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/CodeGen/RegAllocRegistry.h"
23 #include "llvm/Target/TargetInstrInfo.h"
24 #include "llvm/Target/TargetMachine.h"
25 #include "llvm/Support/CommandLine.h"
26 #include "llvm/Support/Debug.h"
27 #include "llvm/Support/Compiler.h"
28 #include "llvm/ADT/DenseMap.h"
29 #include "llvm/ADT/Statistic.h"
35 static Statistic<> NumStores("ra-local", "Number of stores added");
36 static Statistic<> NumLoads ("ra-local", "Number of loads added");
37 static Statistic<> NumFolded("ra-local", "Number of loads/stores folded "
40 static RegisterRegAlloc
41 localRegAlloc("local", " local register allocator",
42 createLocalRegisterAllocator);
45 class VISIBILITY_HIDDEN RA : public MachineFunctionPass {
46 const TargetMachine *TM;
48 const MRegisterInfo *RegInfo;
50 bool *PhysRegsEverUsed;
52 // StackSlotForVirtReg - Maps virtual regs to the frame index where these
53 // values are spilled.
54 std::map<unsigned, int> StackSlotForVirtReg;
56 // Virt2PhysRegMap - This map contains entries for each virtual register
57 // that is currently available in a physical register.
58 DenseMap<unsigned, VirtReg2IndexFunctor> Virt2PhysRegMap;
60 unsigned &getVirt2PhysRegMapSlot(unsigned VirtReg) {
61 return Virt2PhysRegMap[VirtReg];
64 // PhysRegsUsed - This array is effectively a map, containing entries for
65 // each physical register that currently has a value (ie, it is in
66 // Virt2PhysRegMap). The value mapped to is the virtual register
67 // corresponding to the physical register (the inverse of the
68 // Virt2PhysRegMap), or 0. The value is set to 0 if this register is pinned
69 // because it is used by a future instruction, and to -2 if it is not
70 // allocatable. If the entry for a physical register is -1, then the
71 // physical register is "not in the map".
73 std::vector<int> PhysRegsUsed;
75 // PhysRegsUseOrder - This contains a list of the physical registers that
76 // currently have a virtual register value in them. This list provides an
77 // ordering of registers, imposing a reallocation order. This list is only
78 // used if all registers are allocated and we have to spill one, in which
79 // case we spill the least recently used register. Entries at the front of
80 // the list are the least recently used registers, entries at the back are
81 // the most recently used.
83 std::vector<unsigned> PhysRegsUseOrder;
85 // VirtRegModified - This bitset contains information about which virtual
86 // registers need to be spilled back to memory when their registers are
87 // scavenged. If a virtual register has simply been rematerialized, there
88 // is no reason to spill it to memory when we need the register back.
90 std::vector<bool> VirtRegModified;
92 void markVirtRegModified(unsigned Reg, bool Val = true) {
93 assert(MRegisterInfo::isVirtualRegister(Reg) && "Illegal VirtReg!");
94 Reg -= MRegisterInfo::FirstVirtualRegister;
95 if (VirtRegModified.size() <= Reg) VirtRegModified.resize(Reg+1);
96 VirtRegModified[Reg] = Val;
99 bool isVirtRegModified(unsigned Reg) const {
100 assert(MRegisterInfo::isVirtualRegister(Reg) && "Illegal VirtReg!");
101 assert(Reg - MRegisterInfo::FirstVirtualRegister < VirtRegModified.size()
102 && "Illegal virtual register!");
103 return VirtRegModified[Reg - MRegisterInfo::FirstVirtualRegister];
106 void MarkPhysRegRecentlyUsed(unsigned Reg) {
107 if (PhysRegsUseOrder.empty() ||
108 PhysRegsUseOrder.back() == Reg) return; // Already most recently used
110 for (unsigned i = PhysRegsUseOrder.size(); i != 0; --i)
111 if (areRegsEqual(Reg, PhysRegsUseOrder[i-1])) {
112 unsigned RegMatch = PhysRegsUseOrder[i-1]; // remove from middle
113 PhysRegsUseOrder.erase(PhysRegsUseOrder.begin()+i-1);
114 // Add it to the end of the list
115 PhysRegsUseOrder.push_back(RegMatch);
117 return; // Found an exact match, exit early
122 virtual const char *getPassName() const {
123 return "Local Register Allocator";
126 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
127 AU.addRequired<LiveVariables>();
128 AU.addRequiredID(PHIEliminationID);
129 AU.addRequiredID(TwoAddressInstructionPassID);
130 MachineFunctionPass::getAnalysisUsage(AU);
134 /// runOnMachineFunction - Register allocate the whole function
135 bool runOnMachineFunction(MachineFunction &Fn);
137 /// AllocateBasicBlock - Register allocate the specified basic block.
138 void AllocateBasicBlock(MachineBasicBlock &MBB);
141 /// areRegsEqual - This method returns true if the specified registers are
142 /// related to each other. To do this, it checks to see if they are equal
143 /// or if the first register is in the alias set of the second register.
145 bool areRegsEqual(unsigned R1, unsigned R2) const {
146 if (R1 == R2) return true;
147 for (const unsigned *AliasSet = RegInfo->getAliasSet(R2);
148 *AliasSet; ++AliasSet) {
149 if (*AliasSet == R1) return true;
154 /// getStackSpaceFor - This returns the frame index of the specified virtual
155 /// register on the stack, allocating space if necessary.
156 int getStackSpaceFor(unsigned VirtReg, const TargetRegisterClass *RC);
158 /// removePhysReg - This method marks the specified physical register as no
159 /// longer being in use.
161 void removePhysReg(unsigned PhysReg);
163 /// spillVirtReg - This method spills the value specified by PhysReg into
164 /// the virtual register slot specified by VirtReg. It then updates the RA
165 /// data structures to indicate the fact that PhysReg is now available.
167 void spillVirtReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator MI,
168 unsigned VirtReg, unsigned PhysReg);
170 /// spillPhysReg - This method spills the specified physical register into
171 /// the virtual register slot associated with it. If OnlyVirtRegs is set to
172 /// true, then the request is ignored if the physical register does not
173 /// contain a virtual register.
175 void spillPhysReg(MachineBasicBlock &MBB, MachineInstr *I,
176 unsigned PhysReg, bool OnlyVirtRegs = false);
178 /// assignVirtToPhysReg - This method updates local state so that we know
179 /// that PhysReg is the proper container for VirtReg now. The physical
180 /// register must not be used for anything else when this is called.
182 void assignVirtToPhysReg(unsigned VirtReg, unsigned PhysReg);
184 /// liberatePhysReg - Make sure the specified physical register is available
185 /// for use. If there is currently a value in it, it is either moved out of
186 /// the way or spilled to memory.
188 void liberatePhysReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator &I,
191 /// isPhysRegAvailable - Return true if the specified physical register is
192 /// free and available for use. This also includes checking to see if
193 /// aliased registers are all free...
195 bool isPhysRegAvailable(unsigned PhysReg) const;
197 /// getFreeReg - Look to see if there is a free register available in the
198 /// specified register class. If not, return 0.
200 unsigned getFreeReg(const TargetRegisterClass *RC);
202 /// getReg - Find a physical register to hold the specified virtual
203 /// register. If all compatible physical registers are used, this method
204 /// spills the last used virtual register to the stack, and uses that
207 unsigned getReg(MachineBasicBlock &MBB, MachineInstr *MI,
210 /// reloadVirtReg - This method transforms the specified specified virtual
211 /// register use to refer to a physical register. This method may do this
212 /// in one of several ways: if the register is available in a physical
213 /// register already, it uses that physical register. If the value is not
214 /// in a physical register, and if there are physical registers available,
215 /// it loads it into a register. If register pressure is high, and it is
216 /// possible, it tries to fold the load of the virtual register into the
217 /// instruction itself. It avoids doing this if register pressure is low to
218 /// improve the chance that subsequent instructions can use the reloaded
219 /// value. This method returns the modified instruction.
221 MachineInstr *reloadVirtReg(MachineBasicBlock &MBB, MachineInstr *MI,
225 void reloadPhysReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator &I,
230 /// getStackSpaceFor - This allocates space for the specified virtual register
231 /// to be held on the stack.
232 int RA::getStackSpaceFor(unsigned VirtReg, const TargetRegisterClass *RC) {
233 // Find the location Reg would belong...
234 std::map<unsigned, int>::iterator I =StackSlotForVirtReg.lower_bound(VirtReg);
236 if (I != StackSlotForVirtReg.end() && I->first == VirtReg)
237 return I->second; // Already has space allocated?
239 // Allocate a new stack object for this spill location...
240 int FrameIdx = MF->getFrameInfo()->CreateStackObject(RC->getSize(),
243 // Assign the slot...
244 StackSlotForVirtReg.insert(I, std::make_pair(VirtReg, FrameIdx));
249 /// removePhysReg - This method marks the specified physical register as no
250 /// longer being in use.
252 void RA::removePhysReg(unsigned PhysReg) {
253 PhysRegsUsed[PhysReg] = -1; // PhyReg no longer used
255 std::vector<unsigned>::iterator It =
256 std::find(PhysRegsUseOrder.begin(), PhysRegsUseOrder.end(), PhysReg);
257 if (It != PhysRegsUseOrder.end())
258 PhysRegsUseOrder.erase(It);
262 /// spillVirtReg - This method spills the value specified by PhysReg into the
263 /// virtual register slot specified by VirtReg. It then updates the RA data
264 /// structures to indicate the fact that PhysReg is now available.
266 void RA::spillVirtReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator I,
267 unsigned VirtReg, unsigned PhysReg) {
268 assert(VirtReg && "Spilling a physical register is illegal!"
269 " Must not have appropriate kill for the register or use exists beyond"
270 " the intended one.");
271 DEBUG(std::cerr << " Spilling register " << RegInfo->getName(PhysReg);
272 std::cerr << " containing %reg" << VirtReg;
273 if (!isVirtRegModified(VirtReg))
274 std::cerr << " which has not been modified, so no store necessary!");
276 // Otherwise, there is a virtual register corresponding to this physical
277 // register. We only need to spill it into its stack slot if it has been
279 if (isVirtRegModified(VirtReg)) {
280 const TargetRegisterClass *RC = MF->getSSARegMap()->getRegClass(VirtReg);
281 int FrameIndex = getStackSpaceFor(VirtReg, RC);
282 DEBUG(std::cerr << " to stack slot #" << FrameIndex);
283 RegInfo->storeRegToStackSlot(MBB, I, PhysReg, FrameIndex, RC);
284 ++NumStores; // Update statistics
287 getVirt2PhysRegMapSlot(VirtReg) = 0; // VirtReg no longer available
289 DEBUG(std::cerr << "\n");
290 removePhysReg(PhysReg);
294 /// spillPhysReg - This method spills the specified physical register into the
295 /// virtual register slot associated with it. If OnlyVirtRegs is set to true,
296 /// then the request is ignored if the physical register does not contain a
297 /// virtual register.
299 void RA::spillPhysReg(MachineBasicBlock &MBB, MachineInstr *I,
300 unsigned PhysReg, bool OnlyVirtRegs) {
301 if (PhysRegsUsed[PhysReg] != -1) { // Only spill it if it's used!
302 assert(PhysRegsUsed[PhysReg] != -2 && "Non allocable reg used!");
303 if (PhysRegsUsed[PhysReg] || !OnlyVirtRegs)
304 spillVirtReg(MBB, I, PhysRegsUsed[PhysReg], PhysReg);
306 // If the selected register aliases any other registers, we must make
307 // sure that one of the aliases isn't alive.
308 for (const unsigned *AliasSet = RegInfo->getAliasSet(PhysReg);
309 *AliasSet; ++AliasSet)
310 if (PhysRegsUsed[*AliasSet] != -1 && // Spill aliased register.
311 PhysRegsUsed[*AliasSet] != -2) // If allocatable.
312 if (PhysRegsUsed[*AliasSet] || !OnlyVirtRegs)
313 spillVirtReg(MBB, I, PhysRegsUsed[*AliasSet], *AliasSet);
318 /// assignVirtToPhysReg - This method updates local state so that we know
319 /// that PhysReg is the proper container for VirtReg now. The physical
320 /// register must not be used for anything else when this is called.
322 void RA::assignVirtToPhysReg(unsigned VirtReg, unsigned PhysReg) {
323 assert(PhysRegsUsed[PhysReg] == -1 && "Phys reg already assigned!");
324 // Update information to note the fact that this register was just used, and
326 PhysRegsUsed[PhysReg] = VirtReg;
327 getVirt2PhysRegMapSlot(VirtReg) = PhysReg;
328 PhysRegsUseOrder.push_back(PhysReg); // New use of PhysReg
332 /// isPhysRegAvailable - Return true if the specified physical register is free
333 /// and available for use. This also includes checking to see if aliased
334 /// registers are all free...
336 bool RA::isPhysRegAvailable(unsigned PhysReg) const {
337 if (PhysRegsUsed[PhysReg] != -1) return false;
339 // If the selected register aliases any other allocated registers, it is
341 for (const unsigned *AliasSet = RegInfo->getAliasSet(PhysReg);
342 *AliasSet; ++AliasSet)
343 if (PhysRegsUsed[*AliasSet] != -1) // Aliased register in use?
344 return false; // Can't use this reg then.
349 /// getFreeReg - Look to see if there is a free register available in the
350 /// specified register class. If not, return 0.
352 unsigned RA::getFreeReg(const TargetRegisterClass *RC) {
353 // Get iterators defining the range of registers that are valid to allocate in
354 // this class, which also specifies the preferred allocation order.
355 TargetRegisterClass::iterator RI = RC->allocation_order_begin(*MF);
356 TargetRegisterClass::iterator RE = RC->allocation_order_end(*MF);
358 for (; RI != RE; ++RI)
359 if (isPhysRegAvailable(*RI)) { // Is reg unused?
360 assert(*RI != 0 && "Cannot use register!");
361 return *RI; // Found an unused register!
367 /// liberatePhysReg - Make sure the specified physical register is available for
368 /// use. If there is currently a value in it, it is either moved out of the way
369 /// or spilled to memory.
371 void RA::liberatePhysReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator &I,
373 spillPhysReg(MBB, I, PhysReg);
377 /// getReg - Find a physical register to hold the specified virtual
378 /// register. If all compatible physical registers are used, this method spills
379 /// the last used virtual register to the stack, and uses that register.
381 unsigned RA::getReg(MachineBasicBlock &MBB, MachineInstr *I,
383 const TargetRegisterClass *RC = MF->getSSARegMap()->getRegClass(VirtReg);
385 // First check to see if we have a free register of the requested type...
386 unsigned PhysReg = getFreeReg(RC);
388 // If we didn't find an unused register, scavenge one now!
390 assert(!PhysRegsUseOrder.empty() && "No allocated registers??");
392 // Loop over all of the preallocated registers from the least recently used
393 // to the most recently used. When we find one that is capable of holding
394 // our register, use it.
395 for (unsigned i = 0; PhysReg == 0; ++i) {
396 assert(i != PhysRegsUseOrder.size() &&
397 "Couldn't find a register of the appropriate class!");
399 unsigned R = PhysRegsUseOrder[i];
401 // We can only use this register if it holds a virtual register (ie, it
402 // can be spilled). Do not use it if it is an explicitly allocated
403 // physical register!
404 assert(PhysRegsUsed[R] != -1 &&
405 "PhysReg in PhysRegsUseOrder, but is not allocated?");
406 if (PhysRegsUsed[R] && PhysRegsUsed[R] != -2) {
407 // If the current register is compatible, use it.
408 if (RC->contains(R)) {
412 // If one of the registers aliased to the current register is
413 // compatible, use it.
414 for (const unsigned *AliasIt = RegInfo->getAliasSet(R);
415 *AliasIt; ++AliasIt) {
416 if (RC->contains(*AliasIt) &&
417 // If this is pinned down for some reason, don't use it. For
418 // example, if CL is pinned, and we run across CH, don't use
419 // CH as justification for using scavenging ECX (which will
421 PhysRegsUsed[*AliasIt] != 0 &&
423 // Make sure the register is allocatable. Don't allocate SIL on
425 PhysRegsUsed[*AliasIt] != -2) {
426 PhysReg = *AliasIt; // Take an aliased register
434 assert(PhysReg && "Physical register not assigned!?!?");
436 // At this point PhysRegsUseOrder[i] is the least recently used register of
437 // compatible register class. Spill it to memory and reap its remains.
438 spillPhysReg(MBB, I, PhysReg);
441 // Now that we know which register we need to assign this to, do it now!
442 assignVirtToPhysReg(VirtReg, PhysReg);
447 /// reloadVirtReg - This method transforms the specified specified virtual
448 /// register use to refer to a physical register. This method may do this in
449 /// one of several ways: if the register is available in a physical register
450 /// already, it uses that physical register. If the value is not in a physical
451 /// register, and if there are physical registers available, it loads it into a
452 /// register. If register pressure is high, and it is possible, it tries to
453 /// fold the load of the virtual register into the instruction itself. It
454 /// avoids doing this if register pressure is low to improve the chance that
455 /// subsequent instructions can use the reloaded value. This method returns the
456 /// modified instruction.
458 MachineInstr *RA::reloadVirtReg(MachineBasicBlock &MBB, MachineInstr *MI,
460 unsigned VirtReg = MI->getOperand(OpNum).getReg();
462 // If the virtual register is already available, just update the instruction
464 if (unsigned PR = getVirt2PhysRegMapSlot(VirtReg)) {
465 MarkPhysRegRecentlyUsed(PR); // Already have this value available!
466 MI->getOperand(OpNum).setReg(PR); // Assign the input register
470 // Otherwise, we need to fold it into the current instruction, or reload it.
471 // If we have registers available to hold the value, use them.
472 const TargetRegisterClass *RC = MF->getSSARegMap()->getRegClass(VirtReg);
473 unsigned PhysReg = getFreeReg(RC);
474 int FrameIndex = getStackSpaceFor(VirtReg, RC);
476 if (PhysReg) { // Register is available, allocate it!
477 assignVirtToPhysReg(VirtReg, PhysReg);
478 } else { // No registers available.
479 // If we can fold this spill into this instruction, do so now.
480 if (MachineInstr* FMI = RegInfo->foldMemoryOperand(MI, OpNum, FrameIndex)){
482 // Since we changed the address of MI, make sure to update live variables
483 // to know that the new instruction has the properties of the old one.
484 LV->instructionChanged(MI, FMI);
485 return MBB.insert(MBB.erase(MI), FMI);
488 // It looks like we can't fold this virtual register load into this
489 // instruction. Force some poor hapless value out of the register file to
490 // make room for the new register, and reload it.
491 PhysReg = getReg(MBB, MI, VirtReg);
494 markVirtRegModified(VirtReg, false); // Note that this reg was just reloaded
496 DEBUG(std::cerr << " Reloading %reg" << VirtReg << " into "
497 << RegInfo->getName(PhysReg) << "\n");
499 // Add move instruction(s)
500 RegInfo->loadRegFromStackSlot(MBB, MI, PhysReg, FrameIndex, RC);
501 ++NumLoads; // Update statistics
503 PhysRegsEverUsed[PhysReg] = true;
504 MI->getOperand(OpNum).setReg(PhysReg); // Assign the input register
510 void RA::AllocateBasicBlock(MachineBasicBlock &MBB) {
511 // loop over each instruction
512 MachineBasicBlock::iterator MII = MBB.begin();
513 const TargetInstrInfo &TII = *TM->getInstrInfo();
515 // If this is the first basic block in the machine function, add live-in
516 // registers as active.
517 if (&MBB == &*MF->begin()) {
518 for (MachineFunction::livein_iterator I = MF->livein_begin(),
519 E = MF->livein_end(); I != E; ++I) {
520 unsigned Reg = I->first;
521 PhysRegsEverUsed[Reg] = true;
522 PhysRegsUsed[Reg] = 0; // It is free and reserved now
523 PhysRegsUseOrder.push_back(Reg);
524 for (const unsigned *AliasSet = RegInfo->getAliasSet(Reg);
525 *AliasSet; ++AliasSet) {
526 if (PhysRegsUsed[*AliasSet] != -2) {
527 PhysRegsUseOrder.push_back(*AliasSet);
528 PhysRegsUsed[*AliasSet] = 0; // It is free and reserved now
529 PhysRegsEverUsed[*AliasSet] = true;
535 // Otherwise, sequentially allocate each instruction in the MBB.
536 while (MII != MBB.end()) {
537 MachineInstr *MI = MII++;
538 const TargetInstrDescriptor &TID = TII.get(MI->getOpcode());
539 DEBUG(std::cerr << "\nStarting RegAlloc of: " << *MI;
540 std::cerr << " Regs have values: ";
541 for (unsigned i = 0; i != RegInfo->getNumRegs(); ++i)
542 if (PhysRegsUsed[i] != -1 && PhysRegsUsed[i] != -2)
543 std::cerr << "[" << RegInfo->getName(i)
544 << ",%reg" << PhysRegsUsed[i] << "] ";
547 // Loop over the implicit uses, making sure that they are at the head of the
548 // use order list, so they don't get reallocated.
549 if (TID.ImplicitUses) {
550 for (const unsigned *ImplicitUses = TID.ImplicitUses;
551 *ImplicitUses; ++ImplicitUses)
552 MarkPhysRegRecentlyUsed(*ImplicitUses);
555 // Get the used operands into registers. This has the potential to spill
556 // incoming values if we are out of registers. Note that we completely
557 // ignore physical register uses here. We assume that if an explicit
558 // physical register is referenced by the instruction, that it is guaranteed
559 // to be live-in, or the input is badly hosed.
561 for (unsigned i = 0; i != MI->getNumOperands(); ++i) {
562 MachineOperand& MO = MI->getOperand(i);
563 // here we are looking for only used operands (never def&use)
564 if (MO.isRegister() && !MO.isDef() && MO.getReg() &&
565 MRegisterInfo::isVirtualRegister(MO.getReg()))
566 MI = reloadVirtReg(MBB, MI, i);
569 // If this instruction is the last user of anything in registers, kill the
570 // value, freeing the register being used, so it doesn't need to be
571 // spilled to memory.
573 for (LiveVariables::killed_iterator KI = LV->killed_begin(MI),
574 KE = LV->killed_end(MI); KI != KE; ++KI) {
575 unsigned VirtReg = *KI;
576 unsigned PhysReg = VirtReg;
577 if (MRegisterInfo::isVirtualRegister(VirtReg)) {
578 // If the virtual register was never materialized into a register, it
579 // might not be in the map, but it won't hurt to zero it out anyway.
580 unsigned &PhysRegSlot = getVirt2PhysRegMapSlot(VirtReg);
581 PhysReg = PhysRegSlot;
583 } else if (PhysRegsUsed[PhysReg] == -2) {
584 // Unallocatable register dead, ignore.
589 DEBUG(std::cerr << " Last use of " << RegInfo->getName(PhysReg)
590 << "[%reg" << VirtReg <<"], removing it from live set\n");
591 removePhysReg(PhysReg);
595 // Loop over all of the operands of the instruction, spilling registers that
596 // are defined, and marking explicit destinations in the PhysRegsUsed map.
597 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
598 MachineOperand& MO = MI->getOperand(i);
599 if (MO.isRegister() && MO.isDef() && MO.getReg() &&
600 MRegisterInfo::isPhysicalRegister(MO.getReg())) {
601 unsigned Reg = MO.getReg();
602 if (PhysRegsUsed[Reg] == -2) continue; // Something like ESP.
604 PhysRegsEverUsed[Reg] = true;
605 spillPhysReg(MBB, MI, Reg, true); // Spill any existing value in the reg
606 PhysRegsUsed[Reg] = 0; // It is free and reserved now
607 PhysRegsUseOrder.push_back(Reg);
608 for (const unsigned *AliasSet = RegInfo->getAliasSet(Reg);
609 *AliasSet; ++AliasSet) {
610 if (PhysRegsUsed[*AliasSet] != -2) {
611 PhysRegsUseOrder.push_back(*AliasSet);
612 PhysRegsUsed[*AliasSet] = 0; // It is free and reserved now
613 PhysRegsEverUsed[*AliasSet] = true;
619 // Loop over the implicit defs, spilling them as well.
620 if (TID.ImplicitDefs) {
621 for (const unsigned *ImplicitDefs = TID.ImplicitDefs;
622 *ImplicitDefs; ++ImplicitDefs) {
623 unsigned Reg = *ImplicitDefs;
624 bool IsNonAllocatable = PhysRegsUsed[Reg] == -2;
625 if (!IsNonAllocatable) {
626 spillPhysReg(MBB, MI, Reg, true);
627 PhysRegsUseOrder.push_back(Reg);
628 PhysRegsUsed[Reg] = 0; // It is free and reserved now
630 PhysRegsEverUsed[Reg] = true;
632 for (const unsigned *AliasSet = RegInfo->getAliasSet(Reg);
633 *AliasSet; ++AliasSet) {
634 if (PhysRegsUsed[*AliasSet] != -2) {
635 if (!IsNonAllocatable) {
636 PhysRegsUseOrder.push_back(*AliasSet);
637 PhysRegsUsed[*AliasSet] = 0; // It is free and reserved now
639 PhysRegsEverUsed[*AliasSet] = true;
645 // Okay, we have allocated all of the source operands and spilled any values
646 // that would be destroyed by defs of this instruction. Loop over the
647 // explicit defs and assign them to a register, spilling incoming values if
648 // we need to scavenge a register.
650 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
651 MachineOperand& MO = MI->getOperand(i);
652 if (MO.isRegister() && MO.isDef() && MO.getReg() &&
653 MRegisterInfo::isVirtualRegister(MO.getReg())) {
654 unsigned DestVirtReg = MO.getReg();
655 unsigned DestPhysReg;
657 // If DestVirtReg already has a value, use it.
658 if (!(DestPhysReg = getVirt2PhysRegMapSlot(DestVirtReg)))
659 DestPhysReg = getReg(MBB, MI, DestVirtReg);
660 PhysRegsEverUsed[DestPhysReg] = true;
661 markVirtRegModified(DestVirtReg);
662 MI->getOperand(i).setReg(DestPhysReg); // Assign the output register
666 // If this instruction defines any registers that are immediately dead,
669 for (LiveVariables::killed_iterator KI = LV->dead_begin(MI),
670 KE = LV->dead_end(MI); KI != KE; ++KI) {
671 unsigned VirtReg = *KI;
672 unsigned PhysReg = VirtReg;
673 if (MRegisterInfo::isVirtualRegister(VirtReg)) {
674 unsigned &PhysRegSlot = getVirt2PhysRegMapSlot(VirtReg);
675 PhysReg = PhysRegSlot;
676 assert(PhysReg != 0);
678 } else if (PhysRegsUsed[PhysReg] == -2) {
679 // Unallocatable register dead, ignore.
684 DEBUG(std::cerr << " Register " << RegInfo->getName(PhysReg)
685 << " [%reg" << VirtReg
686 << "] is never used, removing it frame live list\n");
687 removePhysReg(PhysReg);
691 // Finally, if this is a noop copy instruction, zap it.
692 unsigned SrcReg, DstReg;
693 if (TII.isMoveInstr(*MI, SrcReg, DstReg) && SrcReg == DstReg) {
694 LV->removeVirtualRegistersKilled(MI);
695 LV->removeVirtualRegistersDead(MI);
700 MachineBasicBlock::iterator MI = MBB.getFirstTerminator();
702 // Spill all physical registers holding virtual registers now.
703 for (unsigned i = 0, e = RegInfo->getNumRegs(); i != e; ++i)
704 if (PhysRegsUsed[i] != -1 && PhysRegsUsed[i] != -2)
705 if (unsigned VirtReg = PhysRegsUsed[i])
706 spillVirtReg(MBB, MI, VirtReg, i);
711 // This checking code is very expensive.
713 for (unsigned i = MRegisterInfo::FirstVirtualRegister,
714 e = MF->getSSARegMap()->getLastVirtReg(); i <= e; ++i)
715 if (unsigned PR = Virt2PhysRegMap[i]) {
716 std::cerr << "Register still mapped: " << i << " -> " << PR << "\n";
719 assert(AllOk && "Virtual registers still in phys regs?");
722 // Clear any physical register which appear live at the end of the basic
723 // block, but which do not hold any virtual registers. e.g., the stack
725 PhysRegsUseOrder.clear();
729 /// runOnMachineFunction - Register allocate the whole function
731 bool RA::runOnMachineFunction(MachineFunction &Fn) {
732 DEBUG(std::cerr << "Machine Function " << "\n");
734 TM = &Fn.getTarget();
735 RegInfo = TM->getRegisterInfo();
736 LV = &getAnalysis<LiveVariables>();
738 PhysRegsEverUsed = new bool[RegInfo->getNumRegs()];
739 std::fill(PhysRegsEverUsed, PhysRegsEverUsed+RegInfo->getNumRegs(), false);
740 Fn.setUsedPhysRegs(PhysRegsEverUsed);
742 PhysRegsUsed.assign(RegInfo->getNumRegs(), -1);
744 // At various places we want to efficiently check to see whether a register
745 // is allocatable. To handle this, we mark all unallocatable registers as
746 // being pinned down, permanently.
748 std::vector<bool> Allocable = RegInfo->getAllocatableSet(Fn);
749 for (unsigned i = 0, e = Allocable.size(); i != e; ++i)
751 PhysRegsUsed[i] = -2; // Mark the reg unallocable.
754 // initialize the virtual->physical register map to have a 'null'
755 // mapping for all virtual registers
756 Virt2PhysRegMap.grow(MF->getSSARegMap()->getLastVirtReg());
758 // Loop over all of the basic blocks, eliminating virtual register references
759 for (MachineFunction::iterator MBB = Fn.begin(), MBBe = Fn.end();
761 AllocateBasicBlock(*MBB);
763 StackSlotForVirtReg.clear();
764 PhysRegsUsed.clear();
765 VirtRegModified.clear();
766 Virt2PhysRegMap.clear();
770 FunctionPass *llvm::createLocalRegisterAllocator() {