X-Git-Url: http://plrg.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FCodeGen%2FRegAllocFast.cpp;h=4724ca2f92e477f1c0561d3f3e4c681155b5626e;hb=8dd26253f54247e77e5accfdd70e7b4bf27b39c2;hp=fc150d55e2265944d227f01526f14687e9f2ada1;hpb=ee72651df4b783c973bb682bef7eab2ff9a703e2;p=oota-llvm.git diff --git a/lib/CodeGen/RegAllocFast.cpp b/lib/CodeGen/RegAllocFast.cpp index fc150d55e22..4724ca2f92e 100644 --- a/lib/CodeGen/RegAllocFast.cpp +++ b/lib/CodeGen/RegAllocFast.cpp @@ -13,6 +13,7 @@ //===----------------------------------------------------------------------===// #define DEBUG_TYPE "regalloc" +#include "RegisterClassInfo.h" #include "llvm/BasicBlock.h" #include "llvm/CodeGen/MachineFunctionPass.h" #include "llvm/CodeGen/MachineInstr.h" @@ -55,6 +56,7 @@ namespace { MachineRegisterInfo *MRI; const TargetRegisterInfo *TRI; const TargetInstrInfo *TII; + RegisterClassInfo RegClassInfo; // Basic block currently being allocated. MachineBasicBlock *MBB; @@ -81,7 +83,7 @@ namespace { // that is currently available in a physical register. LiveRegMap LiveVirtRegs; - DenseMap LiveDbgValueMap; + DenseMap > LiveDbgValueMap; // RegState - Track the state of a physical register. enum RegState { @@ -94,7 +96,7 @@ namespace { // immediately without checking aliases. regFree, - // A reserved register has been assigned expolicitly (e.g., setting up a + // A reserved register has been assigned explicitly (e.g., setting up a // call parameter), and it remains reserved until it is used. regReserved @@ -110,13 +112,10 @@ namespace { // instruction, and so cannot be allocated. BitVector UsedInInstr; - // Allocatable - vector of allocatable physical registers. - BitVector Allocatable; - // SkippedInstrs - Descriptors of instructions whose clobber list was // ignored because all registers were spilled. It is still necessary to // mark all the clobbered registers as used by the function. - SmallPtrSet SkippedInstrs; + SmallPtrSet SkippedInstrs; // isBulkSpilling - This flag is set when LiveRegMap will be cleared // completely after spilling all live registers. LiveRegMap entries should @@ -135,8 +134,6 @@ namespace { virtual void getAnalysisUsage(AnalysisUsage &AU) const { AU.setPreservesCFG(); - AU.addRequiredID(PHIEliminationID); - AU.addRequiredID(TwoAddressInstructionPassID); MachineFunctionPass::getAnalysisUsage(AU); } @@ -165,6 +162,7 @@ namespace { unsigned VirtReg, unsigned Hint); void spillAll(MachineInstr *MI); bool setPhysReg(MachineInstr *MI, unsigned OpNum, unsigned PhysReg); + void addRetOperands(MachineBasicBlock *MBB); }; char RAFast::ID = 0; } @@ -259,8 +257,8 @@ void RAFast::spillVirtReg(MachineBasicBlock::iterator MI, // instruction, not on the spill. bool SpillKill = LR.LastUse != MI; LR.Dirty = false; - DEBUG(dbgs() << "Spilling %reg" << LRI->first - << " in " << TRI->getName(LR.PhysReg)); + DEBUG(dbgs() << "Spilling " << PrintReg(LRI->first, TRI) + << " in " << PrintReg(LR.PhysReg, TRI)); const TargetRegisterClass *RC = MRI->getRegClass(LRI->first); int FI = getStackSpaceFor(LRI->first, RC); DEBUG(dbgs() << " to stack slot #" << FI << "\n"); @@ -270,7 +268,9 @@ void RAFast::spillVirtReg(MachineBasicBlock::iterator MI, // If this register is used by DBG_VALUE then insert new DBG_VALUE to // identify spilled location as the place to find corresponding variable's // value. - if (MachineInstr *DBG = LiveDbgValueMap.lookup(LRI->first)) { + SmallVector &LRIDbgValues = LiveDbgValueMap[LRI->first]; + for (unsigned li = 0, le = LRIDbgValues.size(); li != le; ++li) { + MachineInstr *DBG = LRIDbgValues[li]; const MDNode *MDPtr = DBG->getOperand(DBG->getNumOperands()-1).getMetadata(); int64_t Offset = 0; @@ -289,9 +289,11 @@ void RAFast::spillVirtReg(MachineBasicBlock::iterator MI, MachineBasicBlock *MBB = DBG->getParent(); MBB->insert(MI, NewDV); DEBUG(dbgs() << "Inserting debug info due to spill:" << "\n" << *NewDV); - LiveDbgValueMap[LRI->first] = NewDV; } } + // Now this register is spilled there is should not be any DBG_VALUE pointing + // to this register because they are all pointing to spilled value now. + LRIDbgValues.clear(); if (SpillKill) LR.LastUse = 0; // Don't kill register again } @@ -331,7 +333,7 @@ void RAFast::usePhysReg(MachineOperand &MO) { MO.setIsKill(); return; default: - // The physreg was allocated to a virtual register. That means to value we + // The physreg was allocated to a virtual register. That means the value we // wanted has been clobbered. llvm_unreachable("Instruction uses an allocated register"); } @@ -393,7 +395,6 @@ void RAFast::definePhysReg(MachineInstr *MI, unsigned PhysReg, PhysRegState[PhysReg] = NewState; for (const unsigned *AS = TRI->getAliasSet(PhysReg); unsigned Alias = *AS; ++AS) { - UsedInInstr.set(Alias); switch (unsigned VirtReg = PhysRegState[Alias]) { case regDisabled: break; @@ -417,20 +418,25 @@ void RAFast::definePhysReg(MachineInstr *MI, unsigned PhysReg, // can be allocated directly. // Returns spillImpossible when PhysReg or an alias can't be spilled. unsigned RAFast::calcSpillCost(unsigned PhysReg) const { - if (UsedInInstr.test(PhysReg)) + if (UsedInInstr.test(PhysReg)) { + DEBUG(dbgs() << PrintReg(PhysReg, TRI) << " is already used in instr.\n"); return spillImpossible; + } switch (unsigned VirtReg = PhysRegState[PhysReg]) { case regDisabled: break; case regFree: return 0; case regReserved: + DEBUG(dbgs() << PrintReg(VirtReg, TRI) << " corresponding " + << PrintReg(PhysReg, TRI) << " is reserved already.\n"); return spillImpossible; default: return LiveVirtRegs.lookup(VirtReg).Dirty ? spillDirty : spillClean; } - // This is a disabled register, add up const of aliases. + // This is a disabled register, add up cost of aliases. + DEBUG(dbgs() << PrintReg(PhysReg, TRI) << " is disabled.\n"); unsigned Cost = 0; for (const unsigned *AS = TRI->getAliasSet(PhysReg); unsigned Alias = *AS; ++AS) { @@ -458,8 +464,8 @@ unsigned RAFast::calcSpillCost(unsigned PhysReg) const { /// register must not be used for anything else when this is called. /// void RAFast::assignVirtToPhysReg(LiveRegEntry &LRE, unsigned PhysReg) { - DEBUG(dbgs() << "Assigning %reg" << LRE.first << " to " - << TRI->getName(PhysReg) << "\n"); + DEBUG(dbgs() << "Assigning " << PrintReg(LRE.first, TRI) << " to " + << PrintReg(PhysReg, TRI) << "\n"); PhysRegState[PhysReg] = LRE.first; assert(!LRE.second.PhysReg && "Already assigned a physreg"); LRE.second.PhysReg = PhysReg; @@ -476,41 +482,38 @@ void RAFast::allocVirtReg(MachineInstr *MI, LiveRegEntry &LRE, unsigned Hint) { // Ignore invalid hints. if (Hint && (!TargetRegisterInfo::isPhysicalRegister(Hint) || - !RC->contains(Hint) || !Allocatable.test(Hint))) + !RC->contains(Hint) || !RegClassInfo.isAllocatable(Hint))) Hint = 0; // Take hint when possible. if (Hint) { - switch(calcSpillCost(Hint)) { - default: - definePhysReg(MI, Hint, regFree); - // Fall through. - case 0: + // Ignore the hint if we would have to spill a dirty register. + unsigned Cost = calcSpillCost(Hint); + if (Cost < spillDirty) { + if (Cost) + definePhysReg(MI, Hint, regFree); return assignVirtToPhysReg(LRE, Hint); - case spillImpossible: - break; } } - TargetRegisterClass::iterator AOB = RC->allocation_order_begin(*MF); - TargetRegisterClass::iterator AOE = RC->allocation_order_end(*MF); + ArrayRef AO = RegClassInfo.getOrder(RC); // First try to find a completely free register. - for (TargetRegisterClass::iterator I = AOB; I != AOE; ++I) { + for (ArrayRef::iterator I = AO.begin(), E = AO.end(); I != E; ++I) { unsigned PhysReg = *I; - if (PhysRegState[PhysReg] == regFree && !UsedInInstr.test(PhysReg) && - Allocatable.test(PhysReg)) + if (PhysRegState[PhysReg] == regFree && !UsedInInstr.test(PhysReg)) return assignVirtToPhysReg(LRE, PhysReg); } - DEBUG(dbgs() << "Allocating %reg" << VirtReg << " from " << RC->getName() - << "\n"); + DEBUG(dbgs() << "Allocating " << PrintReg(VirtReg) << " from " + << RC->getName() << "\n"); unsigned BestReg = 0, BestCost = spillImpossible; - for (TargetRegisterClass::iterator I = AOB; I != AOE; ++I) { - if (!Allocatable.test(*I)) - continue; + for (ArrayRef::iterator I = AO.begin(), E = AO.end(); I != E; ++I) { unsigned Cost = calcSpillCost(*I); + DEBUG(dbgs() << "\tRegister: " << PrintReg(*I, TRI) << "\n"); + DEBUG(dbgs() << "\tCost: " << Cost << "\n"); + DEBUG(dbgs() << "\tBestCost: " << BestCost << "\n"); // Cost is 0 when all aliases are already disabled. if (Cost == 0) return assignVirtToPhysReg(LRE, *I); @@ -523,16 +526,10 @@ void RAFast::allocVirtReg(MachineInstr *MI, LiveRegEntry &LRE, unsigned Hint) { return assignVirtToPhysReg(LRE, BestReg); } - // Nothing we can do. - std::string msg; - raw_string_ostream Msg(msg); - Msg << "Ran out of registers during register allocation!"; - if (MI->isInlineAsm()) { - Msg << "\nPlease check your inline asm statement for " - << "invalid constraints:\n"; - MI->print(Msg, TM); - } - report_fatal_error(Msg.str()); + // Nothing we can do. Report an error and keep going with a bad allocation. + MI->emitError("ran out of registers during register allocation"); + definePhysReg(MI, *AO.begin(), regFree); + assignVirtToPhysReg(LRE, *AO.begin()); } /// defineVirtReg - Allocate a register for VirtReg and mark it as dirty. @@ -584,8 +581,8 @@ RAFast::reloadVirtReg(MachineInstr *MI, unsigned OpNum, allocVirtReg(MI, *LRI, Hint); const TargetRegisterClass *RC = MRI->getRegClass(VirtReg); int FrameIndex = getStackSpaceFor(VirtReg, RC); - DEBUG(dbgs() << "Reloading %reg" << VirtReg << " into " - << TRI->getName(LR.PhysReg) << "\n"); + DEBUG(dbgs() << "Reloading " << PrintReg(VirtReg, TRI) << " into " + << PrintReg(LR.PhysReg, TRI) << "\n"); TII->loadRegFromStackSlot(*MBB, MI, LR.PhysReg, FrameIndex, RC, TRI); ++NumLoads; } else if (LR.Dirty) { @@ -653,11 +650,12 @@ void RAFast::handleThroughOperands(MachineInstr *MI, MachineOperand &MO = MI->getOperand(i); if (!MO.isReg()) continue; unsigned Reg = MO.getReg(); - if (!Reg || TargetRegisterInfo::isPhysicalRegister(Reg)) continue; + if (!TargetRegisterInfo::isVirtualRegister(Reg)) + continue; if (MO.isEarlyClobber() || MI->isRegTiedToDefOperand(i) || (MO.getSubReg() && MI->readsVirtualRegister(Reg))) { if (ThroughRegs.insert(Reg)) - DEBUG(dbgs() << " %reg" << Reg); + DEBUG(dbgs() << ' ' << PrintReg(Reg)); } } @@ -680,12 +678,12 @@ void RAFast::handleThroughOperands(MachineInstr *MI, } SmallVector PartialDefs; - DEBUG(dbgs() << "Allocating tied uses and early clobbers.\n"); + DEBUG(dbgs() << "Allocating tied uses.\n"); for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) { MachineOperand &MO = MI->getOperand(i); if (!MO.isReg()) continue; unsigned Reg = MO.getReg(); - if (!Reg || TargetRegisterInfo::isPhysicalRegister(Reg)) continue; + if (!TargetRegisterInfo::isVirtualRegister(Reg)) continue; if (MO.isUse()) { unsigned DefIdx = 0; if (!MI->isRegTiedToDefOperand(i, &DefIdx)) continue; @@ -702,15 +700,24 @@ void RAFast::handleThroughOperands(MachineInstr *MI, // That would confuse the later phys-def processing pass. LiveRegMap::iterator LRI = reloadVirtReg(MI, i, Reg, 0); PartialDefs.push_back(LRI->second.PhysReg); - } else if (MO.isEarlyClobber()) { - // Note: defineVirtReg may invalidate MO. - LiveRegMap::iterator LRI = defineVirtReg(MI, i, Reg, 0); - unsigned PhysReg = LRI->second.PhysReg; - if (setPhysReg(MI, i, PhysReg)) - VirtDead.push_back(Reg); } } + DEBUG(dbgs() << "Allocating early clobbers.\n"); + for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) { + MachineOperand &MO = MI->getOperand(i); + if (!MO.isReg()) continue; + unsigned Reg = MO.getReg(); + if (!TargetRegisterInfo::isVirtualRegister(Reg)) continue; + if (!MO.isEarlyClobber()) + continue; + // Note: defineVirtReg may invalidate MO. + LiveRegMap::iterator LRI = defineVirtReg(MI, i, Reg, 0); + unsigned PhysReg = LRI->second.PhysReg; + if (setPhysReg(MI, i, PhysReg)) + VirtDead.push_back(Reg); + } + // Restore UsedInInstr to a state usable for allocating normal virtual uses. UsedInInstr.reset(); for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) { @@ -718,9 +725,9 @@ void RAFast::handleThroughOperands(MachineInstr *MI, if (!MO.isReg() || (MO.isDef() && !MO.isEarlyClobber())) continue; unsigned Reg = MO.getReg(); if (!Reg || !TargetRegisterInfo::isPhysicalRegister(Reg)) continue; + DEBUG(dbgs() << "\tSetting " << PrintReg(Reg, TRI) + << " as used in instr\n"); UsedInInstr.set(Reg); - for (const unsigned *AS = TRI->getAliasSet(Reg); *AS; ++AS) - UsedInInstr.set(*AS); } // Also mark PartialDefs as used to avoid reallocation. @@ -728,6 +735,61 @@ void RAFast::handleThroughOperands(MachineInstr *MI, UsedInInstr.set(PartialDefs[i]); } +/// addRetOperand - ensure that a return instruction has an operand for each +/// value live out of the function. +/// +/// Things marked both call and return are tail calls; do not do this for them. +/// The tail callee need not take the same registers as input that it produces +/// as output, and there are dependencies for its input registers elsewhere. +/// +/// FIXME: This should be done as part of instruction selection, and this helper +/// should be deleted. Until then, we use custom logic here to create the proper +/// operand under all circumstances. We can't use addRegisterKilled because that +/// doesn't make sense for undefined values. We can't simply avoid calling it +/// for undefined values, because we must ensure that the operand always exists. +void RAFast::addRetOperands(MachineBasicBlock *MBB) { + if (MBB->empty() || !MBB->back().isReturn() || MBB->back().isCall()) + return; + + MachineInstr *MI = &MBB->back(); + + for (MachineRegisterInfo::liveout_iterator + I = MBB->getParent()->getRegInfo().liveout_begin(), + E = MBB->getParent()->getRegInfo().liveout_end(); I != E; ++I) { + unsigned Reg = *I; + assert(TargetRegisterInfo::isPhysicalRegister(Reg) && + "Cannot have a live-out virtual register."); + + bool hasDef = PhysRegState[Reg] == regReserved; + + // Check if this register already has an operand. + bool Found = false; + for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) { + MachineOperand &MO = MI->getOperand(i); + if (!MO.isReg() || !MO.isUse()) + continue; + + unsigned OperReg = MO.getReg(); + if (!TargetRegisterInfo::isPhysicalRegister(OperReg)) + continue; + + if (OperReg == Reg || TRI->isSuperRegister(OperReg, Reg)) { + // If the ret already has an operand for this physreg or a superset, + // don't duplicate it. Set the kill flag if the value is defined. + if (hasDef && !MO.isKill()) + MO.setIsKill(); + Found = true; + break; + } + } + if (!Found) + MI->addOperand(MachineOperand::CreateReg(Reg, + false /*IsDef*/, + true /*IsImp*/, + hasDef/*IsKill*/)); + } +} + void RAFast::AllocateBasicBlock() { DEBUG(dbgs() << "\nAllocating " << *MBB); @@ -739,7 +801,7 @@ void RAFast::AllocateBasicBlock() { // Add live-in registers as live. for (MachineBasicBlock::livein_iterator I = MBB->livein_begin(), E = MBB->livein_end(); I != E; ++I) - if (Allocatable.test(*I)) + if (RegClassInfo.isAllocatable(*I)) definePhysReg(MII, *I, regReserved); SmallVector VirtDead; @@ -748,7 +810,7 @@ void RAFast::AllocateBasicBlock() { // Otherwise, sequentially allocate each instruction in the MBB. while (MII != MBB->end()) { MachineInstr *MI = MII++; - const TargetInstrDesc &TID = MI->getDesc(); + const MCInstrDesc &MCID = MI->getDesc(); DEBUG({ dbgs() << "\n>> " << *MI << "Regs:"; for (unsigned Reg = 1, E = TRI->getNumRegs(); Reg != E; ++Reg) { @@ -761,7 +823,7 @@ void RAFast::AllocateBasicBlock() { dbgs() << "*"; break; default: - dbgs() << "=%reg" << PhysRegState[Reg]; + dbgs() << '=' << PrintReg(PhysRegState[Reg]); if (LiveVirtRegs[PhysRegState[Reg]].Dirty) dbgs() << "*"; assert(LiveVirtRegs[PhysRegState[Reg]].PhysReg == Reg && @@ -791,16 +853,17 @@ void RAFast::AllocateBasicBlock() { MachineOperand &MO = MI->getOperand(i); if (!MO.isReg()) continue; unsigned Reg = MO.getReg(); - if (!Reg || TargetRegisterInfo::isPhysicalRegister(Reg)) continue; - LiveDbgValueMap[Reg] = MI; + if (!TargetRegisterInfo::isVirtualRegister(Reg)) continue; LiveRegMap::iterator LRI = LiveVirtRegs.find(Reg); if (LRI != LiveVirtRegs.end()) setPhysReg(MI, i, LRI->second.PhysReg); else { int SS = StackSlotForVirtReg[Reg]; - if (SS == -1) + if (SS == -1) { // We can't allocate a physreg for a DebugValue, sorry! + DEBUG(dbgs() << "Unable to allocate vreg used by DBG_VALUE"); MO.setReg(0); + } else { // Modify DBG_VALUE now that the value is in a spill slot. int64_t Offset = MI->getOperand(1).getImm(); @@ -817,11 +880,14 @@ void RAFast::AllocateBasicBlock() { MI = NewDV; ScanDbgValue = true; break; - } else + } else { // We can't allocate a physreg for a DebugValue; sorry! + DEBUG(dbgs() << "Unable to allocate vreg used by DBG_VALUE"); MO.setReg(0); + } } } + LiveDbgValueMap[Reg].push_back(MI); } } // Next instruction. @@ -857,7 +923,7 @@ void RAFast::AllocateBasicBlock() { VirtOpEnd = i+1; if (MO.isUse()) { hasTiedOps = hasTiedOps || - TID.getOperandConstraint(i, TOI::TIED_TO) != -1; + MCID.getOperandConstraint(i, MCOI::TIED_TO) != -1; } else { if (MO.isEarlyClobber()) hasEarlyClobbers = true; @@ -866,7 +932,7 @@ void RAFast::AllocateBasicBlock() { } continue; } - if (!Allocatable.test(Reg)) continue; + if (!RegClassInfo.isAllocatable(Reg)) continue; if (MO.isUse()) { usePhysReg(MO); } else if (MO.isEarlyClobber()) { @@ -887,7 +953,7 @@ void RAFast::AllocateBasicBlock() { // We didn't detect inline asm tied operands above, so just make this extra // pass for all inline asm. if (MI->isInlineAsm() || hasEarlyClobbers || hasPartialRedefs || - (hasTiedOps && (hasPhysDefs || TID.getNumDefs() > 1))) { + (hasTiedOps && (hasPhysDefs || MCID.getNumDefs() > 1))) { handleThroughOperands(MI, VirtDead); // Don't attempt coalescing when we have funny stuff going on. CopyDst = 0; @@ -902,7 +968,7 @@ void RAFast::AllocateBasicBlock() { MachineOperand &MO = MI->getOperand(i); if (!MO.isReg()) continue; unsigned Reg = MO.getReg(); - if (!Reg || TargetRegisterInfo::isPhysicalRegister(Reg)) continue; + if (!TargetRegisterInfo::isVirtualRegister(Reg)) continue; if (MO.isUse()) { LiveRegMap::iterator LRI = reloadVirtReg(MI, i, Reg, CopyDst); unsigned PhysReg = LRI->second.PhysReg; @@ -932,7 +998,7 @@ void RAFast::AllocateBasicBlock() { } unsigned DefOpEnd = MI->getNumOperands(); - if (TID.isCall()) { + if (MI->isCall()) { // Spill all virtregs before a call. This serves two purposes: 1. If an // exception is thrown, the landing pad is going to expect to find // registers in their spill slots, and 2. we don't have to wade through @@ -943,7 +1009,7 @@ void RAFast::AllocateBasicBlock() { // The imp-defs are skipped below, but we still need to mark those // registers as used by the function. - SkippedInstrs.insert(&TID); + SkippedInstrs.insert(&MCID); } // Third scan. @@ -955,7 +1021,7 @@ void RAFast::AllocateBasicBlock() { unsigned Reg = MO.getReg(); if (TargetRegisterInfo::isPhysicalRegister(Reg)) { - if (!Allocatable.test(Reg)) continue; + if (!RegClassInfo.isAllocatable(Reg)) continue; definePhysReg(MI, Reg, (MO.isImplicit() || MO.isDead()) ? regFree : regReserved); continue; @@ -997,6 +1063,9 @@ void RAFast::AllocateBasicBlock() { MBB->erase(Coalesced[i]); NumCopies += Coalesced.size(); + // addRetOperands must run after we've seen all defs in this block. + addRetOperands(MBB); + DEBUG(MBB->dump()); } @@ -1011,14 +1080,15 @@ bool RAFast::runOnMachineFunction(MachineFunction &Fn) { TM = &Fn.getTarget(); TRI = TM->getRegisterInfo(); TII = TM->getInstrInfo(); - + MRI->freezeReservedRegs(Fn); + RegClassInfo.runOnMachineFunction(Fn); UsedInInstr.resize(TRI->getNumRegs()); - Allocatable = TRI->getAllocatableSet(*MF); + + assert(!MRI->isSSA() && "regalloc requires leaving SSA"); // initialize the virtual->physical register map to have a 'null' // mapping for all virtual registers - unsigned LastVirtReg = MRI->getLastVirtReg(); - StackSlotForVirtReg.grow(LastVirtReg); + StackSlotForVirtReg.resize(MRI->getNumVirtRegs()); // Loop over all of the basic blocks, eliminating virtual register references for (MachineFunction::iterator MBBi = Fn.begin(), MBBe = Fn.end(); @@ -1031,7 +1101,7 @@ bool RAFast::runOnMachineFunction(MachineFunction &Fn) { MRI->closePhysRegsUsed(*TRI); // Add the clobber lists for all the instructions we skipped earlier. - for (SmallPtrSet::const_iterator + for (SmallPtrSet::const_iterator I = SkippedInstrs.begin(), E = SkippedInstrs.end(); I != E; ++I) if (const unsigned *Defs = (*I)->getImplicitDefs()) while (*Defs)