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 Statistic<> NumFused ("ra-local", "Number of reloads fused into instructions");
34 class RA : public MachineFunctionPass {
35 const TargetMachine *TM;
37 const MRegisterInfo *RegInfo;
40 // StackSlotForVirtReg - Maps virtual regs to the frame index where these
41 // values are spilled.
42 std::map<unsigned, int> StackSlotForVirtReg;
44 // Virt2PhysRegMap - This map contains entries for each virtual register
45 // that is currently available in a physical register. This is "logically"
46 // a map from virtual register numbers to physical register numbers.
47 // Instead of using a map, however, which is slow, we use a vector. The
48 // index is the VREG number - FirstVirtualRegister. If the entry is zero,
49 // then it is logically "not in the map".
51 std::vector<unsigned> Virt2PhysRegMap;
53 unsigned &getVirt2PhysRegMapSlot(unsigned VirtReg) {
54 assert(MRegisterInfo::isVirtualRegister(VirtReg) &&"Illegal VREG #");
55 assert(VirtReg-MRegisterInfo::FirstVirtualRegister <Virt2PhysRegMap.size()
56 && "VirtReg not in map!");
57 return Virt2PhysRegMap[VirtReg-MRegisterInfo::FirstVirtualRegister];
60 // PhysRegsUsed - This array is effectively a map, containing entries for
61 // each physical register that currently has a value (ie, it is in
62 // Virt2PhysRegMap). The value mapped to is the virtual register
63 // corresponding to the physical register (the inverse of the
64 // Virt2PhysRegMap), or 0. The value is set to 0 if this register is pinned
65 // because it is used by a future instruction. If the entry for a physical
66 // register is -1, then the physical register is "not in the map".
68 std::vector<int> PhysRegsUsed;
70 // PhysRegsUseOrder - This contains a list of the physical registers that
71 // currently have a virtual register value in them. This list provides an
72 // ordering of registers, imposing a reallocation order. This list is only
73 // used if all registers are allocated and we have to spill one, in which
74 // case we spill the least recently used register. Entries at the front of
75 // the list are the least recently used registers, entries at the back are
76 // the most recently used.
78 std::vector<unsigned> PhysRegsUseOrder;
80 // VirtRegModified - This bitset contains information about which virtual
81 // registers need to be spilled back to memory when their registers are
82 // scavenged. If a virtual register has simply been rematerialized, there
83 // is no reason to spill it to memory when we need the register back.
85 std::vector<bool> VirtRegModified;
87 void markVirtRegModified(unsigned Reg, bool Val = true) {
88 assert(MRegisterInfo::isVirtualRegister(Reg) && "Illegal VirtReg!");
89 Reg -= MRegisterInfo::FirstVirtualRegister;
90 if (VirtRegModified.size() <= Reg) VirtRegModified.resize(Reg+1);
91 VirtRegModified[Reg] = Val;
94 bool isVirtRegModified(unsigned Reg) const {
95 assert(MRegisterInfo::isVirtualRegister(Reg) && "Illegal VirtReg!");
96 assert(Reg - MRegisterInfo::FirstVirtualRegister < VirtRegModified.size()
97 && "Illegal virtual register!");
98 return VirtRegModified[Reg - MRegisterInfo::FirstVirtualRegister];
101 void MarkPhysRegRecentlyUsed(unsigned Reg) {
102 assert(!PhysRegsUseOrder.empty() && "No registers used!");
103 if (PhysRegsUseOrder.back() == Reg) return; // Already most recently used
105 for (unsigned i = PhysRegsUseOrder.size(); i != 0; --i)
106 if (areRegsEqual(Reg, PhysRegsUseOrder[i-1])) {
107 unsigned RegMatch = PhysRegsUseOrder[i-1]; // remove from middle
108 PhysRegsUseOrder.erase(PhysRegsUseOrder.begin()+i-1);
109 // Add it to the end of the list
110 PhysRegsUseOrder.push_back(RegMatch);
112 return; // Found an exact match, exit early
117 virtual const char *getPassName() const {
118 return "Local Register Allocator";
121 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
122 AU.addRequired<LiveVariables>();
123 AU.addRequiredID(PHIEliminationID);
124 AU.addRequiredID(TwoAddressInstructionPassID);
125 MachineFunctionPass::getAnalysisUsage(AU);
129 /// runOnMachineFunction - Register allocate the whole function
130 bool runOnMachineFunction(MachineFunction &Fn);
132 /// AllocateBasicBlock - Register allocate the specified basic block.
133 void AllocateBasicBlock(MachineBasicBlock &MBB);
136 /// areRegsEqual - This method returns true if the specified registers are
137 /// related to each other. To do this, it checks to see if they are equal
138 /// or if the first register is in the alias set of the second register.
140 bool areRegsEqual(unsigned R1, unsigned R2) const {
141 if (R1 == R2) return true;
142 for (const unsigned *AliasSet = RegInfo->getAliasSet(R2);
143 *AliasSet; ++AliasSet) {
144 if (*AliasSet == R1) return true;
149 /// getStackSpaceFor - This returns the frame index of the specified virtual
150 /// register on the stack, allocating space if necessary.
151 int getStackSpaceFor(unsigned VirtReg, const TargetRegisterClass *RC);
153 /// removePhysReg - This method marks the specified physical register as no
154 /// longer being in use.
156 void removePhysReg(unsigned PhysReg);
158 /// spillVirtReg - This method spills the value specified by PhysReg into
159 /// the virtual register slot specified by VirtReg. It then updates the RA
160 /// data structures to indicate the fact that PhysReg is now available.
162 void spillVirtReg(MachineBasicBlock &MBB, MachineInstr *MI,
163 unsigned VirtReg, unsigned PhysReg);
165 /// spillPhysReg - This method spills the specified physical register into
166 /// the virtual register slot associated with it. If OnlyVirtRegs is set to
167 /// true, then the request is ignored if the physical register does not
168 /// contain a virtual register.
170 void spillPhysReg(MachineBasicBlock &MBB, MachineInstr *I,
171 unsigned PhysReg, bool OnlyVirtRegs = false);
173 /// assignVirtToPhysReg - This method updates local state so that we know
174 /// that PhysReg is the proper container for VirtReg now. The physical
175 /// register must not be used for anything else when this is called.
177 void assignVirtToPhysReg(unsigned VirtReg, unsigned PhysReg);
179 /// liberatePhysReg - Make sure the specified physical register is available
180 /// for use. If there is currently a value in it, it is either moved out of
181 /// the way or spilled to memory.
183 void liberatePhysReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator &I,
186 /// isPhysRegAvailable - Return true if the specified physical register is
187 /// free and available for use. This also includes checking to see if
188 /// aliased registers are all free...
190 bool isPhysRegAvailable(unsigned PhysReg) const;
192 /// getFreeReg - Look to see if there is a free register available in the
193 /// specified register class. If not, return 0.
195 unsigned getFreeReg(const TargetRegisterClass *RC);
197 /// getReg - Find a physical register to hold the specified virtual
198 /// register. If all compatible physical registers are used, this method
199 /// spills the last used virtual register to the stack, and uses that
202 unsigned getReg(MachineBasicBlock &MBB, MachineInstr *MI,
205 /// reloadVirtReg - This method transforms the specified specified virtual
206 /// register use to refer to a physical register. This method may do this
207 /// in one of several ways: if the register is available in a physical
208 /// register already, it uses that physical register. If the value is not
209 /// in a physical register, and if there are physical registers available,
210 /// it loads it into a register. If register pressure is high, and it is
211 /// possible, it tries to fold the load of the virtual register into the
212 /// instruction itself. It avoids doing this if register pressure is low to
213 /// improve the chance that subsequent instructions can use the reloaded
214 /// value. This method returns the modified instruction.
216 MachineInstr *reloadVirtReg(MachineBasicBlock &MBB, MachineInstr *MI,
220 void reloadPhysReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator &I,
225 /// getStackSpaceFor - This allocates space for the specified virtual register
226 /// to be held on the stack.
227 int RA::getStackSpaceFor(unsigned VirtReg, const TargetRegisterClass *RC) {
228 // Find the location Reg would belong...
229 std::map<unsigned, int>::iterator I =StackSlotForVirtReg.lower_bound(VirtReg);
231 if (I != StackSlotForVirtReg.end() && I->first == VirtReg)
232 return I->second; // Already has space allocated?
234 // Allocate a new stack object for this spill location...
235 int FrameIdx = MF->getFrameInfo()->CreateStackObject(RC);
237 // Assign the slot...
238 StackSlotForVirtReg.insert(I, std::make_pair(VirtReg, FrameIdx));
243 /// removePhysReg - This method marks the specified physical register as no
244 /// longer being in use.
246 void RA::removePhysReg(unsigned PhysReg) {
247 PhysRegsUsed[PhysReg] = -1; // PhyReg no longer used
249 std::vector<unsigned>::iterator It =
250 std::find(PhysRegsUseOrder.begin(), PhysRegsUseOrder.end(), PhysReg);
251 if (It != PhysRegsUseOrder.end())
252 PhysRegsUseOrder.erase(It);
256 /// spillVirtReg - This method spills the value specified by PhysReg into the
257 /// virtual register slot specified by VirtReg. It then updates the RA data
258 /// structures to indicate the fact that PhysReg is now available.
260 void RA::spillVirtReg(MachineBasicBlock &MBB, MachineInstr *I,
261 unsigned VirtReg, unsigned PhysReg) {
262 assert(VirtReg && "Spilling a physical register is illegal!"
263 " Must not have appropriate kill for the register or use exists beyond"
264 " the intended one.");
265 DEBUG(std::cerr << " Spilling register " << RegInfo->getName(PhysReg);
266 std::cerr << " containing %reg" << VirtReg;
267 if (!isVirtRegModified(VirtReg))
268 std::cerr << " which has not been modified, so no store necessary!");
270 // Otherwise, there is a virtual register corresponding to this physical
271 // register. We only need to spill it into its stack slot if it has been
273 if (isVirtRegModified(VirtReg)) {
274 const TargetRegisterClass *RC = MF->getSSARegMap()->getRegClass(VirtReg);
275 int FrameIndex = getStackSpaceFor(VirtReg, RC);
276 DEBUG(std::cerr << " to stack slot #" << FrameIndex);
277 RegInfo->storeRegToStackSlot(MBB, I, PhysReg, FrameIndex, RC);
278 ++NumSpilled; // Update statistics
281 getVirt2PhysRegMapSlot(VirtReg) = 0; // VirtReg no longer available
283 DEBUG(std::cerr << "\n");
284 removePhysReg(PhysReg);
288 /// spillPhysReg - This method spills the specified physical register into the
289 /// virtual register slot associated with it. If OnlyVirtRegs is set to true,
290 /// then the request is ignored if the physical register does not contain a
291 /// virtual register.
293 void RA::spillPhysReg(MachineBasicBlock &MBB, MachineInstr *I,
294 unsigned PhysReg, bool OnlyVirtRegs) {
295 if (PhysRegsUsed[PhysReg] != -1) { // Only spill it if it's used!
296 if (PhysRegsUsed[PhysReg] || !OnlyVirtRegs)
297 spillVirtReg(MBB, I, PhysRegsUsed[PhysReg], PhysReg);
299 // If the selected register aliases any other registers, we must make
300 // sure that one of the aliases isn't alive...
301 for (const unsigned *AliasSet = RegInfo->getAliasSet(PhysReg);
302 *AliasSet; ++AliasSet)
303 if (PhysRegsUsed[*AliasSet] != -1) // Spill aliased register...
304 if (PhysRegsUsed[*AliasSet] || !OnlyVirtRegs)
305 spillVirtReg(MBB, I, PhysRegsUsed[*AliasSet], *AliasSet);
310 /// assignVirtToPhysReg - This method updates local state so that we know
311 /// that PhysReg is the proper container for VirtReg now. The physical
312 /// register must not be used for anything else when this is called.
314 void RA::assignVirtToPhysReg(unsigned VirtReg, unsigned PhysReg) {
315 assert(PhysRegsUsed[PhysReg] == -1 && "Phys reg already assigned!");
316 // Update information to note the fact that this register was just used, and
318 PhysRegsUsed[PhysReg] = VirtReg;
319 getVirt2PhysRegMapSlot(VirtReg) = PhysReg;
320 PhysRegsUseOrder.push_back(PhysReg); // New use of PhysReg
324 /// isPhysRegAvailable - Return true if the specified physical register is free
325 /// and available for use. This also includes checking to see if aliased
326 /// registers are all free...
328 bool RA::isPhysRegAvailable(unsigned PhysReg) const {
329 if (PhysRegsUsed[PhysReg] != -1) return false;
331 // If the selected register aliases any other allocated registers, it is
333 for (const unsigned *AliasSet = RegInfo->getAliasSet(PhysReg);
334 *AliasSet; ++AliasSet)
335 if (PhysRegsUsed[*AliasSet] != -1) // Aliased register in use?
336 return false; // Can't use this reg then.
341 /// getFreeReg - Look to see if there is a free register available in the
342 /// specified register class. If not, return 0.
344 unsigned RA::getFreeReg(const TargetRegisterClass *RC) {
345 // Get iterators defining the range of registers that are valid to allocate in
346 // this class, which also specifies the preferred allocation order.
347 TargetRegisterClass::iterator RI = RC->allocation_order_begin(*MF);
348 TargetRegisterClass::iterator RE = RC->allocation_order_end(*MF);
350 for (; RI != RE; ++RI)
351 if (isPhysRegAvailable(*RI)) { // Is reg unused?
352 assert(*RI != 0 && "Cannot use register!");
353 return *RI; // Found an unused register!
359 /// liberatePhysReg - Make sure the specified physical register is available for
360 /// use. If there is currently a value in it, it is either moved out of the way
361 /// or spilled to memory.
363 void RA::liberatePhysReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator &I,
365 // FIXME: This code checks to see if a register is available, but it really
366 // wants to know if a reg is available BEFORE the instruction executes. If
367 // called after killed operands are freed, it runs the risk of reallocating a
370 if (isPhysRegAvailable(PhysReg)) return; // Already available...
372 // Check to see if the register is directly used, not indirectly used through
373 // aliases. If aliased registers are the ones actually used, we cannot be
374 // sure that we will be able to save the whole thing if we do a reg-reg copy.
375 if (PhysRegsUsed[PhysReg] != -1) {
376 // The virtual register held...
377 unsigned VirtReg = PhysRegsUsed[PhysReg]->second;
379 // Check to see if there is a compatible register available. If so, we can
380 // move the value into the new register...
382 const TargetRegisterClass *RC = RegInfo->getRegClass(PhysReg);
383 if (unsigned NewReg = getFreeReg(RC)) {
384 // Emit the code to copy the value...
385 RegInfo->copyRegToReg(MBB, I, NewReg, PhysReg, RC);
387 // Update our internal state to indicate that PhysReg is available and Reg
389 getVirt2PhysRegMapSlot[VirtReg] = 0;
390 removePhysReg(PhysReg); // Free the physreg
392 // Move reference over to new register...
393 assignVirtToPhysReg(VirtReg, NewReg);
398 spillPhysReg(MBB, I, PhysReg);
402 /// getReg - Find a physical register to hold the specified virtual
403 /// register. If all compatible physical registers are used, this method spills
404 /// the last used virtual register to the stack, and uses that register.
406 unsigned RA::getReg(MachineBasicBlock &MBB, MachineInstr *I,
408 const TargetRegisterClass *RC = MF->getSSARegMap()->getRegClass(VirtReg);
410 // First check to see if we have a free register of the requested type...
411 unsigned PhysReg = getFreeReg(RC);
413 // If we didn't find an unused register, scavenge one now!
415 assert(!PhysRegsUseOrder.empty() && "No allocated registers??");
417 // Loop over all of the preallocated registers from the least recently used
418 // to the most recently used. When we find one that is capable of holding
419 // our register, use it.
420 for (unsigned i = 0; PhysReg == 0; ++i) {
421 assert(i != PhysRegsUseOrder.size() &&
422 "Couldn't find a register of the appropriate class!");
424 unsigned R = PhysRegsUseOrder[i];
426 // We can only use this register if it holds a virtual register (ie, it
427 // can be spilled). Do not use it if it is an explicitly allocated
428 // physical register!
429 assert(PhysRegsUsed[R] != -1 &&
430 "PhysReg in PhysRegsUseOrder, but is not allocated?");
431 if (PhysRegsUsed[R]) {
432 // If the current register is compatible, use it.
433 if (RegInfo->getRegClass(R) == RC) {
437 // If one of the registers aliased to the current register is
438 // compatible, use it.
439 for (const unsigned *AliasSet = RegInfo->getAliasSet(R);
440 *AliasSet; ++AliasSet) {
441 if (RegInfo->getRegClass(*AliasSet) == RC) {
442 PhysReg = *AliasSet; // Take an aliased register
450 assert(PhysReg && "Physical register not assigned!?!?");
452 // At this point PhysRegsUseOrder[i] is the least recently used register of
453 // compatible register class. Spill it to memory and reap its remains.
454 spillPhysReg(MBB, I, PhysReg);
457 // Now that we know which register we need to assign this to, do it now!
458 assignVirtToPhysReg(VirtReg, PhysReg);
463 /// reloadVirtReg - This method transforms the specified specified virtual
464 /// register use to refer to a physical register. This method may do this in
465 /// one of several ways: if the register is available in a physical register
466 /// already, it uses that physical register. If the value is not in a physical
467 /// register, and if there are physical registers available, it loads it into a
468 /// register. If register pressure is high, and it is possible, it tries to
469 /// fold the load of the virtual register into the instruction itself. It
470 /// avoids doing this if register pressure is low to improve the chance that
471 /// subsequent instructions can use the reloaded value. This method returns the
472 /// modified instruction.
474 MachineInstr *RA::reloadVirtReg(MachineBasicBlock &MBB, MachineInstr *MI,
476 unsigned VirtReg = MI->getOperand(OpNum).getReg();
478 // If the virtual register is already available, just update the instruction
480 if (unsigned PR = getVirt2PhysRegMapSlot(VirtReg)) {
481 MarkPhysRegRecentlyUsed(PR); // Already have this value available!
482 MI->SetMachineOperandReg(OpNum, PR); // Assign the input register
486 // Otherwise, we need to fold it into the current instruction, or reload it.
487 // If we have registers available to hold the value, use them.
488 const TargetRegisterClass *RC = MF->getSSARegMap()->getRegClass(VirtReg);
489 unsigned PhysReg = getFreeReg(RC);
490 int FrameIndex = getStackSpaceFor(VirtReg, RC);
492 if (PhysReg) { // Register is available, allocate it!
493 assignVirtToPhysReg(VirtReg, PhysReg);
494 } else { // No registers available.
495 // If we can fold this spill into this instruction, do so now.
496 MachineBasicBlock::iterator MII = MI;
497 if (RegInfo->foldMemoryOperand(MII, OpNum, FrameIndex)) {
502 // It looks like we can't fold this virtual register load into this
503 // instruction. Force some poor hapless value out of the register file to
504 // make room for the new register, and reload it.
505 PhysReg = getReg(MBB, MI, VirtReg);
508 markVirtRegModified(VirtReg, false); // Note that this reg was just reloaded
510 DEBUG(std::cerr << " Reloading %reg" << VirtReg << " into "
511 << RegInfo->getName(PhysReg) << "\n");
513 // Add move instruction(s)
514 RegInfo->loadRegFromStackSlot(MBB, MI, PhysReg, FrameIndex, RC);
515 ++NumReloaded; // Update statistics
517 MI->SetMachineOperandReg(OpNum, PhysReg); // Assign the input register
523 void RA::AllocateBasicBlock(MachineBasicBlock &MBB) {
524 // loop over each instruction
525 MachineBasicBlock::iterator MI = MBB.begin();
526 for (; MI != MBB.end(); ++MI) {
527 const TargetInstrDescriptor &TID = TM->getInstrInfo().get(MI->getOpcode());
528 DEBUG(std::cerr << "\nStarting RegAlloc of: " << *MI;
529 std::cerr << " Regs have values: ";
530 for (unsigned i = 0; i != RegInfo->getNumRegs(); ++i)
531 if (PhysRegsUsed[i] != -1)
532 std::cerr << "[" << RegInfo->getName(i)
533 << ",%reg" << PhysRegsUsed[i] << "] ";
536 // Loop over the implicit uses, making sure that they are at the head of the
537 // use order list, so they don't get reallocated.
538 for (const unsigned *ImplicitUses = TID.ImplicitUses;
539 *ImplicitUses; ++ImplicitUses)
540 MarkPhysRegRecentlyUsed(*ImplicitUses);
542 // Get the used operands into registers. This has the potential to spill
543 // incoming values if we are out of registers. Note that we completely
544 // ignore physical register uses here. We assume that if an explicit
545 // physical register is referenced by the instruction, that it is guaranteed
546 // to be live-in, or the input is badly hosed.
548 for (unsigned i = 0; i != MI->getNumOperands(); ++i)
549 if (MI->getOperand(i).isUse() &&
550 !MI->getOperand(i).isDef() && MI->getOperand(i).isRegister() &&
551 MRegisterInfo::isVirtualRegister(MI->getOperand(i).getReg()))
552 MI = reloadVirtReg(MBB, MI, i);
554 // If this instruction is the last user of anything in registers, kill the
555 // value, freeing the register being used, so it doesn't need to be
556 // spilled to memory.
558 for (LiveVariables::killed_iterator KI = LV->killed_begin(MI),
559 KE = LV->killed_end(MI); KI != KE; ++KI) {
560 unsigned VirtReg = KI->second;
561 unsigned PhysReg = VirtReg;
562 if (MRegisterInfo::isVirtualRegister(VirtReg)) {
563 // If the virtual register was never materialized into a register, it
564 // might not be in the map, but it won't hurt to zero it out anyway.
565 unsigned &PhysRegSlot = getVirt2PhysRegMapSlot(VirtReg);
566 PhysReg = PhysRegSlot;
571 DEBUG(std::cerr << " Last use of " << RegInfo->getName(PhysReg)
572 << "[%reg" << VirtReg <<"], removing it from live set\n");
573 removePhysReg(PhysReg);
577 // Loop over all of the operands of the instruction, spilling registers that
578 // are defined, and marking explicit destinations in the PhysRegsUsed map.
579 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i)
580 if (MI->getOperand(i).isDef() && MI->getOperand(i).isRegister() &&
581 MRegisterInfo::isPhysicalRegister(MI->getOperand(i).getReg())) {
582 unsigned Reg = MI->getOperand(i).getReg();
583 spillPhysReg(MBB, MI, Reg, true); // Spill any existing value in the reg
584 PhysRegsUsed[Reg] = 0; // It is free and reserved now
585 PhysRegsUseOrder.push_back(Reg);
586 for (const unsigned *AliasSet = RegInfo->getAliasSet(Reg);
587 *AliasSet; ++AliasSet) {
588 PhysRegsUseOrder.push_back(*AliasSet);
589 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 if (MI->getOperand(i).isDef() && MI->getOperand(i).isRegister() &&
614 MRegisterInfo::isVirtualRegister(MI->getOperand(i).getReg())) {
615 unsigned DestVirtReg = MI->getOperand(i).getReg();
616 unsigned DestPhysReg;
618 // If DestVirtReg already has a value, use it.
619 if (!(DestPhysReg = getVirt2PhysRegMapSlot(DestVirtReg)))
620 DestPhysReg = getReg(MBB, MI, DestVirtReg);
621 markVirtRegModified(DestVirtReg);
622 MI->SetMachineOperandReg(i, DestPhysReg); // Assign the output register
625 // If this instruction defines any registers that are immediately dead,
628 for (LiveVariables::killed_iterator KI = LV->dead_begin(MI),
629 KE = LV->dead_end(MI); KI != KE; ++KI) {
630 unsigned VirtReg = KI->second;
631 unsigned PhysReg = VirtReg;
632 if (MRegisterInfo::isVirtualRegister(VirtReg)) {
633 unsigned &PhysRegSlot = getVirt2PhysRegMapSlot(VirtReg);
634 PhysReg = PhysRegSlot;
635 assert(PhysReg != 0);
640 DEBUG(std::cerr << " Register " << RegInfo->getName(PhysReg)
641 << " [%reg" << VirtReg
642 << "] is never used, removing it frame live list\n");
643 removePhysReg(PhysReg);
648 // Rewind the iterator to point to the first flow control instruction...
649 const TargetInstrInfo &TII = TM->getInstrInfo();
651 while (MI != MBB.begin() && TII.isTerminatorInstr((--MI)->getOpcode()));
654 // Spill all physical registers holding virtual registers now.
655 for (unsigned i = 0, e = RegInfo->getNumRegs(); i != e; ++i)
656 if (PhysRegsUsed[i] != -1)
657 if (unsigned VirtReg = PhysRegsUsed[i])
658 spillVirtReg(MBB, MI, VirtReg, i);
664 for (unsigned i = 0, e = Virt2PhysRegMap.size(); i != e; ++i)
665 if (unsigned PR = Virt2PhysRegMap[i]) {
666 std::cerr << "Register still mapped: " << i << " -> " << PR << "\n";
669 assert(AllOk && "Virtual registers still in phys regs?");
672 // Clear any physical register which appear live at the end of the basic
673 // block, but which do not hold any virtual registers. e.g., the stack
675 PhysRegsUseOrder.clear();
679 /// runOnMachineFunction - Register allocate the whole function
681 bool RA::runOnMachineFunction(MachineFunction &Fn) {
682 DEBUG(std::cerr << "Machine Function " << "\n");
684 TM = &Fn.getTarget();
685 RegInfo = TM->getRegisterInfo();
686 LV = &getAnalysis<LiveVariables>();
688 PhysRegsUsed.assign(RegInfo->getNumRegs(), -1);
690 // initialize the virtual->physical register map to have a 'null'
691 // mapping for all virtual registers
692 Virt2PhysRegMap.assign(MF->getSSARegMap()->getNumVirtualRegs(), 0);
694 // Loop over all of the basic blocks, eliminating virtual register references
695 for (MachineFunction::iterator MBB = Fn.begin(), MBBe = Fn.end();
697 AllocateBasicBlock(*MBB);
699 StackSlotForVirtReg.clear();
700 PhysRegsUsed.clear();
701 VirtRegModified.clear();
702 Virt2PhysRegMap.clear();
706 FunctionPass *llvm::createLocalRegisterAllocator() {