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 "Support/CommandLine.h"
25 #include "Support/Debug.h"
26 #include "Support/DenseMap.h"
27 #include "Support/Statistic.h"
31 Statistic<> NumStores("ra-local", "Number of stores added");
32 Statistic<> NumLoads ("ra-local", "Number of loads added");
33 Statistic<> NumFolded("ra-local", "Number of loads/stores folded into "
35 class RA : public MachineFunctionPass {
36 const TargetMachine *TM;
38 const MRegisterInfo *RegInfo;
41 // StackSlotForVirtReg - Maps virtual regs to the frame index where these
42 // values are spilled.
43 std::map<unsigned, int> StackSlotForVirtReg;
45 // Virt2PhysRegMap - This map contains entries for each virtual register
46 // that is currently available in a physical register.
47 DenseMap<unsigned, VirtReg2IndexFunctor> Virt2PhysRegMap;
49 unsigned &getVirt2PhysRegMapSlot(unsigned VirtReg) {
50 return Virt2PhysRegMap[VirtReg];
53 // PhysRegsUsed - This array is effectively a map, containing entries for
54 // each physical register that currently has a value (ie, it is in
55 // Virt2PhysRegMap). The value mapped to is the virtual register
56 // corresponding to the physical register (the inverse of the
57 // Virt2PhysRegMap), or 0. The value is set to 0 if this register is pinned
58 // because it is used by a future instruction. If the entry for a physical
59 // register is -1, then the physical register is "not in the map".
61 std::vector<int> PhysRegsUsed;
63 // PhysRegsUseOrder - This contains a list of the physical registers that
64 // currently have a virtual register value in them. This list provides an
65 // ordering of registers, imposing a reallocation order. This list is only
66 // used if all registers are allocated and we have to spill one, in which
67 // case we spill the least recently used register. Entries at the front of
68 // the list are the least recently used registers, entries at the back are
69 // the most recently used.
71 std::vector<unsigned> PhysRegsUseOrder;
73 // VirtRegModified - This bitset contains information about which virtual
74 // registers need to be spilled back to memory when their registers are
75 // scavenged. If a virtual register has simply been rematerialized, there
76 // is no reason to spill it to memory when we need the register back.
78 std::vector<bool> VirtRegModified;
80 void markVirtRegModified(unsigned Reg, bool Val = true) {
81 assert(MRegisterInfo::isVirtualRegister(Reg) && "Illegal VirtReg!");
82 Reg -= MRegisterInfo::FirstVirtualRegister;
83 if (VirtRegModified.size() <= Reg) VirtRegModified.resize(Reg+1);
84 VirtRegModified[Reg] = Val;
87 bool isVirtRegModified(unsigned Reg) const {
88 assert(MRegisterInfo::isVirtualRegister(Reg) && "Illegal VirtReg!");
89 assert(Reg - MRegisterInfo::FirstVirtualRegister < VirtRegModified.size()
90 && "Illegal virtual register!");
91 return VirtRegModified[Reg - MRegisterInfo::FirstVirtualRegister];
94 void MarkPhysRegRecentlyUsed(unsigned Reg) {
95 if(PhysRegsUseOrder.empty() ||
96 PhysRegsUseOrder.back() == Reg) return; // Already most recently used
98 for (unsigned i = PhysRegsUseOrder.size(); i != 0; --i)
99 if (areRegsEqual(Reg, PhysRegsUseOrder[i-1])) {
100 unsigned RegMatch = PhysRegsUseOrder[i-1]; // remove from middle
101 PhysRegsUseOrder.erase(PhysRegsUseOrder.begin()+i-1);
102 // Add it to the end of the list
103 PhysRegsUseOrder.push_back(RegMatch);
105 return; // Found an exact match, exit early
110 virtual const char *getPassName() const {
111 return "Local Register Allocator";
114 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
115 AU.addRequired<LiveVariables>();
116 AU.addRequiredID(PHIEliminationID);
117 AU.addRequiredID(TwoAddressInstructionPassID);
118 MachineFunctionPass::getAnalysisUsage(AU);
122 /// runOnMachineFunction - Register allocate the whole function
123 bool runOnMachineFunction(MachineFunction &Fn);
125 /// AllocateBasicBlock - Register allocate the specified basic block.
126 void AllocateBasicBlock(MachineBasicBlock &MBB);
129 /// areRegsEqual - This method returns true if the specified registers are
130 /// related to each other. To do this, it checks to see if they are equal
131 /// or if the first register is in the alias set of the second register.
133 bool areRegsEqual(unsigned R1, unsigned R2) const {
134 if (R1 == R2) return true;
135 for (const unsigned *AliasSet = RegInfo->getAliasSet(R2);
136 *AliasSet; ++AliasSet) {
137 if (*AliasSet == R1) return true;
142 /// getStackSpaceFor - This returns the frame index of the specified virtual
143 /// register on the stack, allocating space if necessary.
144 int getStackSpaceFor(unsigned VirtReg, const TargetRegisterClass *RC);
146 /// removePhysReg - This method marks the specified physical register as no
147 /// longer being in use.
149 void removePhysReg(unsigned PhysReg);
151 /// spillVirtReg - This method spills the value specified by PhysReg into
152 /// the virtual register slot specified by VirtReg. It then updates the RA
153 /// data structures to indicate the fact that PhysReg is now available.
155 void spillVirtReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator MI,
156 unsigned VirtReg, unsigned PhysReg);
158 /// spillPhysReg - This method spills the specified physical register into
159 /// the virtual register slot associated with it. If OnlyVirtRegs is set to
160 /// true, then the request is ignored if the physical register does not
161 /// contain a virtual register.
163 void spillPhysReg(MachineBasicBlock &MBB, MachineInstr *I,
164 unsigned PhysReg, bool OnlyVirtRegs = false);
166 /// assignVirtToPhysReg - This method updates local state so that we know
167 /// that PhysReg is the proper container for VirtReg now. The physical
168 /// register must not be used for anything else when this is called.
170 void assignVirtToPhysReg(unsigned VirtReg, unsigned PhysReg);
172 /// liberatePhysReg - Make sure the specified physical register is available
173 /// for use. If there is currently a value in it, it is either moved out of
174 /// the way or spilled to memory.
176 void liberatePhysReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator &I,
179 /// isPhysRegAvailable - Return true if the specified physical register is
180 /// free and available for use. This also includes checking to see if
181 /// aliased registers are all free...
183 bool isPhysRegAvailable(unsigned PhysReg) const;
185 /// getFreeReg - Look to see if there is a free register available in the
186 /// specified register class. If not, return 0.
188 unsigned getFreeReg(const TargetRegisterClass *RC);
190 /// getReg - Find a physical register to hold the specified virtual
191 /// register. If all compatible physical registers are used, this method
192 /// spills the last used virtual register to the stack, and uses that
195 unsigned getReg(MachineBasicBlock &MBB, MachineInstr *MI,
198 /// reloadVirtReg - This method transforms the specified specified virtual
199 /// register use to refer to a physical register. This method may do this
200 /// in one of several ways: if the register is available in a physical
201 /// register already, it uses that physical register. If the value is not
202 /// in a physical register, and if there are physical registers available,
203 /// it loads it into a register. If register pressure is high, and it is
204 /// possible, it tries to fold the load of the virtual register into the
205 /// instruction itself. It avoids doing this if register pressure is low to
206 /// improve the chance that subsequent instructions can use the reloaded
207 /// value. This method returns the modified instruction.
209 MachineInstr *reloadVirtReg(MachineBasicBlock &MBB, MachineInstr *MI,
213 void reloadPhysReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator &I,
218 /// getStackSpaceFor - This allocates space for the specified virtual register
219 /// to be held on the stack.
220 int RA::getStackSpaceFor(unsigned VirtReg, const TargetRegisterClass *RC) {
221 // Find the location Reg would belong...
222 std::map<unsigned, int>::iterator I =StackSlotForVirtReg.lower_bound(VirtReg);
224 if (I != StackSlotForVirtReg.end() && I->first == VirtReg)
225 return I->second; // Already has space allocated?
227 // Allocate a new stack object for this spill location...
228 int FrameIdx = MF->getFrameInfo()->CreateStackObject(RC);
230 // Assign the slot...
231 StackSlotForVirtReg.insert(I, std::make_pair(VirtReg, FrameIdx));
236 /// removePhysReg - This method marks the specified physical register as no
237 /// longer being in use.
239 void RA::removePhysReg(unsigned PhysReg) {
240 PhysRegsUsed[PhysReg] = -1; // PhyReg no longer used
242 std::vector<unsigned>::iterator It =
243 std::find(PhysRegsUseOrder.begin(), PhysRegsUseOrder.end(), PhysReg);
244 if (It != PhysRegsUseOrder.end())
245 PhysRegsUseOrder.erase(It);
249 /// spillVirtReg - This method spills the value specified by PhysReg into the
250 /// virtual register slot specified by VirtReg. It then updates the RA data
251 /// structures to indicate the fact that PhysReg is now available.
253 void RA::spillVirtReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator I,
254 unsigned VirtReg, unsigned PhysReg) {
255 assert(VirtReg && "Spilling a physical register is illegal!"
256 " Must not have appropriate kill for the register or use exists beyond"
257 " the intended one.");
258 DEBUG(std::cerr << " Spilling register " << RegInfo->getName(PhysReg);
259 std::cerr << " containing %reg" << VirtReg;
260 if (!isVirtRegModified(VirtReg))
261 std::cerr << " which has not been modified, so no store necessary!");
263 // Otherwise, there is a virtual register corresponding to this physical
264 // register. We only need to spill it into its stack slot if it has been
266 if (isVirtRegModified(VirtReg)) {
267 const TargetRegisterClass *RC = MF->getSSARegMap()->getRegClass(VirtReg);
268 int FrameIndex = getStackSpaceFor(VirtReg, RC);
269 DEBUG(std::cerr << " to stack slot #" << FrameIndex);
270 RegInfo->storeRegToStackSlot(MBB, I, PhysReg, FrameIndex, RC);
271 ++NumStores; // Update statistics
274 getVirt2PhysRegMapSlot(VirtReg) = 0; // VirtReg no longer available
276 DEBUG(std::cerr << "\n");
277 removePhysReg(PhysReg);
281 /// spillPhysReg - This method spills the specified physical register into the
282 /// virtual register slot associated with it. If OnlyVirtRegs is set to true,
283 /// then the request is ignored if the physical register does not contain a
284 /// virtual register.
286 void RA::spillPhysReg(MachineBasicBlock &MBB, MachineInstr *I,
287 unsigned PhysReg, bool OnlyVirtRegs) {
288 if (PhysRegsUsed[PhysReg] != -1) { // Only spill it if it's used!
289 if (PhysRegsUsed[PhysReg] || !OnlyVirtRegs)
290 spillVirtReg(MBB, I, PhysRegsUsed[PhysReg], PhysReg);
292 // If the selected register aliases any other registers, we must make
293 // sure that one of the aliases isn't alive...
294 for (const unsigned *AliasSet = RegInfo->getAliasSet(PhysReg);
295 *AliasSet; ++AliasSet)
296 if (PhysRegsUsed[*AliasSet] != -1) // Spill aliased register...
297 if (PhysRegsUsed[*AliasSet] || !OnlyVirtRegs)
298 spillVirtReg(MBB, I, PhysRegsUsed[*AliasSet], *AliasSet);
303 /// assignVirtToPhysReg - This method updates local state so that we know
304 /// that PhysReg is the proper container for VirtReg now. The physical
305 /// register must not be used for anything else when this is called.
307 void RA::assignVirtToPhysReg(unsigned VirtReg, unsigned PhysReg) {
308 assert(PhysRegsUsed[PhysReg] == -1 && "Phys reg already assigned!");
309 // Update information to note the fact that this register was just used, and
311 PhysRegsUsed[PhysReg] = VirtReg;
312 getVirt2PhysRegMapSlot(VirtReg) = PhysReg;
313 PhysRegsUseOrder.push_back(PhysReg); // New use of PhysReg
317 /// isPhysRegAvailable - Return true if the specified physical register is free
318 /// and available for use. This also includes checking to see if aliased
319 /// registers are all free...
321 bool RA::isPhysRegAvailable(unsigned PhysReg) const {
322 if (PhysRegsUsed[PhysReg] != -1) return false;
324 // If the selected register aliases any other allocated registers, it is
326 for (const unsigned *AliasSet = RegInfo->getAliasSet(PhysReg);
327 *AliasSet; ++AliasSet)
328 if (PhysRegsUsed[*AliasSet] != -1) // Aliased register in use?
329 return false; // Can't use this reg then.
334 /// getFreeReg - Look to see if there is a free register available in the
335 /// specified register class. If not, return 0.
337 unsigned RA::getFreeReg(const TargetRegisterClass *RC) {
338 // Get iterators defining the range of registers that are valid to allocate in
339 // this class, which also specifies the preferred allocation order.
340 TargetRegisterClass::iterator RI = RC->allocation_order_begin(*MF);
341 TargetRegisterClass::iterator RE = RC->allocation_order_end(*MF);
343 for (; RI != RE; ++RI)
344 if (isPhysRegAvailable(*RI)) { // Is reg unused?
345 assert(*RI != 0 && "Cannot use register!");
346 return *RI; // Found an unused register!
352 /// liberatePhysReg - Make sure the specified physical register is available for
353 /// use. If there is currently a value in it, it is either moved out of the way
354 /// or spilled to memory.
356 void RA::liberatePhysReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator &I,
358 // FIXME: This code checks to see if a register is available, but it really
359 // wants to know if a reg is available BEFORE the instruction executes. If
360 // called after killed operands are freed, it runs the risk of reallocating a
363 if (isPhysRegAvailable(PhysReg)) return; // Already available...
365 // Check to see if the register is directly used, not indirectly used through
366 // aliases. If aliased registers are the ones actually used, we cannot be
367 // sure that we will be able to save the whole thing if we do a reg-reg copy.
368 if (PhysRegsUsed[PhysReg] != -1) {
369 // The virtual register held...
370 unsigned VirtReg = PhysRegsUsed[PhysReg]->second;
372 // Check to see if there is a compatible register available. If so, we can
373 // move the value into the new register...
375 const TargetRegisterClass *RC = RegInfo->getRegClass(PhysReg);
376 if (unsigned NewReg = getFreeReg(RC)) {
377 // Emit the code to copy the value...
378 RegInfo->copyRegToReg(MBB, I, NewReg, PhysReg, RC);
380 // Update our internal state to indicate that PhysReg is available and Reg
382 getVirt2PhysRegMapSlot[VirtReg] = 0;
383 removePhysReg(PhysReg); // Free the physreg
385 // Move reference over to new register...
386 assignVirtToPhysReg(VirtReg, NewReg);
391 spillPhysReg(MBB, I, PhysReg);
395 /// getReg - Find a physical register to hold the specified virtual
396 /// register. If all compatible physical registers are used, this method spills
397 /// the last used virtual register to the stack, and uses that register.
399 unsigned RA::getReg(MachineBasicBlock &MBB, MachineInstr *I,
401 const TargetRegisterClass *RC = MF->getSSARegMap()->getRegClass(VirtReg);
403 // First check to see if we have a free register of the requested type...
404 unsigned PhysReg = getFreeReg(RC);
406 // If we didn't find an unused register, scavenge one now!
408 assert(!PhysRegsUseOrder.empty() && "No allocated registers??");
410 // Loop over all of the preallocated registers from the least recently used
411 // to the most recently used. When we find one that is capable of holding
412 // our register, use it.
413 for (unsigned i = 0; PhysReg == 0; ++i) {
414 assert(i != PhysRegsUseOrder.size() &&
415 "Couldn't find a register of the appropriate class!");
417 unsigned R = PhysRegsUseOrder[i];
419 // We can only use this register if it holds a virtual register (ie, it
420 // can be spilled). Do not use it if it is an explicitly allocated
421 // physical register!
422 assert(PhysRegsUsed[R] != -1 &&
423 "PhysReg in PhysRegsUseOrder, but is not allocated?");
424 if (PhysRegsUsed[R]) {
425 // If the current register is compatible, use it.
426 if (RegInfo->getRegClass(R) == RC) {
430 // If one of the registers aliased to the current register is
431 // compatible, use it.
432 for (const unsigned *AliasSet = RegInfo->getAliasSet(R);
433 *AliasSet; ++AliasSet) {
434 if (RegInfo->getRegClass(*AliasSet) == RC) {
435 PhysReg = *AliasSet; // Take an aliased register
443 assert(PhysReg && "Physical register not assigned!?!?");
445 // At this point PhysRegsUseOrder[i] is the least recently used register of
446 // compatible register class. Spill it to memory and reap its remains.
447 spillPhysReg(MBB, I, PhysReg);
450 // Now that we know which register we need to assign this to, do it now!
451 assignVirtToPhysReg(VirtReg, PhysReg);
456 /// reloadVirtReg - This method transforms the specified specified virtual
457 /// register use to refer to a physical register. This method may do this in
458 /// one of several ways: if the register is available in a physical register
459 /// already, it uses that physical register. If the value is not in a physical
460 /// register, and if there are physical registers available, it loads it into a
461 /// register. If register pressure is high, and it is possible, it tries to
462 /// fold the load of the virtual register into the instruction itself. It
463 /// avoids doing this if register pressure is low to improve the chance that
464 /// subsequent instructions can use the reloaded value. This method returns the
465 /// modified instruction.
467 MachineInstr *RA::reloadVirtReg(MachineBasicBlock &MBB, MachineInstr *MI,
469 unsigned VirtReg = MI->getOperand(OpNum).getReg();
471 // If the virtual register is already available, just update the instruction
473 if (unsigned PR = getVirt2PhysRegMapSlot(VirtReg)) {
474 MarkPhysRegRecentlyUsed(PR); // Already have this value available!
475 MI->SetMachineOperandReg(OpNum, PR); // Assign the input register
479 // Otherwise, we need to fold it into the current instruction, or reload it.
480 // If we have registers available to hold the value, use them.
481 const TargetRegisterClass *RC = MF->getSSARegMap()->getRegClass(VirtReg);
482 unsigned PhysReg = getFreeReg(RC);
483 int FrameIndex = getStackSpaceFor(VirtReg, RC);
485 if (PhysReg) { // Register is available, allocate it!
486 assignVirtToPhysReg(VirtReg, PhysReg);
487 } else { // No registers available.
488 // If we can fold this spill into this instruction, do so now.
489 if (MachineInstr* FMI = RegInfo->foldMemoryOperand(MI, OpNum, FrameIndex)){
491 // Since we changed the address of MI, make sure to update live variables
492 // to know that the new instruction has the properties of the old one.
493 LV->instructionChanged(MI, FMI);
494 return MBB.insert(MBB.erase(MI), FMI);
497 // It looks like we can't fold this virtual register load into this
498 // instruction. Force some poor hapless value out of the register file to
499 // make room for the new register, and reload it.
500 PhysReg = getReg(MBB, MI, VirtReg);
503 markVirtRegModified(VirtReg, false); // Note that this reg was just reloaded
505 DEBUG(std::cerr << " Reloading %reg" << VirtReg << " into "
506 << RegInfo->getName(PhysReg) << "\n");
508 // Add move instruction(s)
509 RegInfo->loadRegFromStackSlot(MBB, MI, PhysReg, FrameIndex, RC);
510 ++NumLoads; // Update statistics
512 MI->SetMachineOperandReg(OpNum, PhysReg); // Assign the input register
518 void RA::AllocateBasicBlock(MachineBasicBlock &MBB) {
519 // loop over each instruction
520 MachineBasicBlock::iterator MI = MBB.begin();
521 for (; MI != MBB.end(); ++MI) {
522 const TargetInstrDescriptor &TID = TM->getInstrInfo()->get(MI->getOpcode());
523 DEBUG(std::cerr << "\nStarting RegAlloc of: " << *MI;
524 std::cerr << " Regs have values: ";
525 for (unsigned i = 0; i != RegInfo->getNumRegs(); ++i)
526 if (PhysRegsUsed[i] != -1)
527 std::cerr << "[" << RegInfo->getName(i)
528 << ",%reg" << PhysRegsUsed[i] << "] ";
531 // Loop over the implicit uses, making sure that they are at the head of the
532 // use order list, so they don't get reallocated.
533 for (const unsigned *ImplicitUses = TID.ImplicitUses;
534 *ImplicitUses; ++ImplicitUses)
535 MarkPhysRegRecentlyUsed(*ImplicitUses);
537 // Get the used operands into registers. This has the potential to spill
538 // incoming values if we are out of registers. Note that we completely
539 // ignore physical register uses here. We assume that if an explicit
540 // physical register is referenced by the instruction, that it is guaranteed
541 // to be live-in, or the input is badly hosed.
543 for (unsigned i = 0; i != MI->getNumOperands(); ++i) {
544 MachineOperand& MO = MI->getOperand(i);
545 // here we are looking for only used operands (never def&use)
546 if (!MO.isDef() && MO.isRegister() && MO.getReg() &&
547 MRegisterInfo::isVirtualRegister(MO.getReg()))
548 MI = reloadVirtReg(MBB, MI, i);
551 // If this instruction is the last user of anything in registers, kill the
552 // value, freeing the register being used, so it doesn't need to be
553 // spilled to memory.
555 for (LiveVariables::killed_iterator KI = LV->killed_begin(MI),
556 KE = LV->killed_end(MI); KI != KE; ++KI) {
557 unsigned VirtReg = KI->second;
558 unsigned PhysReg = VirtReg;
559 if (MRegisterInfo::isVirtualRegister(VirtReg)) {
560 // If the virtual register was never materialized into a register, it
561 // might not be in the map, but it won't hurt to zero it out anyway.
562 unsigned &PhysRegSlot = getVirt2PhysRegMapSlot(VirtReg);
563 PhysReg = PhysRegSlot;
568 DEBUG(std::cerr << " Last use of " << RegInfo->getName(PhysReg)
569 << "[%reg" << VirtReg <<"], removing it from live set\n");
570 removePhysReg(PhysReg);
574 // Loop over all of the operands of the instruction, spilling registers that
575 // are defined, and marking explicit destinations in the PhysRegsUsed map.
576 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
577 MachineOperand& MO = MI->getOperand(i);
578 if (MO.isDef() && MO.isRegister() && MO.getReg() &&
579 MRegisterInfo::isPhysicalRegister(MO.getReg())) {
580 unsigned Reg = MO.getReg();
581 spillPhysReg(MBB, MI, Reg, true); // Spill any existing value in the reg
582 PhysRegsUsed[Reg] = 0; // It is free and reserved now
583 PhysRegsUseOrder.push_back(Reg);
584 for (const unsigned *AliasSet = RegInfo->getAliasSet(Reg);
585 *AliasSet; ++AliasSet) {
586 PhysRegsUseOrder.push_back(*AliasSet);
587 PhysRegsUsed[*AliasSet] = 0; // It is free and reserved now
592 // Loop over the implicit defs, spilling them as well.
593 for (const unsigned *ImplicitDefs = TID.ImplicitDefs;
594 *ImplicitDefs; ++ImplicitDefs) {
595 unsigned Reg = *ImplicitDefs;
596 spillPhysReg(MBB, MI, Reg, true);
597 PhysRegsUseOrder.push_back(Reg);
598 PhysRegsUsed[Reg] = 0; // It is free and reserved now
599 for (const unsigned *AliasSet = RegInfo->getAliasSet(Reg);
600 *AliasSet; ++AliasSet) {
601 PhysRegsUseOrder.push_back(*AliasSet);
602 PhysRegsUsed[*AliasSet] = 0; // It is free and reserved now
606 // Okay, we have allocated all of the source operands and spilled any values
607 // that would be destroyed by defs of this instruction. Loop over the
608 // implicit defs and assign them to a register, spilling incoming values if
609 // we need to scavenge a register.
611 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
612 MachineOperand& MO = MI->getOperand(i);
613 if (MO.isDef() && MO.isRegister() && MO.getReg() &&
614 MRegisterInfo::isVirtualRegister(MO.getReg())) {
615 unsigned DestVirtReg = MO.getReg();
616 unsigned DestPhysReg;
618 // If DestVirtReg already has a value, use it.
619 if (!(DestPhysReg = getVirt2PhysRegMapSlot(DestVirtReg)))
620 DestPhysReg = getReg(MBB, MI, DestVirtReg);
621 markVirtRegModified(DestVirtReg);
622 MI->SetMachineOperandReg(i, DestPhysReg); // Assign the output register
626 // If this instruction defines any registers that are immediately dead,
629 for (LiveVariables::killed_iterator KI = LV->dead_begin(MI),
630 KE = LV->dead_end(MI); KI != KE; ++KI) {
631 unsigned VirtReg = KI->second;
632 unsigned PhysReg = VirtReg;
633 if (MRegisterInfo::isVirtualRegister(VirtReg)) {
634 unsigned &PhysRegSlot = getVirt2PhysRegMapSlot(VirtReg);
635 PhysReg = PhysRegSlot;
636 assert(PhysReg != 0);
641 DEBUG(std::cerr << " Register " << RegInfo->getName(PhysReg)
642 << " [%reg" << VirtReg
643 << "] is never used, removing it frame live list\n");
644 removePhysReg(PhysReg);
649 MI = MBB.getFirstTerminator();
651 // Spill all physical registers holding virtual registers now.
652 for (unsigned i = 0, e = RegInfo->getNumRegs(); i != e; ++i)
653 if (PhysRegsUsed[i] != -1)
654 if (unsigned VirtReg = PhysRegsUsed[i])
655 spillVirtReg(MBB, MI, VirtReg, i);
661 for (unsigned i = MRegisterInfo::FirstVirtualRegister,
662 e = MF->getSSARegMap()->getLastVirtReg(); i <= e; ++i)
663 if (unsigned PR = Virt2PhysRegMap[i]) {
664 std::cerr << "Register still mapped: " << i << " -> " << PR << "\n";
667 assert(AllOk && "Virtual registers still in phys regs?");
670 // Clear any physical register which appear live at the end of the basic
671 // block, but which do not hold any virtual registers. e.g., the stack
673 PhysRegsUseOrder.clear();
677 /// runOnMachineFunction - Register allocate the whole function
679 bool RA::runOnMachineFunction(MachineFunction &Fn) {
680 DEBUG(std::cerr << "Machine Function " << "\n");
682 TM = &Fn.getTarget();
683 RegInfo = TM->getRegisterInfo();
684 LV = &getAnalysis<LiveVariables>();
686 PhysRegsUsed.assign(RegInfo->getNumRegs(), -1);
688 // initialize the virtual->physical register map to have a 'null'
689 // mapping for all virtual registers
690 Virt2PhysRegMap.grow(MF->getSSARegMap()->getLastVirtReg());
692 // Loop over all of the basic blocks, eliminating virtual register references
693 for (MachineFunction::iterator MBB = Fn.begin(), MBBe = Fn.end();
695 AllocateBasicBlock(*MBB);
697 StackSlotForVirtReg.clear();
698 PhysRegsUsed.clear();
699 VirtRegModified.clear();
700 Virt2PhysRegMap.clear();
704 FunctionPass *llvm::createLocalRegisterAllocator() {