 0; AliasSet[i]; ++i)
125 if (AliasSet[i] == R1) return true;
129 /// getStackSpaceFor - This returns the frame index of the specified virtual
130 /// register on the stack, allocating space if necessary.
131 int getStackSpaceFor(unsigned VirtReg, const TargetRegisterClass *RC);
133 /// removePhysReg - This method marks the specified physical register as no
134 /// longer being in use.
136 void removePhysReg(unsigned PhysReg);
138 /// spillVirtReg - This method spills the value specified by PhysReg into
139 /// the virtual register slot specified by VirtReg. It then updates the RA
140 /// data structures to indicate the fact that PhysReg is now available.
142 void spillVirtReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator &I,
143 unsigned VirtReg, unsigned PhysReg);
145 /// spillPhysReg - This method spills the specified physical register into
146 /// the virtual register slot associated with it. If OnlyVirtRegs is set to
147 /// true, then the request is ignored if the physical register does not
148 /// contain a virtual register.
150 void spillPhysReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator &I,
151 unsigned PhysReg, bool OnlyVirtRegs = false);
153 /// assignVirtToPhysReg - This method updates local state so that we know
154 /// that PhysReg is the proper container for VirtReg now. The physical
155 /// register must not be used for anything else when this is called.
157 void assignVirtToPhysReg(unsigned VirtReg, unsigned PhysReg);
159 /// liberatePhysReg - Make sure the specified physical register is available
160 /// for use. If there is currently a value in it, it is either moved out of
161 /// the way or spilled to memory.
163 void liberatePhysReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator &I,
166 /// isPhysRegAvailable - Return true if the specified physical register is
167 /// free and available for use. This also includes checking to see if
168 /// aliased registers are all free...
170 bool isPhysRegAvailable(unsigned PhysReg) const;
172 /// getFreeReg - Look to see if there is a free register available in the
173 /// specified register class. If not, return 0.
175 unsigned getFreeReg(const TargetRegisterClass *RC);
177 /// getReg - Find a physical register to hold the specified virtual
178 /// register. If all compatible physical registers are used, this method
179 /// spills the last used virtual register to the stack, and uses that
182 unsigned getReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator &I,
185 /// reloadVirtReg - This method loads the specified virtual register into a
186 /// physical register, returning the physical register chosen. This updates
187 /// the regalloc data structures to reflect the fact that the virtual reg is
188 /// now alive in a physical register, and the previous one isn't.
190 unsigned reloadVirtReg(MachineBasicBlock &MBB,
191 MachineBasicBlock::iterator &I, unsigned VirtReg);
193 void reloadPhysReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator &I,
199 /// getStackSpaceFor - This allocates space for the specified virtual register
200 /// to be held on the stack.
201 int RA::getStackSpaceFor(unsigned VirtReg, const TargetRegisterClass *RC) {
202 // Find the location Reg would belong...
203 std::map<unsigned, int>::iterator I =StackSlotForVirtReg.lower_bound(VirtReg);
205 if (I != StackSlotForVirtReg.end() && I->first == VirtReg)
206 return I->second; // Already has space allocated?
208 // Allocate a new stack object for this spill location...
209 int FrameIdx = MF->getFrameInfo()->CreateStackObject(RC);
211 // Assign the slot...
212 StackSlotForVirtReg.insert(I, std::make_pair(VirtReg, FrameIdx));
217 /// removePhysReg - This method marks the specified physical register as no
218 /// longer being in use.
220 void RA::removePhysReg(unsigned PhysReg) {
221 PhysRegsUsed.erase(PhysReg); // PhyReg no longer used
223 std::vector<unsigned>::iterator It =
224 std::find(PhysRegsUseOrder.begin(), PhysRegsUseOrder.end(), PhysReg);
225 assert(It != PhysRegsUseOrder.end() &&
226 "Spilled a physical register, but it was not in use list!");
227 PhysRegsUseOrder.erase(It);
231 /// spillVirtReg - This method spills the value specified by PhysReg into the
232 /// virtual register slot specified by VirtReg. It then updates the RA data
233 /// structures to indicate the fact that PhysReg is now available.
235 void RA::spillVirtReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator &I,
236 unsigned VirtReg, unsigned PhysReg) {
237 if (!VirtReg && DisableKill) return;
238 assert(VirtReg && "Spilling a physical register is illegal!"
239 " Must not have appropriate kill for the register or use exists beyond"
240 " the intended one.");
241 DEBUG(std::cerr << " Spilling register " << RegInfo->getName(PhysReg);
242 std::cerr << " containing %reg" << VirtReg;
243 if (!isVirtRegModified(VirtReg))
244 std::cerr << " which has not been modified, so no store necessary!");
246 // Otherwise, there is a virtual register corresponding to this physical
247 // register. We only need to spill it into its stack slot if it has been
249 if (isVirtRegModified(VirtReg)) {
250 const TargetRegisterClass *RC = MF->getSSARegMap()->getRegClass(VirtReg);
251 int FrameIndex = getStackSpaceFor(VirtReg, RC);
252 DEBUG(std::cerr << " to stack slot #" << FrameIndex);
253 RegInfo->storeRegToStackSlot(MBB, I, PhysReg, FrameIndex, RC);
254 ++NumSpilled; // Update statistics
256 Virt2PhysRegMap.erase(VirtReg); // VirtReg no longer available
258 DEBUG(std::cerr << "\n");
259 removePhysReg(PhysReg);
263 /// spillPhysReg - This method spills the specified physical register into the
264 /// virtual register slot associated with it. If OnlyVirtRegs is set to true,
265 /// then the request is ignored if the physical register does not contain a
266 /// virtual register.
268 void RA::spillPhysReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator &I,
269 unsigned PhysReg, bool OnlyVirtRegs) {
270 std::map<unsigned, unsigned>::iterator PI = PhysRegsUsed.find(PhysReg);
271 if (PI != PhysRegsUsed.end()) { // Only spill it if it's used!
272 if (PI->second || !OnlyVirtRegs)
273 spillVirtReg(MBB, I, PI->second, PhysReg);
274 } else if (const unsigned *AliasSet = RegInfo->getAliasSet(PhysReg)) {
275 // If the selected register aliases any other registers, we must make
276 // sure that one of the aliases isn't alive...
277 for (unsigned i = 0; AliasSet[i]; ++i) {
278 PI = PhysRegsUsed.find(AliasSet[i]);
279 if (PI != PhysRegsUsed.end()) // Spill aliased register...
280 if (PI->second || !OnlyVirtRegs)
281 spillVirtReg(MBB, I, PI->second, AliasSet[i]);
287 /// assignVirtToPhysReg - This method updates local state so that we know
288 /// that PhysReg is the proper container for VirtReg now. The physical
289 /// register must not be used for anything else when this is called.
291 void RA::assignVirtToPhysReg(unsigned VirtReg, unsigned PhysReg) {
292 assert(PhysRegsUsed.find(PhysReg) == PhysRegsUsed.end() &&
293 "Phys reg already assigned!");
294 // Update information to note the fact that this register was just used, and
296 PhysRegsUsed[PhysReg] = VirtReg;
297 Virt2PhysRegMap[VirtReg] = PhysReg;
298 PhysRegsUseOrder.push_back(PhysReg); // New use of PhysReg
302 /// isPhysRegAvailable - Return true if the specified physical register is free
303 /// and available for use. This also includes checking to see if aliased
304 /// registers are all free...
306 bool RA::isPhysRegAvailable(unsigned PhysReg) const {
307 if (PhysRegsUsed.count(PhysReg)) return false;
309 // If the selected register aliases any other allocated registers, it is
311 if (const unsigned *AliasSet = RegInfo->getAliasSet(PhysReg))
312 for (unsigned i = 0; AliasSet[i]; ++i)
313 if (PhysRegsUsed.count(AliasSet[i])) // Aliased register in use?
314 return false; // Can't use this reg then.
319 /// getFreeReg - Look to see if there is a free register available in the
320 /// specified register class. If not, return 0.
322 unsigned RA::getFreeReg(const TargetRegisterClass *RC) {
323 // Get iterators defining the range of registers that are valid to allocate in
324 // this class, which also specifies the preferred allocation order.
325 TargetRegisterClass::iterator RI = RC->allocation_order_begin(*MF);
326 TargetRegisterClass::iterator RE = RC->allocation_order_end(*MF);
328 for (; RI != RE; ++RI)
329 if (isPhysRegAvailable(*RI)) { // Is reg unused?
330 assert(*RI != 0 && "Cannot use register!");
331 return *RI; // Found an unused register!
337 /// liberatePhysReg - Make sure the specified physical register is available for
338 /// use. If there is currently a value in it, it is either moved out of the way
339 /// or spilled to memory.
341 void RA::liberatePhysReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator &I,
343 // FIXME: This code checks to see if a register is available, but it really
344 // wants to know if a reg is available BEFORE the instruction executes. If
345 // called after killed operands are freed, it runs the risk of reallocating a
348 if (isPhysRegAvailable(PhysReg)) return; // Already available...
350 // Check to see if the register is directly used, not indirectly used through
351 // aliases. If aliased registers are the ones actually used, we cannot be
352 // sure that we will be able to save the whole thing if we do a reg-reg copy.
353 std::map<unsigned, unsigned>::iterator PRUI = PhysRegsUsed.find(PhysReg);
354 if (PRUI != PhysRegsUsed.end()) {
355 unsigned VirtReg = PRUI->second; // The virtual register held...
357 // Check to see if there is a compatible register available. If so, we can
358 // move the value into the new register...
360 const TargetRegisterClass *RC = RegInfo->getRegClass(PhysReg);
361 if (unsigned NewReg = getFreeReg(RC)) {
362 // Emit the code to copy the value...
363 RegInfo->copyRegToReg(MBB, I, NewReg, PhysReg, RC);
365 // Update our internal state to indicate that PhysReg is available and Reg
367 Virt2PhysRegMap.erase(VirtReg);
368 removePhysReg(PhysReg); // Free the physreg
370 // Move reference over to new register...
371 assignVirtToPhysReg(VirtReg, NewReg);
376 spillPhysReg(MBB, I, PhysReg);
380 /// getReg - Find a physical register to hold the specified virtual
381 /// register. If all compatible physical registers are used, this method spills
382 /// the last used virtual register to the stack, and uses that register.
384 unsigned RA::getReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator &I,
386 const TargetRegisterClass *RC = MF->getSSARegMap()->getRegClass(VirtReg);
388 // First check to see if we have a free register of the requested type...
389 unsigned PhysReg = getFreeReg(RC);
391 // If we didn't find an unused register, scavenge one now!
393 assert(!PhysRegsUseOrder.empty() && "No allocated registers??");
395 // Loop over all of the preallocated registers from the least recently used
396 // to the most recently used. When we find one that is capable of holding
397 // our register, use it.
398 for (unsigned i = 0; PhysReg == 0; ++i) {
399 assert(i != PhysRegsUseOrder.size() &&
400 "Couldn't find a register of the appropriate class!");
402 unsigned R = PhysRegsUseOrder[i];
403 // If the current register is compatible, use it.
404 if (RegInfo->getRegClass(R) == RC) {
408 // If one of the registers aliased to the current register is
409 // compatible, use it.
410 if (const unsigned *AliasSet = RegInfo->getAliasSet(R))
411 for (unsigned a = 0; AliasSet[a]; ++a)
412 if (RegInfo->getRegClass(AliasSet[a]) == RC) {
413 PhysReg = AliasSet[a]; // Take an aliased register
419 assert(PhysReg && "Physical register not assigned!?!?");
421 // At this point PhysRegsUseOrder[i] is the least recently used register of
422 // compatible register class. Spill it to memory and reap its remains.
423 spillPhysReg(MBB, I, PhysReg);
426 // Now that we know which register we need to assign this to, do it now!
427 assignVirtToPhysReg(VirtReg, PhysReg);
432 /// reloadVirtReg - This method loads the specified virtual register into a
433 /// physical register, returning the physical register chosen. This updates the
434 /// regalloc data structures to reflect the fact that the virtual reg is now
435 /// alive in a physical register, and the previous one isn't.
437 unsigned RA::reloadVirtReg(MachineBasicBlock &MBB,
438 MachineBasicBlock::iterator &I,
440 std::map<unsigned, unsigned>::iterator It = Virt2PhysRegMap.find(VirtReg);
441 if (It != Virt2PhysRegMap.end()) {
442 MarkPhysRegRecentlyUsed(It->second);
443 return It->second; // Already have this value available!
446 unsigned PhysReg = getReg(MBB, I, VirtReg);
448 const TargetRegisterClass *RC = MF->getSSARegMap()->getRegClass(VirtReg);
449 int FrameIndex = getStackSpaceFor(VirtReg, RC);
451 markVirtRegModified(VirtReg, false); // Note that this reg was just reloaded
453 DEBUG(std::cerr << " Reloading %reg" << VirtReg << " into "
454 << RegInfo->getName(PhysReg) << "\n");
456 // Add move instruction(s)
457 RegInfo->loadRegFromStackSlot(MBB, I, PhysReg, FrameIndex, RC);
458 ++NumReloaded; // Update statistics
464 void RA::AllocateBasicBlock(MachineBasicBlock &MBB) {
465 // loop over each instruction
466 MachineBasicBlock::iterator I = MBB.begin();
467 for (; I != MBB.end(); ++I) {
468 MachineInstr *MI = *I;
469 const TargetInstrDescriptor &TID = TM->getInstrInfo().get(MI->getOpcode());
470 DEBUG(std::cerr << "\nStarting RegAlloc of: " << *MI;
471 std::cerr << " Regs have values: ";
472 for (std::map<unsigned, unsigned>::const_iterator
473 I = PhysRegsUsed.begin(), E = PhysRegsUsed.end(); I != E; ++I)
474 std::cerr << "[" << RegInfo->getName(I->first)
475 << ",%reg" << I->second << "] ";
478 // Loop over the implicit uses, making sure that they are at the head of the
479 // use order list, so they don't get reallocated.
480 if (const unsigned *ImplicitUses = TID.ImplicitUses)
481 for (unsigned i = 0; ImplicitUses[i]; ++i)
482 MarkPhysRegRecentlyUsed(ImplicitUses[i]);
484 // Get the used operands into registers. This has the potential to spill
485 // incoming values if we are out of registers. Note that we completely
486 // ignore physical register uses here. We assume that if an explicit
487 // physical register is referenced by the instruction, that it is guaranteed
488 // to be live-in, or the input is badly hosed.
490 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i)
491 if (MI->getOperand(i).opIsUse() && MI->getOperand(i).isVirtualRegister()){
492 unsigned VirtSrcReg = MI->getOperand(i).getAllocatedRegNum();
493 unsigned PhysSrcReg = reloadVirtReg(MBB, I, VirtSrcReg);
494 MI->SetMachineOperandReg(i, PhysSrcReg); // Assign the input register
498 // If this instruction is the last user of anything in registers, kill the
499 // value, freeing the register being used, so it doesn't need to be
500 // spilled to memory.
502 for (LiveVariables::killed_iterator KI = LV->killed_begin(MI),
503 KE = LV->killed_end(MI); KI != KE; ++KI) {
504 unsigned VirtReg = KI->second;
505 unsigned PhysReg = VirtReg;
506 if (VirtReg >= MRegisterInfo::FirstVirtualRegister) {
507 std::map<unsigned, unsigned>::iterator I =
508 Virt2PhysRegMap.find(VirtReg);
509 assert(I != Virt2PhysRegMap.end());
511 Virt2PhysRegMap.erase(I);
515 DEBUG(std::cerr << " Last use of " << RegInfo->getName(PhysReg)
516 << "[%reg" << VirtReg <<"], removing it from live set\n");
517 removePhysReg(PhysReg);
522 // Loop over all of the operands of the instruction, spilling registers that
523 // are defined, and marking explicit destinations in the PhysRegsUsed map.
524 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i)
525 if ((MI->getOperand(i).opIsDefOnly() ||
526 MI->getOperand(i).opIsDefAndUse()) &&
527 MI->getOperand(i).isPhysicalRegister()) {
528 unsigned Reg = MI->getOperand(i).getAllocatedRegNum();
529 spillPhysReg(MBB, I, Reg, true); // Spill any existing value in the reg
530 PhysRegsUsed[Reg] = 0; // It is free and reserved now
531 PhysRegsUseOrder.push_back(Reg);
534 // Loop over the implicit defs, spilling them as well.
535 if (const unsigned *ImplicitDefs = TID.ImplicitDefs)
536 for (unsigned i = 0; ImplicitDefs[i]; ++i) {
537 unsigned Reg = ImplicitDefs[i];
538 spillPhysReg(MBB, I, Reg);
539 PhysRegsUseOrder.push_back(Reg);
540 PhysRegsUsed[Reg] = 0; // It is free and reserved now
543 // Okay, we have allocated all of the source operands and spilled any values
544 // that would be destroyed by defs of this instruction. Loop over the
545 // implicit defs and assign them to a register, spilling incoming values if
546 // we need to scavenge a register.
548 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i)
549 if ((MI->getOperand(i).opIsDefOnly() || MI->getOperand(i).opIsDefAndUse())
550 && MI->getOperand(i).isVirtualRegister()) {
551 unsigned DestVirtReg = MI->getOperand(i).getAllocatedRegNum();
552 unsigned DestPhysReg;
554 // If DestVirtReg already has a value, forget about it. Why doesn't
555 // getReg do this right?
556 std::map<unsigned, unsigned>::iterator DestI =
557 Virt2PhysRegMap.find(DestVirtReg);
558 if (DestI != Virt2PhysRegMap.end()) {
559 unsigned PhysReg = DestI->second;
560 Virt2PhysRegMap.erase(DestI);
561 removePhysReg(PhysReg);
564 if (TM->getInstrInfo().isTwoAddrInstr(MI->getOpcode()) && i == 0) {
565 // must be same register number as the first operand
566 // This maps a = b + c into b += c, and saves b into a's spot
567 assert(MI->getOperand(1).isRegister() &&
568 MI->getOperand(1).getAllocatedRegNum() &&
569 MI->getOperand(1).opIsUse() &&
570 "Two address instruction invalid!");
571 DestPhysReg = MI->getOperand(1).getAllocatedRegNum();
573 liberatePhysReg(MBB, I, DestPhysReg);
574 assignVirtToPhysReg(DestVirtReg, DestPhysReg);
576 DestPhysReg = getReg(MBB, I, DestVirtReg);
578 markVirtRegModified(DestVirtReg);
579 MI->SetMachineOperandReg(i, DestPhysReg); // Assign the output register
583 // If this instruction defines any registers that are immediately dead,
586 for (LiveVariables::killed_iterator KI = LV->dead_begin(MI),
587 KE = LV->dead_end(MI); KI != KE; ++KI) {
588 unsigned VirtReg = KI->second;
589 unsigned PhysReg = VirtReg;
590 if (VirtReg >= MRegisterInfo::FirstVirtualRegister) {
591 std::map<unsigned, unsigned>::iterator I =
592 Virt2PhysRegMap.find(VirtReg);
593 assert(I != Virt2PhysRegMap.end());
595 Virt2PhysRegMap.erase(I);
599 DEBUG(std::cerr << " Register " << RegInfo->getName(PhysReg)
600 << " [%reg" << VirtReg
601 << "] is never used, removing it frame live list\n");
602 removePhysReg(PhysReg);
608 // Rewind the iterator to point to the first flow control instruction...
609 const TargetInstrInfo &TII = TM->getInstrInfo();
611 while (I != MBB.begin() && TII.isTerminatorInstr((*(I-1))->getOpcode()))
614 // Spill all physical registers holding virtual registers now.
615 while (!PhysRegsUsed.empty())
616 if (unsigned VirtReg = PhysRegsUsed.begin()->second)
617 spillVirtReg(MBB, I, VirtReg, PhysRegsUsed.begin()->first);
619 removePhysReg(PhysRegsUsed.begin()->first);
621 for (std::map<unsigned, unsigned>::iterator I = Virt2PhysRegMap.begin(),
622 E = Virt2PhysRegMap.end(); I != E; ++I)
623 std::cerr << "Register still mapped: " << I->first << " -> "
624 << I->second << "\n";
626 assert(Virt2PhysRegMap.empty() && "Virtual registers still in phys regs?");
628 // Clear any physical register which appear live at the end of the basic
629 // block, but which do not hold any virtual registers. e.g., the stack
631 PhysRegsUseOrder.clear();
635 /// runOnMachineFunction - Register allocate the whole function
637 bool RA::runOnMachineFunction(MachineFunction &Fn) {
638 DEBUG(std::cerr << "Machine Function " << "\n");
640 TM = &Fn.getTarget();
641 RegInfo = TM->getRegisterInfo();
644 LV = &getAnalysis<LiveVariables>();
646 // Loop over all of the basic blocks, eliminating virtual register references
647 for (MachineFunction::iterator MBB = Fn.begin(), MBBe = Fn.end();
649 AllocateBasicBlock(*MBB);
651 StackSlotForVirtReg.clear();
652 VirtRegModified.clear();
656 FunctionPass *createLocalRegisterAllocator() {