--- /dev/null
+//===- RegAllocBigBlock.cpp - A register allocator for large basic blocks -===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file was developed by the LLVM research group and is distributed under
+// the University of Illinois Open Source License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This register allocator is derived from RegAllocLocal.cpp. Like it, this
+// allocator works on one basic block at a time, oblivious to others.
+// However, the algorithm used here is suited for long blocks of
+// instructions - registers are spilled by greedily choosing those holding
+// values that will not be needed for the longest amount of time. This works
+// particularly well for blocks with 10 or more times as many instructions
+// as machine registers, but can be used for general code.
+//
+//===----------------------------------------------------------------------===//
+//
+// TODO: - automagically invoke linearscan for (groups of) small BBs?
+// - break ties when picking regs? (probably not worth it in a
+// JIT context)
+//
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "regalloc"
+#include "llvm/BasicBlock.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/MachineInstr.h"
+#include "llvm/CodeGen/SSARegMap.h"
+#include "llvm/CodeGen/MachineFrameInfo.h"
+#include "llvm/CodeGen/LiveVariables.h"
+#include "llvm/CodeGen/RegAllocRegistry.h"
+#include "llvm/Target/TargetInstrInfo.h"
+#include "llvm/Target/TargetMachine.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/Compiler.h"
+#include "llvm/ADT/IndexedMap.h"
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/Statistic.h"
+#include <algorithm>
+using namespace llvm;
+
+STATISTIC(NumStores, "Number of stores added");
+STATISTIC(NumLoads , "Number of loads added");
+STATISTIC(NumFolded, "Number of loads/stores folded into instructions");
+
+namespace {
+ static RegisterRegAlloc
+ bigBlockRegAlloc("bigblock", " Big-block register allocator",
+ createBigBlockRegisterAllocator);
+
+ struct VRegKeyInfo {
+ static inline unsigned getEmptyKey() { return -1U; }
+ static inline unsigned getTombstoneKey() { return -2U; }
+ static unsigned getHashValue(const unsigned &Key) { return Key; }
+ };
+
+ class VISIBILITY_HIDDEN RABigBlock : public MachineFunctionPass {
+ public:
+ static char ID;
+ RABigBlock() : MachineFunctionPass((intptr_t)&ID) {}
+ private:
+ const TargetMachine *TM;
+ MachineFunction *MF;
+ const MRegisterInfo *RegInfo;
+ LiveVariables *LV;
+
+ // InsnTimes - maps machine instructions to their "execute times"
+ std::map<MachineInstr *, unsigned> InsnTimes;
+
+ // VRegReadTable - maps VRegs in a BB to the set of times they are read
+ DenseMap<unsigned, SmallVector<unsigned, 2>*, VRegKeyInfo> VRegReadTable;
+
+ // StackSlotForVirtReg - Maps virtual regs to the frame index where these
+ // values are spilled.
+ std::map<unsigned, int> StackSlotForVirtReg;
+
+ // Virt2PhysRegMap - This map contains entries for each virtual register
+ // that is currently available in a physical register.
+ IndexedMap<unsigned, VirtReg2IndexFunctor> Virt2PhysRegMap;
+
+ unsigned &getVirt2PhysRegMapSlot(unsigned VirtReg) {
+ return Virt2PhysRegMap[VirtReg];
+ }
+
+ // PhysRegsUsed - This array is effectively a map, containing entries for
+ // each physical register that currently has a value (ie, it is in
+ // Virt2PhysRegMap). The value mapped to is the virtual register
+ // corresponding to the physical register (the inverse of the
+ // Virt2PhysRegMap), or 0. The value is set to 0 if this register is pinned
+ // because it is used by a future instruction, and to -2 if it is not
+ // allocatable. If the entry for a physical register is -1, then the
+ // physical register is "not in the map".
+ //
+ std::vector<int> PhysRegsUsed;
+
+ // PhysRegsUseOrder - This contains a list of the physical registers that
+ // currently have a virtual register value in them. This list provides an
+ // ordering of registers, imposing a reallocation order. This list is only
+ // used if all registers are allocated and we have to spill one, in which
+ // case we spill the least recently used register. Entries at the front of
+ // the list are the least recently used registers, entries at the back are
+ // the most recently used.
+ //
+ std::vector<unsigned> PhysRegsUseOrder;
+
+ // VirtRegModified - This bitset contains information about which virtual
+ // registers need to be spilled back to memory when their registers are
+ // scavenged. If a virtual register has simply been rematerialized, there
+ // is no reason to spill it to memory when we need the register back.
+ //
+ std::vector<bool> VirtRegModified;
+
+ void markVirtRegModified(unsigned Reg, bool Val = true) {
+ assert(MRegisterInfo::isVirtualRegister(Reg) && "Illegal VirtReg!");
+ Reg -= MRegisterInfo::FirstVirtualRegister;
+ if (VirtRegModified.size() <= Reg) VirtRegModified.resize(Reg+1);
+ VirtRegModified[Reg] = Val;
+ }
+
+ bool isVirtRegModified(unsigned Reg) const {
+ assert(MRegisterInfo::isVirtualRegister(Reg) && "Illegal VirtReg!");
+ assert(Reg - MRegisterInfo::FirstVirtualRegister < VirtRegModified.size()
+ && "Illegal virtual register!");
+ return VirtRegModified[Reg - MRegisterInfo::FirstVirtualRegister];
+ }
+
+ void MarkPhysRegRecentlyUsed(unsigned Reg) {
+ if (PhysRegsUseOrder.empty() ||
+ PhysRegsUseOrder.back() == Reg) return; // Already most recently used
+
+ for (unsigned i = PhysRegsUseOrder.size(); i != 0; --i)
+ if (areRegsEqual(Reg, PhysRegsUseOrder[i-1])) {
+ unsigned RegMatch = PhysRegsUseOrder[i-1]; // remove from middle
+ PhysRegsUseOrder.erase(PhysRegsUseOrder.begin()+i-1);
+ // Add it to the end of the list
+ PhysRegsUseOrder.push_back(RegMatch);
+ if (RegMatch == Reg)
+ return; // Found an exact match, exit early
+ }
+ }
+
+ public:
+ virtual const char *getPassName() const {
+ return "BigBlock Register Allocator";
+ }
+
+ virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.addRequired<LiveVariables>();
+ AU.addRequiredID(PHIEliminationID);
+ AU.addRequiredID(TwoAddressInstructionPassID);
+ MachineFunctionPass::getAnalysisUsage(AU);
+ }
+
+ private:
+ /// runOnMachineFunction - Register allocate the whole function
+ bool runOnMachineFunction(MachineFunction &Fn);
+
+ /// AllocateBasicBlock - Register allocate the specified basic block.
+ void AllocateBasicBlock(MachineBasicBlock &MBB);
+
+ /// FillVRegReadTable - Fill out the table of vreg read times given a BB
+ void FillVRegReadTable(MachineBasicBlock &MBB);
+
+ /// areRegsEqual - This method returns true if the specified registers are
+ /// related to each other. To do this, it checks to see if they are equal
+ /// or if the first register is in the alias set of the second register.
+ ///
+ bool areRegsEqual(unsigned R1, unsigned R2) const {
+ if (R1 == R2) return true;
+ for (const unsigned *AliasSet = RegInfo->getAliasSet(R2);
+ *AliasSet; ++AliasSet) {
+ if (*AliasSet == R1) return true;
+ }
+ return false;
+ }
+
+ /// getStackSpaceFor - This returns the frame index of the specified virtual
+ /// register on the stack, allocating space if necessary.
+ int getStackSpaceFor(unsigned VirtReg, const TargetRegisterClass *RC);
+
+ /// removePhysReg - This method marks the specified physical register as no
+ /// longer being in use.
+ ///
+ void removePhysReg(unsigned PhysReg);
+
+ /// spillVirtReg - This method spills the value specified by PhysReg into
+ /// the virtual register slot specified by VirtReg. It then updates the RA
+ /// data structures to indicate the fact that PhysReg is now available.
+ ///
+ void spillVirtReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator MI,
+ unsigned VirtReg, unsigned PhysReg);
+
+ /// spillPhysReg - This method spills the specified physical register into
+ /// the virtual register slot associated with it. If OnlyVirtRegs is set to
+ /// true, then the request is ignored if the physical register does not
+ /// contain a virtual register.
+ ///
+ void spillPhysReg(MachineBasicBlock &MBB, MachineInstr *I,
+ unsigned PhysReg, bool OnlyVirtRegs = false);
+
+ /// assignVirtToPhysReg - This method updates local state so that we know
+ /// that PhysReg is the proper container for VirtReg now. The physical
+ /// register must not be used for anything else when this is called.
+ ///
+ void assignVirtToPhysReg(unsigned VirtReg, unsigned PhysReg);
+
+ /// liberatePhysReg - Make sure the specified physical register is available
+ /// for use. If there is currently a value in it, it is either moved out of
+ /// the way or spilled to memory.
+ ///
+ void liberatePhysReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator &I,
+ unsigned PhysReg);
+
+ /// isPhysRegAvailable - Return true if the specified physical register is
+ /// free and available for use. This also includes checking to see if
+ /// aliased registers are all free...
+ ///
+ bool isPhysRegAvailable(unsigned PhysReg) const;
+
+ /// getFreeReg - Look to see if there is a free register available in the
+ /// specified register class. If not, return 0.
+ ///
+ unsigned getFreeReg(const TargetRegisterClass *RC);
+
+ /// chooseReg - Pick a physical register to hold the specified
+ /// virtual register by choosing the one which will be read furthest
+ /// in the future.
+ ///
+ unsigned chooseReg(MachineBasicBlock &MBB, MachineInstr *MI,
+ unsigned VirtReg);
+
+ /// reloadVirtReg - This method transforms the specified specified virtual
+ /// register use to refer to a physical register. This method may do this
+ /// in one of several ways: if the register is available in a physical
+ /// register already, it uses that physical register. If the value is not
+ /// in a physical register, and if there are physical registers available,
+ /// it loads it into a register. If register pressure is high, and it is
+ /// possible, it tries to fold the load of the virtual register into the
+ /// instruction itself. It avoids doing this if register pressure is low to
+ /// improve the chance that subsequent instructions can use the reloaded
+ /// value. This method returns the modified instruction.
+ ///
+ MachineInstr *reloadVirtReg(MachineBasicBlock &MBB, MachineInstr *MI,
+ unsigned OpNum);
+
+ };
+ char RABigBlock::ID = 0;
+}
+
+/// getStackSpaceFor - This allocates space for the specified virtual register
+/// to be held on the stack.
+int RABigBlock::getStackSpaceFor(unsigned VirtReg, const TargetRegisterClass *RC) {
+ // Find the location Reg would belong...
+ std::map<unsigned, int>::iterator I =StackSlotForVirtReg.lower_bound(VirtReg);
+
+ if (I != StackSlotForVirtReg.end() && I->first == VirtReg)
+ return I->second; // Already has space allocated?
+
+ // Allocate a new stack object for this spill location...
+ int FrameIdx = MF->getFrameInfo()->CreateStackObject(RC->getSize(),
+ RC->getAlignment());
+
+ // Assign the slot...
+ StackSlotForVirtReg.insert(I, std::make_pair(VirtReg, FrameIdx));
+ return FrameIdx;
+}
+
+
+/// removePhysReg - This method marks the specified physical register as no
+/// longer being in use.
+///
+void RABigBlock::removePhysReg(unsigned PhysReg) {
+ PhysRegsUsed[PhysReg] = -1; // PhyReg no longer used
+
+ std::vector<unsigned>::iterator It =
+ std::find(PhysRegsUseOrder.begin(), PhysRegsUseOrder.end(), PhysReg);
+ if (It != PhysRegsUseOrder.end())
+ PhysRegsUseOrder.erase(It);
+}
+
+
+/// spillVirtReg - This method spills the value specified by PhysReg into the
+/// virtual register slot specified by VirtReg. It then updates the RA data
+/// structures to indicate the fact that PhysReg is now available.
+///
+void RABigBlock::spillVirtReg(MachineBasicBlock &MBB,
+ MachineBasicBlock::iterator I,
+ unsigned VirtReg, unsigned PhysReg) {
+ assert(VirtReg && "Spilling a physical register is illegal!"
+ " Must not have appropriate kill for the register or use exists beyond"
+ " the intended one.");
+ DOUT << " Spilling register " << RegInfo->getName(PhysReg)
+ << " containing %reg" << VirtReg;
+ if (!isVirtRegModified(VirtReg))
+ DOUT << " which has not been modified, so no store necessary!";
+
+ // Otherwise, there is a virtual register corresponding to this physical
+ // register. We only need to spill it into its stack slot if it has been
+ // modified.
+ if (isVirtRegModified(VirtReg)) {
+ const TargetRegisterClass *RC = MF->getSSARegMap()->getRegClass(VirtReg);
+ int FrameIndex = getStackSpaceFor(VirtReg, RC);
+ DOUT << " to stack slot #" << FrameIndex;
+ RegInfo->storeRegToStackSlot(MBB, I, PhysReg, FrameIndex, RC);
+ ++NumStores; // Update statistics
+ }
+
+ getVirt2PhysRegMapSlot(VirtReg) = 0; // VirtReg no longer available
+
+ DOUT << "\n";
+ removePhysReg(PhysReg);
+}
+
+
+/// spillPhysReg - This method spills the specified physical register into the
+/// virtual register slot associated with it. If OnlyVirtRegs is set to true,
+/// then the request is ignored if the physical register does not contain a
+/// virtual register.
+///
+void RABigBlock::spillPhysReg(MachineBasicBlock &MBB, MachineInstr *I,
+ unsigned PhysReg, bool OnlyVirtRegs) {
+ if (PhysRegsUsed[PhysReg] != -1) { // Only spill it if it's used!
+ assert(PhysRegsUsed[PhysReg] != -2 && "Non allocable reg used!");
+ if (PhysRegsUsed[PhysReg] || !OnlyVirtRegs)
+ spillVirtReg(MBB, I, PhysRegsUsed[PhysReg], PhysReg);
+ } else {
+ // If the selected register aliases any other registers, we must make
+ // sure that one of the aliases isn't alive.
+ for (const unsigned *AliasSet = RegInfo->getAliasSet(PhysReg);
+ *AliasSet; ++AliasSet)
+ if (PhysRegsUsed[*AliasSet] != -1 && // Spill aliased register.
+ PhysRegsUsed[*AliasSet] != -2) // If allocatable.
+ if (PhysRegsUsed[*AliasSet] == 0) {
+ // This must have been a dead def due to something like this:
+ // %EAX :=
+ // := op %AL
+ // No more use of %EAX, %AH, etc.
+ // %EAX isn't dead upon definition, but %AH is. However %AH isn't
+ // an operand of definition MI so it's not marked as such.
+ DOUT << " Register " << RegInfo->getName(*AliasSet)
+ << " [%reg" << *AliasSet
+ << "] is never used, removing it frame live list\n";
+ removePhysReg(*AliasSet);
+ } else
+ spillVirtReg(MBB, I, PhysRegsUsed[*AliasSet], *AliasSet);
+ }
+}
+
+
+/// assignVirtToPhysReg - This method updates local state so that we know
+/// that PhysReg is the proper container for VirtReg now. The physical
+/// register must not be used for anything else when this is called.
+///
+void RABigBlock::assignVirtToPhysReg(unsigned VirtReg, unsigned PhysReg) {
+ assert(PhysRegsUsed[PhysReg] == -1 && "Phys reg already assigned!");
+ // Update information to note the fact that this register was just used, and
+ // it holds VirtReg.
+ PhysRegsUsed[PhysReg] = VirtReg;
+ getVirt2PhysRegMapSlot(VirtReg) = PhysReg;
+ PhysRegsUseOrder.push_back(PhysReg); // New use of PhysReg
+}
+
+
+/// isPhysRegAvailable - Return true if the specified physical register is free
+/// and available for use. This also includes checking to see if aliased
+/// registers are all free...
+///
+bool RABigBlock::isPhysRegAvailable(unsigned PhysReg) const {
+ if (PhysRegsUsed[PhysReg] != -1) return false;
+
+ // If the selected register aliases any other allocated registers, it is
+ // not free!
+ for (const unsigned *AliasSet = RegInfo->getAliasSet(PhysReg);
+ *AliasSet; ++AliasSet)
+ if (PhysRegsUsed[*AliasSet] != -1) // Aliased register in use?
+ return false; // Can't use this reg then.
+ return true;
+}
+
+
+//////// FIX THIS:
+/// getFreeReg - Look to see if there is a free register available in the
+/// specified register class. If not, return 0.
+///
+unsigned RABigBlock::getFreeReg(const TargetRegisterClass *RC) {
+ // Get iterators defining the range of registers that are valid to allocate in
+ // this class, which also specifies the preferred allocation order.
+ TargetRegisterClass::iterator RI = RC->allocation_order_begin(*MF);
+ TargetRegisterClass::iterator RE = RC->allocation_order_end(*MF);
+
+ for (; RI != RE; ++RI)
+ if (isPhysRegAvailable(*RI)) { // Is reg unused?
+ assert(*RI != 0 && "Cannot use register!");
+ return *RI; // Found an unused register!
+ }
+ return 0;
+}
+
+
+/// liberatePhysReg - Make sure the specified physical register is available for
+/// use. If there is currently a value in it, it is either moved out of the way
+/// or spilled to memory.
+///
+void RABigBlock::liberatePhysReg(MachineBasicBlock &MBB,
+ MachineBasicBlock::iterator &I,
+ unsigned PhysReg) {
+ spillPhysReg(MBB, I, PhysReg);
+}
+
+/// chooseReg - Pick a physical register to hold the specified
+/// virtual register by choosing the one whose value will be read
+/// furthest in the future.
+///
+unsigned RABigBlock::chooseReg(MachineBasicBlock &MBB, MachineInstr *I,
+ unsigned VirtReg) {
+ const TargetRegisterClass *RC = MF->getSSARegMap()->getRegClass(VirtReg);
+ // First check to see if we have a free register of the requested type...
+ unsigned PhysReg = getFreeReg(RC);
+
+ // If we didn't find an unused register, find the one which will be
+ // read at the most distant point in time.
+ if (PhysReg == 0) {
+ unsigned delay=0, longest_delay=0;
+ SmallVector<unsigned, 2> *ReadTimes;
+
+ unsigned curTime = InsnTimes[I];
+
+ // for all physical regs in the RC,
+ for(TargetRegisterClass::iterator pReg = RC->begin();
+ pReg != RC->end(); ++pReg) {
+ // how long until they're read?
+ if(PhysRegsUsed[*pReg]>0) { // ignore non-allocatable regs
+ ReadTimes = VRegReadTable[PhysRegsUsed[*pReg]];
+ SmallVector<unsigned, 2>::iterator pt =
+ std::lower_bound(ReadTimes->begin(),
+ ReadTimes->end(),
+ curTime);
+ delay = *pt - curTime;
+
+ if(delay > longest_delay) {
+ longest_delay = delay;
+ PhysReg = *pReg;
+ }
+ }
+ }
+
+ assert(PhysReg && "couldn't grab a register from the table?");
+ // TODO: assert that RC->contains(PhysReg) / handle aliased registers
+
+ // since we needed to look in the table we need to spill this register.
+ spillPhysReg(MBB, I, PhysReg);
+ }
+
+ // assign the vreg to our chosen physical register
+ assignVirtToPhysReg(VirtReg, PhysReg);
+ return PhysReg; // and return it
+}
+
+
+/// reloadVirtReg - This method transforms an instruction with a virtual
+/// register use to one that references a physical register. It does this as
+/// follows:
+///
+/// 1) If the register is already in a physical register, it uses it.
+/// 2) Otherwise, if there is a free physical register, it uses that.
+/// 3) Otherwise, it calls chooseReg() to get the physical register
+/// holding the most distantly needed value, generating a spill in
+/// the process.
+///
+/// This method returns the modified instruction.
+MachineInstr *RABigBlock::reloadVirtReg(MachineBasicBlock &MBB, MachineInstr *MI,
+ unsigned OpNum) {
+ unsigned VirtReg = MI->getOperand(OpNum).getReg();
+
+ // If the virtual register is already available in a physical register,
+ // just update the instruction and return.
+ if (unsigned PR = getVirt2PhysRegMapSlot(VirtReg)) {
+ MI->getOperand(OpNum).setReg(PR);
+ return MI;
+ }
+
+ // Otherwise, if we have free physical registers available to hold the
+ // value, use them.
+ const TargetRegisterClass *RC = MF->getSSARegMap()->getRegClass(VirtReg);
+ unsigned PhysReg = getFreeReg(RC);
+ int FrameIndex = getStackSpaceFor(VirtReg, RC);
+
+ if (PhysReg) { // we have a free register, so use it.
+ assignVirtToPhysReg(VirtReg, PhysReg);
+ } else { // no free registers available.
+ // try to fold the spill into the instruction
+ if(MachineInstr* FMI = RegInfo->foldMemoryOperand(MI, OpNum, FrameIndex)) {
+ ++NumFolded;
+ // Since we changed the address of MI, make sure to update live variables
+ // to know that the new instruction has the properties of the old one.
+ LV->instructionChanged(MI, FMI);
+ return MBB.insert(MBB.erase(MI), FMI);
+ }
+
+ // determine which of the physical registers we'll kill off, since we
+ // couldn't fold.
+ PhysReg = chooseReg(MBB, MI, VirtReg);
+ }
+
+ // this virtual register is now unmodified (since we just reloaded it)
+ markVirtRegModified(VirtReg, false);
+
+ DOUT << " Reloading %reg" << VirtReg << " into "
+ << RegInfo->getName(PhysReg) << "\n";
+
+ // Add move instruction(s)
+ RegInfo->loadRegFromStackSlot(MBB, MI, PhysReg, FrameIndex, RC);
+ ++NumLoads; // Update statistics
+
+ MF->setPhysRegUsed(PhysReg);
+ MI->getOperand(OpNum).setReg(PhysReg); // Assign the input register
+ return MI;
+}
+
+/// Fill out the vreg read timetable. Since ReadTime increases
+/// monotonically, the individual readtime sets will be sorted
+/// in ascending order.
+void RABigBlock::FillVRegReadTable(MachineBasicBlock &MBB) {
+ // loop over each instruction
+ MachineBasicBlock::iterator MII;
+ unsigned ReadTime;
+
+ for(ReadTime=0, MII = MBB.begin(); MII != MBB.end(); ++ReadTime, ++MII) {
+ MachineInstr *MI = MII;
+
+ InsnTimes[MI] = ReadTime;
+
+ for (unsigned i = 0; i != MI->getNumOperands(); ++i) {
+ MachineOperand& MO = MI->getOperand(i);
+ // look for vreg reads..
+ if (MO.isRegister() && !MO.isDef() && MO.getReg() &&
+ MRegisterInfo::isVirtualRegister(MO.getReg())) {
+ // ..and add them to the read table.
+ if(!VRegReadTable[MO.getReg()])
+ VRegReadTable[MO.getReg()] = new SmallVector<unsigned, 2>;
+
+ VRegReadTable[MO.getReg()]->push_back(ReadTime);
+ }
+ }
+
+ }
+
+}
+
+void RABigBlock::AllocateBasicBlock(MachineBasicBlock &MBB) {
+ // loop over each instruction
+ MachineBasicBlock::iterator MII = MBB.begin();
+ const TargetInstrInfo &TII = *TM->getInstrInfo();
+
+ DEBUG(const BasicBlock *LBB = MBB.getBasicBlock();
+ if (LBB) DOUT << "\nStarting RegAlloc of BB: " << LBB->getName());
+
+ // If this is the first basic block in the machine function, add live-in
+ // registers as active.
+ if (&MBB == &*MF->begin()) {
+ for (MachineFunction::livein_iterator I = MF->livein_begin(),
+ E = MF->livein_end(); I != E; ++I) {
+ unsigned Reg = I->first;
+ MF->setPhysRegUsed(Reg);
+ PhysRegsUsed[Reg] = 0; // It is free and reserved now
+ PhysRegsUseOrder.push_back(Reg);
+ for (const unsigned *AliasSet = RegInfo->getAliasSet(Reg);
+ *AliasSet; ++AliasSet) {
+ if (PhysRegsUsed[*AliasSet] != -2) {
+ PhysRegsUseOrder.push_back(*AliasSet);
+ PhysRegsUsed[*AliasSet] = 0; // It is free and reserved now
+ MF->setPhysRegUsed(*AliasSet);
+ }
+ }
+ }
+ }
+
+ // Otherwise, sequentially allocate each instruction in the MBB.
+ while (MII != MBB.end()) {
+ MachineInstr *MI = MII++;
+ const TargetInstrDescriptor &TID = TII.get(MI->getOpcode());
+ DEBUG(DOUT << "\nStarting RegAlloc of: " << *MI;
+ DOUT << " Regs have values: ";
+ for (unsigned i = 0; i != RegInfo->getNumRegs(); ++i)
+ if (PhysRegsUsed[i] != -1 && PhysRegsUsed[i] != -2)
+ DOUT << "[" << RegInfo->getName(i)
+ << ",%reg" << PhysRegsUsed[i] << "] ";
+ DOUT << "\n");
+
+ // Loop over the implicit uses, making sure that they are at the head of the
+ // use order list, so they don't get reallocated.
+ if (TID.ImplicitUses) {
+ for (const unsigned *ImplicitUses = TID.ImplicitUses;
+ *ImplicitUses; ++ImplicitUses)
+ MarkPhysRegRecentlyUsed(*ImplicitUses);
+ }
+
+ SmallVector<unsigned, 8> Kills;
+ for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
+ MachineOperand& MO = MI->getOperand(i);
+ if (MO.isRegister() && MO.isKill())
+ Kills.push_back(MO.getReg());
+ }
+
+ // Get the used operands into registers. This has the potential to spill
+ // incoming values if we are out of registers. Note that we completely
+ // ignore physical register uses here. We assume that if an explicit
+ // physical register is referenced by the instruction, that it is guaranteed
+ // to be live-in, or the input is badly hosed.
+ //
+ for (unsigned i = 0; i != MI->getNumOperands(); ++i) {
+ MachineOperand& MO = MI->getOperand(i);
+ // here we are looking for only used operands (never def&use)
+ if (MO.isRegister() && !MO.isDef() && MO.getReg() && !MO.isImplicit() &&
+ MRegisterInfo::isVirtualRegister(MO.getReg()))
+ MI = reloadVirtReg(MBB, MI, i);
+ }
+
+ // If this instruction is the last user of this register, kill the
+ // value, freeing the register being used, so it doesn't need to be
+ // spilled to memory.
+ //
+ for (unsigned i = 0, e = Kills.size(); i != e; ++i) {
+ unsigned VirtReg = Kills[i];
+ unsigned PhysReg = VirtReg;
+ if (MRegisterInfo::isVirtualRegister(VirtReg)) {
+ // If the virtual register was never materialized into a register, it
+ // might not be in the map, but it won't hurt to zero it out anyway.
+ unsigned &PhysRegSlot = getVirt2PhysRegMapSlot(VirtReg);
+ PhysReg = PhysRegSlot;
+ PhysRegSlot = 0;
+ } else if (PhysRegsUsed[PhysReg] == -2) {
+ // Unallocatable register dead, ignore.
+ continue;
+ }
+
+ if (PhysReg) {
+ DOUT << " Last use of " << RegInfo->getName(PhysReg)
+ << "[%reg" << VirtReg <<"], removing it from live set\n";
+ removePhysReg(PhysReg);
+ for (const unsigned *AliasSet = RegInfo->getAliasSet(PhysReg);
+ *AliasSet; ++AliasSet) {
+ if (PhysRegsUsed[*AliasSet] != -2) {
+ DOUT << " Last use of "
+ << RegInfo->getName(*AliasSet)
+ << "[%reg" << VirtReg <<"], removing it from live set\n";
+ removePhysReg(*AliasSet);
+ }
+ }
+ }
+ }
+
+ // Loop over all of the operands of the instruction, spilling registers that
+ // are defined, and marking explicit destinations in the PhysRegsUsed map.
+ for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
+ MachineOperand& MO = MI->getOperand(i);
+ if (MO.isRegister() && MO.isDef() && !MO.isImplicit() && MO.getReg() &&
+ MRegisterInfo::isPhysicalRegister(MO.getReg())) {
+ unsigned Reg = MO.getReg();
+ if (PhysRegsUsed[Reg] == -2) continue; // Something like ESP.
+
+ MF->setPhysRegUsed(Reg);
+ spillPhysReg(MBB, MI, Reg, true); // Spill any existing value in reg
+ PhysRegsUsed[Reg] = 0; // It is free and reserved now
+ PhysRegsUseOrder.push_back(Reg);
+ for (const unsigned *AliasSet = RegInfo->getAliasSet(Reg);
+ *AliasSet; ++AliasSet) {
+ if (PhysRegsUsed[*AliasSet] != -2) {
+ PhysRegsUseOrder.push_back(*AliasSet);
+ PhysRegsUsed[*AliasSet] = 0; // It is free and reserved now
+ MF->setPhysRegUsed(*AliasSet);
+ }
+ }
+ }
+ }
+
+ // Loop over the implicit defs, spilling them as well.
+ if (TID.ImplicitDefs) {
+ for (const unsigned *ImplicitDefs = TID.ImplicitDefs;
+ *ImplicitDefs; ++ImplicitDefs) {
+ unsigned Reg = *ImplicitDefs;
+ bool IsNonAllocatable = PhysRegsUsed[Reg] == -2;
+ if (!IsNonAllocatable) {
+ spillPhysReg(MBB, MI, Reg, true);
+ PhysRegsUseOrder.push_back(Reg);
+ PhysRegsUsed[Reg] = 0; // It is free and reserved now
+ }
+ MF->setPhysRegUsed(Reg);
+
+ for (const unsigned *AliasSet = RegInfo->getAliasSet(Reg);
+ *AliasSet; ++AliasSet) {
+ if (PhysRegsUsed[*AliasSet] != -2) {
+ if (!IsNonAllocatable) {
+ PhysRegsUseOrder.push_back(*AliasSet);
+ PhysRegsUsed[*AliasSet] = 0; // It is free and reserved now
+ }
+ MF->setPhysRegUsed(*AliasSet);
+ }
+ }
+ }
+ }
+
+ SmallVector<unsigned, 8> DeadDefs;
+ for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
+ MachineOperand& MO = MI->getOperand(i);
+ if (MO.isRegister() && MO.isDead())
+ DeadDefs.push_back(MO.getReg());
+ }
+
+ // Okay, we have allocated all of the source operands and spilled any values
+ // that would be destroyed by defs of this instruction. Loop over the
+ // explicit defs and assign them to a register, spilling incoming values if
+ // we need to scavenge a register.
+ //
+ for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
+ MachineOperand& MO = MI->getOperand(i);
+ if (MO.isRegister() && MO.isDef() && MO.getReg() &&
+ MRegisterInfo::isVirtualRegister(MO.getReg())) {
+ unsigned DestVirtReg = MO.getReg();
+ unsigned DestPhysReg;
+
+ // If DestVirtReg already has a value, use it.
+ if (!(DestPhysReg = getVirt2PhysRegMapSlot(DestVirtReg)))
+ DestPhysReg = chooseReg(MBB, MI, DestVirtReg);
+ MF->setPhysRegUsed(DestPhysReg);
+ markVirtRegModified(DestVirtReg);
+ MI->getOperand(i).setReg(DestPhysReg); // Assign the output register
+ }
+ }
+
+ // If this instruction defines any registers that are immediately dead,
+ // kill them now.
+ //
+ for (unsigned i = 0, e = DeadDefs.size(); i != e; ++i) {
+ unsigned VirtReg = DeadDefs[i];
+ unsigned PhysReg = VirtReg;
+ if (MRegisterInfo::isVirtualRegister(VirtReg)) {
+ unsigned &PhysRegSlot = getVirt2PhysRegMapSlot(VirtReg);
+ PhysReg = PhysRegSlot;
+ assert(PhysReg != 0);
+ PhysRegSlot = 0;
+ } else if (PhysRegsUsed[PhysReg] == -2) {
+ // Unallocatable register dead, ignore.
+ continue;
+ }
+
+ if (PhysReg) {
+ DOUT << " Register " << RegInfo->getName(PhysReg)
+ << " [%reg" << VirtReg
+ << "] is never used, removing it frame live list\n";
+ removePhysReg(PhysReg);
+ for (const unsigned *AliasSet = RegInfo->getAliasSet(PhysReg);
+ *AliasSet; ++AliasSet) {
+ if (PhysRegsUsed[*AliasSet] != -2) {
+ DOUT << " Register " << RegInfo->getName(*AliasSet)
+ << " [%reg" << *AliasSet
+ << "] is never used, removing it frame live list\n";
+ removePhysReg(*AliasSet);
+ }
+ }
+ }
+ }
+
+ // Finally, if this is a noop copy instruction, zap it.
+ unsigned SrcReg, DstReg;
+ if (TII.isMoveInstr(*MI, SrcReg, DstReg) && SrcReg == DstReg) {
+ LV->removeVirtualRegistersKilled(MI);
+ LV->removeVirtualRegistersDead(MI);
+ MBB.erase(MI);
+ }
+ }
+
+ MachineBasicBlock::iterator MI = MBB.getFirstTerminator();
+
+ // Spill all physical registers holding virtual registers now.
+ for (unsigned i = 0, e = RegInfo->getNumRegs(); i != e; ++i)
+ if (PhysRegsUsed[i] != -1 && PhysRegsUsed[i] != -2)
+ if (unsigned VirtReg = PhysRegsUsed[i])
+ spillVirtReg(MBB, MI, VirtReg, i);
+ else
+ removePhysReg(i);
+
+#if 0
+ // This checking code is very expensive.
+ bool AllOk = true;
+ for (unsigned i = MRegisterInfo::FirstVirtualRegister,
+ e = MF->getSSARegMap()->getLastVirtReg(); i <= e; ++i)
+ if (unsigned PR = Virt2PhysRegMap[i]) {
+ cerr << "Register still mapped: " << i << " -> " << PR << "\n";
+ AllOk = false;
+ }
+ assert(AllOk && "Virtual registers still in phys regs?");
+#endif
+
+ // Clear any physical register which appear live at the end of the basic
+ // block, but which do not hold any virtual registers. e.g., the stack
+ // pointer.
+ PhysRegsUseOrder.clear();
+}
+
+/// runOnMachineFunction - Register allocate the whole function
+///
+bool RABigBlock::runOnMachineFunction(MachineFunction &Fn) {
+ DOUT << "Machine Function " << "\n";
+ MF = &Fn;
+ TM = &Fn.getTarget();
+ RegInfo = TM->getRegisterInfo();
+ LV = &getAnalysis<LiveVariables>();
+
+ PhysRegsUsed.assign(RegInfo->getNumRegs(), -1);
+
+ // At various places we want to efficiently check to see whether a register
+ // is allocatable. To handle this, we mark all unallocatable registers as
+ // being pinned down, permanently.
+ {
+ BitVector Allocable = RegInfo->getAllocatableSet(Fn);
+ for (unsigned i = 0, e = Allocable.size(); i != e; ++i)
+ if (!Allocable[i])
+ PhysRegsUsed[i] = -2; // Mark the reg unallocable.
+ }
+
+ // initialize the virtual->physical register map to have a 'null'
+ // mapping for all virtual registers
+ Virt2PhysRegMap.grow(MF->getSSARegMap()->getLastVirtReg());
+
+ // Loop over all of the basic blocks, eliminating virtual register references
+ for (MachineFunction::iterator MBB = Fn.begin(), MBBe = Fn.end();
+ MBB != MBBe; ++MBB) {
+ // fill out the read timetable
+ FillVRegReadTable(*MBB);
+ // use it to allocate the BB
+ AllocateBasicBlock(*MBB);
+ // clear it
+ VRegReadTable.clear();
+ }
+
+ StackSlotForVirtReg.clear();
+ PhysRegsUsed.clear();
+ VirtRegModified.clear();
+ Virt2PhysRegMap.clear();
+ return true;
+}
+
+FunctionPass *llvm::createBigBlockRegisterAllocator() {
+ return new RABigBlock();
+}
+
projects / oota-llvm.git / commitdiff