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"
32 Statistic<> NumStores("ra-local", "Number of stores added");
33 Statistic<> NumLoads ("ra-local", "Number of loads added");
34 Statistic<> NumFolded("ra-local", "Number of loads/stores folded into "
36 class RA : public MachineFunctionPass {
37 const TargetMachine *TM;
39 const MRegisterInfo *RegInfo;
42 // StackSlotForVirtReg - Maps virtual regs to the frame index where these
43 // values are spilled.
44 std::map<unsigned, int> StackSlotForVirtReg;
46 // Virt2PhysRegMap - This map contains entries for each virtual register
47 // that is currently available in a physical register.
48 DenseMap<unsigned, VirtReg2IndexFunctor> Virt2PhysRegMap;
50 unsigned &getVirt2PhysRegMapSlot(unsigned VirtReg) {
51 return Virt2PhysRegMap[VirtReg];
54 // PhysRegsUsed - This array is effectively a map, containing entries for
55 // each physical register that currently has a value (ie, it is in
56 // Virt2PhysRegMap). The value mapped to is the virtual register
57 // corresponding to the physical register (the inverse of the
58 // Virt2PhysRegMap), or 0. The value is set to 0 if this register is pinned
59 // because it is used by a future instruction. If the entry for a physical
60 // register is -1, then the physical register is "not in the map".
62 std::vector<int> PhysRegsUsed;
64 // PhysRegsUseOrder - This contains a list of the physical registers that
65 // currently have a virtual register value in them. This list provides an
66 // ordering of registers, imposing a reallocation order. This list is only
67 // used if all registers are allocated and we have to spill one, in which
68 // case we spill the least recently used register. Entries at the front of
69 // the list are the least recently used registers, entries at the back are
70 // the most recently used.
72 std::vector<unsigned> PhysRegsUseOrder;
74 // VirtRegModified - This bitset contains information about which virtual
75 // registers need to be spilled back to memory when their registers are
76 // scavenged. If a virtual register has simply been rematerialized, there
77 // is no reason to spill it to memory when we need the register back.
79 std::vector<bool> VirtRegModified;
81 void markVirtRegModified(unsigned Reg, bool Val = true) {
82 assert(MRegisterInfo::isVirtualRegister(Reg) && "Illegal VirtReg!");
83 Reg -= MRegisterInfo::FirstVirtualRegister;
84 if (VirtRegModified.size() <= Reg) VirtRegModified.resize(Reg+1);
85 VirtRegModified[Reg] = Val;
88 bool isVirtRegModified(unsigned Reg) const {
89 assert(MRegisterInfo::isVirtualRegister(Reg) && "Illegal VirtReg!");
90 assert(Reg - MRegisterInfo::FirstVirtualRegister < VirtRegModified.size()
91 && "Illegal virtual register!");
92 return VirtRegModified[Reg - MRegisterInfo::FirstVirtualRegister];
95 void MarkPhysRegRecentlyUsed(unsigned Reg) {
96 assert(!PhysRegsUseOrder.empty() && "No registers used!");
97 if (PhysRegsUseOrder.back() == Reg) return; // Already most recently used
99 for (unsigned i = PhysRegsUseOrder.size(); i != 0; --i)
100 if (areRegsEqual(Reg, PhysRegsUseOrder[i-1])) {
101 unsigned RegMatch = PhysRegsUseOrder[i-1]; // remove from middle
102 PhysRegsUseOrder.erase(PhysRegsUseOrder.begin()+i-1);
103 // Add it to the end of the list
104 PhysRegsUseOrder.push_back(RegMatch);
106 return; // Found an exact match, exit early
111 virtual const char *getPassName() const {
112 return "Local Register Allocator";
115 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
116 AU.addRequired<LiveVariables>();
117 AU.addRequiredID(PHIEliminationID);
118 AU.addRequiredID(TwoAddressInstructionPassID);
119 MachineFunctionPass::getAnalysisUsage(AU);
123 /// runOnMachineFunction - Register allocate the whole function
124 bool runOnMachineFunction(MachineFunction &Fn);
126 /// AllocateBasicBlock - Register allocate the specified basic block.
127 void AllocateBasicBlock(MachineBasicBlock &MBB);
130 /// areRegsEqual - This method returns true if the specified registers are
131 /// related to each other. To do this, it checks to see if they are equal
132 /// or if the first register is in the alias set of the second register.
134 bool areRegsEqual(unsigned R1, unsigned R2) const {
135 if (R1 == R2) return true;
136 for (const unsigned *AliasSet = RegInfo->getAliasSet(R2);
137 *AliasSet; ++AliasSet) {
138 if (*AliasSet == R1) return true;
143 /// getStackSpaceFor - This returns the frame index of the specified virtual
144 /// register on the stack, allocating space if necessary.
145 int getStackSpaceFor(unsigned VirtReg, const TargetRegisterClass *RC);
147 /// removePhysReg - This method marks the specified physical register as no
148 /// longer being in use.
150 void removePhysReg(unsigned PhysReg);
152 /// spillVirtReg - This method spills the value specified by PhysReg into
153 /// the virtual register slot specified by VirtReg. It then updates the RA
154 /// data structures to indicate the fact that PhysReg is now available.
156 void spillVirtReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator MI,
157 unsigned VirtReg, unsigned PhysReg);
159 /// spillPhysReg - This method spills the specified physical register into
160 /// the virtual register slot associated with it. If OnlyVirtRegs is set to
161 /// true, then the request is ignored if the physical register does not
162 /// contain a virtual register.
164 void spillPhysReg(MachineBasicBlock &MBB, MachineInstr *I,
165 unsigned PhysReg, bool OnlyVirtRegs = false);
167 /// assignVirtToPhysReg - This method updates local state so that we know
168 /// that PhysReg is the proper container for VirtReg now. The physical
169 /// register must not be used for anything else when this is called.
171 void assignVirtToPhysReg(unsigned VirtReg, unsigned PhysReg);
173 /// liberatePhysReg - Make sure the specified physical register is available
174 /// for use. If there is currently a value in it, it is either moved out of
175 /// the way or spilled to memory.
177 void liberatePhysReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator &I,
180 /// isPhysRegAvailable - Return true if the specified physical register is
181 /// free and available for use. This also includes checking to see if
182 /// aliased registers are all free...
184 bool isPhysRegAvailable(unsigned PhysReg) const;
186 /// getFreeReg - Look to see if there is a free register available in the
187 /// specified register class. If not, return 0.
189 unsigned getFreeReg(const TargetRegisterClass *RC);
191 /// getReg - Find a physical register to hold the specified virtual
192 /// register. If all compatible physical registers are used, this method
193 /// spills the last used virtual register to the stack, and uses that
196 unsigned getReg(MachineBasicBlock &MBB, MachineInstr *MI,
199 /// reloadVirtReg - This method transforms the specified specified virtual
200 /// register use to refer to a physical register. This method may do this
201 /// in one of several ways: if the register is available in a physical
202 /// register already, it uses that physical register. If the value is not
203 /// in a physical register, and if there are physical registers available,
204 /// it loads it into a register. If register pressure is high, and it is
205 /// possible, it tries to fold the load of the virtual register into the
206 /// instruction itself. It avoids doing this if register pressure is low to
207 /// improve the chance that subsequent instructions can use the reloaded
208 /// value. This method returns the modified instruction.
210 MachineInstr *reloadVirtReg(MachineBasicBlock &MBB, MachineInstr *MI,
214 void reloadPhysReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator &I,
219 /// getStackSpaceFor - This allocates space for the specified virtual register
220 /// to be held on the stack.
221 int RA::getStackSpaceFor(unsigned VirtReg, const TargetRegisterClass *RC) {
222 // Find the location Reg would belong...
223 std::map<unsigned, int>::iterator I =StackSlotForVirtReg.lower_bound(VirtReg);
225 if (I != StackSlotForVirtReg.end() && I->first == VirtReg)
226 return I->second; // Already has space allocated?
228 // Allocate a new stack object for this spill location...
229 int FrameIdx = MF->getFrameInfo()->CreateStackObject(RC);
231 // Assign the slot...
232 StackSlotForVirtReg.insert(I, std::make_pair(VirtReg, FrameIdx));
237 /// removePhysReg - This method marks the specified physical register as no
238 /// longer being in use.
240 void RA::removePhysReg(unsigned PhysReg) {
241 PhysRegsUsed[PhysReg] = -1; // PhyReg no longer used
243 std::vector<unsigned>::iterator It =
244 std::find(PhysRegsUseOrder.begin(), PhysRegsUseOrder.end(), PhysReg);
245 if (It != PhysRegsUseOrder.end())
246 PhysRegsUseOrder.erase(It);
250 /// spillVirtReg - This method spills the value specified by PhysReg into the
251 /// virtual register slot specified by VirtReg. It then updates the RA data
252 /// structures to indicate the fact that PhysReg is now available.
254 void RA::spillVirtReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator I,
255 unsigned VirtReg, unsigned PhysReg) {
256 assert(VirtReg && "Spilling a physical register is illegal!"
257 " Must not have appropriate kill for the register or use exists beyond"
258 " the intended one.");
259 DEBUG(std::cerr << " Spilling register " << RegInfo->getName(PhysReg);
260 std::cerr << " containing %reg" << VirtReg;
261 if (!isVirtRegModified(VirtReg))
262 std::cerr << " which has not been modified, so no store necessary!");
264 // Otherwise, there is a virtual register corresponding to this physical
265 // register. We only need to spill it into its stack slot if it has been
267 if (isVirtRegModified(VirtReg)) {
268 const TargetRegisterClass *RC = MF->getSSARegMap()->getRegClass(VirtReg);
269 int FrameIndex = getStackSpaceFor(VirtReg, RC);
270 DEBUG(std::cerr << " to stack slot #" << FrameIndex);
271 RegInfo->storeRegToStackSlot(MBB, I, PhysReg, FrameIndex, RC);
272 ++NumStores; // Update statistics
275 getVirt2PhysRegMapSlot(VirtReg) = 0; // VirtReg no longer available
277 DEBUG(std::cerr << "\n");
278 removePhysReg(PhysReg);
282 /// spillPhysReg - This method spills the specified physical register into the
283 /// virtual register slot associated with it. If OnlyVirtRegs is set to true,
284 /// then the request is ignored if the physical register does not contain a
285 /// virtual register.
287 void RA::spillPhysReg(MachineBasicBlock &MBB, MachineInstr *I,
288 unsigned PhysReg, bool OnlyVirtRegs) {
289 if (PhysRegsUsed[PhysReg] != -1) { // Only spill it if it's used!
290 if (PhysRegsUsed[PhysReg] || !OnlyVirtRegs)
291 spillVirtReg(MBB, I, PhysRegsUsed[PhysReg], PhysReg);
293 // If the selected register aliases any other registers, we must make
294 // sure that one of the aliases isn't alive...
295 for (const unsigned *AliasSet = RegInfo->getAliasSet(PhysReg);
296 *AliasSet; ++AliasSet)
297 if (PhysRegsUsed[*AliasSet] != -1) // Spill aliased register...
298 if (PhysRegsUsed[*AliasSet] || !OnlyVirtRegs)
299 spillVirtReg(MBB, I, PhysRegsUsed[*AliasSet], *AliasSet);
304 /// assignVirtToPhysReg - This method updates local state so that we know
305 /// that PhysReg is the proper container for VirtReg now. The physical
306 /// register must not be used for anything else when this is called.
308 void RA::assignVirtToPhysReg(unsigned VirtReg, unsigned PhysReg) {
309 assert(PhysRegsUsed[PhysReg] == -1 && "Phys reg already assigned!");
310 // Update information to note the fact that this register was just used, and
312 PhysRegsUsed[PhysReg] = VirtReg;
313 getVirt2PhysRegMapSlot(VirtReg) = PhysReg;
314 PhysRegsUseOrder.push_back(PhysReg); // New use of PhysReg
318 /// isPhysRegAvailable - Return true if the specified physical register is free
319 /// and available for use. This also includes checking to see if aliased
320 /// registers are all free...
322 bool RA::isPhysRegAvailable(unsigned PhysReg) const {
323 if (PhysRegsUsed[PhysReg] != -1) return false;
325 // If the selected register aliases any other allocated registers, it is
327 for (const unsigned *AliasSet = RegInfo->getAliasSet(PhysReg);
328 *AliasSet; ++AliasSet)
329 if (PhysRegsUsed[*AliasSet] != -1) // Aliased register in use?
330 return false; // Can't use this reg then.
335 /// getFreeReg - Look to see if there is a free register available in the
336 /// specified register class. If not, return 0.
338 unsigned RA::getFreeReg(const TargetRegisterClass *RC) {
339 // Get iterators defining the range of registers that are valid to allocate in
340 // this class, which also specifies the preferred allocation order.
341 TargetRegisterClass::iterator RI = RC->allocation_order_begin(*MF);
342 TargetRegisterClass::iterator RE = RC->allocation_order_end(*MF);
344 for (; RI != RE; ++RI)
345 if (isPhysRegAvailable(*RI)) { // Is reg unused?
346 assert(*RI != 0 && "Cannot use register!");
347 return *RI; // Found an unused register!
353 /// liberatePhysReg - Make sure the specified physical register is available for
354 /// use. If there is currently a value in it, it is either moved out of the way
355 /// or spilled to memory.
357 void RA::liberatePhysReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator &I,
359 // FIXME: This code checks to see if a register is available, but it really
360 // wants to know if a reg is available BEFORE the instruction executes. If
361 // called after killed operands are freed, it runs the risk of reallocating a
364 if (isPhysRegAvailable(PhysReg)) return; // Already available...
366 // Check to see if the register is directly used, not indirectly used through
367 // aliases. If aliased registers are the ones actually used, we cannot be
368 // sure that we will be able to save the whole thing if we do a reg-reg copy.
369 if (PhysRegsUsed[PhysReg] != -1) {
370 // The virtual register held...
371 unsigned VirtReg = PhysRegsUsed[PhysReg]->second;
373 // Check to see if there is a compatible register available. If so, we can
374 // move the value into the new register...
376 const TargetRegisterClass *RC = RegInfo->getRegClass(PhysReg);
377 if (unsigned NewReg = getFreeReg(RC)) {
378 // Emit the code to copy the value...
379 RegInfo->copyRegToReg(MBB, I, NewReg, PhysReg, RC);
381 // Update our internal state to indicate that PhysReg is available and Reg
383 getVirt2PhysRegMapSlot[VirtReg] = 0;
384 removePhysReg(PhysReg); // Free the physreg
386 // Move reference over to new register...
387 assignVirtToPhysReg(VirtReg, NewReg);
392 spillPhysReg(MBB, I, PhysReg);
396 /// getReg - Find a physical register to hold the specified virtual
397 /// register. If all compatible physical registers are used, this method spills
398 /// the last used virtual register to the stack, and uses that register.
400 unsigned RA::getReg(MachineBasicBlock &MBB, MachineInstr *I,
402 const TargetRegisterClass *RC = MF->getSSARegMap()->getRegClass(VirtReg);
404 // First check to see if we have a free register of the requested type...
405 unsigned PhysReg = getFreeReg(RC);
407 // If we didn't find an unused register, scavenge one now!
409 assert(!PhysRegsUseOrder.empty() && "No allocated registers??");
411 // Loop over all of the preallocated registers from the least recently used
412 // to the most recently used. When we find one that is capable of holding
413 // our register, use it.
414 for (unsigned i = 0; PhysReg == 0; ++i) {
415 assert(i != PhysRegsUseOrder.size() &&
416 "Couldn't find a register of the appropriate class!");
418 unsigned R = PhysRegsUseOrder[i];
420 // We can only use this register if it holds a virtual register (ie, it
421 // can be spilled). Do not use it if it is an explicitly allocated
422 // physical register!
423 assert(PhysRegsUsed[R] != -1 &&
424 "PhysReg in PhysRegsUseOrder, but is not allocated?");
425 if (PhysRegsUsed[R]) {
426 // If the current register is compatible, use it.
427 if (RegInfo->getRegClass(R) == RC) {
431 // If one of the registers aliased to the current register is
432 // compatible, use it.
433 for (const unsigned *AliasSet = RegInfo->getAliasSet(R);
434 *AliasSet; ++AliasSet) {
435 if (RegInfo->getRegClass(*AliasSet) == RC) {
436 PhysReg = *AliasSet; // Take an aliased register
444 assert(PhysReg && "Physical register not assigned!?!?");
446 // At this point PhysRegsUseOrder[i] is the least recently used register of
447 // compatible register class. Spill it to memory and reap its remains.
448 spillPhysReg(MBB, I, PhysReg);
451 // Now that we know which register we need to assign this to, do it now!
452 assignVirtToPhysReg(VirtReg, PhysReg);
457 /// reloadVirtReg - This method transforms the specified specified virtual
458 /// register use to refer to a physical register. This method may do this in
459 /// one of several ways: if the register is available in a physical register
460 /// already, it uses that physical register. If the value is not in a physical
461 /// register, and if there are physical registers available, it loads it into a
462 /// register. If register pressure is high, and it is possible, it tries to
463 /// fold the load of the virtual register into the instruction itself. It
464 /// avoids doing this if register pressure is low to improve the chance that
465 /// subsequent instructions can use the reloaded value. This method returns the
466 /// modified instruction.
468 MachineInstr *RA::reloadVirtReg(MachineBasicBlock &MBB, MachineInstr *MI,
470 unsigned VirtReg = MI->getOperand(OpNum).getReg();
472 // If the virtual register is already available, just update the instruction
474 if (unsigned PR = getVirt2PhysRegMapSlot(VirtReg)) {
475 MarkPhysRegRecentlyUsed(PR); // Already have this value available!
476 MI->SetMachineOperandReg(OpNum, PR); // Assign the input register
480 // Otherwise, we need to fold it into the current instruction, or reload it.
481 // If we have registers available to hold the value, use them.
482 const TargetRegisterClass *RC = MF->getSSARegMap()->getRegClass(VirtReg);
483 unsigned PhysReg = getFreeReg(RC);
484 int FrameIndex = getStackSpaceFor(VirtReg, RC);
486 if (PhysReg) { // Register is available, allocate it!
487 assignVirtToPhysReg(VirtReg, PhysReg);
488 } else { // No registers available.
489 // If we can fold this spill into this instruction, do so now.
490 if (MachineInstr* FMI = RegInfo->foldMemoryOperand(MI, OpNum, FrameIndex)){
492 // Since we changed the address of MI, make sure to update live variables
493 // to know that the new instruction has the properties of the old one.
494 LV->instructionChanged(MI, FMI);
495 return MBB.insert(MBB.erase(MI), FMI);
498 // It looks like we can't fold this virtual register load into this
499 // instruction. Force some poor hapless value out of the register file to
500 // make room for the new register, and reload it.
501 PhysReg = getReg(MBB, MI, VirtReg);
504 markVirtRegModified(VirtReg, false); // Note that this reg was just reloaded
506 DEBUG(std::cerr << " Reloading %reg" << VirtReg << " into "
507 << RegInfo->getName(PhysReg) << "\n");
509 // Add move instruction(s)
510 RegInfo->loadRegFromStackSlot(MBB, MI, PhysReg, FrameIndex, RC);
511 ++NumLoads; // Update statistics
513 MI->SetMachineOperandReg(OpNum, PhysReg); // Assign the input register
519 void RA::AllocateBasicBlock(MachineBasicBlock &MBB) {
520 // loop over each instruction
521 MachineBasicBlock::iterator MI = MBB.begin();
522 for (; MI != MBB.end(); ++MI) {
523 const TargetInstrDescriptor &TID = TM->getInstrInfo()->get(MI->getOpcode());
524 DEBUG(std::cerr << "\nStarting RegAlloc of: " << *MI;
525 std::cerr << " Regs have values: ";
526 for (unsigned i = 0; i != RegInfo->getNumRegs(); ++i)
527 if (PhysRegsUsed[i] != -1)
528 std::cerr << "[" << RegInfo->getName(i)
529 << ",%reg" << PhysRegsUsed[i] << "] ";
532 // Loop over the implicit uses, making sure that they are at the head of the
533 // use order list, so they don't get reallocated.
534 for (const unsigned *ImplicitUses = TID.ImplicitUses;
535 *ImplicitUses; ++ImplicitUses)
536 MarkPhysRegRecentlyUsed(*ImplicitUses);
538 // Get the used operands into registers. This has the potential to spill
539 // incoming values if we are out of registers. Note that we completely
540 // ignore physical register uses here. We assume that if an explicit
541 // physical register is referenced by the instruction, that it is guaranteed
542 // to be live-in, or the input is badly hosed.
544 for (unsigned i = 0; i != MI->getNumOperands(); ++i) {
545 MachineOperand& MO = MI->getOperand(i);
546 // here we are looking for only used operands (never def&use)
547 if (!MO.isDef() && MO.isRegister() && MO.getReg() &&
548 MRegisterInfo::isVirtualRegister(MO.getReg()))
549 MI = reloadVirtReg(MBB, MI, i);
552 // If this instruction is the last user of anything in registers, kill the
553 // value, freeing the register being used, so it doesn't need to be
554 // spilled to memory.
556 for (LiveVariables::killed_iterator KI = LV->killed_begin(MI),
557 KE = LV->killed_end(MI); KI != KE; ++KI) {
558 unsigned VirtReg = KI->second;
559 unsigned PhysReg = VirtReg;
560 if (MRegisterInfo::isVirtualRegister(VirtReg)) {
561 // If the virtual register was never materialized into a register, it
562 // might not be in the map, but it won't hurt to zero it out anyway.
563 unsigned &PhysRegSlot = getVirt2PhysRegMapSlot(VirtReg);
564 PhysReg = PhysRegSlot;
569 DEBUG(std::cerr << " Last use of " << RegInfo->getName(PhysReg)
570 << "[%reg" << VirtReg <<"], removing it from live set\n");
571 removePhysReg(PhysReg);
575 // Loop over all of the operands of the instruction, spilling registers that
576 // are defined, and marking explicit destinations in the PhysRegsUsed map.
577 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
578 MachineOperand& MO = MI->getOperand(i);
579 if (MO.isDef() && MO.isRegister() && MO.getReg() &&
580 MRegisterInfo::isPhysicalRegister(MO.getReg())) {
581 unsigned Reg = MO.getReg();
582 spillPhysReg(MBB, MI, Reg, true); // Spill any existing value in the reg
583 PhysRegsUsed[Reg] = 0; // It is free and reserved now
584 PhysRegsUseOrder.push_back(Reg);
585 for (const unsigned *AliasSet = RegInfo->getAliasSet(Reg);
586 *AliasSet; ++AliasSet) {
587 PhysRegsUseOrder.push_back(*AliasSet);
588 PhysRegsUsed[*AliasSet] = 0; // It is free and reserved now
593 // Loop over the implicit defs, spilling them as well.
594 for (const unsigned *ImplicitDefs = TID.ImplicitDefs;
595 *ImplicitDefs; ++ImplicitDefs) {
596 unsigned Reg = *ImplicitDefs;
597 spillPhysReg(MBB, MI, Reg, true);
598 PhysRegsUseOrder.push_back(Reg);
599 PhysRegsUsed[Reg] = 0; // It is free and reserved now
600 for (const unsigned *AliasSet = RegInfo->getAliasSet(Reg);
601 *AliasSet; ++AliasSet) {
602 PhysRegsUseOrder.push_back(*AliasSet);
603 PhysRegsUsed[*AliasSet] = 0; // It is free and reserved now
607 // Okay, we have allocated all of the source operands and spilled any values
608 // that would be destroyed by defs of this instruction. Loop over the
609 // implicit defs and assign them to a register, spilling incoming values if
610 // we need to scavenge a register.
612 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
613 MachineOperand& MO = MI->getOperand(i);
614 if (MO.isDef() && MO.isRegister() && MO.getReg() &&
615 MRegisterInfo::isVirtualRegister(MO.getReg())) {
616 unsigned DestVirtReg = MO.getReg();
617 unsigned DestPhysReg;
619 // If DestVirtReg already has a value, use it.
620 if (!(DestPhysReg = getVirt2PhysRegMapSlot(DestVirtReg)))
621 DestPhysReg = getReg(MBB, MI, DestVirtReg);
622 markVirtRegModified(DestVirtReg);
623 MI->SetMachineOperandReg(i, DestPhysReg); // Assign the output register
627 // If this instruction defines any registers that are immediately dead,
630 for (LiveVariables::killed_iterator KI = LV->dead_begin(MI),
631 KE = LV->dead_end(MI); KI != KE; ++KI) {
632 unsigned VirtReg = KI->second;
633 unsigned PhysReg = VirtReg;
634 if (MRegisterInfo::isVirtualRegister(VirtReg)) {
635 unsigned &PhysRegSlot = getVirt2PhysRegMapSlot(VirtReg);
636 PhysReg = PhysRegSlot;
637 assert(PhysReg != 0);
642 DEBUG(std::cerr << " Register " << RegInfo->getName(PhysReg)
643 << " [%reg" << VirtReg
644 << "] is never used, removing it frame live list\n");
645 removePhysReg(PhysReg);
650 MI = MBB.getFirstTerminator();
652 // Spill all physical registers holding virtual registers now.
653 for (unsigned i = 0, e = RegInfo->getNumRegs(); i != e; ++i)
654 if (PhysRegsUsed[i] != -1)
655 if (unsigned VirtReg = PhysRegsUsed[i])
656 spillVirtReg(MBB, MI, VirtReg, i);
662 for (unsigned i = MRegisterInfo::FirstVirtualRegister,
663 e = MF->getSSARegMap()->getLastVirtReg(); i <= e; ++i)
664 if (unsigned PR = Virt2PhysRegMap[i]) {
665 std::cerr << "Register still mapped: " << i << " -> " << PR << "\n";
668 assert(AllOk && "Virtual registers still in phys regs?");
671 // Clear any physical register which appear live at the end of the basic
672 // block, but which do not hold any virtual registers. e.g., the stack
674 PhysRegsUseOrder.clear();
678 /// runOnMachineFunction - Register allocate the whole function
680 bool RA::runOnMachineFunction(MachineFunction &Fn) {
681 DEBUG(std::cerr << "Machine Function " << "\n");
683 TM = &Fn.getTarget();
684 RegInfo = TM->getRegisterInfo();
685 LV = &getAnalysis<LiveVariables>();
687 PhysRegsUsed.assign(RegInfo->getNumRegs(), -1);
689 // initialize the virtual->physical register map to have a 'null'
690 // mapping for all virtual registers
691 Virt2PhysRegMap.grow(MF->getSSARegMap()->getLastVirtReg());
693 // Loop over all of the basic blocks, eliminating virtual register references
694 for (MachineFunction::iterator MBB = Fn.begin(), MBBe = Fn.end();
696 AllocateBasicBlock(*MBB);
698 StackSlotForVirtReg.clear();
699 PhysRegsUsed.clear();
700 VirtRegModified.clear();
701 Virt2PhysRegMap.clear();
705 FunctionPass *llvm::createLocalRegisterAllocator() {