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 cl::opt<bool> DisableKill("disable-kill", cl::Hidden,
35 cl::desc("Disable register kill in local-ra"));
37 class RA : public MachineFunctionPass {
38 const TargetMachine *TM;
40 const MRegisterInfo *RegInfo;
43 // StackSlotForVirtReg - Maps virtual regs to the frame index where these
44 // values are spilled.
45 std::map<unsigned, int> StackSlotForVirtReg;
47 // Virt2PhysRegMap - This map contains entries for each virtual register
48 // that is currently available in a physical register. This is "logically"
49 // a map from virtual register numbers to physical register numbers.
50 // Instead of using a map, however, which is slow, we use a vector. The
51 // index is the VREG number - FirstVirtualRegister. If the entry is zero,
52 // then it is logically "not in the map".
54 std::vector<unsigned> Virt2PhysRegMap;
56 unsigned &getVirt2PhysRegMapSlot(unsigned VirtReg) {
57 assert(MRegisterInfo::isVirtualRegister(VirtReg) &&"Illegal VREG #");
58 assert(VirtReg-MRegisterInfo::FirstVirtualRegister <Virt2PhysRegMap.size()
59 && "VirtReg not in map!");
60 return Virt2PhysRegMap[VirtReg-MRegisterInfo::FirstVirtualRegister];
63 // PhysRegsUsed - This array is effectively a map, containing entries for
64 // each physical register that currently has a value (ie, it is in
65 // Virt2PhysRegMap). The value mapped to is the virtual register
66 // corresponding to the physical register (the inverse of the
67 // Virt2PhysRegMap), or 0. The value is set to 0 if this register is pinned
68 // because it is used by a future instruction. If the entry for a physical
69 // register is -1, then the physical register is "not in the map".
71 std::vector<int> PhysRegsUsed;
73 // PhysRegsUseOrder - This contains a list of the physical registers that
74 // currently have a virtual register value in them. This list provides an
75 // ordering of registers, imposing a reallocation order. This list is only
76 // used if all registers are allocated and we have to spill one, in which
77 // case we spill the least recently used register. Entries at the front of
78 // the list are the least recently used registers, entries at the back are
79 // the most recently used.
81 std::vector<unsigned> PhysRegsUseOrder;
83 // VirtRegModified - This bitset contains information about which virtual
84 // registers need to be spilled back to memory when their registers are
85 // scavenged. If a virtual register has simply been rematerialized, there
86 // is no reason to spill it to memory when we need the register back.
88 std::vector<bool> VirtRegModified;
90 void markVirtRegModified(unsigned Reg, bool Val = true) {
91 assert(MRegisterInfo::isVirtualRegister(Reg) && "Illegal VirtReg!");
92 Reg -= MRegisterInfo::FirstVirtualRegister;
93 if (VirtRegModified.size() <= Reg) VirtRegModified.resize(Reg+1);
94 VirtRegModified[Reg] = Val;
97 bool isVirtRegModified(unsigned Reg) const {
98 assert(MRegisterInfo::isVirtualRegister(Reg) && "Illegal VirtReg!");
99 assert(Reg - MRegisterInfo::FirstVirtualRegister < VirtRegModified.size()
100 && "Illegal virtual register!");
101 return VirtRegModified[Reg - MRegisterInfo::FirstVirtualRegister];
104 void MarkPhysRegRecentlyUsed(unsigned Reg) {
105 assert(!PhysRegsUseOrder.empty() && "No registers used!");
106 if (PhysRegsUseOrder.back() == Reg) return; // Already most recently used
108 for (unsigned i = PhysRegsUseOrder.size(); i != 0; --i)
109 if (areRegsEqual(Reg, PhysRegsUseOrder[i-1])) {
110 unsigned RegMatch = PhysRegsUseOrder[i-1]; // remove from middle
111 PhysRegsUseOrder.erase(PhysRegsUseOrder.begin()+i-1);
112 // Add it to the end of the list
113 PhysRegsUseOrder.push_back(RegMatch);
115 return; // Found an exact match, exit early
120 virtual const char *getPassName() const {
121 return "Local Register Allocator";
124 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
126 AU.addRequired<LiveVariables>();
127 AU.addRequiredID(PHIEliminationID);
128 AU.addRequiredID(TwoAddressInstructionPassID);
129 MachineFunctionPass::getAnalysisUsage(AU);
133 /// runOnMachineFunction - Register allocate the whole function
134 bool runOnMachineFunction(MachineFunction &Fn);
136 /// AllocateBasicBlock - Register allocate the specified basic block.
137 void AllocateBasicBlock(MachineBasicBlock &MBB);
140 /// areRegsEqual - This method returns true if the specified registers are
141 /// related to each other. To do this, it checks to see if they are equal
142 /// or if the first register is in the alias set of the second register.
144 bool areRegsEqual(unsigned R1, unsigned R2) const {
145 if (R1 == R2) return true;
146 for (const unsigned *AliasSet = RegInfo->getAliasSet(R2);
147 *AliasSet; ++AliasSet) {
148 if (*AliasSet == R1) return true;
153 /// getStackSpaceFor - This returns the frame index of the specified virtual
154 /// register on the stack, allocating space if necessary.
155 int getStackSpaceFor(unsigned VirtReg, const TargetRegisterClass *RC);
157 /// removePhysReg - This method marks the specified physical register as no
158 /// longer being in use.
160 void removePhysReg(unsigned PhysReg);
162 /// spillVirtReg - This method spills the value specified by PhysReg into
163 /// the virtual register slot specified by VirtReg. It then updates the RA
164 /// data structures to indicate the fact that PhysReg is now available.
166 void spillVirtReg(MachineBasicBlock &MBB, MachineInstr *MI,
167 unsigned VirtReg, unsigned PhysReg);
169 /// spillPhysReg - This method spills the specified physical register into
170 /// the virtual register slot associated with it. If OnlyVirtRegs is set to
171 /// true, then the request is ignored if the physical register does not
172 /// contain a virtual register.
174 void spillPhysReg(MachineBasicBlock &MBB, MachineInstr *I,
175 unsigned PhysReg, bool OnlyVirtRegs = false);
177 /// assignVirtToPhysReg - This method updates local state so that we know
178 /// that PhysReg is the proper container for VirtReg now. The physical
179 /// register must not be used for anything else when this is called.
181 void assignVirtToPhysReg(unsigned VirtReg, unsigned PhysReg);
183 /// liberatePhysReg - Make sure the specified physical register is available
184 /// for use. If there is currently a value in it, it is either moved out of
185 /// the way or spilled to memory.
187 void liberatePhysReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator &I,
190 /// isPhysRegAvailable - Return true if the specified physical register is
191 /// free and available for use. This also includes checking to see if
192 /// aliased registers are all free...
194 bool isPhysRegAvailable(unsigned PhysReg) const;
196 /// getFreeReg - Look to see if there is a free register available in the
197 /// specified register class. If not, return 0.
199 unsigned getFreeReg(const TargetRegisterClass *RC);
201 /// getReg - Find a physical register to hold the specified virtual
202 /// register. If all compatible physical registers are used, this method
203 /// spills the last used virtual register to the stack, and uses that
206 unsigned getReg(MachineBasicBlock &MBB, MachineInstr *MI,
209 /// reloadVirtReg - This method transforms the specified specified virtual
210 /// register use to refer to a physical register. This method may do this
211 /// in one of several ways: if the register is available in a physical
212 /// register already, it uses that physical register. If the value is not
213 /// in a physical register, and if there are physical registers available,
214 /// it loads it into a register. If register pressure is high, and it is
215 /// possible, it tries to fold the load of the virtual register into the
216 /// instruction itself. It avoids doing this if register pressure is low to
217 /// improve the chance that subsequent instructions can use the reloaded
218 /// value. This method returns the modified instruction.
220 MachineInstr *reloadVirtReg(MachineBasicBlock &MBB, MachineInstr *MI,
224 void reloadPhysReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator &I,
229 /// getStackSpaceFor - This allocates space for the specified virtual register
230 /// to be held on the stack.
231 int RA::getStackSpaceFor(unsigned VirtReg, const TargetRegisterClass *RC) {
232 // Find the location Reg would belong...
233 std::map<unsigned, int>::iterator I =StackSlotForVirtReg.lower_bound(VirtReg);
235 if (I != StackSlotForVirtReg.end() && I->first == VirtReg)
236 return I->second; // Already has space allocated?
238 // Allocate a new stack object for this spill location...
239 int FrameIdx = MF->getFrameInfo()->CreateStackObject(RC);
241 // Assign the slot...
242 StackSlotForVirtReg.insert(I, std::make_pair(VirtReg, FrameIdx));
247 /// removePhysReg - This method marks the specified physical register as no
248 /// longer being in use.
250 void RA::removePhysReg(unsigned PhysReg) {
251 PhysRegsUsed[PhysReg] = -1; // PhyReg no longer used
253 std::vector<unsigned>::iterator It =
254 std::find(PhysRegsUseOrder.begin(), PhysRegsUseOrder.end(), PhysReg);
255 if (It != PhysRegsUseOrder.end())
256 PhysRegsUseOrder.erase(It);
260 /// spillVirtReg - This method spills the value specified by PhysReg into the
261 /// virtual register slot specified by VirtReg. It then updates the RA data
262 /// structures to indicate the fact that PhysReg is now available.
264 void RA::spillVirtReg(MachineBasicBlock &MBB, MachineInstr *I,
265 unsigned VirtReg, unsigned PhysReg) {
266 if (!VirtReg && DisableKill) return;
267 assert(VirtReg && "Spilling a physical register is illegal!"
268 " Must not have appropriate kill for the register or use exists beyond"
269 " the intended one.");
270 DEBUG(std::cerr << " Spilling register " << RegInfo->getName(PhysReg);
271 std::cerr << " containing %reg" << VirtReg;
272 if (!isVirtRegModified(VirtReg))
273 std::cerr << " which has not been modified, so no store necessary!");
275 // Otherwise, there is a virtual register corresponding to this physical
276 // register. We only need to spill it into its stack slot if it has been
278 if (isVirtRegModified(VirtReg)) {
279 const TargetRegisterClass *RC = MF->getSSARegMap()->getRegClass(VirtReg);
280 int FrameIndex = getStackSpaceFor(VirtReg, RC);
281 DEBUG(std::cerr << " to stack slot #" << FrameIndex);
282 RegInfo->storeRegToStackSlot(MBB, I, PhysReg, FrameIndex, RC);
283 ++NumSpilled; // Update statistics
286 getVirt2PhysRegMapSlot(VirtReg) = 0; // VirtReg no longer available
288 DEBUG(std::cerr << "\n");
289 removePhysReg(PhysReg);
293 /// spillPhysReg - This method spills the specified physical register into the
294 /// virtual register slot associated with it. If OnlyVirtRegs is set to true,
295 /// then the request is ignored if the physical register does not contain a
296 /// virtual register.
298 void RA::spillPhysReg(MachineBasicBlock &MBB, MachineInstr *I,
299 unsigned PhysReg, bool OnlyVirtRegs) {
300 if (PhysRegsUsed[PhysReg] != -1) { // Only spill it if it's used!
301 if (PhysRegsUsed[PhysReg] || !OnlyVirtRegs)
302 spillVirtReg(MBB, I, PhysRegsUsed[PhysReg], PhysReg);
304 // If the selected register aliases any other registers, we must make
305 // sure that one of the aliases isn't alive...
306 for (const unsigned *AliasSet = RegInfo->getAliasSet(PhysReg);
307 *AliasSet; ++AliasSet)
308 if (PhysRegsUsed[*AliasSet] != -1) // Spill aliased register...
309 if (PhysRegsUsed[*AliasSet] || !OnlyVirtRegs)
310 spillVirtReg(MBB, I, PhysRegsUsed[*AliasSet], *AliasSet);
315 /// assignVirtToPhysReg - This method updates local state so that we know
316 /// that PhysReg is the proper container for VirtReg now. The physical
317 /// register must not be used for anything else when this is called.
319 void RA::assignVirtToPhysReg(unsigned VirtReg, unsigned PhysReg) {
320 assert(PhysRegsUsed[PhysReg] == -1 && "Phys reg already assigned!");
321 // Update information to note the fact that this register was just used, and
323 PhysRegsUsed[PhysReg] = VirtReg;
324 getVirt2PhysRegMapSlot(VirtReg) = PhysReg;
325 PhysRegsUseOrder.push_back(PhysReg); // New use of PhysReg
329 /// isPhysRegAvailable - Return true if the specified physical register is free
330 /// and available for use. This also includes checking to see if aliased
331 /// registers are all free...
333 bool RA::isPhysRegAvailable(unsigned PhysReg) const {
334 if (PhysRegsUsed[PhysReg] != -1) return false;
336 // If the selected register aliases any other allocated registers, it is
338 for (const unsigned *AliasSet = RegInfo->getAliasSet(PhysReg);
339 *AliasSet; ++AliasSet)
340 if (PhysRegsUsed[*AliasSet] != -1) // Aliased register in use?
341 return false; // Can't use this reg then.
346 /// getFreeReg - Look to see if there is a free register available in the
347 /// specified register class. If not, return 0.
349 unsigned RA::getFreeReg(const TargetRegisterClass *RC) {
350 // Get iterators defining the range of registers that are valid to allocate in
351 // this class, which also specifies the preferred allocation order.
352 TargetRegisterClass::iterator RI = RC->allocation_order_begin(*MF);
353 TargetRegisterClass::iterator RE = RC->allocation_order_end(*MF);
355 for (; RI != RE; ++RI)
356 if (isPhysRegAvailable(*RI)) { // Is reg unused?
357 assert(*RI != 0 && "Cannot use register!");
358 return *RI; // Found an unused register!
364 /// liberatePhysReg - Make sure the specified physical register is available for
365 /// use. If there is currently a value in it, it is either moved out of the way
366 /// or spilled to memory.
368 void RA::liberatePhysReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator &I,
370 // FIXME: This code checks to see if a register is available, but it really
371 // wants to know if a reg is available BEFORE the instruction executes. If
372 // called after killed operands are freed, it runs the risk of reallocating a
375 if (isPhysRegAvailable(PhysReg)) return; // Already available...
377 // Check to see if the register is directly used, not indirectly used through
378 // aliases. If aliased registers are the ones actually used, we cannot be
379 // sure that we will be able to save the whole thing if we do a reg-reg copy.
380 if (PhysRegsUsed[PhysReg] != -1) {
381 // The virtual register held...
382 unsigned VirtReg = PhysRegsUsed[PhysReg]->second;
384 // Check to see if there is a compatible register available. If so, we can
385 // move the value into the new register...
387 const TargetRegisterClass *RC = RegInfo->getRegClass(PhysReg);
388 if (unsigned NewReg = getFreeReg(RC)) {
389 // Emit the code to copy the value...
390 RegInfo->copyRegToReg(MBB, I, NewReg, PhysReg, RC);
392 // Update our internal state to indicate that PhysReg is available and Reg
394 getVirt2PhysRegMapSlot[VirtReg] = 0;
395 removePhysReg(PhysReg); // Free the physreg
397 // Move reference over to new register...
398 assignVirtToPhysReg(VirtReg, NewReg);
403 spillPhysReg(MBB, I, PhysReg);
407 /// getReg - Find a physical register to hold the specified virtual
408 /// register. If all compatible physical registers are used, this method spills
409 /// the last used virtual register to the stack, and uses that register.
411 unsigned RA::getReg(MachineBasicBlock &MBB, MachineInstr *I,
413 const TargetRegisterClass *RC = MF->getSSARegMap()->getRegClass(VirtReg);
415 // First check to see if we have a free register of the requested type...
416 unsigned PhysReg = getFreeReg(RC);
418 // If we didn't find an unused register, scavenge one now!
420 assert(!PhysRegsUseOrder.empty() && "No allocated registers??");
422 // Loop over all of the preallocated registers from the least recently used
423 // to the most recently used. When we find one that is capable of holding
424 // our register, use it.
425 for (unsigned i = 0; PhysReg == 0; ++i) {
426 assert(i != PhysRegsUseOrder.size() &&
427 "Couldn't find a register of the appropriate class!");
429 unsigned R = PhysRegsUseOrder[i];
431 // We can only use this register if it holds a virtual register (ie, it
432 // can be spilled). Do not use it if it is an explicitly allocated
433 // physical register!
434 assert(PhysRegsUsed[R] != -1 &&
435 "PhysReg in PhysRegsUseOrder, but is not allocated?");
436 if (PhysRegsUsed[R]) {
437 // If the current register is compatible, use it.
438 if (RegInfo->getRegClass(R) == RC) {
442 // If one of the registers aliased to the current register is
443 // compatible, use it.
444 for (const unsigned *AliasSet = RegInfo->getAliasSet(R);
445 *AliasSet; ++AliasSet) {
446 if (RegInfo->getRegClass(*AliasSet) == RC) {
447 PhysReg = *AliasSet; // Take an aliased register
455 assert(PhysReg && "Physical register not assigned!?!?");
457 // At this point PhysRegsUseOrder[i] is the least recently used register of
458 // compatible register class. Spill it to memory and reap its remains.
459 spillPhysReg(MBB, I, PhysReg);
462 // Now that we know which register we need to assign this to, do it now!
463 assignVirtToPhysReg(VirtReg, PhysReg);
468 /// reloadVirtReg - This method transforms the specified specified virtual
469 /// register use to refer to a physical register. This method may do this in
470 /// one of several ways: if the register is available in a physical register
471 /// already, it uses that physical register. If the value is not in a physical
472 /// register, and if there are physical registers available, it loads it into a
473 /// register. If register pressure is high, and it is possible, it tries to
474 /// fold the load of the virtual register into the instruction itself. It
475 /// avoids doing this if register pressure is low to improve the chance that
476 /// subsequent instructions can use the reloaded value. This method returns the
477 /// modified instruction.
479 MachineInstr *RA::reloadVirtReg(MachineBasicBlock &MBB, MachineInstr *MI,
481 unsigned VirtReg = MI->getOperand(OpNum).getReg();
483 // If the virtual register is already available, just update the instruction
485 if (unsigned PR = getVirt2PhysRegMapSlot(VirtReg)) {
486 MarkPhysRegRecentlyUsed(PR); // Already have this value available!
487 MI->SetMachineOperandReg(OpNum, PR); // Assign the input register
491 // Otherwise, we need to fold it into the current instruction, or reload it.
492 // If we have registers available to hold the value, use them.
493 const TargetRegisterClass *RC = MF->getSSARegMap()->getRegClass(VirtReg);
494 unsigned PhysReg = getFreeReg(RC);
495 int FrameIndex = getStackSpaceFor(VirtReg, RC);
497 if (PhysReg) { // Register is available, allocate it!
498 assignVirtToPhysReg(VirtReg, PhysReg);
499 } else { // No registers available.
500 // If we can fold this spill into this instruction, do so now.
501 MachineBasicBlock::iterator MII = MI;
502 if (RegInfo->foldMemoryOperand(MII, OpNum, FrameIndex)) {
507 // It looks like we can't fold this virtual register load into this
508 // instruction. Force some poor hapless value out of the register file to
509 // make room for the new register, and reload it.
510 PhysReg = getReg(MBB, MI, VirtReg);
513 markVirtRegModified(VirtReg, false); // Note that this reg was just reloaded
515 DEBUG(std::cerr << " Reloading %reg" << VirtReg << " into "
516 << RegInfo->getName(PhysReg) << "\n");
518 // Add move instruction(s)
519 RegInfo->loadRegFromStackSlot(MBB, MI, PhysReg, FrameIndex, RC);
520 ++NumReloaded; // Update statistics
522 MI->SetMachineOperandReg(OpNum, PhysReg); // Assign the input register
528 void RA::AllocateBasicBlock(MachineBasicBlock &MBB) {
529 // loop over each instruction
530 MachineBasicBlock::iterator MI = MBB.begin();
531 for (; MI != MBB.end(); ++MI) {
532 const TargetInstrDescriptor &TID = TM->getInstrInfo().get(MI->getOpcode());
533 DEBUG(std::cerr << "\nStarting RegAlloc of: " << *MI;
534 std::cerr << " Regs have values: ";
535 for (unsigned i = 0; i != RegInfo->getNumRegs(); ++i)
536 if (PhysRegsUsed[i] != -1)
537 std::cerr << "[" << RegInfo->getName(i)
538 << ",%reg" << PhysRegsUsed[i] << "] ";
541 // Loop over the implicit uses, making sure that they are at the head of the
542 // use order list, so they don't get reallocated.
543 for (const unsigned *ImplicitUses = TID.ImplicitUses;
544 *ImplicitUses; ++ImplicitUses)
545 MarkPhysRegRecentlyUsed(*ImplicitUses);
547 // Get the used operands into registers. This has the potential to spill
548 // incoming values if we are out of registers. Note that we completely
549 // ignore physical register uses here. We assume that if an explicit
550 // physical register is referenced by the instruction, that it is guaranteed
551 // to be live-in, or the input is badly hosed.
553 for (unsigned i = 0; i != MI->getNumOperands(); ++i)
554 if (MI->getOperand(i).isUse() &&
555 !MI->getOperand(i).isDef() && MI->getOperand(i).isRegister() &&
556 MRegisterInfo::isVirtualRegister(MI->getOperand(i).getReg()))
557 MI = reloadVirtReg(MBB, MI, i);
560 // If this instruction is the last user of anything in registers, kill the
561 // value, freeing the register being used, so it doesn't need to be
562 // spilled to memory.
564 for (LiveVariables::killed_iterator KI = LV->killed_begin(MI),
565 KE = LV->killed_end(MI); KI != KE; ++KI) {
566 unsigned VirtReg = KI->second;
567 unsigned PhysReg = VirtReg;
568 if (MRegisterInfo::isVirtualRegister(VirtReg)) {
569 // If the virtual register was never materialized into a register, it
570 // might not be in the map, but it won't hurt to zero it out anyway.
571 unsigned &PhysRegSlot = getVirt2PhysRegMapSlot(VirtReg);
572 PhysReg = PhysRegSlot;
577 DEBUG(std::cerr << " Last use of " << RegInfo->getName(PhysReg)
578 << "[%reg" << VirtReg <<"], removing it from live set\n");
579 removePhysReg(PhysReg);
584 // Loop over all of the operands of the instruction, spilling registers that
585 // are defined, and marking explicit destinations in the PhysRegsUsed map.
586 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i)
587 if (MI->getOperand(i).isDef() && MI->getOperand(i).isRegister() &&
588 MRegisterInfo::isPhysicalRegister(MI->getOperand(i).getReg())) {
589 unsigned Reg = MI->getOperand(i).getReg();
590 spillPhysReg(MBB, MI, Reg, true); // Spill any existing value in the reg
591 PhysRegsUsed[Reg] = 0; // It is free and reserved now
592 PhysRegsUseOrder.push_back(Reg);
593 for (const unsigned *AliasSet = RegInfo->getAliasSet(Reg);
594 *AliasSet; ++AliasSet) {
595 PhysRegsUseOrder.push_back(*AliasSet);
596 PhysRegsUsed[*AliasSet] = 0; // It is free and reserved now
600 // Loop over the implicit defs, spilling them as well.
601 for (const unsigned *ImplicitDefs = TID.ImplicitDefs;
602 *ImplicitDefs; ++ImplicitDefs) {
603 unsigned Reg = *ImplicitDefs;
604 spillPhysReg(MBB, MI, Reg, true);
605 PhysRegsUseOrder.push_back(Reg);
606 PhysRegsUsed[Reg] = 0; // It is free and reserved now
607 for (const unsigned *AliasSet = RegInfo->getAliasSet(Reg);
608 *AliasSet; ++AliasSet) {
609 PhysRegsUseOrder.push_back(*AliasSet);
610 PhysRegsUsed[*AliasSet] = 0; // It is free and reserved now
614 // Okay, we have allocated all of the source operands and spilled any values
615 // that would be destroyed by defs of this instruction. Loop over the
616 // implicit defs and assign them to a register, spilling incoming values if
617 // we need to scavenge a register.
619 for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i)
620 if (MI->getOperand(i).isDef() && MI->getOperand(i).isRegister() &&
621 MRegisterInfo::isVirtualRegister(MI->getOperand(i).getReg())) {
622 unsigned DestVirtReg = MI->getOperand(i).getReg();
623 unsigned DestPhysReg;
625 // If DestVirtReg already has a value, use it.
626 if (!(DestPhysReg = getVirt2PhysRegMapSlot(DestVirtReg)))
627 DestPhysReg = getReg(MBB, MI, DestVirtReg);
628 markVirtRegModified(DestVirtReg);
629 MI->SetMachineOperandReg(i, DestPhysReg); // Assign the output register
633 // If this instruction defines any registers that are immediately dead,
636 for (LiveVariables::killed_iterator KI = LV->dead_begin(MI),
637 KE = LV->dead_end(MI); KI != KE; ++KI) {
638 unsigned VirtReg = KI->second;
639 unsigned PhysReg = VirtReg;
640 if (MRegisterInfo::isVirtualRegister(VirtReg)) {
641 unsigned &PhysRegSlot = getVirt2PhysRegMapSlot(VirtReg);
642 PhysReg = PhysRegSlot;
643 assert(PhysReg != 0);
648 DEBUG(std::cerr << " Register " << RegInfo->getName(PhysReg)
649 << " [%reg" << VirtReg
650 << "] is never used, removing it frame live list\n");
651 removePhysReg(PhysReg);
657 // Rewind the iterator to point to the first flow control instruction...
658 const TargetInstrInfo &TII = TM->getInstrInfo();
660 while (MI != MBB.begin() && TII.isTerminatorInstr((--MI)->getOpcode()));
663 // Spill all physical registers holding virtual registers now.
664 for (unsigned i = 0, e = RegInfo->getNumRegs(); i != e; ++i)
665 if (PhysRegsUsed[i] != -1)
666 if (unsigned VirtReg = PhysRegsUsed[i])
667 spillVirtReg(MBB, MI, VirtReg, i);
673 for (unsigned i = 0, e = Virt2PhysRegMap.size(); i != e; ++i)
674 if (unsigned PR = Virt2PhysRegMap[i]) {
675 std::cerr << "Register still mapped: " << i << " -> " << PR << "\n";
678 assert(AllOk && "Virtual registers still in phys regs?");
681 // Clear any physical register which appear live at the end of the basic
682 // block, but which do not hold any virtual registers. e.g., the stack
684 PhysRegsUseOrder.clear();
688 /// runOnMachineFunction - Register allocate the whole function
690 bool RA::runOnMachineFunction(MachineFunction &Fn) {
691 DEBUG(std::cerr << "Machine Function " << "\n");
693 TM = &Fn.getTarget();
694 RegInfo = TM->getRegisterInfo();
696 PhysRegsUsed.assign(RegInfo->getNumRegs(), -1);
698 // initialize the virtual->physical register map to have a 'null'
699 // mapping for all virtual registers
700 Virt2PhysRegMap.assign(MF->getSSARegMap()->getNumVirtualRegs(), 0);
703 LV = &getAnalysis<LiveVariables>();
705 // Loop over all of the basic blocks, eliminating virtual register references
706 for (MachineFunction::iterator MBB = Fn.begin(), MBBe = Fn.end();
708 AllocateBasicBlock(*MBB);
710 StackSlotForVirtReg.clear();
711 PhysRegsUsed.clear();
712 VirtRegModified.clear();
713 Virt2PhysRegMap.clear();
717 FunctionPass *llvm::createLocalRegisterAllocator() {