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Diffstat (limited to 'contrib/llvm/lib/CodeGen/VirtRegRewriter.cpp')
| -rw-r--r-- | contrib/llvm/lib/CodeGen/VirtRegRewriter.cpp | 2587 |
1 files changed, 2587 insertions, 0 deletions
diff --git a/contrib/llvm/lib/CodeGen/VirtRegRewriter.cpp b/contrib/llvm/lib/CodeGen/VirtRegRewriter.cpp new file mode 100644 index 0000000..57a1500 --- /dev/null +++ b/contrib/llvm/lib/CodeGen/VirtRegRewriter.cpp @@ -0,0 +1,2587 @@ +//===-- llvm/CodeGen/Rewriter.cpp - Rewriter -----------------------------===// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// + +#define DEBUG_TYPE "virtregrewriter" +#include "VirtRegRewriter.h" +#include "VirtRegMap.h" +#include "llvm/Function.h" +#include "llvm/CodeGen/LiveIntervalAnalysis.h" +#include "llvm/CodeGen/MachineFrameInfo.h" +#include "llvm/CodeGen/MachineInstrBuilder.h" +#include "llvm/CodeGen/MachineRegisterInfo.h" +#include "llvm/Support/CommandLine.h" +#include "llvm/Support/Debug.h" +#include "llvm/Support/ErrorHandling.h" +#include "llvm/Support/raw_ostream.h" +#include "llvm/Target/TargetInstrInfo.h" +#include "llvm/Target/TargetLowering.h" +#include "llvm/ADT/DepthFirstIterator.h" +#include "llvm/ADT/Statistic.h" +#include <algorithm> +using namespace llvm; + +STATISTIC(NumDSE , "Number of dead stores elided"); +STATISTIC(NumDSS , "Number of dead spill slots removed"); +STATISTIC(NumCommutes, "Number of instructions commuted"); +STATISTIC(NumDRM , "Number of re-materializable defs elided"); +STATISTIC(NumStores , "Number of stores added"); +STATISTIC(NumPSpills , "Number of physical register spills"); +STATISTIC(NumOmitted , "Number of reloads omited"); +STATISTIC(NumAvoided , "Number of reloads deemed unnecessary"); +STATISTIC(NumCopified, "Number of available reloads turned into copies"); +STATISTIC(NumReMats , "Number of re-materialization"); +STATISTIC(NumLoads , "Number of loads added"); +STATISTIC(NumReused , "Number of values reused"); +STATISTIC(NumDCE , "Number of copies elided"); +STATISTIC(NumSUnfold , "Number of stores unfolded"); +STATISTIC(NumModRefUnfold, "Number of modref unfolded"); + +namespace { + enum RewriterName { local, trivial }; +} + +static cl::opt<RewriterName> +RewriterOpt("rewriter", + cl::desc("Rewriter to use (default=local)"), + cl::Prefix, + cl::values(clEnumVal(local, "local rewriter"), + clEnumVal(trivial, "trivial rewriter"), + clEnumValEnd), + cl::init(local)); + +static cl::opt<bool> +ScheduleSpills("schedule-spills", + cl::desc("Schedule spill code"), + cl::init(false)); + +VirtRegRewriter::~VirtRegRewriter() {} + +/// substitutePhysReg - Replace virtual register in MachineOperand with a +/// physical register. Do the right thing with the sub-register index. +/// Note that operands may be added, so the MO reference is no longer valid. +static void substitutePhysReg(MachineOperand &MO, unsigned Reg, + const TargetRegisterInfo &TRI) { + if (unsigned SubIdx = MO.getSubReg()) { + // Insert the physical subreg and reset the subreg field. + MO.setReg(TRI.getSubReg(Reg, SubIdx)); + MO.setSubReg(0); + + // Any def, dead, and kill flags apply to the full virtual register, so they + // also apply to the full physical register. Add imp-def/dead and imp-kill + // as needed. + MachineInstr &MI = *MO.getParent(); + if (MO.isDef()) + if (MO.isDead()) + MI.addRegisterDead(Reg, &TRI, /*AddIfNotFound=*/ true); + else + MI.addRegisterDefined(Reg, &TRI); + else if (!MO.isUndef() && + (MO.isKill() || + MI.isRegTiedToDefOperand(&MO-&MI.getOperand(0)))) + MI.addRegisterKilled(Reg, &TRI, /*AddIfNotFound=*/ true); + } else { + MO.setReg(Reg); + } +} + +namespace { + +/// This class is intended for use with the new spilling framework only. It +/// rewrites vreg def/uses to use the assigned preg, but does not insert any +/// spill code. +struct TrivialRewriter : public VirtRegRewriter { + + bool runOnMachineFunction(MachineFunction &MF, VirtRegMap &VRM, + LiveIntervals* LIs) { + DEBUG(dbgs() << "********** REWRITE MACHINE CODE **********\n"); + DEBUG(dbgs() << "********** Function: " + << MF.getFunction()->getName() << '\n'); + DEBUG(dbgs() << "**** Machine Instrs" + << "(NOTE! Does not include spills and reloads!) ****\n"); + DEBUG(MF.dump()); + + MachineRegisterInfo *mri = &MF.getRegInfo(); + const TargetRegisterInfo *tri = MF.getTarget().getRegisterInfo(); + + bool changed = false; + + for (LiveIntervals::iterator liItr = LIs->begin(), liEnd = LIs->end(); + liItr != liEnd; ++liItr) { + + const LiveInterval *li = liItr->second; + unsigned reg = li->reg; + + if (TargetRegisterInfo::isPhysicalRegister(reg)) { + if (!li->empty()) + mri->setPhysRegUsed(reg); + } + else { + if (!VRM.hasPhys(reg)) + continue; + unsigned pReg = VRM.getPhys(reg); + mri->setPhysRegUsed(pReg); + // Copy the register use-list before traversing it. + SmallVector<std::pair<MachineInstr*, unsigned>, 32> reglist; + for (MachineRegisterInfo::reg_iterator I = mri->reg_begin(reg), + E = mri->reg_end(); I != E; ++I) + reglist.push_back(std::make_pair(&*I, I.getOperandNo())); + for (unsigned N=0; N != reglist.size(); ++N) + substitutePhysReg(reglist[N].first->getOperand(reglist[N].second), + pReg, *tri); + changed |= !reglist.empty(); + } + } + + DEBUG(dbgs() << "**** Post Machine Instrs ****\n"); + DEBUG(MF.dump()); + + return changed; + } + +}; + +} + +// ************************************************************************ // + +namespace { + +/// AvailableSpills - As the local rewriter is scanning and rewriting an MBB +/// from top down, keep track of which spill slots or remat are available in +/// each register. +/// +/// Note that not all physregs are created equal here. In particular, some +/// physregs are reloads that we are allowed to clobber or ignore at any time. +/// Other physregs are values that the register allocated program is using +/// that we cannot CHANGE, but we can read if we like. We keep track of this +/// on a per-stack-slot / remat id basis as the low bit in the value of the +/// SpillSlotsAvailable entries. The predicate 'canClobberPhysReg()' checks +/// this bit and addAvailable sets it if. +class AvailableSpills { + const TargetRegisterInfo *TRI; + const TargetInstrInfo *TII; + + // SpillSlotsOrReMatsAvailable - This map keeps track of all of the spilled + // or remat'ed virtual register values that are still available, due to + // being loaded or stored to, but not invalidated yet. + std::map<int, unsigned> SpillSlotsOrReMatsAvailable; + + // PhysRegsAvailable - This is the inverse of SpillSlotsOrReMatsAvailable, + // indicating which stack slot values are currently held by a physreg. This + // is used to invalidate entries in SpillSlotsOrReMatsAvailable when a + // physreg is modified. + std::multimap<unsigned, int> PhysRegsAvailable; + + void disallowClobberPhysRegOnly(unsigned PhysReg); + + void ClobberPhysRegOnly(unsigned PhysReg); +public: + AvailableSpills(const TargetRegisterInfo *tri, const TargetInstrInfo *tii) + : TRI(tri), TII(tii) { + } + + /// clear - Reset the state. + void clear() { + SpillSlotsOrReMatsAvailable.clear(); + PhysRegsAvailable.clear(); + } + + const TargetRegisterInfo *getRegInfo() const { return TRI; } + + /// getSpillSlotOrReMatPhysReg - If the specified stack slot or remat is + /// available in a physical register, return that PhysReg, otherwise + /// return 0. + unsigned getSpillSlotOrReMatPhysReg(int Slot) const { + std::map<int, unsigned>::const_iterator I = + SpillSlotsOrReMatsAvailable.find(Slot); + if (I != SpillSlotsOrReMatsAvailable.end()) { + return I->second >> 1; // Remove the CanClobber bit. + } + return 0; + } + + /// addAvailable - Mark that the specified stack slot / remat is available + /// in the specified physreg. If CanClobber is true, the physreg can be + /// modified at any time without changing the semantics of the program. + void addAvailable(int SlotOrReMat, unsigned Reg, bool CanClobber = true) { + // If this stack slot is thought to be available in some other physreg, + // remove its record. + ModifyStackSlotOrReMat(SlotOrReMat); + + PhysRegsAvailable.insert(std::make_pair(Reg, SlotOrReMat)); + SpillSlotsOrReMatsAvailable[SlotOrReMat]= (Reg << 1) | + (unsigned)CanClobber; + + if (SlotOrReMat > VirtRegMap::MAX_STACK_SLOT) + DEBUG(dbgs() << "Remembering RM#" + << SlotOrReMat-VirtRegMap::MAX_STACK_SLOT-1); + else + DEBUG(dbgs() << "Remembering SS#" << SlotOrReMat); + DEBUG(dbgs() << " in physreg " << TRI->getName(Reg) << "\n"); + } + + /// canClobberPhysRegForSS - Return true if the spiller is allowed to change + /// the value of the specified stackslot register if it desires. The + /// specified stack slot must be available in a physreg for this query to + /// make sense. + bool canClobberPhysRegForSS(int SlotOrReMat) const { + assert(SpillSlotsOrReMatsAvailable.count(SlotOrReMat) && + "Value not available!"); + return SpillSlotsOrReMatsAvailable.find(SlotOrReMat)->second & 1; + } + + /// canClobberPhysReg - Return true if the spiller is allowed to clobber the + /// physical register where values for some stack slot(s) might be + /// available. + bool canClobberPhysReg(unsigned PhysReg) const { + std::multimap<unsigned, int>::const_iterator I = + PhysRegsAvailable.lower_bound(PhysReg); + while (I != PhysRegsAvailable.end() && I->first == PhysReg) { + int SlotOrReMat = I->second; + I++; + if (!canClobberPhysRegForSS(SlotOrReMat)) + return false; + } + return true; + } + + /// disallowClobberPhysReg - Unset the CanClobber bit of the specified + /// stackslot register. The register is still available but is no longer + /// allowed to be modifed. + void disallowClobberPhysReg(unsigned PhysReg); + + /// ClobberPhysReg - This is called when the specified physreg changes + /// value. We use this to invalidate any info about stuff that lives in + /// it and any of its aliases. + void ClobberPhysReg(unsigned PhysReg); + + /// ModifyStackSlotOrReMat - This method is called when the value in a stack + /// slot changes. This removes information about which register the + /// previous value for this slot lives in (as the previous value is dead + /// now). + void ModifyStackSlotOrReMat(int SlotOrReMat); + + /// AddAvailableRegsToLiveIn - Availability information is being kept coming + /// into the specified MBB. Add available physical registers as potential + /// live-in's. If they are reused in the MBB, they will be added to the + /// live-in set to make register scavenger and post-allocation scheduler. + void AddAvailableRegsToLiveIn(MachineBasicBlock &MBB, BitVector &RegKills, + std::vector<MachineOperand*> &KillOps); +}; + +} + +// ************************************************************************ // + +// Given a location where a reload of a spilled register or a remat of +// a constant is to be inserted, attempt to find a safe location to +// insert the load at an earlier point in the basic-block, to hide +// latency of the load and to avoid address-generation interlock +// issues. +static MachineBasicBlock::iterator +ComputeReloadLoc(MachineBasicBlock::iterator const InsertLoc, + MachineBasicBlock::iterator const Begin, + unsigned PhysReg, + const TargetRegisterInfo *TRI, + bool DoReMat, + int SSorRMId, + const TargetInstrInfo *TII, + const MachineFunction &MF) +{ + if (!ScheduleSpills) + return InsertLoc; + + // Spill backscheduling is of primary interest to addresses, so + // don't do anything if the register isn't in the register class + // used for pointers. + + const TargetLowering *TL = MF.getTarget().getTargetLowering(); + + if (!TL->isTypeLegal(TL->getPointerTy())) + // Believe it or not, this is true on PIC16. + return InsertLoc; + + const TargetRegisterClass *ptrRegClass = + TL->getRegClassFor(TL->getPointerTy()); + if (!ptrRegClass->contains(PhysReg)) + return InsertLoc; + + // Scan upwards through the preceding instructions. If an instruction doesn't + // reference the stack slot or the register we're loading, we can + // backschedule the reload up past it. + MachineBasicBlock::iterator NewInsertLoc = InsertLoc; + while (NewInsertLoc != Begin) { + MachineBasicBlock::iterator Prev = prior(NewInsertLoc); + for (unsigned i = 0; i < Prev->getNumOperands(); ++i) { + MachineOperand &Op = Prev->getOperand(i); + if (!DoReMat && Op.isFI() && Op.getIndex() == SSorRMId) + goto stop; + } + if (Prev->findRegisterUseOperandIdx(PhysReg) != -1 || + Prev->findRegisterDefOperand(PhysReg)) + goto stop; + for (const unsigned *Alias = TRI->getAliasSet(PhysReg); *Alias; ++Alias) + if (Prev->findRegisterUseOperandIdx(*Alias) != -1 || + Prev->findRegisterDefOperand(*Alias)) + goto stop; + NewInsertLoc = Prev; + } +stop:; + + // If we made it to the beginning of the block, turn around and move back + // down just past any existing reloads. They're likely to be reloads/remats + // for instructions earlier than what our current reload/remat is for, so + // they should be scheduled earlier. + if (NewInsertLoc == Begin) { + int FrameIdx; + while (InsertLoc != NewInsertLoc && + (TII->isLoadFromStackSlot(NewInsertLoc, FrameIdx) || + TII->isTriviallyReMaterializable(NewInsertLoc))) + ++NewInsertLoc; + } + + return NewInsertLoc; +} + +namespace { + +// ReusedOp - For each reused operand, we keep track of a bit of information, +// in case we need to rollback upon processing a new operand. See comments +// below. +struct ReusedOp { + // The MachineInstr operand that reused an available value. + unsigned Operand; + + // StackSlotOrReMat - The spill slot or remat id of the value being reused. + unsigned StackSlotOrReMat; + + // PhysRegReused - The physical register the value was available in. + unsigned PhysRegReused; + + // AssignedPhysReg - The physreg that was assigned for use by the reload. + unsigned AssignedPhysReg; + + // VirtReg - The virtual register itself. + unsigned VirtReg; + + ReusedOp(unsigned o, unsigned ss, unsigned prr, unsigned apr, + unsigned vreg) + : Operand(o), StackSlotOrReMat(ss), PhysRegReused(prr), + AssignedPhysReg(apr), VirtReg(vreg) {} +}; + +/// ReuseInfo - This maintains a collection of ReuseOp's for each operand that +/// is reused instead of reloaded. +class ReuseInfo { + MachineInstr &MI; + std::vector<ReusedOp> Reuses; + BitVector PhysRegsClobbered; +public: + ReuseInfo(MachineInstr &mi, const TargetRegisterInfo *tri) : MI(mi) { + PhysRegsClobbered.resize(tri->getNumRegs()); + } + + bool hasReuses() const { + return !Reuses.empty(); + } + + /// addReuse - If we choose to reuse a virtual register that is already + /// available instead of reloading it, remember that we did so. + void addReuse(unsigned OpNo, unsigned StackSlotOrReMat, + unsigned PhysRegReused, unsigned AssignedPhysReg, + unsigned VirtReg) { + // If the reload is to the assigned register anyway, no undo will be + // required. + if (PhysRegReused == AssignedPhysReg) return; + + // Otherwise, remember this. + Reuses.push_back(ReusedOp(OpNo, StackSlotOrReMat, PhysRegReused, + AssignedPhysReg, VirtReg)); + } + + void markClobbered(unsigned PhysReg) { + PhysRegsClobbered.set(PhysReg); + } + + bool isClobbered(unsigned PhysReg) const { + return PhysRegsClobbered.test(PhysReg); + } + + /// GetRegForReload - We are about to emit a reload into PhysReg. If there + /// is some other operand that is using the specified register, either pick + /// a new register to use, or evict the previous reload and use this reg. + unsigned GetRegForReload(const TargetRegisterClass *RC, unsigned PhysReg, + MachineFunction &MF, MachineInstr *MI, + AvailableSpills &Spills, + std::vector<MachineInstr*> &MaybeDeadStores, + SmallSet<unsigned, 8> &Rejected, + BitVector &RegKills, + std::vector<MachineOperand*> &KillOps, + VirtRegMap &VRM); + + /// GetRegForReload - Helper for the above GetRegForReload(). Add a + /// 'Rejected' set to remember which registers have been considered and + /// rejected for the reload. This avoids infinite looping in case like + /// this: + /// t1 := op t2, t3 + /// t2 <- assigned r0 for use by the reload but ended up reuse r1 + /// t3 <- assigned r1 for use by the reload but ended up reuse r0 + /// t1 <- desires r1 + /// sees r1 is taken by t2, tries t2's reload register r0 + /// sees r0 is taken by t3, tries t3's reload register r1 + /// sees r1 is taken by t2, tries t2's reload register r0 ... + unsigned GetRegForReload(unsigned VirtReg, unsigned PhysReg, MachineInstr *MI, + AvailableSpills &Spills, + std::vector<MachineInstr*> &MaybeDeadStores, + BitVector &RegKills, + std::vector<MachineOperand*> &KillOps, + VirtRegMap &VRM) { + SmallSet<unsigned, 8> Rejected; + MachineFunction &MF = *MI->getParent()->getParent(); + const TargetRegisterClass* RC = MF.getRegInfo().getRegClass(VirtReg); + return GetRegForReload(RC, PhysReg, MF, MI, Spills, MaybeDeadStores, + Rejected, RegKills, KillOps, VRM); + } +}; + +} + +// ****************** // +// Utility Functions // +// ****************** // + +/// findSinglePredSuccessor - Return via reference a vector of machine basic +/// blocks each of which is a successor of the specified BB and has no other +/// predecessor. +static void findSinglePredSuccessor(MachineBasicBlock *MBB, + SmallVectorImpl<MachineBasicBlock *> &Succs) { + for (MachineBasicBlock::succ_iterator SI = MBB->succ_begin(), + SE = MBB->succ_end(); SI != SE; ++SI) { + MachineBasicBlock *SuccMBB = *SI; + if (SuccMBB->pred_size() == 1) + Succs.push_back(SuccMBB); + } +} + +/// InvalidateKill - Invalidate register kill information for a specific +/// register. This also unsets the kills marker on the last kill operand. +static void InvalidateKill(unsigned Reg, + const TargetRegisterInfo* TRI, + BitVector &RegKills, + std::vector<MachineOperand*> &KillOps) { + if (RegKills[Reg]) { + KillOps[Reg]->setIsKill(false); + // KillOps[Reg] might be a def of a super-register. + unsigned KReg = KillOps[Reg]->getReg(); + KillOps[KReg] = NULL; + RegKills.reset(KReg); + for (const unsigned *SR = TRI->getSubRegisters(KReg); *SR; ++SR) { + if (RegKills[*SR]) { + KillOps[*SR]->setIsKill(false); + KillOps[*SR] = NULL; + RegKills.reset(*SR); + } + } + } +} + +/// InvalidateKills - MI is going to be deleted. If any of its operands are +/// marked kill, then invalidate the information. +static void InvalidateKills(MachineInstr &MI, + const TargetRegisterInfo* TRI, + BitVector &RegKills, + std::vector<MachineOperand*> &KillOps, + SmallVector<unsigned, 2> *KillRegs = NULL) { + for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) { + MachineOperand &MO = MI.getOperand(i); + if (!MO.isReg() || !MO.isUse() || !MO.isKill() || MO.isUndef()) + continue; + unsigned Reg = MO.getReg(); + if (TargetRegisterInfo::isVirtualRegister(Reg)) + continue; + if (KillRegs) + KillRegs->push_back(Reg); + assert(Reg < KillOps.size()); + if (KillOps[Reg] == &MO) { + KillOps[Reg] = NULL; + RegKills.reset(Reg); + for (const unsigned *SR = TRI->getSubRegisters(Reg); *SR; ++SR) { + if (RegKills[*SR]) { + KillOps[*SR] = NULL; + RegKills.reset(*SR); + } + } + } + } +} + +/// InvalidateRegDef - If the def operand of the specified def MI is now dead +/// (since its spill instruction is removed), mark it isDead. Also checks if +/// the def MI has other definition operands that are not dead. Returns it by +/// reference. +static bool InvalidateRegDef(MachineBasicBlock::iterator I, + MachineInstr &NewDef, unsigned Reg, + bool &HasLiveDef, + const TargetRegisterInfo *TRI) { + // Due to remat, it's possible this reg isn't being reused. That is, + // the def of this reg (by prev MI) is now dead. + MachineInstr *DefMI = I; + MachineOperand *DefOp = NULL; + for (unsigned i = 0, e = DefMI->getNumOperands(); i != e; ++i) { + MachineOperand &MO = DefMI->getOperand(i); + if (!MO.isReg() || !MO.isDef() || !MO.isKill() || MO.isUndef()) + continue; + if (MO.getReg() == Reg) + DefOp = &MO; + else if (!MO.isDead()) + HasLiveDef = true; + } + if (!DefOp) + return false; + + bool FoundUse = false, Done = false; + MachineBasicBlock::iterator E = &NewDef; + ++I; ++E; + for (; !Done && I != E; ++I) { + MachineInstr *NMI = I; + for (unsigned j = 0, ee = NMI->getNumOperands(); j != ee; ++j) { + MachineOperand &MO = NMI->getOperand(j); + if (!MO.isReg() || MO.getReg() == 0 || + (MO.getReg() != Reg && !TRI->isSubRegister(Reg, MO.getReg()))) + continue; + if (MO.isUse()) + FoundUse = true; + Done = true; // Stop after scanning all the operands of this MI. + } + } + if (!FoundUse) { + // Def is dead! + DefOp->setIsDead(); + return true; + } + return false; +} + +/// UpdateKills - Track and update kill info. If a MI reads a register that is +/// marked kill, then it must be due to register reuse. Transfer the kill info +/// over. +static void UpdateKills(MachineInstr &MI, const TargetRegisterInfo* TRI, + BitVector &RegKills, + std::vector<MachineOperand*> &KillOps) { + // These do not affect kill info at all. + if (MI.isDebugValue()) + return; + for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) { + MachineOperand &MO = MI.getOperand(i); + if (!MO.isReg() || !MO.isUse() || MO.isUndef()) + continue; + unsigned Reg = MO.getReg(); + if (Reg == 0) + continue; + + if (RegKills[Reg] && KillOps[Reg]->getParent() != &MI) { + // That can't be right. Register is killed but not re-defined and it's + // being reused. Let's fix that. + KillOps[Reg]->setIsKill(false); + // KillOps[Reg] might be a def of a super-register. + unsigned KReg = KillOps[Reg]->getReg(); + KillOps[KReg] = NULL; + RegKills.reset(KReg); + + // Must be a def of a super-register. Its other sub-regsters are no + // longer killed as well. + for (const unsigned *SR = TRI->getSubRegisters(KReg); *SR; ++SR) { + KillOps[*SR] = NULL; + RegKills.reset(*SR); + } + } else { + // Check for subreg kills as well. + // d4 = + // store d4, fi#0 + // ... + // = s8<kill> + // ... + // = d4 <avoiding reload> + for (const unsigned *SR = TRI->getSubRegisters(Reg); *SR; ++SR) { + unsigned SReg = *SR; + if (RegKills[SReg] && KillOps[SReg]->getParent() != &MI) { + KillOps[SReg]->setIsKill(false); + unsigned KReg = KillOps[SReg]->getReg(); + KillOps[KReg] = NULL; + RegKills.reset(KReg); + + for (const unsigned *SSR = TRI->getSubRegisters(KReg); *SSR; ++SSR) { + KillOps[*SSR] = NULL; + RegKills.reset(*SSR); + } + } + } + } + + if (MO.isKill()) { + RegKills.set(Reg); + KillOps[Reg] = &MO; + for (const unsigned *SR = TRI->getSubRegisters(Reg); *SR; ++SR) { + RegKills.set(*SR); + KillOps[*SR] = &MO; + } + } + } + + for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) { + const MachineOperand &MO = MI.getOperand(i); + if (!MO.isReg() || !MO.getReg() || !MO.isDef()) + continue; + unsigned Reg = MO.getReg(); + RegKills.reset(Reg); + KillOps[Reg] = NULL; + // It also defines (or partially define) aliases. + for (const unsigned *SR = TRI->getSubRegisters(Reg); *SR; ++SR) { + RegKills.reset(*SR); + KillOps[*SR] = NULL; + } + for (const unsigned *SR = TRI->getSuperRegisters(Reg); *SR; ++SR) { + RegKills.reset(*SR); + KillOps[*SR] = NULL; + } + } +} + +/// ReMaterialize - Re-materialize definition for Reg targetting DestReg. +/// +static void ReMaterialize(MachineBasicBlock &MBB, + MachineBasicBlock::iterator &MII, + unsigned DestReg, unsigned Reg, + const TargetInstrInfo *TII, + const TargetRegisterInfo *TRI, + VirtRegMap &VRM) { + MachineInstr *ReMatDefMI = VRM.getReMaterializedMI(Reg); +#ifndef NDEBUG + const TargetInstrDesc &TID = ReMatDefMI->getDesc(); + assert(TID.getNumDefs() == 1 && + "Don't know how to remat instructions that define > 1 values!"); +#endif + TII->reMaterialize(MBB, MII, DestReg, 0, ReMatDefMI, *TRI); + MachineInstr *NewMI = prior(MII); + for (unsigned i = 0, e = NewMI->getNumOperands(); i != e; ++i) { + MachineOperand &MO = NewMI->getOperand(i); + if (!MO.isReg() || MO.getReg() == 0) + continue; + unsigned VirtReg = MO.getReg(); + if (TargetRegisterInfo::isPhysicalRegister(VirtReg)) + continue; + assert(MO.isUse()); + unsigned Phys = VRM.getPhys(VirtReg); + assert(Phys && "Virtual register is not assigned a register?"); + substitutePhysReg(MO, Phys, *TRI); + } + ++NumReMats; +} + +/// findSuperReg - Find the SubReg's super-register of given register class +/// where its SubIdx sub-register is SubReg. +static unsigned findSuperReg(const TargetRegisterClass *RC, unsigned SubReg, + unsigned SubIdx, const TargetRegisterInfo *TRI) { + for (TargetRegisterClass::iterator I = RC->begin(), E = RC->end(); + I != E; ++I) { + unsigned Reg = *I; + if (TRI->getSubReg(Reg, SubIdx) == SubReg) + return Reg; + } + return 0; +} + +// ******************************** // +// Available Spills Implementation // +// ******************************** // + +/// disallowClobberPhysRegOnly - Unset the CanClobber bit of the specified +/// stackslot register. The register is still available but is no longer +/// allowed to be modifed. +void AvailableSpills::disallowClobberPhysRegOnly(unsigned PhysReg) { + std::multimap<unsigned, int>::iterator I = + PhysRegsAvailable.lower_bound(PhysReg); + while (I != PhysRegsAvailable.end() && I->first == PhysReg) { + int SlotOrReMat = I->second; + I++; + assert((SpillSlotsOrReMatsAvailable[SlotOrReMat] >> 1) == PhysReg && + "Bidirectional map mismatch!"); + SpillSlotsOrReMatsAvailable[SlotOrReMat] &= ~1; + DEBUG(dbgs() << "PhysReg " << TRI->getName(PhysReg) + << " copied, it is available for use but can no longer be modified\n"); + } +} + +/// disallowClobberPhysReg - Unset the CanClobber bit of the specified +/// stackslot register and its aliases. The register and its aliases may +/// still available but is no longer allowed to be modifed. +void AvailableSpills::disallowClobberPhysReg(unsigned PhysReg) { + for (const unsigned *AS = TRI->getAliasSet(PhysReg); *AS; ++AS) + disallowClobberPhysRegOnly(*AS); + disallowClobberPhysRegOnly(PhysReg); +} + +/// ClobberPhysRegOnly - This is called when the specified physreg changes +/// value. We use this to invalidate any info about stuff we thing lives in it. +void AvailableSpills::ClobberPhysRegOnly(unsigned PhysReg) { + std::multimap<unsigned, int>::iterator I = + PhysRegsAvailable.lower_bound(PhysReg); + while (I != PhysRegsAvailable.end() && I->first == PhysReg) { + int SlotOrReMat = I->second; + PhysRegsAvailable.erase(I++); + assert((SpillSlotsOrReMatsAvailable[SlotOrReMat] >> 1) == PhysReg && + "Bidirectional map mismatch!"); + SpillSlotsOrReMatsAvailable.erase(SlotOrReMat); + DEBUG(dbgs() << "PhysReg " << TRI->getName(PhysReg) + << " clobbered, invalidating "); + if (SlotOrReMat > VirtRegMap::MAX_STACK_SLOT) + DEBUG(dbgs() << "RM#" << SlotOrReMat-VirtRegMap::MAX_STACK_SLOT-1 <<"\n"); + else + DEBUG(dbgs() << "SS#" << SlotOrReMat << "\n"); + } +} + +/// ClobberPhysReg - This is called when the specified physreg changes +/// value. We use this to invalidate any info about stuff we thing lives in +/// it and any of its aliases. +void AvailableSpills::ClobberPhysReg(unsigned PhysReg) { + for (const unsigned *AS = TRI->getAliasSet(PhysReg); *AS; ++AS) + ClobberPhysRegOnly(*AS); + ClobberPhysRegOnly(PhysReg); +} + +/// AddAvailableRegsToLiveIn - Availability information is being kept coming +/// into the specified MBB. Add available physical registers as potential +/// live-in's. If they are reused in the MBB, they will be added to the +/// live-in set to make register scavenger and post-allocation scheduler. +void AvailableSpills::AddAvailableRegsToLiveIn(MachineBasicBlock &MBB, + BitVector &RegKills, + std::vector<MachineOperand*> &KillOps) { + std::set<unsigned> NotAvailable; + for (std::multimap<unsigned, int>::iterator + I = PhysRegsAvailable.begin(), E = PhysRegsAvailable.end(); + I != E; ++I) { + unsigned Reg = I->first; + const TargetRegisterClass* RC = TRI->getMinimalPhysRegClass(Reg); + // FIXME: A temporary workaround. We can't reuse available value if it's + // not safe to move the def of the virtual register's class. e.g. + // X86::RFP* register classes. Do not add it as a live-in. + if (!TII->isSafeToMoveRegClassDefs(RC)) + // This is no longer available. + NotAvailable.insert(Reg); + else { + MBB.addLiveIn(Reg); + InvalidateKill(Reg, TRI, RegKills, KillOps); + } + + // Skip over the same register. + std::multimap<unsigned, int>::iterator NI = llvm::next(I); + while (NI != E && NI->first == Reg) { + ++I; + ++NI; + } + } + + for (std::set<unsigned>::iterator I = NotAvailable.begin(), + E = NotAvailable.end(); I != E; ++I) { + ClobberPhysReg(*I); + for (const unsigned *SubRegs = TRI->getSubRegisters(*I); + *SubRegs; ++SubRegs) + ClobberPhysReg(*SubRegs); + } +} + +/// ModifyStackSlotOrReMat - This method is called when the value in a stack +/// slot changes. This removes information about which register the previous +/// value for this slot lives in (as the previous value is dead now). +void AvailableSpills::ModifyStackSlotOrReMat(int SlotOrReMat) { + std::map<int, unsigned>::iterator It = + SpillSlotsOrReMatsAvailable.find(SlotOrReMat); + if (It == SpillSlotsOrReMatsAvailable.end()) return; + unsigned Reg = It->second >> 1; + SpillSlotsOrReMatsAvailable.erase(It); + + // This register may hold the value of multiple stack slots, only remove this + // stack slot from the set of values the register contains. + std::multimap<unsigned, int>::iterator I = PhysRegsAvailable.lower_bound(Reg); + for (; ; ++I) { + assert(I != PhysRegsAvailable.end() && I->first == Reg && + "Map inverse broken!"); + if (I->second == SlotOrReMat) break; + } + PhysRegsAvailable.erase(I); +} + +// ************************** // +// Reuse Info Implementation // +// ************************** // + +/// GetRegForReload - We are about to emit a reload into PhysReg. If there +/// is some other operand that is using the specified register, either pick +/// a new register to use, or evict the previous reload and use this reg. +unsigned ReuseInfo::GetRegForReload(const TargetRegisterClass *RC, + unsigned PhysReg, + MachineFunction &MF, + MachineInstr *MI, AvailableSpills &Spills, + std::vector<MachineInstr*> &MaybeDeadStores, + SmallSet<unsigned, 8> &Rejected, + BitVector &RegKills, + std::vector<MachineOperand*> &KillOps, + VirtRegMap &VRM) { + const TargetInstrInfo* TII = MF.getTarget().getInstrInfo(); + const TargetRegisterInfo *TRI = Spills.getRegInfo(); + + if (Reuses.empty()) return PhysReg; // This is most often empty. + + for (unsigned ro = 0, e = Reuses.size(); ro != e; ++ro) { + ReusedOp &Op = Reuses[ro]; + // If we find some other reuse that was supposed to use this register + // exactly for its reload, we can change this reload to use ITS reload + // register. That is, unless its reload register has already been + // considered and subsequently rejected because it has also been reused + // by another operand. + if (Op.PhysRegReused == PhysReg && + Rejected.count(Op.AssignedPhysReg) == 0 && + RC->contains(Op.AssignedPhysReg)) { + // Yup, use the reload register that we didn't use before. + unsigned NewReg = Op.AssignedPhysReg; + Rejected.insert(PhysReg); + return GetRegForReload(RC, NewReg, MF, MI, Spills, MaybeDeadStores, Rejected, + RegKills, KillOps, VRM); + } else { + // Otherwise, we might also have a problem if a previously reused + // value aliases the new register. If so, codegen the previous reload + // and use this one. + unsigned PRRU = Op.PhysRegReused; + if (TRI->regsOverlap(PRRU, PhysReg)) { + // Okay, we found out that an alias of a reused register + // was used. This isn't good because it means we have + // to undo a previous reuse. + MachineBasicBlock *MBB = MI->getParent(); + const TargetRegisterClass *AliasRC = + MBB->getParent()->getRegInfo().getRegClass(Op.VirtReg); + + // Copy Op out of the vector and remove it, we're going to insert an + // explicit load for it. + ReusedOp NewOp = Op; + Reuses.erase(Reuses.begin()+ro); + + // MI may be using only a sub-register of PhysRegUsed. + unsigned RealPhysRegUsed = MI->getOperand(NewOp.Operand).getReg(); + unsigned SubIdx = 0; + assert(TargetRegisterInfo::isPhysicalRegister(RealPhysRegUsed) && + "A reuse cannot be a virtual register"); + if (PRRU != RealPhysRegUsed) { + // What was the sub-register index? + SubIdx = TRI->getSubRegIndex(PRRU, RealPhysRegUsed); + assert(SubIdx && + "Operand physreg is not a sub-register of PhysRegUsed"); + } + + // Ok, we're going to try to reload the assigned physreg into the + // slot that we were supposed to in the first place. However, that + // register could hold a reuse. Check to see if it conflicts or + // would prefer us to use a different register. + unsigned NewPhysReg = GetRegForReload(RC, NewOp.AssignedPhysReg, + MF, MI, Spills, MaybeDeadStores, + Rejected, RegKills, KillOps, VRM); + + bool DoReMat = NewOp.StackSlotOrReMat > VirtRegMap::MAX_STACK_SLOT; + int SSorRMId = DoReMat + ? VRM.getReMatId(NewOp.VirtReg) : (int) NewOp.StackSlotOrReMat; + + // Back-schedule reloads and remats. + MachineBasicBlock::iterator InsertLoc = + ComputeReloadLoc(MI, MBB->begin(), PhysReg, TRI, + DoReMat, SSorRMId, TII, MF); + + if (DoReMat) { + ReMaterialize(*MBB, InsertLoc, NewPhysReg, NewOp.VirtReg, TII, + TRI, VRM); + } else { + TII->loadRegFromStackSlot(*MBB, InsertLoc, NewPhysReg, + NewOp.StackSlotOrReMat, AliasRC, TRI); + MachineInstr *LoadMI = prior(InsertLoc); + VRM.addSpillSlotUse(NewOp.StackSlotOrReMat, LoadMI); + // Any stores to this stack slot are not dead anymore. + MaybeDeadStores[NewOp.StackSlotOrReMat] = NULL; + ++NumLoads; + } + Spills.ClobberPhysReg(NewPhysReg); + Spills.ClobberPhysReg(NewOp.PhysRegReused); + + unsigned RReg = SubIdx ? TRI->getSubReg(NewPhysReg, SubIdx) :NewPhysReg; + MI->getOperand(NewOp.Operand).setReg(RReg); + MI->getOperand(NewOp.Operand).setSubReg(0); + + Spills.addAvailable(NewOp.StackSlotOrReMat, NewPhysReg); + UpdateKills(*prior(InsertLoc), TRI, RegKills, KillOps); + DEBUG(dbgs() << '\t' << *prior(InsertLoc)); + + DEBUG(dbgs() << "Reuse undone!\n"); + --NumReused; + + // Finally, PhysReg is now available, go ahead and use it. + return PhysReg; + } + } + } + return PhysReg; +} + +// ************************************************************************ // + +/// FoldsStackSlotModRef - Return true if the specified MI folds the specified +/// stack slot mod/ref. It also checks if it's possible to unfold the +/// instruction by having it define a specified physical register instead. +static bool FoldsStackSlotModRef(MachineInstr &MI, int SS, unsigned PhysReg, + const TargetInstrInfo *TII, + const TargetRegisterInfo *TRI, + VirtRegMap &VRM) { + if (VRM.hasEmergencySpills(&MI) || VRM.isSpillPt(&MI)) + return false; + + bool Found = false; + VirtRegMap::MI2VirtMapTy::const_iterator I, End; + for (tie(I, End) = VRM.getFoldedVirts(&MI); I != End; ++I) { + unsigned VirtReg = I->second.first; + VirtRegMap::ModRef MR = I->second.second; + if (MR & VirtRegMap::isModRef) + if (VRM.getStackSlot(VirtReg) == SS) { + Found= TII->getOpcodeAfterMemoryUnfold(MI.getOpcode(), true, true) != 0; + break; + } + } + if (!Found) + return false; + + // Does the instruction uses a register that overlaps the scratch register? + for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) { + MachineOperand &MO = MI.getOperand(i); + if (!MO.isReg() || MO.getReg() == 0) + continue; + unsigned Reg = MO.getReg(); + if (TargetRegisterInfo::isVirtualRegister(Reg)) { + if (!VRM.hasPhys(Reg)) + continue; + Reg = VRM.getPhys(Reg); + } + if (TRI->regsOverlap(PhysReg, Reg)) + return false; + } + return true; +} + +/// FindFreeRegister - Find a free register of a given register class by looking +/// at (at most) the last two machine instructions. +static unsigned FindFreeRegister(MachineBasicBlock::iterator MII, + MachineBasicBlock &MBB, + const TargetRegisterClass *RC, + const TargetRegisterInfo *TRI, + BitVector &AllocatableRegs) { + BitVector Defs(TRI->getNumRegs()); + BitVector Uses(TRI->getNumRegs()); + SmallVector<unsigned, 4> LocalUses; + SmallVector<unsigned, 4> Kills; + + // Take a look at 2 instructions at most. + unsigned Count = 0; + while (Count < 2) { + if (MII == MBB.begin()) + break; + MachineInstr *PrevMI = prior(MII); + MII = PrevMI; + + if (PrevMI->isDebugValue()) + continue; // Skip over dbg_value instructions. + ++Count; + + for (unsigned i = 0, e = PrevMI->getNumOperands(); i != e; ++i) { + MachineOperand &MO = PrevMI->getOperand(i); + if (!MO.isReg() || MO.getReg() == 0) + continue; + unsigned Reg = MO.getReg(); + if (MO.isDef()) { + Defs.set(Reg); + for (const unsigned *AS = TRI->getAliasSet(Reg); *AS; ++AS) + Defs.set(*AS); + } else { + LocalUses.push_back(Reg); + if (MO.isKill() && AllocatableRegs[Reg]) + Kills.push_back(Reg); + } + } + + for (unsigned i = 0, e = Kills.size(); i != e; ++i) { + unsigned Kill = Kills[i]; + if (!Defs[Kill] && !Uses[Kill] && + RC->contains(Kill)) + return Kill; + } + for (unsigned i = 0, e = LocalUses.size(); i != e; ++i) { + unsigned Reg = LocalUses[i]; + Uses.set(Reg); + for (const unsigned *AS = TRI->getAliasSet(Reg); *AS; ++AS) + Uses.set(*AS); + } + } + + return 0; +} + +static +void AssignPhysToVirtReg(MachineInstr *MI, unsigned VirtReg, unsigned PhysReg, + const TargetRegisterInfo &TRI) { + for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) { + MachineOperand &MO = MI->getOperand(i); + if (MO.isReg() && MO.getReg() == VirtReg) + substitutePhysReg(MO, PhysReg, TRI); + } +} + +namespace { + +struct RefSorter { + bool operator()(const std::pair<MachineInstr*, int> &A, + const std::pair<MachineInstr*, int> &B) { + return A.second < B.second; + } +}; + +// ***************************** // +// Local Spiller Implementation // +// ***************************** // + +class LocalRewriter : public VirtRegRewriter { + MachineRegisterInfo *MRI; + const TargetRegisterInfo *TRI; + const TargetInstrInfo *TII; + VirtRegMap *VRM; + BitVector AllocatableRegs; + DenseMap<MachineInstr*, unsigned> DistanceMap; + DenseMap<int, SmallVector<MachineInstr*,4> > Slot2DbgValues; + + MachineBasicBlock *MBB; // Basic block currently being processed. + +public: + + bool runOnMachineFunction(MachineFunction &MF, VirtRegMap &VRM, + LiveIntervals* LIs); + +private: + + bool OptimizeByUnfold2(unsigned VirtReg, int SS, + MachineBasicBlock::iterator &MII, + std::vector<MachineInstr*> &MaybeDeadStores, + AvailableSpills &Spills, + BitVector &RegKills, + std::vector<MachineOperand*> &KillOps); + + bool OptimizeByUnfold(MachineBasicBlock::iterator &MII, + std::vector<MachineInstr*> &MaybeDeadStores, + AvailableSpills &Spills, + BitVector &RegKills, + std::vector<MachineOperand*> &KillOps); + + bool CommuteToFoldReload(MachineBasicBlock::iterator &MII, + unsigned VirtReg, unsigned SrcReg, int SS, + AvailableSpills &Spills, + BitVector &RegKills, + std::vector<MachineOperand*> &KillOps, + const TargetRegisterInfo *TRI); + + void SpillRegToStackSlot(MachineBasicBlock::iterator &MII, + int Idx, unsigned PhysReg, int StackSlot, + const TargetRegisterClass *RC, + bool isAvailable, MachineInstr *&LastStore, + AvailableSpills &Spills, + SmallSet<MachineInstr*, 4> &ReMatDefs, + BitVector &RegKills, + std::vector<MachineOperand*> &KillOps); + + void TransferDeadness(unsigned Reg, BitVector &RegKills, + std::vector<MachineOperand*> &KillOps); + + bool InsertEmergencySpills(MachineInstr *MI); + + bool InsertRestores(MachineInstr *MI, + AvailableSpills &Spills, + BitVector &RegKills, + std::vector<MachineOperand*> &KillOps); + + bool InsertSpills(MachineInstr *MI); + + void RewriteMBB(LiveIntervals *LIs, + AvailableSpills &Spills, BitVector &RegKills, + std::vector<MachineOperand*> &KillOps); +}; +} + +bool LocalRewriter::runOnMachineFunction(MachineFunction &MF, VirtRegMap &vrm, + LiveIntervals* LIs) { + MRI = &MF.getRegInfo(); + TRI = MF.getTarget().getRegisterInfo(); + TII = MF.getTarget().getInstrInfo(); + VRM = &vrm; + AllocatableRegs = TRI->getAllocatableSet(MF); + DEBUG(dbgs() << "\n**** Local spiller rewriting function '" + << MF.getFunction()->getName() << "':\n"); + DEBUG(dbgs() << "**** Machine Instrs (NOTE! Does not include spills and" + " reloads!) ****\n"); + DEBUG(MF.dump()); + + // Spills - Keep track of which spilled values are available in physregs + // so that we can choose to reuse the physregs instead of emitting + // reloads. This is usually refreshed per basic block. + AvailableSpills Spills(TRI, TII); + + // Keep track of kill information. + BitVector RegKills(TRI->getNumRegs()); + std::vector<MachineOperand*> KillOps; + KillOps.resize(TRI->getNumRegs(), NULL); + + // SingleEntrySuccs - Successor blocks which have a single predecessor. + SmallVector<MachineBasicBlock*, 4> SinglePredSuccs; + SmallPtrSet<MachineBasicBlock*,16> EarlyVisited; + + // Traverse the basic blocks depth first. + MachineBasicBlock *Entry = MF.begin(); + SmallPtrSet<MachineBasicBlock*,16> Visited; + for (df_ext_iterator<MachineBasicBlock*, + SmallPtrSet<MachineBasicBlock*,16> > + DFI = df_ext_begin(Entry, Visited), E = df_ext_end(Entry, Visited); + DFI != E; ++DFI) { + MBB = *DFI; + if (!EarlyVisited.count(MBB)) + RewriteMBB(LIs, Spills, RegKills, KillOps); + + // If this MBB is the only predecessor of a successor. Keep the + // availability information and visit it next. + do { + // Keep visiting single predecessor successor as long as possible. + SinglePredSuccs.clear(); + findSinglePredSuccessor(MBB, SinglePredSuccs); + if (SinglePredSuccs.empty()) + MBB = 0; + else { + // FIXME: More than one successors, each of which has MBB has + // the only predecessor. + MBB = SinglePredSuccs[0]; + if (!Visited.count(MBB) && EarlyVisited.insert(MBB)) { + Spills.AddAvailableRegsToLiveIn(*MBB, RegKills, KillOps); + RewriteMBB(LIs, Spills, RegKills, KillOps); + } + } + } while (MBB); + + // Clear the availability info. + Spills.clear(); + } + + DEBUG(dbgs() << "**** Post Machine Instrs ****\n"); + DEBUG(MF.dump()); + + // Mark unused spill slots. + MachineFrameInfo *MFI = MF.getFrameInfo(); + int SS = VRM->getLowSpillSlot(); + if (SS != VirtRegMap::NO_STACK_SLOT) { + for (int e = VRM->getHighSpillSlot(); SS <= e; ++SS) { + SmallVector<MachineInstr*, 4> &DbgValues = Slot2DbgValues[SS]; + if (!VRM->isSpillSlotUsed(SS)) { + MFI->RemoveStackObject(SS); + for (unsigned j = 0, ee = DbgValues.size(); j != ee; ++j) { + MachineInstr *DVMI = DbgValues[j]; + MachineBasicBlock *DVMBB = DVMI->getParent(); + DEBUG(dbgs() << "Removing debug info referencing FI#" << SS << '\n'); + VRM->RemoveMachineInstrFromMaps(DVMI); + DVMBB->erase(DVMI); + } + ++NumDSS; + } + DbgValues.clear(); + } + } + Slot2DbgValues.clear(); + + return true; +} + +/// OptimizeByUnfold2 - Unfold a series of load / store folding instructions if +/// a scratch register is available. +/// xorq %r12<kill>, %r13 +/// addq %rax, -184(%rbp) +/// addq %r13, -184(%rbp) +/// ==> +/// xorq %r12<kill>, %r13 +/// movq -184(%rbp), %r12 +/// addq %rax, %r12 +/// addq %r13, %r12 +/// movq %r12, -184(%rbp) +bool LocalRewriter:: +OptimizeByUnfold2(unsigned VirtReg, int SS, + MachineBasicBlock::iterator &MII, + std::vector<MachineInstr*> &MaybeDeadStores, + AvailableSpills &Spills, + BitVector &RegKills, + std::vector<MachineOperand*> &KillOps) { + + MachineBasicBlock::iterator NextMII = llvm::next(MII); + // Skip over dbg_value instructions. + while (NextMII != MBB->end() && NextMII->isDebugValue()) + NextMII = llvm::next(NextMII); + if (NextMII == MBB->end()) + return false; + + if (TII->getOpcodeAfterMemoryUnfold(MII->getOpcode(), true, true) == 0) + return false; + + // Now let's see if the last couple of instructions happens to have freed up + // a register. + const TargetRegisterClass* RC = MRI->getRegClass(VirtReg); + unsigned PhysReg = FindFreeRegister(MII, *MBB, RC, TRI, AllocatableRegs); + if (!PhysReg) + return false; + + MachineFunction &MF = *MBB->getParent(); + TRI = MF.getTarget().getRegisterInfo(); + MachineInstr &MI = *MII; + if (!FoldsStackSlotModRef(MI, SS, PhysReg, TII, TRI, *VRM)) + return false; + + // If the next instruction also folds the same SS modref and can be unfoled, + // then it's worthwhile to issue a load from SS into the free register and + // then unfold these instructions. + if (!FoldsStackSlotModRef(*NextMII, SS, PhysReg, TII, TRI, *VRM)) + return false; + + // Back-schedule reloads and remats. + ComputeReloadLoc(MII, MBB->begin(), PhysReg, TRI, false, SS, TII, MF); + + // Load from SS to the spare physical register. + TII->loadRegFromStackSlot(*MBB, MII, PhysReg, SS, RC, TRI); + // This invalidates Phys. + Spills.ClobberPhysReg(PhysReg); + // Remember it's available. + Spills.addAvailable(SS, PhysReg); + MaybeDeadStores[SS] = NULL; + + // Unfold current MI. + SmallVector<MachineInstr*, 4> NewMIs; + if (!TII->unfoldMemoryOperand(MF, &MI, VirtReg, false, false, NewMIs)) + llvm_unreachable("Unable unfold the load / store folding instruction!"); + assert(NewMIs.size() == 1); + AssignPhysToVirtReg(NewMIs[0], VirtReg, PhysReg, *TRI); + VRM->transferRestorePts(&MI, NewMIs[0]); + MII = MBB->insert(MII, NewMIs[0]); + InvalidateKills(MI, TRI, RegKills, KillOps); + VRM->RemoveMachineInstrFromMaps(&MI); + MBB->erase(&MI); + ++NumModRefUnfold; + + // Unfold next instructions that fold the same SS. + do { + MachineInstr &NextMI = *NextMII; + NextMII = llvm::next(NextMII); + NewMIs.clear(); + if (!TII->unfoldMemoryOperand(MF, &NextMI, VirtReg, false, false, NewMIs)) + llvm_unreachable("Unable unfold the load / store folding instruction!"); + assert(NewMIs.size() == 1); + AssignPhysToVirtReg(NewMIs[0], VirtReg, PhysReg, *TRI); + VRM->transferRestorePts(&NextMI, NewMIs[0]); + MBB->insert(NextMII, NewMIs[0]); + InvalidateKills(NextMI, TRI, RegKills, KillOps); + VRM->RemoveMachineInstrFromMaps(&NextMI); + MBB->erase(&NextMI); + ++NumModRefUnfold; + // Skip over dbg_value instructions. + while (NextMII != MBB->end() && NextMII->isDebugValue()) + NextMII = llvm::next(NextMII); + if (NextMII == MBB->end()) + break; + } while (FoldsStackSlotModRef(*NextMII, SS, PhysReg, TII, TRI, *VRM)); + + // Store the value back into SS. + TII->storeRegToStackSlot(*MBB, NextMII, PhysReg, true, SS, RC, TRI); + MachineInstr *StoreMI = prior(NextMII); + VRM->addSpillSlotUse(SS, StoreMI); + VRM->virtFolded(VirtReg, StoreMI, VirtRegMap::isMod); + + return true; +} + +/// OptimizeByUnfold - Turn a store folding instruction into a load folding +/// instruction. e.g. +/// xorl %edi, %eax +/// movl %eax, -32(%ebp) +/// movl -36(%ebp), %eax +/// orl %eax, -32(%ebp) +/// ==> +/// xorl %edi, %eax +/// orl -36(%ebp), %eax +/// mov %eax, -32(%ebp) +/// This enables unfolding optimization for a subsequent instruction which will +/// also eliminate the newly introduced store instruction. +bool LocalRewriter:: +OptimizeByUnfold(MachineBasicBlock::iterator &MII, + std::vector<MachineInstr*> &MaybeDeadStores, + AvailableSpills &Spills, + BitVector &RegKills, + std::vector<MachineOperand*> &KillOps) { + MachineFunction &MF = *MBB->getParent(); + MachineInstr &MI = *MII; + unsigned UnfoldedOpc = 0; + unsigned UnfoldPR = 0; + unsigned UnfoldVR = 0; + int FoldedSS = VirtRegMap::NO_STACK_SLOT; + VirtRegMap::MI2VirtMapTy::const_iterator I, End; + for (tie(I, End) = VRM->getFoldedVirts(&MI); I != End; ) { + // Only transform a MI that folds a single register. + if (UnfoldedOpc) + return false; + UnfoldVR = I->second.first; + VirtRegMap::ModRef MR = I->second.second; + // MI2VirtMap be can updated which invalidate the iterator. + // Increment the iterator first. + ++I; + if (VRM->isAssignedReg(UnfoldVR)) + continue; + // If this reference is not a use, any previous store is now dead. + // Otherwise, the store to this stack slot is not dead anymore. + FoldedSS = VRM->getStackSlot(UnfoldVR); + MachineInstr* DeadStore = MaybeDeadStores[FoldedSS]; + if (DeadStore && (MR & VirtRegMap::isModRef)) { + unsigned PhysReg = Spills.getSpillSlotOrReMatPhysReg(FoldedSS); + if (!PhysReg || !DeadStore->readsRegister(PhysReg)) + continue; + UnfoldPR = PhysReg; + UnfoldedOpc = TII->getOpcodeAfterMemoryUnfold(MI.getOpcode(), + false, true); + } + } + + if (!UnfoldedOpc) { + if (!UnfoldVR) + return false; + + // Look for other unfolding opportunities. + return OptimizeByUnfold2(UnfoldVR, FoldedSS, MII, MaybeDeadStores, Spills, + RegKills, KillOps); + } + + for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) { + MachineOperand &MO = MI.getOperand(i); + if (!MO.isReg() || MO.getReg() == 0 || !MO.isUse()) + continue; + unsigned VirtReg = MO.getReg(); + if (TargetRegisterInfo::isPhysicalRegister(VirtReg) || MO.getSubReg()) + continue; + if (VRM->isAssignedReg(VirtReg)) { + unsigned PhysReg = VRM->getPhys(VirtReg); + if (PhysReg && TRI->regsOverlap(PhysReg, UnfoldPR)) + return false; + } else if (VRM->isReMaterialized(VirtReg)) + continue; + int SS = VRM->getStackSlot(VirtReg); + unsigned PhysReg = Spills.getSpillSlotOrReMatPhysReg(SS); + if (PhysReg) { + if (TRI->regsOverlap(PhysReg, UnfoldPR)) + return false; + continue; + } + if (VRM->hasPhys(VirtReg)) { + PhysReg = VRM->getPhys(VirtReg); + if (!TRI->regsOverlap(PhysReg, UnfoldPR)) + continue; + } + + // Ok, we'll need to reload the value into a register which makes + // it impossible to perform the store unfolding optimization later. + // Let's see if it is possible to fold the load if the store is + // unfolded. This allows us to perform the store unfolding + // optimization. + SmallVector<MachineInstr*, 4> NewMIs; + if (TII->unfoldMemoryOperand(MF, &MI, UnfoldVR, false, false, NewMIs)) { + assert(NewMIs.size() == 1); + MachineInstr *NewMI = NewMIs.back(); + MBB->insert(MII, NewMI); + NewMIs.clear(); + int Idx = NewMI->findRegisterUseOperandIdx(VirtReg, false); + assert(Idx != -1); + SmallVector<unsigned, 1> Ops; + Ops.push_back(Idx); + MachineInstr *FoldedMI = TII->foldMemoryOperand(NewMI, Ops, SS); + NewMI->eraseFromParent(); + if (FoldedMI) { + VRM->addSpillSlotUse(SS, FoldedMI); + if (!VRM->hasPhys(UnfoldVR)) + VRM->assignVirt2Phys(UnfoldVR, UnfoldPR); + VRM->virtFolded(VirtReg, FoldedMI, VirtRegMap::isRef); + MII = FoldedMI; + InvalidateKills(MI, TRI, RegKills, KillOps); + VRM->RemoveMachineInstrFromMaps(&MI); + MBB->erase(&MI); + return true; + } + } + } + + return false; +} + +/// CommuteChangesDestination - We are looking for r0 = op r1, r2 and +/// where SrcReg is r1 and it is tied to r0. Return true if after +/// commuting this instruction it will be r0 = op r2, r1. +static bool CommuteChangesDestination(MachineInstr *DefMI, + const TargetInstrDesc &TID, + unsigned SrcReg, + const TargetInstrInfo *TII, + unsigned &DstIdx) { + if (TID.getNumDefs() != 1 && TID.getNumOperands() != 3) + return false; + if (!DefMI->getOperand(1).isReg() || + DefMI->getOperand(1).getReg() != SrcReg) + return false; + unsigned DefIdx; + if (!DefMI->isRegTiedToDefOperand(1, &DefIdx) || DefIdx != 0) + return false; + unsigned SrcIdx1, SrcIdx2; + if (!TII->findCommutedOpIndices(DefMI, SrcIdx1, SrcIdx2)) + return false; + if (SrcIdx1 == 1 && SrcIdx2 == 2) { + DstIdx = 2; + return true; + } + return false; +} + +/// CommuteToFoldReload - +/// Look for +/// r1 = load fi#1 +/// r1 = op r1, r2<kill> +/// store r1, fi#1 +/// +/// If op is commutable and r2 is killed, then we can xform these to +/// r2 = op r2, fi#1 +/// store r2, fi#1 +bool LocalRewriter:: +CommuteToFoldReload(MachineBasicBlock::iterator &MII, + unsigned VirtReg, unsigned SrcReg, int SS, + AvailableSpills &Spills, + BitVector &RegKills, + std::vector<MachineOperand*> &KillOps, + const TargetRegisterInfo *TRI) { + if (MII == MBB->begin() || !MII->killsRegister(SrcReg)) + return false; + + MachineInstr &MI = *MII; + MachineBasicBlock::iterator DefMII = prior(MII); + MachineInstr *DefMI = DefMII; + const TargetInstrDesc &TID = DefMI->getDesc(); + unsigned NewDstIdx; + if (DefMII != MBB->begin() && + TID.isCommutable() && + CommuteChangesDestination(DefMI, TID, SrcReg, TII, NewDstIdx)) { + MachineOperand &NewDstMO = DefMI->getOperand(NewDstIdx); + unsigned NewReg = NewDstMO.getReg(); + if (!NewDstMO.isKill() || TRI->regsOverlap(NewReg, SrcReg)) + return false; + MachineInstr *ReloadMI = prior(DefMII); + int FrameIdx; + unsigned DestReg = TII->isLoadFromStackSlot(ReloadMI, FrameIdx); + if (DestReg != SrcReg || FrameIdx != SS) + return false; + int UseIdx = DefMI->findRegisterUseOperandIdx(DestReg, false); + if (UseIdx == -1) + return false; + unsigned DefIdx; + if (!MI.isRegTiedToDefOperand(UseIdx, &DefIdx)) + return false; + assert(DefMI->getOperand(DefIdx).isReg() && + DefMI->getOperand(DefIdx).getReg() == SrcReg); + + // Now commute def instruction. + MachineInstr *CommutedMI = TII->commuteInstruction(DefMI, true); + if (!CommutedMI) + return false; + MBB->insert(MII, CommutedMI); + SmallVector<unsigned, 1> Ops; + Ops.push_back(NewDstIdx); + MachineInstr *FoldedMI = TII->foldMemoryOperand(CommutedMI, Ops, SS); + // Not needed since foldMemoryOperand returns new MI. + CommutedMI->eraseFromParent(); + if (!FoldedMI) + return false; + + VRM->addSpillSlotUse(SS, FoldedMI); + VRM->virtFolded(VirtReg, FoldedMI, VirtRegMap::isRef); + // Insert new def MI and spill MI. + const TargetRegisterClass* RC = MRI->getRegClass(VirtReg); + TII->storeRegToStackSlot(*MBB, &MI, NewReg, true, SS, RC, TRI); + MII = prior(MII); + MachineInstr *StoreMI = MII; + VRM->addSpillSlotUse(SS, StoreMI); + VRM->virtFolded(VirtReg, StoreMI, VirtRegMap::isMod); + MII = FoldedMI; // Update MII to backtrack. + + // Delete all 3 old instructions. + InvalidateKills(*ReloadMI, TRI, RegKills, KillOps); + VRM->RemoveMachineInstrFromMaps(ReloadMI); + MBB->erase(ReloadMI); + InvalidateKills(*DefMI, TRI, RegKills, KillOps); + VRM->RemoveMachineInstrFromMaps(DefMI); + MBB->erase(DefMI); + InvalidateKills(MI, TRI, RegKills, KillOps); + VRM->RemoveMachineInstrFromMaps(&MI); + MBB->erase(&MI); + + // If NewReg was previously holding value of some SS, it's now clobbered. + // This has to be done now because it's a physical register. When this + // instruction is re-visited, it's ignored. + Spills.ClobberPhysReg(NewReg); + + ++NumCommutes; + return true; + } + + return false; +} + +/// SpillRegToStackSlot - Spill a register to a specified stack slot. Check if +/// the last store to the same slot is now dead. If so, remove the last store. +void LocalRewriter:: +SpillRegToStackSlot(MachineBasicBlock::iterator &MII, + int Idx, unsigned PhysReg, int StackSlot, + const TargetRegisterClass *RC, + bool isAvailable, MachineInstr *&LastStore, + AvailableSpills &Spills, + SmallSet<MachineInstr*, 4> &ReMatDefs, + BitVector &RegKills, + std::vector<MachineOperand*> &KillOps) { + + MachineBasicBlock::iterator oldNextMII = llvm::next(MII); + TII->storeRegToStackSlot(*MBB, llvm::next(MII), PhysReg, true, StackSlot, RC, + TRI); + MachineInstr *StoreMI = prior(oldNextMII); + VRM->addSpillSlotUse(StackSlot, StoreMI); + DEBUG(dbgs() << "Store:\t" << *StoreMI); + + // If there is a dead store to this stack slot, nuke it now. + if (LastStore) { + DEBUG(dbgs() << "Removed dead store:\t" << *LastStore); + ++NumDSE; + SmallVector<unsigned, 2> KillRegs; + InvalidateKills(*LastStore, TRI, RegKills, KillOps, &KillRegs); + MachineBasicBlock::iterator PrevMII = LastStore; + bool CheckDef = PrevMII != MBB->begin(); + if (CheckDef) + --PrevMII; + VRM->RemoveMachineInstrFromMaps(LastStore); + MBB->erase(LastStore); + if (CheckDef) { + // Look at defs of killed registers on the store. Mark the defs + // as dead since the store has been deleted and they aren't + // being reused. + for (unsigned j = 0, ee = KillRegs.size(); j != ee; ++j) { + bool HasOtherDef = false; + if (InvalidateRegDef(PrevMII, *MII, KillRegs[j], HasOtherDef, TRI)) { + MachineInstr *DeadDef = PrevMII; + if (ReMatDefs.count(DeadDef) && !HasOtherDef) { + // FIXME: This assumes a remat def does not have side effects. + VRM->RemoveMachineInstrFromMaps(DeadDef); + MBB->erase(DeadDef); + ++NumDRM; + } + } + } + } + } + + // Allow for multi-instruction spill sequences, as on PPC Altivec. Presume + // the last of multiple instructions is the actual store. + LastStore = prior(oldNextMII); + + // If the stack slot value was previously available in some other + // register, change it now. Otherwise, make the register available, + // in PhysReg. + Spills.ModifyStackSlotOrReMat(StackSlot); + Spills.ClobberPhysReg(PhysReg); + Spills.addAvailable(StackSlot, PhysReg, isAvailable); + ++NumStores; +} + +/// isSafeToDelete - Return true if this instruction doesn't produce any side +/// effect and all of its defs are dead. +static bool isSafeToDelete(MachineInstr &MI) { + const TargetInstrDesc &TID = MI.getDesc(); + if (TID.mayLoad() || TID.mayStore() || TID.isCall() || TID.isTerminator() || + TID.isCall() || TID.isBarrier() || TID.isReturn() || + TID.hasUnmodeledSideEffects()) + return false; + for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) { + MachineOperand &MO = MI.getOperand(i); + if (!MO.isReg() || !MO.getReg()) + continue; + if (MO.isDef() && !MO.isDead()) + return false; + if (MO.isUse() && MO.isKill()) + // FIXME: We can't remove kill markers or else the scavenger will assert. + // An alternative is to add a ADD pseudo instruction to replace kill + // markers. + return false; + } + return true; +} + +/// TransferDeadness - A identity copy definition is dead and it's being +/// removed. Find the last def or use and mark it as dead / kill. +void LocalRewriter:: +TransferDeadness(unsigned Reg, BitVector &RegKills, + std::vector<MachineOperand*> &KillOps) { + SmallPtrSet<MachineInstr*, 4> Seens; + SmallVector<std::pair<MachineInstr*, int>,8> Refs; + for (MachineRegisterInfo::reg_iterator RI = MRI->reg_begin(Reg), + RE = MRI->reg_end(); RI != RE; ++RI) { + MachineInstr *UDMI = &*RI; + if (UDMI->isDebugValue() || UDMI->getParent() != MBB) + continue; + DenseMap<MachineInstr*, unsigned>::iterator DI = DistanceMap.find(UDMI); + if (DI == DistanceMap.end()) + continue; + if (Seens.insert(UDMI)) + Refs.push_back(std::make_pair(UDMI, DI->second)); + } + + if (Refs.empty()) + return; + std::sort(Refs.begin(), Refs.end(), RefSorter()); + + while (!Refs.empty()) { + MachineInstr *LastUDMI = Refs.back().first; + Refs.pop_back(); + + MachineOperand *LastUD = NULL; + for (unsigned i = 0, e = LastUDMI->getNumOperands(); i != e; ++i) { + MachineOperand &MO = LastUDMI->getOperand(i); + if (!MO.isReg() || MO.getReg() != Reg) + continue; + if (!LastUD || (LastUD->isUse() && MO.isDef())) + LastUD = &MO; + if (LastUDMI->isRegTiedToDefOperand(i)) + break; + } + if (LastUD->isDef()) { + // If the instruction has no side effect, delete it and propagate + // backward further. Otherwise, mark is dead and we are done. + if (!isSafeToDelete(*LastUDMI)) { + LastUD->setIsDead(); + break; + } + VRM->RemoveMachineInstrFromMaps(LastUDMI); + MBB->erase(LastUDMI); + } else { + LastUD->setIsKill(); + RegKills.set(Reg); + KillOps[Reg] = LastUD; + break; + } + } +} + +/// InsertEmergencySpills - Insert emergency spills before MI if requested by +/// VRM. Return true if spills were inserted. +bool LocalRewriter::InsertEmergencySpills(MachineInstr *MI) { + if (!VRM->hasEmergencySpills(MI)) + return false; + MachineBasicBlock::iterator MII = MI; + SmallSet<int, 4> UsedSS; + std::vector<unsigned> &EmSpills = VRM->getEmergencySpills(MI); + for (unsigned i = 0, e = EmSpills.size(); i != e; ++i) { + unsigned PhysReg = EmSpills[i]; + const TargetRegisterClass *RC = TRI->getMinimalPhysRegClass(PhysReg); + assert(RC && "Unable to determine register class!"); + int SS = VRM->getEmergencySpillSlot(RC); + if (UsedSS.count(SS)) + llvm_unreachable("Need to spill more than one physical registers!"); + UsedSS.insert(SS); + TII->storeRegToStackSlot(*MBB, MII, PhysReg, true, SS, RC, TRI); + MachineInstr *StoreMI = prior(MII); + VRM->addSpillSlotUse(SS, StoreMI); + + // Back-schedule reloads and remats. + MachineBasicBlock::iterator InsertLoc = + ComputeReloadLoc(llvm::next(MII), MBB->begin(), PhysReg, TRI, false, SS, + TII, *MBB->getParent()); + + TII->loadRegFromStackSlot(*MBB, InsertLoc, PhysReg, SS, RC, TRI); + + MachineInstr *LoadMI = prior(InsertLoc); + VRM->addSpillSlotUse(SS, LoadMI); + ++NumPSpills; + DistanceMap.insert(std::make_pair(LoadMI, DistanceMap.size())); + } + return true; +} + +/// InsertRestores - Restore registers before MI is requested by VRM. Return +/// true is any instructions were inserted. +bool LocalRewriter::InsertRestores(MachineInstr *MI, + AvailableSpills &Spills, + BitVector &RegKills, + std::vector<MachineOperand*> &KillOps) { + if (!VRM->isRestorePt(MI)) + return false; + MachineBasicBlock::iterator MII = MI; + std::vector<unsigned> &RestoreRegs = VRM->getRestorePtRestores(MI); + for (unsigned i = 0, e = RestoreRegs.size(); i != e; ++i) { + unsigned VirtReg = RestoreRegs[e-i-1]; // Reverse order. + if (!VRM->getPreSplitReg(VirtReg)) + continue; // Split interval spilled again. + unsigned Phys = VRM->getPhys(VirtReg); + MRI->setPhysRegUsed(Phys); + + // Check if the value being restored if available. If so, it must be + // from a predecessor BB that fallthrough into this BB. We do not + // expect: + // BB1: + // r1 = load fi#1 + // ... + // = r1<kill> + // ... # r1 not clobbered + // ... + // = load fi#1 + bool DoReMat = VRM->isReMaterialized(VirtReg); + int SSorRMId = DoReMat + ? VRM->getReMatId(VirtReg) : VRM->getStackSlot(VirtReg); + unsigned InReg = Spills.getSpillSlotOrReMatPhysReg(SSorRMId); + if (InReg == Phys) { + // If the value is already available in the expected register, save + // a reload / remat. + if (SSorRMId) + DEBUG(dbgs() << "Reusing RM#" + << SSorRMId-VirtRegMap::MAX_STACK_SLOT-1); + else + DEBUG(dbgs() << "Reusing SS#" << SSorRMId); + DEBUG(dbgs() << " from physreg " + << TRI->getName(InReg) << " for vreg" + << VirtReg <<" instead of reloading into physreg " + << TRI->getName(Phys) << '\n'); + ++NumOmitted; + continue; + } else if (InReg && InReg != Phys) { + if (SSorRMId) + DEBUG(dbgs() << "Reusing RM#" + << SSorRMId-VirtRegMap::MAX_STACK_SLOT-1); + else + DEBUG(dbgs() << "Reusing SS#" << SSorRMId); + DEBUG(dbgs() << " from physreg " + << TRI->getName(InReg) << " for vreg" + << VirtReg <<" by copying it into physreg " + << TRI->getName(Phys) << '\n'); + + // If the reloaded / remat value is available in another register, + // copy it to the desired register. + + // Back-schedule reloads and remats. + MachineBasicBlock::iterator InsertLoc = + ComputeReloadLoc(MII, MBB->begin(), Phys, TRI, DoReMat, SSorRMId, TII, + *MBB->getParent()); + MachineInstr *CopyMI = BuildMI(*MBB, InsertLoc, MI->getDebugLoc(), + TII->get(TargetOpcode::COPY), Phys) + .addReg(InReg, RegState::Kill); + + // This invalidates Phys. + Spills.ClobberPhysReg(Phys); + // Remember it's available. + Spills.addAvailable(SSorRMId, Phys); + + CopyMI->setAsmPrinterFlag(MachineInstr::ReloadReuse); + UpdateKills(*CopyMI, TRI, RegKills, KillOps); + + DEBUG(dbgs() << '\t' << *CopyMI); + ++NumCopified; + continue; + } + + // Back-schedule reloads and remats. + MachineBasicBlock::iterator InsertLoc = + ComputeReloadLoc(MII, MBB->begin(), Phys, TRI, DoReMat, SSorRMId, TII, + *MBB->getParent()); + + if (VRM->isReMaterialized(VirtReg)) { + ReMaterialize(*MBB, InsertLoc, Phys, VirtReg, TII, TRI, *VRM); + } else { + const TargetRegisterClass* RC = MRI->getRegClass(VirtReg); + TII->loadRegFromStackSlot(*MBB, InsertLoc, Phys, SSorRMId, RC, TRI); + MachineInstr *LoadMI = prior(InsertLoc); + VRM->addSpillSlotUse(SSorRMId, LoadMI); + ++NumLoads; + DistanceMap.insert(std::make_pair(LoadMI, DistanceMap.size())); + } + + // This invalidates Phys. + Spills.ClobberPhysReg(Phys); + // Remember it's available. + Spills.addAvailable(SSorRMId, Phys); + + UpdateKills(*prior(InsertLoc), TRI, RegKills, KillOps); + DEBUG(dbgs() << '\t' << *prior(MII)); + } + return true; +} + +/// InsertEmergencySpills - Insert spills after MI if requested by VRM. Return +/// true if spills were inserted. +bool LocalRewriter::InsertSpills(MachineInstr *MI) { + if (!VRM->isSpillPt(MI)) + return false; + MachineBasicBlock::iterator MII = MI; + std::vector<std::pair<unsigned,bool> > &SpillRegs = + VRM->getSpillPtSpills(MI); + for (unsigned i = 0, e = SpillRegs.size(); i != e; ++i) { + unsigned VirtReg = SpillRegs[i].first; + bool isKill = SpillRegs[i].second; + if (!VRM->getPreSplitReg(VirtReg)) + continue; // Split interval spilled again. + const TargetRegisterClass *RC = MRI->getRegClass(VirtReg); + unsigned Phys = VRM->getPhys(VirtReg); + int StackSlot = VRM->getStackSlot(VirtReg); + MachineBasicBlock::iterator oldNextMII = llvm::next(MII); + TII->storeRegToStackSlot(*MBB, llvm::next(MII), Phys, isKill, StackSlot, + RC, TRI); + MachineInstr *StoreMI = prior(oldNextMII); + VRM->addSpillSlotUse(StackSlot, StoreMI); + DEBUG(dbgs() << "Store:\t" << *StoreMI); + VRM->virtFolded(VirtReg, StoreMI, VirtRegMap::isMod); + } + return true; +} + + +/// rewriteMBB - Keep track of which spills are available even after the +/// register allocator is done with them. If possible, avid reloading vregs. +void +LocalRewriter::RewriteMBB(LiveIntervals *LIs, + AvailableSpills &Spills, BitVector &RegKills, + std::vector<MachineOperand*> &KillOps) { + + DEBUG(dbgs() << "\n**** Local spiller rewriting MBB '" + << MBB->getName() << "':\n"); + + MachineFunction &MF = *MBB->getParent(); + + // MaybeDeadStores - When we need to write a value back into a stack slot, + // keep track of the inserted store. If the stack slot value is never read + // (because the value was used from some available register, for example), and + // subsequently stored to, the original store is dead. This map keeps track + // of inserted stores that are not used. If we see a subsequent store to the + // same stack slot, the original store is deleted. + std::vector<MachineInstr*> MaybeDeadStores; + MaybeDeadStores.resize(MF.getFrameInfo()->getObjectIndexEnd(), NULL); + + // ReMatDefs - These are rematerializable def MIs which are not deleted. + SmallSet<MachineInstr*, 4> ReMatDefs; + + // Clear kill info. + SmallSet<unsigned, 2> KilledMIRegs; + + // Keep track of the registers we have already spilled in case there are + // multiple defs of the same register in MI. + SmallSet<unsigned, 8> SpilledMIRegs; + + RegKills.reset(); + KillOps.clear(); + KillOps.resize(TRI->getNumRegs(), NULL); + + DistanceMap.clear(); + for (MachineBasicBlock::iterator MII = MBB->begin(), E = MBB->end(); + MII != E; ) { + MachineBasicBlock::iterator NextMII = llvm::next(MII); + + if (OptimizeByUnfold(MII, MaybeDeadStores, Spills, RegKills, KillOps)) + NextMII = llvm::next(MII); + + if (InsertEmergencySpills(MII)) + NextMII = llvm::next(MII); + + InsertRestores(MII, Spills, RegKills, KillOps); + + if (InsertSpills(MII)) + NextMII = llvm::next(MII); + + VirtRegMap::MI2VirtMapTy::const_iterator I, End; + bool Erased = false; + bool BackTracked = false; + MachineInstr &MI = *MII; + + // Remember DbgValue's which reference stack slots. + if (MI.isDebugValue() && MI.getOperand(0).isFI()) + Slot2DbgValues[MI.getOperand(0).getIndex()].push_back(&MI); + + /// ReusedOperands - Keep track of operand reuse in case we need to undo + /// reuse. + ReuseInfo ReusedOperands(MI, TRI); + SmallVector<unsigned, 4> VirtUseOps; + for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) { + MachineOperand &MO = MI.getOperand(i); + if (!MO.isReg() || MO.getReg() == 0) + continue; // Ignore non-register operands. + + unsigned VirtReg = MO.getReg(); + if (TargetRegisterInfo::isPhysicalRegister(VirtReg)) { + // Ignore physregs for spilling, but remember that it is used by this + // function. + MRI->setPhysRegUsed(VirtReg); + continue; + } + + // We want to process implicit virtual register uses first. + if (MO.isImplicit()) + // If the virtual register is implicitly defined, emit a implicit_def + // before so scavenger knows it's "defined". + // FIXME: This is a horrible hack done the by register allocator to + // remat a definition with virtual register operand. + VirtUseOps.insert(VirtUseOps.begin(), i); + else + VirtUseOps.push_back(i); + } + + // Process all of the spilled uses and all non spilled reg references. + SmallVector<int, 2> PotentialDeadStoreSlots; + KilledMIRegs.clear(); + for (unsigned j = 0, e = VirtUseOps.size(); j != e; ++j) { + unsigned i = VirtUseOps[j]; + unsigned VirtReg = MI.getOperand(i).getReg(); + assert(TargetRegisterInfo::isVirtualRegister(VirtReg) && + "Not a virtual register?"); + + unsigned SubIdx = MI.getOperand(i).getSubReg(); + if (VRM->isAssignedReg(VirtReg)) { + // This virtual register was assigned a physreg! + unsigned Phys = VRM->getPhys(VirtReg); + MRI->setPhysRegUsed(Phys); + if (MI.getOperand(i).isDef()) + ReusedOperands.markClobbered(Phys); + substitutePhysReg(MI.getOperand(i), Phys, *TRI); + if (VRM->isImplicitlyDefined(VirtReg)) + // FIXME: Is this needed? + BuildMI(*MBB, &MI, MI.getDebugLoc(), + TII->get(TargetOpcode::IMPLICIT_DEF), Phys); + continue; + } + + // This virtual register is now known to be a spilled value. + if (!MI.getOperand(i).isUse()) + continue; // Handle defs in the loop below (handle use&def here though) + + bool AvoidReload = MI.getOperand(i).isUndef(); + // Check if it is defined by an implicit def. It should not be spilled. + // Note, this is for correctness reason. e.g. + // 8 %reg1024<def> = IMPLICIT_DEF + // 12 %reg1024<def> = INSERT_SUBREG %reg1024<kill>, %reg1025, 2 + // The live range [12, 14) are not part of the r1024 live interval since + // it's defined by an implicit def. It will not conflicts with live + // interval of r1025. Now suppose both registers are spilled, you can + // easily see a situation where both registers are reloaded before + // the INSERT_SUBREG and both target registers that would overlap. + bool DoReMat = VRM->isReMaterialized(VirtReg); + int SSorRMId = DoReMat + ? VRM->getReMatId(VirtReg) : VRM->getStackSlot(VirtReg); + int ReuseSlot = SSorRMId; + + // Check to see if this stack slot is available. + unsigned PhysReg = Spills.getSpillSlotOrReMatPhysReg(SSorRMId); + + // If this is a sub-register use, make sure the reuse register is in the + // right register class. For example, for x86 not all of the 32-bit + // registers have accessible sub-registers. + // Similarly so for EXTRACT_SUBREG. Consider this: + // EDI = op + // MOV32_mr fi#1, EDI + // ... + // = EXTRACT_SUBREG fi#1 + // fi#1 is available in EDI, but it cannot be reused because it's not in + // the right register file. + if (PhysReg && !AvoidReload && SubIdx) { + const TargetRegisterClass* RC = MRI->getRegClass(VirtReg); + if (!RC->contains(PhysReg)) + PhysReg = 0; + } + + if (PhysReg && !AvoidReload) { + // This spilled operand might be part of a two-address operand. If this + // is the case, then changing it will necessarily require changing the + // def part of the instruction as well. However, in some cases, we + // aren't allowed to modify the reused register. If none of these cases + // apply, reuse it. + bool CanReuse = true; + bool isTied = MI.isRegTiedToDefOperand(i); + if (isTied) { + // Okay, we have a two address operand. We can reuse this physreg as + // long as we are allowed to clobber the value and there isn't an + // earlier def that has already clobbered the physreg. + CanReuse = !ReusedOperands.isClobbered(PhysReg) && + Spills.canClobberPhysReg(PhysReg); + } + // If this is an asm, and PhysReg is used elsewhere as an earlyclobber + // operand, we can't also use it as an input. (Outputs always come + // before inputs, so we can stop looking at i.) + if (MI.isInlineAsm()) { + for (unsigned k=0; k<i; ++k) { + MachineOperand &MOk = MI.getOperand(k); + if (MOk.isReg() && MOk.getReg()==PhysReg && MOk.isEarlyClobber()) { + CanReuse = false; + break; + } + } + } + + if (CanReuse) { + // If this stack slot value is already available, reuse it! + if (ReuseSlot > VirtRegMap::MAX_STACK_SLOT) + DEBUG(dbgs() << "Reusing RM#" + << ReuseSlot-VirtRegMap::MAX_STACK_SLOT-1); + else + DEBUG(dbgs() << "Reusing SS#" << ReuseSlot); + DEBUG(dbgs() << " from physreg " + << TRI->getName(PhysReg) << " for vreg" + << VirtReg <<" instead of reloading into physreg " + << TRI->getName(VRM->getPhys(VirtReg)) << '\n'); + unsigned RReg = SubIdx ? TRI->getSubReg(PhysReg, SubIdx) : PhysReg; + MI.getOperand(i).setReg(RReg); + MI.getOperand(i).setSubReg(0); + + // The only technical detail we have is that we don't know that + // PhysReg won't be clobbered by a reloaded stack slot that occurs + // later in the instruction. In particular, consider 'op V1, V2'. + // If V1 is available in physreg R0, we would choose to reuse it + // here, instead of reloading it into the register the allocator + // indicated (say R1). However, V2 might have to be reloaded + // later, and it might indicate that it needs to live in R0. When + // this occurs, we need to have information available that + // indicates it is safe to use R1 for the reload instead of R0. + // + // To further complicate matters, we might conflict with an alias, + // or R0 and R1 might not be compatible with each other. In this + // case, we actually insert a reload for V1 in R1, ensuring that + // we can get at R0 or its alias. + ReusedOperands.addReuse(i, ReuseSlot, PhysReg, + VRM->getPhys(VirtReg), VirtReg); + if (isTied) + // Only mark it clobbered if this is a use&def operand. + ReusedOperands.markClobbered(PhysReg); + ++NumReused; + + if (MI.getOperand(i).isKill() && + ReuseSlot <= VirtRegMap::MAX_STACK_SLOT) { + + // The store of this spilled value is potentially dead, but we + // won't know for certain until we've confirmed that the re-use + // above is valid, which means waiting until the other operands + // are processed. For now we just track the spill slot, we'll + // remove it after the other operands are processed if valid. + + PotentialDeadStoreSlots.push_back(ReuseSlot); + } + + // Mark is isKill if it's there no other uses of the same virtual + // register and it's not a two-address operand. IsKill will be + // unset if reg is reused. + if (!isTied && KilledMIRegs.count(VirtReg) == 0) { + MI.getOperand(i).setIsKill(); + KilledMIRegs.insert(VirtReg); + } + + continue; + } // CanReuse + + // Otherwise we have a situation where we have a two-address instruction + // whose mod/ref operand needs to be reloaded. This reload is already + // available in some register "PhysReg", but if we used PhysReg as the + // operand to our 2-addr instruction, the instruction would modify + // PhysReg. This isn't cool if something later uses PhysReg and expects + // to get its initial value. + // + // To avoid this problem, and to avoid doing a load right after a store, + // we emit a copy from PhysReg into the designated register for this + // operand. + // + // This case also applies to an earlyclobber'd PhysReg. + unsigned DesignatedReg = VRM->getPhys(VirtReg); + assert(DesignatedReg && "Must map virtreg to physreg!"); + + // Note that, if we reused a register for a previous operand, the + // register we want to reload into might not actually be + // available. If this occurs, use the register indicated by the + // reuser. + if (ReusedOperands.hasReuses()) + DesignatedReg = ReusedOperands. + GetRegForReload(VirtReg, DesignatedReg, &MI, Spills, + MaybeDeadStores, RegKills, KillOps, *VRM); + + // If the mapped designated register is actually the physreg we have + // incoming, we don't need to inserted a dead copy. + if (DesignatedReg == PhysReg) { + // If this stack slot value is already available, reuse it! + if (ReuseSlot > VirtRegMap::MAX_STACK_SLOT) + DEBUG(dbgs() << "Reusing RM#" + << ReuseSlot-VirtRegMap::MAX_STACK_SLOT-1); + else + DEBUG(dbgs() << "Reusing SS#" << ReuseSlot); + DEBUG(dbgs() << " from physreg " << TRI->getName(PhysReg) + << " for vreg" << VirtReg + << " instead of reloading into same physreg.\n"); + unsigned RReg = SubIdx ? TRI->getSubReg(PhysReg, SubIdx) : PhysReg; + MI.getOperand(i).setReg(RReg); + MI.getOperand(i).setSubReg(0); + ReusedOperands.markClobbered(RReg); + ++NumReused; + continue; + } + + MRI->setPhysRegUsed(DesignatedReg); + ReusedOperands.markClobbered(DesignatedReg); + + // Back-schedule reloads and remats. + MachineBasicBlock::iterator InsertLoc = + ComputeReloadLoc(&MI, MBB->begin(), PhysReg, TRI, DoReMat, + SSorRMId, TII, MF); + MachineInstr *CopyMI = BuildMI(*MBB, InsertLoc, MI.getDebugLoc(), + TII->get(TargetOpcode::COPY), + DesignatedReg).addReg(PhysReg); + CopyMI->setAsmPrinterFlag(MachineInstr::ReloadReuse); + UpdateKills(*CopyMI, TRI, RegKills, KillOps); + + // This invalidates DesignatedReg. + Spills.ClobberPhysReg(DesignatedReg); + + Spills.addAvailable(ReuseSlot, DesignatedReg); + unsigned RReg = + SubIdx ? TRI->getSubReg(DesignatedReg, SubIdx) : DesignatedReg; + MI.getOperand(i).setReg(RReg); + MI.getOperand(i).setSubReg(0); + DEBUG(dbgs() << '\t' << *prior(MII)); + ++NumReused; + continue; + } // if (PhysReg) + + // Otherwise, reload it and remember that we have it. + PhysReg = VRM->getPhys(VirtReg); + assert(PhysReg && "Must map virtreg to physreg!"); + + // Note that, if we reused a register for a previous operand, the + // register we want to reload into might not actually be + // available. If this occurs, use the register indicated by the + // reuser. + if (ReusedOperands.hasReuses()) + PhysReg = ReusedOperands.GetRegForReload(VirtReg, PhysReg, &MI, + Spills, MaybeDeadStores, RegKills, KillOps, *VRM); + + MRI->setPhysRegUsed(PhysReg); + ReusedOperands.markClobbered(PhysReg); + if (AvoidReload) + ++NumAvoided; + else { + // Back-schedule reloads and remats. + MachineBasicBlock::iterator InsertLoc = + ComputeReloadLoc(MII, MBB->begin(), PhysReg, TRI, DoReMat, + SSorRMId, TII, MF); + + if (DoReMat) { + ReMaterialize(*MBB, InsertLoc, PhysReg, VirtReg, TII, TRI, *VRM); + } else { + const TargetRegisterClass* RC = MRI->getRegClass(VirtReg); + TII->loadRegFromStackSlot(*MBB, InsertLoc, PhysReg, SSorRMId, RC,TRI); + MachineInstr *LoadMI = prior(InsertLoc); + VRM->addSpillSlotUse(SSorRMId, LoadMI); + ++NumLoads; + DistanceMap.insert(std::make_pair(LoadMI, DistanceMap.size())); + } + // This invalidates PhysReg. + Spills.ClobberPhysReg(PhysReg); + + // Any stores to this stack slot are not dead anymore. + if (!DoReMat) + MaybeDeadStores[SSorRMId] = NULL; + Spills.addAvailable(SSorRMId, PhysReg); + // Assumes this is the last use. IsKill will be unset if reg is reused + // unless it's a two-address operand. + if (!MI.isRegTiedToDefOperand(i) && + KilledMIRegs.count(VirtReg) == 0) { + MI.getOperand(i).setIsKill(); + KilledMIRegs.insert(VirtReg); + } + + UpdateKills(*prior(InsertLoc), TRI, RegKills, KillOps); + DEBUG(dbgs() << '\t' << *prior(InsertLoc)); + } + unsigned RReg = SubIdx ? TRI->getSubReg(PhysReg, SubIdx) : PhysReg; + MI.getOperand(i).setReg(RReg); + MI.getOperand(i).setSubReg(0); + } + + // Ok - now we can remove stores that have been confirmed dead. + for (unsigned j = 0, e = PotentialDeadStoreSlots.size(); j != e; ++j) { + // This was the last use and the spilled value is still available + // for reuse. That means the spill was unnecessary! + int PDSSlot = PotentialDeadStoreSlots[j]; + MachineInstr* DeadStore = MaybeDeadStores[PDSSlot]; + if (DeadStore) { + DEBUG(dbgs() << "Removed dead store:\t" << *DeadStore); + InvalidateKills(*DeadStore, TRI, RegKills, KillOps); + VRM->RemoveMachineInstrFromMaps(DeadStore); + MBB->erase(DeadStore); + MaybeDeadStores[PDSSlot] = NULL; + ++NumDSE; + } + } + + + DEBUG(dbgs() << '\t' << MI); + + + // If we have folded references to memory operands, make sure we clear all + // physical registers that may contain the value of the spilled virtual + // register + SmallSet<int, 2> FoldedSS; + for (tie(I, End) = VRM->getFoldedVirts(&MI); I != End; ) { + unsigned VirtReg = I->second.first; + VirtRegMap::ModRef MR = I->second.second; + DEBUG(dbgs() << "Folded vreg: " << VirtReg << " MR: " << MR); + + // MI2VirtMap be can updated which invalidate the iterator. + // Increment the iterator first. + ++I; + int SS = VRM->getStackSlot(VirtReg); + if (SS == VirtRegMap::NO_STACK_SLOT) + continue; + FoldedSS.insert(SS); + DEBUG(dbgs() << " - StackSlot: " << SS << "\n"); + + // If this folded instruction is just a use, check to see if it's a + // straight load from the virt reg slot. + if ((MR & VirtRegMap::isRef) && !(MR & VirtRegMap::isMod)) { + int FrameIdx; + unsigned DestReg = TII->isLoadFromStackSlot(&MI, FrameIdx); + if (DestReg && FrameIdx == SS) { + // If this spill slot is available, turn it into a copy (or nothing) + // instead of leaving it as a load! + if (unsigned InReg = Spills.getSpillSlotOrReMatPhysReg(SS)) { + DEBUG(dbgs() << "Promoted Load To Copy: " << MI); + if (DestReg != InReg) { + MachineOperand *DefMO = MI.findRegisterDefOperand(DestReg); + MachineInstr *CopyMI = BuildMI(*MBB, &MI, MI.getDebugLoc(), + TII->get(TargetOpcode::COPY)) + .addReg(DestReg, RegState::Define, DefMO->getSubReg()) + .addReg(InReg, RegState::Kill); + // Revisit the copy so we make sure to notice the effects of the + // operation on the destreg (either needing to RA it if it's + // virtual or needing to clobber any values if it's physical). + NextMII = CopyMI; + NextMII->setAsmPrinterFlag(MachineInstr::ReloadReuse); + BackTracked = true; + } else { + DEBUG(dbgs() << "Removing now-noop copy: " << MI); + // Unset last kill since it's being reused. + InvalidateKill(InReg, TRI, RegKills, KillOps); + Spills.disallowClobberPhysReg(InReg); + } + + InvalidateKills(MI, TRI, RegKills, KillOps); + VRM->RemoveMachineInstrFromMaps(&MI); + MBB->erase(&MI); + Erased = true; + goto ProcessNextInst; + } + } else { + unsigned PhysReg = Spills.getSpillSlotOrReMatPhysReg(SS); + SmallVector<MachineInstr*, 4> NewMIs; + if (PhysReg && + TII->unfoldMemoryOperand(MF, &MI, PhysReg, false, false, NewMIs)) { + MBB->insert(MII, NewMIs[0]); + InvalidateKills(MI, TRI, RegKills, KillOps); + VRM->RemoveMachineInstrFromMaps(&MI); + MBB->erase(&MI); + Erased = true; + --NextMII; // backtrack to the unfolded instruction. + BackTracked = true; + goto ProcessNextInst; + } + } + } + + // If this reference is not a use, any previous store is now dead. + // Otherwise, the store to this stack slot is not dead anymore. + MachineInstr* DeadStore = MaybeDeadStores[SS]; + if (DeadStore) { + bool isDead = !(MR & VirtRegMap::isRef); + MachineInstr *NewStore = NULL; + if (MR & VirtRegMap::isModRef) { + unsigned PhysReg = Spills.getSpillSlotOrReMatPhysReg(SS); + SmallVector<MachineInstr*, 4> NewMIs; + // We can reuse this physreg as long as we are allowed to clobber + // the value and there isn't an earlier def that has already clobbered + // the physreg. + if (PhysReg && + !ReusedOperands.isClobbered(PhysReg) && + Spills.canClobberPhysReg(PhysReg) && + !TII->isStoreToStackSlot(&MI, SS)) { // Not profitable! + MachineOperand *KillOpnd = + DeadStore->findRegisterUseOperand(PhysReg, true); + // Note, if the store is storing a sub-register, it's possible the + // super-register is needed below. + if (KillOpnd && !KillOpnd->getSubReg() && + TII->unfoldMemoryOperand(MF, &MI, PhysReg, false, true,NewMIs)){ + MBB->insert(MII, NewMIs[0]); + NewStore = NewMIs[1]; + MBB->insert(MII, NewStore); + VRM->addSpillSlotUse(SS, NewStore); + InvalidateKills(MI, TRI, RegKills, KillOps); + VRM->RemoveMachineInstrFromMaps(&MI); + MBB->erase(&MI); + Erased = true; + --NextMII; + --NextMII; // backtrack to the unfolded instruction. + BackTracked = true; + isDead = true; + ++NumSUnfold; + } + } + } + + if (isDead) { // Previous store is dead. + // If we get here, the store is dead, nuke it now. + DEBUG(dbgs() << "Removed dead store:\t" << *DeadStore); + InvalidateKills(*DeadStore, TRI, RegKills, KillOps); + VRM->RemoveMachineInstrFromMaps(DeadStore); + MBB->erase(DeadStore); + if (!NewStore) + ++NumDSE; + } + + MaybeDeadStores[SS] = NULL; + if (NewStore) { + // Treat this store as a spill merged into a copy. That makes the + // stack slot value available. + VRM->virtFolded(VirtReg, NewStore, VirtRegMap::isMod); + goto ProcessNextInst; + } + } + + // If the spill slot value is available, and this is a new definition of + // the value, the value is not available anymore. + if (MR & VirtRegMap::isMod) { + // Notice that the value in this stack slot has been modified. + Spills.ModifyStackSlotOrReMat(SS); + + // If this is *just* a mod of the value, check to see if this is just a + // store to the spill slot (i.e. the spill got merged into the copy). If + // so, realize that the vreg is available now, and add the store to the + // MaybeDeadStore info. + int StackSlot; + if (!(MR & VirtRegMap::isRef)) { + if (unsigned SrcReg = TII->isStoreToStackSlot(&MI, StackSlot)) { + assert(TargetRegisterInfo::isPhysicalRegister(SrcReg) && + "Src hasn't been allocated yet?"); + + if (CommuteToFoldReload(MII, VirtReg, SrcReg, StackSlot, + Spills, RegKills, KillOps, TRI)) { + NextMII = llvm::next(MII); + BackTracked = true; + goto ProcessNextInst; + } + + // Okay, this is certainly a store of SrcReg to [StackSlot]. Mark + // this as a potentially dead store in case there is a subsequent + // store into the stack slot without a read from it. + MaybeDeadStores[StackSlot] = &MI; + + // If the stack slot value was previously available in some other + // register, change it now. Otherwise, make the register + // available in PhysReg. + Spills.addAvailable(StackSlot, SrcReg, MI.killsRegister(SrcReg)); + } + } + } + } + + // Process all of the spilled defs. + SpilledMIRegs.clear(); + for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) { + MachineOperand &MO = MI.getOperand(i); + if (!(MO.isReg() && MO.getReg() && MO.isDef())) + continue; + + unsigned VirtReg = MO.getReg(); + if (!TargetRegisterInfo::isVirtualRegister(VirtReg)) { + // Check to see if this is a noop copy. If so, eliminate the + // instruction before considering the dest reg to be changed. + // Also check if it's copying from an "undef", if so, we can't + // eliminate this or else the undef marker is lost and it will + // confuses the scavenger. This is extremely rare. + if (MI.isIdentityCopy() && !MI.getOperand(1).isUndef() && + MI.getNumOperands() == 2) { + ++NumDCE; + DEBUG(dbgs() << "Removing now-noop copy: " << MI); + SmallVector<unsigned, 2> KillRegs; + InvalidateKills(MI, TRI, RegKills, KillOps, &KillRegs); + if (MO.isDead() && !KillRegs.empty()) { + // Source register or an implicit super/sub-register use is killed. + assert(TRI->regsOverlap(KillRegs[0], MI.getOperand(0).getReg())); + // Last def is now dead. + TransferDeadness(MI.getOperand(1).getReg(), RegKills, KillOps); + } + VRM->RemoveMachineInstrFromMaps(&MI); + MBB->erase(&MI); + Erased = true; + Spills.disallowClobberPhysReg(VirtReg); + goto ProcessNextInst; + } + unsigned Src, Dst, SrcSR, DstSR; + if (TII->isMoveInstr(MI, Src, Dst, SrcSR, DstSR) && + Src == Dst && SrcSR == DstSR && + !MI.findRegisterUseOperand(Src)->isUndef()) { + ++NumDCE; + DEBUG(dbgs() << "Removing now-noop copy: " << MI); + SmallVector<unsigned, 2> KillRegs; + InvalidateKills(MI, TRI, RegKills, KillOps, &KillRegs); + if (MO.isDead() && !KillRegs.empty()) { + // Source register or an implicit super/sub-register use is killed. + assert(KillRegs[0] == Dst || + TRI->isSubRegister(KillRegs[0], Dst) || + TRI->isSuperRegister(KillRegs[0], Dst)); + // Last def is now dead. + TransferDeadness(Src, RegKills, KillOps); + } + VRM->RemoveMachineInstrFromMaps(&MI); + MBB->erase(&MI); + Erased = true; + Spills.disallowClobberPhysReg(VirtReg); + goto ProcessNextInst; + } + + // If it's not a no-op copy, it clobbers the value in the destreg. + Spills.ClobberPhysReg(VirtReg); + ReusedOperands.markClobbered(VirtReg); + + // Check to see if this instruction is a load from a stack slot into + // a register. If so, this provides the stack slot value in the reg. + int FrameIdx; + if (unsigned DestReg = TII->isLoadFromStackSlot(&MI, FrameIdx)) { + assert(DestReg == VirtReg && "Unknown load situation!"); + + // If it is a folded reference, then it's not safe to clobber. + bool Folded = FoldedSS.count(FrameIdx); + // Otherwise, if it wasn't available, remember that it is now! + Spills.addAvailable(FrameIdx, DestReg, !Folded); + goto ProcessNextInst; + } + + continue; + } + + unsigned SubIdx = MO.getSubReg(); + bool DoReMat = VRM->isReMaterialized(VirtReg); + if (DoReMat) + ReMatDefs.insert(&MI); + + // The only vregs left are stack slot definitions. + int StackSlot = VRM->getStackSlot(VirtReg); + const TargetRegisterClass *RC = MRI->getRegClass(VirtReg); + + // If this def is part of a two-address operand, make sure to execute + // the store from the correct physical register. + unsigned PhysReg; + unsigned TiedOp; + if (MI.isRegTiedToUseOperand(i, &TiedOp)) { + PhysReg = MI.getOperand(TiedOp).getReg(); + if (SubIdx) { + unsigned SuperReg = findSuperReg(RC, PhysReg, SubIdx, TRI); + assert(SuperReg && TRI->getSubReg(SuperReg, SubIdx) == PhysReg && + "Can't find corresponding super-register!"); + PhysReg = SuperReg; + } + } else { + PhysReg = VRM->getPhys(VirtReg); + if (ReusedOperands.isClobbered(PhysReg)) { + // Another def has taken the assigned physreg. It must have been a + // use&def which got it due to reuse. Undo the reuse! + PhysReg = ReusedOperands.GetRegForReload(VirtReg, PhysReg, &MI, + Spills, MaybeDeadStores, RegKills, KillOps, *VRM); + } + } + + assert(PhysReg && "VR not assigned a physical register?"); + MRI->setPhysRegUsed(PhysReg); + unsigned RReg = SubIdx ? TRI->getSubReg(PhysReg, SubIdx) : PhysReg; + ReusedOperands.markClobbered(RReg); + MI.getOperand(i).setReg(RReg); + MI.getOperand(i).setSubReg(0); + + if (!MO.isDead() && SpilledMIRegs.insert(VirtReg)) { + MachineInstr *&LastStore = MaybeDeadStores[StackSlot]; + SpillRegToStackSlot(MII, -1, PhysReg, StackSlot, RC, true, + LastStore, Spills, ReMatDefs, RegKills, KillOps); + NextMII = llvm::next(MII); + + // Check to see if this is a noop copy. If so, eliminate the + // instruction before considering the dest reg to be changed. + if (MI.isIdentityCopy()) { + ++NumDCE; + DEBUG(dbgs() << "Removing now-noop copy: " << MI); + InvalidateKills(MI, TRI, RegKills, KillOps); + VRM->RemoveMachineInstrFromMaps(&MI); + MBB->erase(&MI); + Erased = true; + UpdateKills(*LastStore, TRI, RegKills, KillOps); + goto ProcessNextInst; + } + { + unsigned Src, Dst, SrcSR, DstSR; + if (TII->isMoveInstr(MI, Src, Dst, SrcSR, DstSR) && + Src == Dst && SrcSR == DstSR) { + ++NumDCE; + DEBUG(dbgs() << "Removing now-noop copy: " << MI); + InvalidateKills(MI, TRI, RegKills, KillOps); + VRM->RemoveMachineInstrFromMaps(&MI); + MBB->erase(&MI); + Erased = true; + UpdateKills(*LastStore, TRI, RegKills, KillOps); + goto ProcessNextInst; + } + } + } + } + ProcessNextInst: + // Delete dead instructions without side effects. + if (!Erased && !BackTracked && isSafeToDelete(MI)) { + InvalidateKills(MI, TRI, RegKills, KillOps); + VRM->RemoveMachineInstrFromMaps(&MI); + MBB->erase(&MI); + Erased = true; + } + if (!Erased) + DistanceMap.insert(std::make_pair(&MI, DistanceMap.size())); + if (!Erased && !BackTracked) { + for (MachineBasicBlock::iterator II = &MI; II != NextMII; ++II) + UpdateKills(*II, TRI, RegKills, KillOps); + } + MII = NextMII; + } + +} + +llvm::VirtRegRewriter* llvm::createVirtRegRewriter() { + switch (RewriterOpt) { + default: llvm_unreachable("Unreachable!"); + case local: + return new LocalRewriter(); + case trivial: + return new TrivialRewriter(); + } +} |
