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/Statistic.h"
31 Statistic<> NumSpilled ("ra-local", "Number of registers spilled");
32 Statistic<> NumReloaded("ra-local", "Number of registers reloaded");
33 cl::opt<bool> DisableKill("disable-kill", cl::Hidden,
34 cl::desc("Disable register kill in local-ra"));
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. This is "logically"
48 // a map from virtual register numbers to physical register numbers.
49 // Instead of using a map, however, which is slow, we use a vector. The
50 // index is the VREG number - FirstVirtualRegister. If the entry is zero,
51 // then it is logically "not in the map".
53 std::vector<unsigned> Virt2PhysRegMap;
55 unsigned &getVirt2PhysRegMapSlot(unsigned VirtReg) {
56 assert(VirtReg >= MRegisterInfo::FirstVirtualRegister &&"Illegal VREG #");
57 assert(VirtReg-MRegisterInfo::FirstVirtualRegister <Virt2PhysRegMap.size()
58 && "VirtReg not in map!");
59 return Virt2PhysRegMap[VirtReg-MRegisterInfo::FirstVirtualRegister];
62 // PhysRegsUsed - This array is effectively a map, containing entries for
63 // each physical register that currently has a value (ie, it is in
64 // Virt2PhysRegMap). The value mapped to is the virtual register
65 // corresponding to the physical register (the inverse of the
66 // Virt2PhysRegMap), or 0. The value is set to 0 if this register is pinned
67 // because it is used by a future instruction. If the entry for a physical
68 // register is -1, then the physical register is "not in the map".
70 std::vector<int> PhysRegsUsed;
72 // PhysRegsUseOrder - This contains a list of the physical registers that
73 // currently have a virtual register value in them. This list provides an
74 // ordering of registers, imposing a reallocation order. This list is only
75 // used if all registers are allocated and we have to spill one, in which
76 // case we spill the least recently used register. Entries at the front of
77 // the list are the least recently used registers, entries at the back are
78 // the most recently used.
80 std::vector<unsigned> PhysRegsUseOrder;
82 // VirtRegModified - This bitset contains information about which virtual
83 // registers need to be spilled back to memory when their registers are
84 // scavenged. If a virtual register has simply been rematerialized, there
85 // is no reason to spill it to memory when we need the register back.
87 std::vector<bool> VirtRegModified;
89 void markVirtRegModified(unsigned Reg, bool Val = true) {
90 assert(MRegisterInfo::isVirtualRegister(Reg) && "Illegal VirtReg!");
91 Reg -= MRegisterInfo::FirstVirtualRegister;
92 if (VirtRegModified.size() <= Reg) VirtRegModified.resize(Reg+1);
93 VirtRegModified[Reg] = Val;
96 bool isVirtRegModified(unsigned Reg) const {
97 assert(MRegisterInfo::isVirtualRegister(Reg) && "Illegal VirtReg!");
98 assert(Reg - MRegisterInfo::FirstVirtualRegister < VirtRegModified.size()
99 && "Illegal virtual register!");
100 return VirtRegModified[Reg - MRegisterInfo::FirstVirtualRegister];
103 void MarkPhysRegRecentlyUsed(unsigned Reg) {
104 assert(!PhysRegsUseOrder.empty() && "No registers used!");
105 if (PhysRegsUseOrder.back() == Reg) return; // Already most recently used
107 for (unsigned i = PhysRegsUseOrder.size(); i != 0; --i)
108 if (areRegsEqual(Reg, PhysRegsUseOrder[i-1])) {
109 unsigned RegMatch = PhysRegsUseOrder[i-1]; // remove from middle
110 PhysRegsUseOrder.erase(PhysRegsUseOrder.begin()+i-1);
111 // Add it to the end of the list
112 PhysRegsUseOrder.push_back(RegMatch);
114 return; // Found an exact match, exit early
119 virtual const char *getPassName() const {
120 return "Local Register Allocator";
123 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
125 AU.addRequired<LiveVariables>();
126 AU.addRequiredID(PHIEliminationID);
127 AU.addRequiredID(TwoAddressInstructionPassID);
128 MachineFunctionPass::getAnalysisUsage(AU);
132 /// runOnMachineFunction - Register allocate the whole function
133 bool runOnMachineFunction(MachineFunction &Fn);
135 /// AllocateBasicBlock - Register allocate the specified basic block.
136 void AllocateBasicBlock(MachineBasicBlock &MBB);
139 /// areRegsEqual - This method returns true if the specified registers are
140 /// related to each other. To do this, it checks to see if they are equal
141 /// or if the first register is in the alias set of the second register.
143 bool areRegsEqual(unsigned R1, unsigned R2) const {
144 if (R1 == R2) return true;
145 for (const unsigned *AliasSet = RegInfo->getAliasSet(R2);
146 *AliasSet; ++AliasSet) {
147 if (*AliasSet == R1) return true;
152 /// getStackSpaceFor - This returns the frame index of the specified virtual
153 /// register on the stack, allocating space if necessary.
154 int getStackSpaceFor(unsigned VirtReg, const TargetRegisterClass *RC);
156 /// removePhysReg - This method marks the specified physical register as no
157 /// longer being in use.
159 void removePhysReg(unsigned PhysReg);
161 /// spillVirtReg - This method spills the value specified by PhysReg into
162 /// the virtual register slot specified by VirtReg. It then updates the RA
163 /// data structures to indicate the fact that PhysReg is now available.
165 void spillVirtReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator &I,
166 unsigned VirtReg, unsigned PhysReg);
168 /// spillPhysReg - This method spills the specified physical register into
169 /// the virtual register slot associated with it. If OnlyVirtRegs is set to
170 /// true, then the request is ignored if the physical register does not
171 /// contain a virtual register.
173 void spillPhysReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator &I,
174 unsigned PhysReg, bool OnlyVirtRegs = false);
176 /// assignVirtToPhysReg - This method updates local state so that we know
177 /// that PhysReg is the proper container for VirtReg now. The physical
178 /// register must not be used for anything else when this is called.
180 void assignVirtToPhysReg(unsigned VirtReg, unsigned PhysReg);
182 /// liberatePhysReg - Make sure the specified physical register is available
183 /// for use. If there is currently a value in it, it is either moved out of
184 /// the way or spilled to memory.
186 void liberatePhysReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator &I,
189 /// isPhysRegAvailable - Return true if the specified physical register is
190 /// free and available for use. This also includes checking to see if
191 /// aliased registers are all free...
193 bool isPhysRegAvailable(unsigned PhysReg) const;
195 /// getFreeReg - Look to see if there is a free register available in the
196 /// specified register class. If not, return 0.
198 unsigned getFreeReg(const TargetRegisterClass *RC);
200 /// getReg - Find a physical register to hold the specified virtual
201 /// register. If all compatible physical registers are used, this method
202 /// spills the last used virtual register to the stack, and uses that
205 unsigned getReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator &I,
208 /// reloadVirtReg - This method loads the specified virtual register into a
209 /// physical register, returning the physical register chosen. This updates
210 /// the regalloc data structures to reflect the fact that the virtual reg is
211 /// now alive in a physical register, and the previous one isn't.
213 unsigned reloadVirtReg(MachineBasicBlock &MBB,
214 MachineBasicBlock::iterator &I, unsigned VirtReg);
216 void reloadPhysReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator &I,
221 /// getStackSpaceFor - This allocates space for the specified virtual register
222 /// to be held on the stack.
223 int RA::getStackSpaceFor(unsigned VirtReg, const TargetRegisterClass *RC) {
224 // Find the location Reg would belong...
225 std::map<unsigned, int>::iterator I =StackSlotForVirtReg.lower_bound(VirtReg);
227 if (I != StackSlotForVirtReg.end() && I->first == VirtReg)
228 return I->second; // Already has space allocated?
230 // Allocate a new stack object for this spill location...
231 int FrameIdx = MF->getFrameInfo()->CreateStackObject(RC);
233 // Assign the slot...
234 StackSlotForVirtReg.insert(I, std::make_pair(VirtReg, FrameIdx));
239 /// removePhysReg - This method marks the specified physical register as no
240 /// longer being in use.
242 void RA::removePhysReg(unsigned PhysReg) {
243 PhysRegsUsed[PhysReg] = -1; // PhyReg no longer used
245 std::vector<unsigned>::iterator It =
246 std::find(PhysRegsUseOrder.begin(), PhysRegsUseOrder.end(), PhysReg);
247 if (It != PhysRegsUseOrder.end())
248 PhysRegsUseOrder.erase(It);
252 /// spillVirtReg - This method spills the value specified by PhysReg into the
253 /// virtual register slot specified by VirtReg. It then updates the RA data
254 /// structures to indicate the fact that PhysReg is now available.
256 void RA::spillVirtReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator &I,
257 unsigned VirtReg, unsigned PhysReg) {
258 if (!VirtReg && DisableKill) return;
259 assert(VirtReg && "Spilling a physical register is illegal!"
260 " Must not have appropriate kill for the register or use exists beyond"
261 " the intended one.");
262 DEBUG(std::cerr << " Spilling register " << RegInfo->getName(PhysReg);
263 std::cerr << " containing %reg" << VirtReg;
264 if (!isVirtRegModified(VirtReg))
265 std::cerr << " which has not been modified, so no store necessary!");
267 // Otherwise, there is a virtual register corresponding to this physical
268 // register. We only need to spill it into its stack slot if it has been
270 if (isVirtRegModified(VirtReg)) {
271 const TargetRegisterClass *RC = MF->getSSARegMap()->getRegClass(VirtReg);
272 int FrameIndex = getStackSpaceFor(VirtReg, RC);
273 DEBUG(std::cerr << " to stack slot #" << FrameIndex);
274 RegInfo->storeRegToStackSlot(MBB, I, PhysReg, FrameIndex, RC);
275 ++NumSpilled; // Update statistics
278 getVirt2PhysRegMapSlot(VirtReg) = 0; // VirtReg no longer available
280 DEBUG(std::cerr << "\n");
281 removePhysReg(PhysReg);
285 /// spillPhysReg - This method spills the specified physical register into the
286 /// virtual register slot associated with it. If OnlyVirtRegs is set to true,
287 /// then the request is ignored if the physical register does not contain a
288 /// virtual register.
290 void RA::spillPhysReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator &I,
291 unsigned PhysReg, bool OnlyVirtRegs) {
292 if (PhysRegsUsed[PhysReg] != -1) { // Only spill it if it's used!
293 if (PhysRegsUsed[PhysReg] || !OnlyVirtRegs)
294 spillVirtReg(MBB, I, PhysRegsUsed[PhysReg], PhysReg);
296 // If the selected register aliases any other registers, we must make
297 // sure that one of the aliases isn't alive...
298 for (const unsigned *AliasSet = RegInfo->getAliasSet(PhysReg);
299 *AliasSet; ++AliasSet)
300 if (PhysRegsUsed[*AliasSet] != -1) // Spill aliased register...
301 if (PhysRegsUsed[*AliasSet] || !OnlyVirtRegs)
302 spillVirtReg(MBB, I, PhysRegsUsed[*AliasSet], *AliasSet);
307 /// assignVirtToPhysReg - This method updates local state so that we know
308 /// that PhysReg is the proper container for VirtReg now. The physical
309 /// register must not be used for anything else when this is called.
311 void RA::assignVirtToPhysReg(unsigned VirtReg, unsigned PhysReg) {
312 assert(PhysRegsUsed[PhysReg] == -1 && "Phys reg already assigned!");
313 // Update information to note the fact that this register was just used, and
315 PhysRegsUsed[PhysReg] = VirtReg;
316 getVirt2PhysRegMapSlot(VirtReg) = PhysReg;
317 PhysRegsUseOrder.push_back(PhysReg); // New use of PhysReg
321 /// isPhysRegAvailable - Return true if the specified physical register is free
322 /// and available for use. This also includes checking to see if aliased
323 /// registers are all free...
325 bool RA::isPhysRegAvailable(unsigned PhysReg) const {
326 if (PhysRegsUsed[PhysReg] != -1) return false;
328 // If the selected register aliases any other allocated registers, it is
330 for (const unsigned *AliasSet = RegInfo->getAliasSet(PhysReg);
331 *AliasSet; ++AliasSet)
332 if (PhysRegsUsed[*AliasSet] != -1) // Aliased register in use?
333 return false; // Can't use this reg then.
338 /// getFreeReg - Look to see if there is a free register available in the
339 /// specified register class. If not, return 0.
341 unsigned RA::getFreeReg(const TargetRegisterClass *RC) {
342 // Get iterators defining the range of registers that are valid to allocate in
343 // this class, which also specifies the preferred allocation order.
344 TargetRegisterClass::iterator RI = RC->allocation_order_begin(*MF);
345 TargetRegisterClass::iterator RE = RC->allocation_order_end(*MF);
347 for (; RI != RE; ++RI)
348 if (isPhysRegAvailable(*RI)) { // Is reg unused?
349 assert(*RI != 0 && "Cannot use register!");
350 return *RI; // Found an unused register!
356 /// liberatePhysReg - Make sure the specified physical register is available for
357 /// use. If there is currently a value in it, it is either moved out of the way
358 /// or spilled to memory.
360 void RA::liberatePhysReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator &I,
362 // FIXME: This code checks to see if a register is available, but it really
363 // wants to know if a reg is available BEFORE the instruction executes. If
364 // called after killed operands are freed, it runs the risk of reallocating a
367 if (isPhysRegAvailable(PhysReg)) return; // Already available...
369 // Check to see if the register is directly used, not indirectly used through
370 // aliases. If aliased registers are the ones actually used, we cannot be
371 // sure that we will be able to save the whole thing if we do a reg-reg copy.
372 if (PhysRegsUsed[PhysReg] != -1) {
373 // The virtual register held...
374 unsigned VirtReg = PhysRegsUsed[PhysReg]->second;
376 // Check to see if there is a compatible register available. If so, we can
377 // move the value into the new register...
379 const TargetRegisterClass *RC = RegInfo->getRegClass(PhysReg);
380 if (unsigned NewReg = getFreeReg(RC)) {
381 // Emit the code to copy the value...
382 RegInfo->copyRegToReg(MBB, I, NewReg, PhysReg, RC);
384 // Update our internal state to indicate that PhysReg is available and Reg
386 getVirt2PhysRegMapSlot[VirtReg] = 0;
387 removePhysReg(PhysReg); // Free the physreg
389 // Move reference over to new register...
390 assignVirtToPhysReg(VirtReg, NewReg);
395 spillPhysReg(MBB, I, PhysReg);
399 /// getReg - Find a physical register to hold the specified virtual
400 /// register. If all compatible physical registers are used, this method spills
401 /// the last used virtual register to the stack, and uses that register.
403 unsigned RA::getReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator &I,
405 const TargetRegisterClass *RC = MF->getSSARegMap()->getRegClass(VirtReg);
407 // First check to see if we have a free register of the requested type...
408 unsigned PhysReg = getFreeReg(RC);
410 // If we didn't find an unused register, scavenge one now!
412 assert(!PhysRegsUseOrder.empty() && "No allocated registers??");
414 // Loop over all of the preallocated registers from the least recently used
415 // to the most recently used. When we find one that is capable of holding
416 // our register, use it.
417 for (unsigned i = 0; PhysReg == 0; ++i) {
418 assert(i != PhysRegsUseOrder.size() &&
419 "Couldn't find a register of the appropriate class!");
421 unsigned R = PhysRegsUseOrder[i];
423 // We can only use this register if it holds a virtual register (ie, it
424 // can be spilled). Do not use it if it is an explicitly allocated
425 // physical register!
426 assert(PhysRegsUsed[R] != -1 &&
427 "PhysReg in PhysRegsUseOrder, but is not allocated?");
428 if (PhysRegsUsed[R]) {
429 // If the current register is compatible, use it.
430 if (RegInfo->getRegClass(R) == RC) {
434 // If one of the registers aliased to the current register is
435 // compatible, use it.
436 for (const unsigned *AliasSet = RegInfo->getAliasSet(R);
437 *AliasSet; ++AliasSet) {
438 if (RegInfo->getRegClass(*AliasSet) == RC) {
439 PhysReg = *AliasSet; // Take an aliased register
447 assert(PhysReg && "Physical register not assigned!?!?");
449 // At this point PhysRegsUseOrder[i] is the least recently used register of
450 // compatible register class. Spill it to memory and reap its remains.
451 spillPhysReg(MBB, I, PhysReg);
454 // Now that we know which register we need to assign this to, do it now!
455 assignVirtToPhysReg(VirtReg, PhysReg);
460 /// reloadVirtReg - This method loads the specified virtual register into a
461 /// physical register, returning the physical register chosen. This updates the
462 /// regalloc data structures to reflect the fact that the virtual reg is now
463 /// alive in a physical register, and the previous one isn't.
465 unsigned RA::reloadVirtReg(MachineBasicBlock &MBB,
466 MachineBasicBlock::iterator &I,
468 if (unsigned PR = getVirt2PhysRegMapSlot(VirtReg)) {
469 MarkPhysRegRecentlyUsed(PR);
470 return PR; // Already have this value available!
473 unsigned PhysReg = getReg(MBB, I, VirtReg);
475 const TargetRegisterClass *RC = MF->getSSARegMap()->getRegClass(VirtReg);
476 int FrameIndex = getStackSpaceFor(VirtReg, RC);
478 markVirtRegModified(VirtReg, false); // Note that this reg was just reloaded
480 DEBUG(std::cerr << " Reloading %reg" << VirtReg << " into "
481 << RegInfo->getName(PhysReg) << "\n");
483 // Add move instruction(s)
484 RegInfo->loadRegFromStackSlot(MBB, I, PhysReg, FrameIndex, RC);
485 ++NumReloaded; // Update statistics
491 void RA::AllocateBasicBlock(MachineBasicBlock &MBB) {
492 // loop over each instruction
493 MachineBasicBlock::iterator MI = MBB.begin();
494 for (; MI != MBB.end(); ++MI) {
495 const TargetInstrDescriptor &TID = TM->getInstrInfo().get(MI->getOpcode());
496 DEBUG(std::cerr << "\nStarting RegAlloc of: " << *MI;
497 std::cerr << " Regs have values: ";
498 for (unsigned i = 0; i != RegInfo->getNumRegs(); ++i)
499 if (PhysRegsUsed[i] != -1)
500 std::cerr << "[" << RegInfo->getName(i)
501 << ",%reg" << PhysRegsUsed[i] << "] ";
504 // Loop over the implicit uses, making sure that they are at the head of the
505 // use order list, so they don't get reallocated.
506 for (const unsigned *ImplicitUses = TID.ImplicitUses;
507 *ImplicitUses; ++ImplicitUses)
508 MarkPhysRegRecentlyUsed(*ImplicitUses);
510 // Get the used operands into registers. This has the potential to spill
511 // incoming values if we are out of registers. Note that we completely
512 // ignore physical register uses here. We assume that if an explicit
513 // physical register is referenced by the instruction, that it is guaranteed
514 // to be live-in, or the input is badly hosed.
516 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i)
517 if (MI->getOperand(i).isUse() &&
518 !MI->getOperand(i).isDef() && MI->getOperand(i).isRegister() &&
519 MRegisterInfo::isVirtualRegister(MI->getOperand(i).getReg())) {
520 unsigned VirtSrcReg = MI->getOperand(i).getAllocatedRegNum();
521 unsigned PhysSrcReg = reloadVirtReg(MBB, MI, VirtSrcReg);
522 MI->SetMachineOperandReg(i, PhysSrcReg); // Assign the input register
526 // If this instruction is the last user of anything in registers, kill the
527 // value, freeing the register being used, so it doesn't need to be
528 // spilled to memory.
530 for (LiveVariables::killed_iterator KI = LV->killed_begin(MI),
531 KE = LV->killed_end(MI); KI != KE; ++KI) {
532 unsigned VirtReg = KI->second;
533 unsigned PhysReg = VirtReg;
534 if (MRegisterInfo::isVirtualRegister(VirtReg)) {
535 unsigned &PhysRegSlot = getVirt2PhysRegMapSlot(VirtReg);
536 PhysReg = PhysRegSlot;
537 assert(PhysReg != 0);
542 DEBUG(std::cerr << " Last use of " << RegInfo->getName(PhysReg)
543 << "[%reg" << VirtReg <<"], removing it from live set\n");
544 removePhysReg(PhysReg);
549 // Loop over all of the operands of the instruction, spilling registers that
550 // are defined, and marking explicit destinations in the PhysRegsUsed map.
551 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i)
552 if (MI->getOperand(i).isDef() && MI->getOperand(i).isRegister() &&
553 MRegisterInfo::isPhysicalRegister(MI->getOperand(i).getReg())) {
554 unsigned Reg = MI->getOperand(i).getAllocatedRegNum();
555 spillPhysReg(MBB, MI, Reg, true); // Spill any existing value in the reg
556 PhysRegsUsed[Reg] = 0; // It is free and reserved now
557 PhysRegsUseOrder.push_back(Reg);
558 for (const unsigned *AliasSet = RegInfo->getAliasSet(Reg);
559 *AliasSet; ++AliasSet) {
560 PhysRegsUseOrder.push_back(*AliasSet);
561 PhysRegsUsed[*AliasSet] = 0; // It is free and reserved now
565 // Loop over the implicit defs, spilling them as well.
566 for (const unsigned *ImplicitDefs = TID.ImplicitDefs;
567 *ImplicitDefs; ++ImplicitDefs) {
568 unsigned Reg = *ImplicitDefs;
569 spillPhysReg(MBB, MI, Reg);
570 PhysRegsUseOrder.push_back(Reg);
571 PhysRegsUsed[Reg] = 0; // It is free and reserved now
572 for (const unsigned *AliasSet = RegInfo->getAliasSet(Reg);
573 *AliasSet; ++AliasSet) {
574 PhysRegsUseOrder.push_back(*AliasSet);
575 PhysRegsUsed[*AliasSet] = 0; // It is free and reserved now
579 // Okay, we have allocated all of the source operands and spilled any values
580 // that would be destroyed by defs of this instruction. Loop over the
581 // implicit defs and assign them to a register, spilling incoming values if
582 // we need to scavenge a register.
584 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i)
585 if (MI->getOperand(i).isDef() && MI->getOperand(i).isRegister() &&
586 MRegisterInfo::isVirtualRegister(MI->getOperand(i).getReg())) {
587 unsigned DestVirtReg = MI->getOperand(i).getAllocatedRegNum();
588 unsigned DestPhysReg;
590 // If DestVirtReg already has a value, use it.
591 if (!(DestPhysReg = getVirt2PhysRegMapSlot(DestVirtReg)))
592 DestPhysReg = getReg(MBB, MI, DestVirtReg);
593 markVirtRegModified(DestVirtReg);
594 MI->SetMachineOperandReg(i, DestPhysReg); // Assign the output register
598 // If this instruction defines any registers that are immediately dead,
601 for (LiveVariables::killed_iterator KI = LV->dead_begin(MI),
602 KE = LV->dead_end(MI); KI != KE; ++KI) {
603 unsigned VirtReg = KI->second;
604 unsigned PhysReg = VirtReg;
605 if (MRegisterInfo::isVirtualRegister(VirtReg)) {
606 unsigned &PhysRegSlot = getVirt2PhysRegMapSlot(VirtReg);
607 PhysReg = PhysRegSlot;
608 assert(PhysReg != 0);
613 DEBUG(std::cerr << " Register " << RegInfo->getName(PhysReg)
614 << " [%reg" << VirtReg
615 << "] is never used, removing it frame live list\n");
616 removePhysReg(PhysReg);
622 // Rewind the iterator to point to the first flow control instruction...
623 const TargetInstrInfo &TII = TM->getInstrInfo();
625 while (MI != MBB.begin() && TII.isTerminatorInstr((--MI)->getOpcode()));
628 // Spill all physical registers holding virtual registers now.
629 for (unsigned i = 0, e = RegInfo->getNumRegs(); i != e; ++i)
630 if (PhysRegsUsed[i] != -1)
631 if (unsigned VirtReg = PhysRegsUsed[i])
632 spillVirtReg(MBB, MI, VirtReg, i);
638 for (unsigned i = 0, e = Virt2PhysRegMap.size(); i != e; ++i)
639 if (unsigned PR = Virt2PhysRegMap[i]) {
640 std::cerr << "Register still mapped: " << i << " -> " << PR << "\n";
643 assert(AllOk && "Virtual registers still in phys regs?");
646 // Clear any physical register which appear live at the end of the basic
647 // block, but which do not hold any virtual registers. e.g., the stack
649 PhysRegsUseOrder.clear();
653 /// runOnMachineFunction - Register allocate the whole function
655 bool RA::runOnMachineFunction(MachineFunction &Fn) {
656 DEBUG(std::cerr << "Machine Function " << "\n");
658 TM = &Fn.getTarget();
659 RegInfo = TM->getRegisterInfo();
661 PhysRegsUsed.assign(RegInfo->getNumRegs(), -1);
663 // initialize the virtual->physical register map to have a 'null'
664 // mapping for all virtual registers
665 Virt2PhysRegMap.assign(MF->getSSARegMap()->getNumVirtualRegs(), 0);
668 LV = &getAnalysis<LiveVariables>();
670 // Loop over all of the basic blocks, eliminating virtual register references
671 for (MachineFunction::iterator MBB = Fn.begin(), MBBe = Fn.end();
673 AllocateBasicBlock(*MBB);
675 StackSlotForVirtReg.clear();
676 PhysRegsUsed.clear();
677 VirtRegModified.clear();
678 Virt2PhysRegMap.clear();
682 FunctionPass *llvm::createLocalRegisterAllocator() {