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/Support/Visibility.h"
27 #include "llvm/ADT/DenseMap.h"
28 #include "llvm/ADT/Statistic.h"
34 static Statistic<> NumStores("ra-local", "Number of stores added");
35 static Statistic<> NumLoads ("ra-local", "Number of loads added");
36 static Statistic<> NumFolded("ra-local", "Number of loads/stores folded into "
38 class VISIBILITY_HIDDEN RA : public MachineFunctionPass {
39 const TargetMachine *TM;
41 const MRegisterInfo *RegInfo;
43 bool *PhysRegsEverUsed;
45 // StackSlotForVirtReg - Maps virtual regs to the frame index where these
46 // values are spilled.
47 std::map<unsigned, int> StackSlotForVirtReg;
49 // Virt2PhysRegMap - This map contains entries for each virtual register
50 // that is currently available in a physical register.
51 DenseMap<unsigned, VirtReg2IndexFunctor> Virt2PhysRegMap;
53 unsigned &getVirt2PhysRegMapSlot(unsigned VirtReg) {
54 return Virt2PhysRegMap[VirtReg];
57 // PhysRegsUsed - This array is effectively a map, containing entries for
58 // each physical register that currently has a value (ie, it is in
59 // Virt2PhysRegMap). The value mapped to is the virtual register
60 // corresponding to the physical register (the inverse of the
61 // Virt2PhysRegMap), or 0. The value is set to 0 if this register is pinned
62 // because it is used by a future instruction. If the entry for a physical
63 // register is -1, then the physical register is "not in the map".
65 std::vector<int> PhysRegsUsed;
67 // PhysRegsUseOrder - This contains a list of the physical registers that
68 // currently have a virtual register value in them. This list provides an
69 // ordering of registers, imposing a reallocation order. This list is only
70 // used if all registers are allocated and we have to spill one, in which
71 // case we spill the least recently used register. Entries at the front of
72 // the list are the least recently used registers, entries at the back are
73 // the most recently used.
75 std::vector<unsigned> PhysRegsUseOrder;
77 // VirtRegModified - This bitset contains information about which virtual
78 // registers need to be spilled back to memory when their registers are
79 // scavenged. If a virtual register has simply been rematerialized, there
80 // is no reason to spill it to memory when we need the register back.
82 std::vector<bool> VirtRegModified;
84 void markVirtRegModified(unsigned Reg, bool Val = true) {
85 assert(MRegisterInfo::isVirtualRegister(Reg) && "Illegal VirtReg!");
86 Reg -= MRegisterInfo::FirstVirtualRegister;
87 if (VirtRegModified.size() <= Reg) VirtRegModified.resize(Reg+1);
88 VirtRegModified[Reg] = Val;
91 bool isVirtRegModified(unsigned Reg) const {
92 assert(MRegisterInfo::isVirtualRegister(Reg) && "Illegal VirtReg!");
93 assert(Reg - MRegisterInfo::FirstVirtualRegister < VirtRegModified.size()
94 && "Illegal virtual register!");
95 return VirtRegModified[Reg - MRegisterInfo::FirstVirtualRegister];
98 void MarkPhysRegRecentlyUsed(unsigned Reg) {
99 if(PhysRegsUseOrder.empty() ||
100 PhysRegsUseOrder.back() == Reg) return; // Already most recently used
102 for (unsigned i = PhysRegsUseOrder.size(); i != 0; --i)
103 if (areRegsEqual(Reg, PhysRegsUseOrder[i-1])) {
104 unsigned RegMatch = PhysRegsUseOrder[i-1]; // remove from middle
105 PhysRegsUseOrder.erase(PhysRegsUseOrder.begin()+i-1);
106 // Add it to the end of the list
107 PhysRegsUseOrder.push_back(RegMatch);
109 return; // Found an exact match, exit early
114 virtual const char *getPassName() const {
115 return "Local Register Allocator";
118 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
119 AU.addRequired<LiveVariables>();
120 AU.addRequiredID(PHIEliminationID);
121 AU.addRequiredID(TwoAddressInstructionPassID);
122 MachineFunctionPass::getAnalysisUsage(AU);
126 /// runOnMachineFunction - Register allocate the whole function
127 bool runOnMachineFunction(MachineFunction &Fn);
129 /// AllocateBasicBlock - Register allocate the specified basic block.
130 void AllocateBasicBlock(MachineBasicBlock &MBB);
133 /// areRegsEqual - This method returns true if the specified registers are
134 /// related to each other. To do this, it checks to see if they are equal
135 /// or if the first register is in the alias set of the second register.
137 bool areRegsEqual(unsigned R1, unsigned R2) const {
138 if (R1 == R2) return true;
139 for (const unsigned *AliasSet = RegInfo->getAliasSet(R2);
140 *AliasSet; ++AliasSet) {
141 if (*AliasSet == R1) return true;
146 /// getStackSpaceFor - This returns the frame index of the specified virtual
147 /// register on the stack, allocating space if necessary.
148 int getStackSpaceFor(unsigned VirtReg, const TargetRegisterClass *RC);
150 /// removePhysReg - This method marks the specified physical register as no
151 /// longer being in use.
153 void removePhysReg(unsigned PhysReg);
155 /// spillVirtReg - This method spills the value specified by PhysReg into
156 /// the virtual register slot specified by VirtReg. It then updates the RA
157 /// data structures to indicate the fact that PhysReg is now available.
159 void spillVirtReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator MI,
160 unsigned VirtReg, unsigned PhysReg);
162 /// spillPhysReg - This method spills the specified physical register into
163 /// the virtual register slot associated with it. If OnlyVirtRegs is set to
164 /// true, then the request is ignored if the physical register does not
165 /// contain a virtual register.
167 void spillPhysReg(MachineBasicBlock &MBB, MachineInstr *I,
168 unsigned PhysReg, bool OnlyVirtRegs = false);
170 /// assignVirtToPhysReg - This method updates local state so that we know
171 /// that PhysReg is the proper container for VirtReg now. The physical
172 /// register must not be used for anything else when this is called.
174 void assignVirtToPhysReg(unsigned VirtReg, unsigned PhysReg);
176 /// liberatePhysReg - Make sure the specified physical register is available
177 /// for use. If there is currently a value in it, it is either moved out of
178 /// the way or spilled to memory.
180 void liberatePhysReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator &I,
183 /// isPhysRegAvailable - Return true if the specified physical register is
184 /// free and available for use. This also includes checking to see if
185 /// aliased registers are all free...
187 bool isPhysRegAvailable(unsigned PhysReg) const;
189 /// getFreeReg - Look to see if there is a free register available in the
190 /// specified register class. If not, return 0.
192 unsigned getFreeReg(const TargetRegisterClass *RC);
194 /// getReg - Find a physical register to hold the specified virtual
195 /// register. If all compatible physical registers are used, this method
196 /// spills the last used virtual register to the stack, and uses that
199 unsigned getReg(MachineBasicBlock &MBB, MachineInstr *MI,
202 /// reloadVirtReg - This method transforms the specified specified virtual
203 /// register use to refer to a physical register. This method may do this
204 /// in one of several ways: if the register is available in a physical
205 /// register already, it uses that physical register. If the value is not
206 /// in a physical register, and if there are physical registers available,
207 /// it loads it into a register. If register pressure is high, and it is
208 /// possible, it tries to fold the load of the virtual register into the
209 /// instruction itself. It avoids doing this if register pressure is low to
210 /// improve the chance that subsequent instructions can use the reloaded
211 /// value. This method returns the modified instruction.
213 MachineInstr *reloadVirtReg(MachineBasicBlock &MBB, MachineInstr *MI,
217 void reloadPhysReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator &I,
222 /// getStackSpaceFor - This allocates space for the specified virtual register
223 /// to be held on the stack.
224 int RA::getStackSpaceFor(unsigned VirtReg, const TargetRegisterClass *RC) {
225 // Find the location Reg would belong...
226 std::map<unsigned, int>::iterator I =StackSlotForVirtReg.lower_bound(VirtReg);
228 if (I != StackSlotForVirtReg.end() && I->first == VirtReg)
229 return I->second; // Already has space allocated?
231 // Allocate a new stack object for this spill location...
232 int FrameIdx = MF->getFrameInfo()->CreateStackObject(RC->getSize(),
235 // Assign the slot...
236 StackSlotForVirtReg.insert(I, std::make_pair(VirtReg, FrameIdx));
241 /// removePhysReg - This method marks the specified physical register as no
242 /// longer being in use.
244 void RA::removePhysReg(unsigned PhysReg) {
245 PhysRegsUsed[PhysReg] = -1; // PhyReg no longer used
247 std::vector<unsigned>::iterator It =
248 std::find(PhysRegsUseOrder.begin(), PhysRegsUseOrder.end(), PhysReg);
249 if (It != PhysRegsUseOrder.end())
250 PhysRegsUseOrder.erase(It);
254 /// spillVirtReg - This method spills the value specified by PhysReg into the
255 /// virtual register slot specified by VirtReg. It then updates the RA data
256 /// structures to indicate the fact that PhysReg is now available.
258 void RA::spillVirtReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator I,
259 unsigned VirtReg, unsigned PhysReg) {
260 assert(VirtReg && "Spilling a physical register is illegal!"
261 " Must not have appropriate kill for the register or use exists beyond"
262 " the intended one.");
263 DEBUG(std::cerr << " Spilling register " << RegInfo->getName(PhysReg);
264 std::cerr << " containing %reg" << VirtReg;
265 if (!isVirtRegModified(VirtReg))
266 std::cerr << " which has not been modified, so no store necessary!");
268 // Otherwise, there is a virtual register corresponding to this physical
269 // register. We only need to spill it into its stack slot if it has been
271 if (isVirtRegModified(VirtReg)) {
272 const TargetRegisterClass *RC = MF->getSSARegMap()->getRegClass(VirtReg);
273 int FrameIndex = getStackSpaceFor(VirtReg, RC);
274 DEBUG(std::cerr << " to stack slot #" << FrameIndex);
275 RegInfo->storeRegToStackSlot(MBB, I, PhysReg, FrameIndex, RC);
276 ++NumStores; // Update statistics
279 getVirt2PhysRegMapSlot(VirtReg) = 0; // VirtReg no longer available
281 DEBUG(std::cerr << "\n");
282 removePhysReg(PhysReg);
286 /// spillPhysReg - This method spills the specified physical register into the
287 /// virtual register slot associated with it. If OnlyVirtRegs is set to true,
288 /// then the request is ignored if the physical register does not contain a
289 /// virtual register.
291 void RA::spillPhysReg(MachineBasicBlock &MBB, MachineInstr *I,
292 unsigned PhysReg, bool OnlyVirtRegs) {
293 if (PhysRegsUsed[PhysReg] != -1) { // Only spill it if it's used!
294 if (PhysRegsUsed[PhysReg] || !OnlyVirtRegs)
295 spillVirtReg(MBB, I, PhysRegsUsed[PhysReg], PhysReg);
297 // If the selected register aliases any other registers, we must make
298 // sure that one of the aliases isn't alive...
299 for (const unsigned *AliasSet = RegInfo->getAliasSet(PhysReg);
300 *AliasSet; ++AliasSet)
301 if (PhysRegsUsed[*AliasSet] != -1) // Spill aliased register...
302 if (PhysRegsUsed[*AliasSet] || !OnlyVirtRegs)
303 spillVirtReg(MBB, I, PhysRegsUsed[*AliasSet], *AliasSet);
308 /// assignVirtToPhysReg - This method updates local state so that we know
309 /// that PhysReg is the proper container for VirtReg now. The physical
310 /// register must not be used for anything else when this is called.
312 void RA::assignVirtToPhysReg(unsigned VirtReg, unsigned PhysReg) {
313 assert(PhysRegsUsed[PhysReg] == -1 && "Phys reg already assigned!");
314 // Update information to note the fact that this register was just used, and
316 PhysRegsUsed[PhysReg] = VirtReg;
317 getVirt2PhysRegMapSlot(VirtReg) = PhysReg;
318 PhysRegsUseOrder.push_back(PhysReg); // New use of PhysReg
322 /// isPhysRegAvailable - Return true if the specified physical register is free
323 /// and available for use. This also includes checking to see if aliased
324 /// registers are all free...
326 bool RA::isPhysRegAvailable(unsigned PhysReg) const {
327 if (PhysRegsUsed[PhysReg] != -1) return false;
329 // If the selected register aliases any other allocated registers, it is
331 for (const unsigned *AliasSet = RegInfo->getAliasSet(PhysReg);
332 *AliasSet; ++AliasSet)
333 if (PhysRegsUsed[*AliasSet] != -1) // Aliased register in use?
334 return false; // Can't use this reg then.
339 /// getFreeReg - Look to see if there is a free register available in the
340 /// specified register class. If not, return 0.
342 unsigned RA::getFreeReg(const TargetRegisterClass *RC) {
343 // Get iterators defining the range of registers that are valid to allocate in
344 // this class, which also specifies the preferred allocation order.
345 TargetRegisterClass::iterator RI = RC->allocation_order_begin(*MF);
346 TargetRegisterClass::iterator RE = RC->allocation_order_end(*MF);
348 for (; RI != RE; ++RI)
349 if (isPhysRegAvailable(*RI)) { // Is reg unused?
350 assert(*RI != 0 && "Cannot use register!");
351 return *RI; // Found an unused register!
357 /// liberatePhysReg - Make sure the specified physical register is available for
358 /// use. If there is currently a value in it, it is either moved out of the way
359 /// or spilled to memory.
361 void RA::liberatePhysReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator &I,
363 spillPhysReg(MBB, I, PhysReg);
367 /// getReg - Find a physical register to hold the specified virtual
368 /// register. If all compatible physical registers are used, this method spills
369 /// the last used virtual register to the stack, and uses that register.
371 unsigned RA::getReg(MachineBasicBlock &MBB, MachineInstr *I,
373 const TargetRegisterClass *RC = MF->getSSARegMap()->getRegClass(VirtReg);
375 // First check to see if we have a free register of the requested type...
376 unsigned PhysReg = getFreeReg(RC);
378 // If we didn't find an unused register, scavenge one now!
380 assert(!PhysRegsUseOrder.empty() && "No allocated registers??");
382 // Loop over all of the preallocated registers from the least recently used
383 // to the most recently used. When we find one that is capable of holding
384 // our register, use it.
385 for (unsigned i = 0; PhysReg == 0; ++i) {
386 assert(i != PhysRegsUseOrder.size() &&
387 "Couldn't find a register of the appropriate class!");
389 unsigned R = PhysRegsUseOrder[i];
391 // We can only use this register if it holds a virtual register (ie, it
392 // can be spilled). Do not use it if it is an explicitly allocated
393 // physical register!
394 assert(PhysRegsUsed[R] != -1 &&
395 "PhysReg in PhysRegsUseOrder, but is not allocated?");
396 if (PhysRegsUsed[R]) {
397 // If the current register is compatible, use it.
398 if (RC->contains(R)) {
402 // If one of the registers aliased to the current register is
403 // compatible, use it.
404 for (const unsigned *AliasSet = RegInfo->getAliasSet(R);
405 *AliasSet; ++AliasSet) {
406 if (RC->contains(*AliasSet)) {
407 PhysReg = *AliasSet; // Take an aliased register
415 assert(PhysReg && "Physical register not assigned!?!?");
417 // At this point PhysRegsUseOrder[i] is the least recently used register of
418 // compatible register class. Spill it to memory and reap its remains.
419 spillPhysReg(MBB, I, PhysReg);
422 // Now that we know which register we need to assign this to, do it now!
423 assignVirtToPhysReg(VirtReg, PhysReg);
428 /// reloadVirtReg - This method transforms the specified specified virtual
429 /// register use to refer to a physical register. This method may do this in
430 /// one of several ways: if the register is available in a physical register
431 /// already, it uses that physical register. If the value is not in a physical
432 /// register, and if there are physical registers available, it loads it into a
433 /// register. If register pressure is high, and it is possible, it tries to
434 /// fold the load of the virtual register into the instruction itself. It
435 /// avoids doing this if register pressure is low to improve the chance that
436 /// subsequent instructions can use the reloaded value. This method returns the
437 /// modified instruction.
439 MachineInstr *RA::reloadVirtReg(MachineBasicBlock &MBB, MachineInstr *MI,
441 unsigned VirtReg = MI->getOperand(OpNum).getReg();
443 // If the virtual register is already available, just update the instruction
445 if (unsigned PR = getVirt2PhysRegMapSlot(VirtReg)) {
446 MarkPhysRegRecentlyUsed(PR); // Already have this value available!
447 MI->getOperand(OpNum).setReg(PR); // Assign the input register
451 // Otherwise, we need to fold it into the current instruction, or reload it.
452 // If we have registers available to hold the value, use them.
453 const TargetRegisterClass *RC = MF->getSSARegMap()->getRegClass(VirtReg);
454 unsigned PhysReg = getFreeReg(RC);
455 int FrameIndex = getStackSpaceFor(VirtReg, RC);
457 if (PhysReg) { // Register is available, allocate it!
458 assignVirtToPhysReg(VirtReg, PhysReg);
459 } else { // No registers available.
460 // If we can fold this spill into this instruction, do so now.
461 if (MachineInstr* FMI = RegInfo->foldMemoryOperand(MI, OpNum, FrameIndex)){
463 // Since we changed the address of MI, make sure to update live variables
464 // to know that the new instruction has the properties of the old one.
465 LV->instructionChanged(MI, FMI);
466 return MBB.insert(MBB.erase(MI), FMI);
469 // It looks like we can't fold this virtual register load into this
470 // instruction. Force some poor hapless value out of the register file to
471 // make room for the new register, and reload it.
472 PhysReg = getReg(MBB, MI, VirtReg);
475 markVirtRegModified(VirtReg, false); // Note that this reg was just reloaded
477 DEBUG(std::cerr << " Reloading %reg" << VirtReg << " into "
478 << RegInfo->getName(PhysReg) << "\n");
480 // Add move instruction(s)
481 RegInfo->loadRegFromStackSlot(MBB, MI, PhysReg, FrameIndex, RC);
482 ++NumLoads; // Update statistics
484 PhysRegsEverUsed[PhysReg] = true;
485 MI->getOperand(OpNum).setReg(PhysReg); // Assign the input register
491 void RA::AllocateBasicBlock(MachineBasicBlock &MBB) {
492 // loop over each instruction
493 MachineBasicBlock::iterator MII = MBB.begin();
494 const TargetInstrInfo &TII = *TM->getInstrInfo();
496 // If this is the first basic block in the machine function, add live-in
497 // registers as active.
498 if (&MBB == &*MF->begin()) {
499 for (MachineFunction::livein_iterator I = MF->livein_begin(),
500 E = MF->livein_end(); I != E; ++I) {
501 unsigned Reg = I->first;
502 PhysRegsEverUsed[Reg] = true;
503 PhysRegsUsed[Reg] = 0; // It is free and reserved now
504 PhysRegsUseOrder.push_back(Reg);
505 for (const unsigned *AliasSet = RegInfo->getAliasSet(Reg);
506 *AliasSet; ++AliasSet) {
507 PhysRegsUseOrder.push_back(*AliasSet);
508 PhysRegsUsed[*AliasSet] = 0; // It is free and reserved now
509 PhysRegsEverUsed[*AliasSet] = true;
514 // Otherwise, sequentially allocate each instruction in the MBB.
515 while (MII != MBB.end()) {
516 MachineInstr *MI = MII++;
517 const TargetInstrDescriptor &TID = TII.get(MI->getOpcode());
518 DEBUG(std::cerr << "\nStarting RegAlloc of: " << *MI;
519 std::cerr << " Regs have values: ";
520 for (unsigned i = 0; i != RegInfo->getNumRegs(); ++i)
521 if (PhysRegsUsed[i] != -1)
522 std::cerr << "[" << RegInfo->getName(i)
523 << ",%reg" << PhysRegsUsed[i] << "] ";
526 // Loop over the implicit uses, making sure that they are at the head of the
527 // use order list, so they don't get reallocated.
528 for (const unsigned *ImplicitUses = TID.ImplicitUses;
529 *ImplicitUses; ++ImplicitUses)
530 MarkPhysRegRecentlyUsed(*ImplicitUses);
532 // Get the used operands into registers. This has the potential to spill
533 // incoming values if we are out of registers. Note that we completely
534 // ignore physical register uses here. We assume that if an explicit
535 // physical register is referenced by the instruction, that it is guaranteed
536 // to be live-in, or the input is badly hosed.
538 for (unsigned i = 0; i != MI->getNumOperands(); ++i) {
539 MachineOperand& MO = MI->getOperand(i);
540 // here we are looking for only used operands (never def&use)
541 if (!MO.isDef() && MO.isRegister() && MO.getReg() &&
542 MRegisterInfo::isVirtualRegister(MO.getReg()))
543 MI = reloadVirtReg(MBB, MI, i);
546 // If this instruction is the last user of anything in registers, kill the
547 // value, freeing the register being used, so it doesn't need to be
548 // spilled to memory.
550 for (LiveVariables::killed_iterator KI = LV->killed_begin(MI),
551 KE = LV->killed_end(MI); KI != KE; ++KI) {
552 unsigned VirtReg = *KI;
553 unsigned PhysReg = VirtReg;
554 if (MRegisterInfo::isVirtualRegister(VirtReg)) {
555 // If the virtual register was never materialized into a register, it
556 // might not be in the map, but it won't hurt to zero it out anyway.
557 unsigned &PhysRegSlot = getVirt2PhysRegMapSlot(VirtReg);
558 PhysReg = PhysRegSlot;
563 DEBUG(std::cerr << " Last use of " << RegInfo->getName(PhysReg)
564 << "[%reg" << VirtReg <<"], removing it from live set\n");
565 removePhysReg(PhysReg);
569 // Loop over all of the operands of the instruction, spilling registers that
570 // are defined, and marking explicit destinations in the PhysRegsUsed map.
571 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
572 MachineOperand& MO = MI->getOperand(i);
573 if (MO.isDef() && MO.isRegister() && MO.getReg() &&
574 MRegisterInfo::isPhysicalRegister(MO.getReg())) {
575 unsigned Reg = MO.getReg();
576 PhysRegsEverUsed[Reg] = true;
577 spillPhysReg(MBB, MI, Reg, true); // Spill any existing value in the reg
578 PhysRegsUsed[Reg] = 0; // It is free and reserved now
579 PhysRegsUseOrder.push_back(Reg);
580 for (const unsigned *AliasSet = RegInfo->getAliasSet(Reg);
581 *AliasSet; ++AliasSet) {
582 PhysRegsUseOrder.push_back(*AliasSet);
583 PhysRegsUsed[*AliasSet] = 0; // It is free and reserved now
584 PhysRegsEverUsed[*AliasSet] = true;
589 // Loop over the implicit defs, spilling them as well.
590 for (const unsigned *ImplicitDefs = TID.ImplicitDefs;
591 *ImplicitDefs; ++ImplicitDefs) {
592 unsigned Reg = *ImplicitDefs;
593 spillPhysReg(MBB, MI, Reg, true);
594 PhysRegsUseOrder.push_back(Reg);
595 PhysRegsUsed[Reg] = 0; // It is free and reserved now
596 PhysRegsEverUsed[Reg] = true;
598 for (const unsigned *AliasSet = RegInfo->getAliasSet(Reg);
599 *AliasSet; ++AliasSet) {
600 PhysRegsUseOrder.push_back(*AliasSet);
601 PhysRegsUsed[*AliasSet] = 0; // It is free and reserved now
602 PhysRegsEverUsed[*AliasSet] = true;
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 // explicit 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 PhysRegsEverUsed[DestPhysReg] = true;
622 markVirtRegModified(DestVirtReg);
623 MI->getOperand(i).setReg(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;
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);
649 // Finally, if this is a noop copy instruction, zap it.
650 unsigned SrcReg, DstReg;
651 if (TII.isMoveInstr(*MI, SrcReg, DstReg) && SrcReg == DstReg)
655 MachineBasicBlock::iterator MI = MBB.getFirstTerminator();
657 // Spill all physical registers holding virtual registers now.
658 for (unsigned i = 0, e = RegInfo->getNumRegs(); i != e; ++i)
659 if (PhysRegsUsed[i] != -1)
660 if (unsigned VirtReg = PhysRegsUsed[i])
661 spillVirtReg(MBB, MI, VirtReg, i);
666 // This checking code is very expensive.
668 for (unsigned i = MRegisterInfo::FirstVirtualRegister,
669 e = MF->getSSARegMap()->getLastVirtReg(); i <= e; ++i)
670 if (unsigned PR = Virt2PhysRegMap[i]) {
671 std::cerr << "Register still mapped: " << i << " -> " << PR << "\n";
674 assert(AllOk && "Virtual registers still in phys regs?");
677 // Clear any physical register which appear live at the end of the basic
678 // block, but which do not hold any virtual registers. e.g., the stack
680 PhysRegsUseOrder.clear();
684 /// runOnMachineFunction - Register allocate the whole function
686 bool RA::runOnMachineFunction(MachineFunction &Fn) {
687 DEBUG(std::cerr << "Machine Function " << "\n");
689 TM = &Fn.getTarget();
690 RegInfo = TM->getRegisterInfo();
691 LV = &getAnalysis<LiveVariables>();
693 PhysRegsEverUsed = new bool[RegInfo->getNumRegs()];
694 std::fill(PhysRegsEverUsed, PhysRegsEverUsed+RegInfo->getNumRegs(), false);
695 Fn.setUsedPhysRegs(PhysRegsEverUsed);
697 PhysRegsUsed.assign(RegInfo->getNumRegs(), -1);
699 // initialize the virtual->physical register map to have a 'null'
700 // mapping for all virtual registers
701 Virt2PhysRegMap.grow(MF->getSSARegMap()->getLastVirtReg());
703 // Loop over all of the basic blocks, eliminating virtual register references
704 for (MachineFunction::iterator MBB = Fn.begin(), MBBe = Fn.end();
706 AllocateBasicBlock(*MBB);
708 StackSlotForVirtReg.clear();
709 PhysRegsUsed.clear();
710 VirtRegModified.clear();
711 Virt2PhysRegMap.clear();
715 FunctionPass *llvm::createLocalRegisterAllocator() {