| //===-- LiveVariables.cpp - Live Variable Analysis for Machine Code -------===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This file implements the LiveVariable analysis pass. For each machine |
| // instruction in the function, this pass calculates the set of registers that |
| // are immediately dead after the instruction (i.e., the instruction calculates |
| // the value, but it is never used) and the set of registers that are used by |
| // the instruction, but are never used after the instruction (i.e., they are |
| // killed). |
| // |
| // This class computes live variables using are sparse implementation based on |
| // the machine code SSA form. This class computes live variable information for |
| // each virtual and _register allocatable_ physical register in a function. It |
| // uses the dominance properties of SSA form to efficiently compute live |
| // variables for virtual registers, and assumes that physical registers are only |
| // live within a single basic block (allowing it to do a single local analysis |
| // to resolve physical register lifetimes in each basic block). If a physical |
| // register is not register allocatable, it is not tracked. This is useful for |
| // things like the stack pointer and condition codes. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #include "llvm/CodeGen/LiveVariables.h" |
| #include "llvm/CodeGen/MachineInstr.h" |
| #include "llvm/CodeGen/MachineRegisterInfo.h" |
| #include "llvm/CodeGen/Passes.h" |
| #include "llvm/Target/TargetRegisterInfo.h" |
| #include "llvm/Target/TargetInstrInfo.h" |
| #include "llvm/Target/TargetMachine.h" |
| #include "llvm/ADT/DepthFirstIterator.h" |
| #include "llvm/ADT/SmallPtrSet.h" |
| #include "llvm/ADT/SmallSet.h" |
| #include "llvm/ADT/STLExtras.h" |
| #include "llvm/Config/alloca.h" |
| #include <algorithm> |
| using namespace llvm; |
| |
| char LiveVariables::ID = 0; |
| static RegisterPass<LiveVariables> X("livevars", "Live Variable Analysis"); |
| |
| |
| void LiveVariables::getAnalysisUsage(AnalysisUsage &AU) const { |
| AU.addRequiredID(UnreachableMachineBlockElimID); |
| AU.setPreservesAll(); |
| MachineFunctionPass::getAnalysisUsage(AU); |
| } |
| |
| void LiveVariables::VarInfo::dump() const { |
| cerr << " Alive in blocks: "; |
| for (SparseBitVector<>::iterator I = AliveBlocks.begin(), |
| E = AliveBlocks.end(); I != E; ++I) |
| cerr << *I << ", "; |
| cerr << "\n Killed by:"; |
| if (Kills.empty()) |
| cerr << " No instructions.\n"; |
| else { |
| for (unsigned i = 0, e = Kills.size(); i != e; ++i) |
| cerr << "\n #" << i << ": " << *Kills[i]; |
| cerr << "\n"; |
| } |
| } |
| |
| /// getVarInfo - Get (possibly creating) a VarInfo object for the given vreg. |
| LiveVariables::VarInfo &LiveVariables::getVarInfo(unsigned RegIdx) { |
| assert(TargetRegisterInfo::isVirtualRegister(RegIdx) && |
| "getVarInfo: not a virtual register!"); |
| RegIdx -= TargetRegisterInfo::FirstVirtualRegister; |
| if (RegIdx >= VirtRegInfo.size()) { |
| if (RegIdx >= 2*VirtRegInfo.size()) |
| VirtRegInfo.resize(RegIdx*2); |
| else |
| VirtRegInfo.resize(2*VirtRegInfo.size()); |
| } |
| return VirtRegInfo[RegIdx]; |
| } |
| |
| void LiveVariables::MarkVirtRegAliveInBlock(VarInfo& VRInfo, |
| MachineBasicBlock *DefBlock, |
| MachineBasicBlock *MBB, |
| std::vector<MachineBasicBlock*> &WorkList) { |
| unsigned BBNum = MBB->getNumber(); |
| |
| // Check to see if this basic block is one of the killing blocks. If so, |
| // remove it. |
| for (unsigned i = 0, e = VRInfo.Kills.size(); i != e; ++i) |
| if (VRInfo.Kills[i]->getParent() == MBB) { |
| VRInfo.Kills.erase(VRInfo.Kills.begin()+i); // Erase entry |
| break; |
| } |
| |
| if (MBB == DefBlock) return; // Terminate recursion |
| |
| if (VRInfo.AliveBlocks.test(BBNum)) |
| return; // We already know the block is live |
| |
| // Mark the variable known alive in this bb |
| VRInfo.AliveBlocks.set(BBNum); |
| |
| for (MachineBasicBlock::const_pred_reverse_iterator PI = MBB->pred_rbegin(), |
| E = MBB->pred_rend(); PI != E; ++PI) |
| WorkList.push_back(*PI); |
| } |
| |
| void LiveVariables::MarkVirtRegAliveInBlock(VarInfo &VRInfo, |
| MachineBasicBlock *DefBlock, |
| MachineBasicBlock *MBB) { |
| std::vector<MachineBasicBlock*> WorkList; |
| MarkVirtRegAliveInBlock(VRInfo, DefBlock, MBB, WorkList); |
| |
| while (!WorkList.empty()) { |
| MachineBasicBlock *Pred = WorkList.back(); |
| WorkList.pop_back(); |
| MarkVirtRegAliveInBlock(VRInfo, DefBlock, Pred, WorkList); |
| } |
| } |
| |
| void LiveVariables::HandleVirtRegUse(unsigned reg, MachineBasicBlock *MBB, |
| MachineInstr *MI) { |
| assert(MRI->getVRegDef(reg) && "Register use before def!"); |
| |
| unsigned BBNum = MBB->getNumber(); |
| |
| VarInfo& VRInfo = getVarInfo(reg); |
| VRInfo.NumUses++; |
| |
| // Check to see if this basic block is already a kill block. |
| if (!VRInfo.Kills.empty() && VRInfo.Kills.back()->getParent() == MBB) { |
| // Yes, this register is killed in this basic block already. Increase the |
| // live range by updating the kill instruction. |
| VRInfo.Kills.back() = MI; |
| return; |
| } |
| |
| #ifndef NDEBUG |
| for (unsigned i = 0, e = VRInfo.Kills.size(); i != e; ++i) |
| assert(VRInfo.Kills[i]->getParent() != MBB && "entry should be at end!"); |
| #endif |
| |
| // This situation can occur: |
| // |
| // ,------. |
| // | | |
| // | v |
| // | t2 = phi ... t1 ... |
| // | | |
| // | v |
| // | t1 = ... |
| // | ... = ... t1 ... |
| // | | |
| // `------' |
| // |
| // where there is a use in a PHI node that's a predecessor to the defining |
| // block. We don't want to mark all predecessors as having the value "alive" |
| // in this case. |
| if (MBB == MRI->getVRegDef(reg)->getParent()) return; |
| |
| // Add a new kill entry for this basic block. If this virtual register is |
| // already marked as alive in this basic block, that means it is alive in at |
| // least one of the successor blocks, it's not a kill. |
| if (!VRInfo.AliveBlocks.test(BBNum)) |
| VRInfo.Kills.push_back(MI); |
| |
| // Update all dominating blocks to mark them as "known live". |
| for (MachineBasicBlock::const_pred_iterator PI = MBB->pred_begin(), |
| E = MBB->pred_end(); PI != E; ++PI) |
| MarkVirtRegAliveInBlock(VRInfo, MRI->getVRegDef(reg)->getParent(), *PI); |
| } |
| |
| void LiveVariables::HandleVirtRegDef(unsigned Reg, MachineInstr *MI) { |
| VarInfo &VRInfo = getVarInfo(Reg); |
| |
| if (VRInfo.AliveBlocks.empty()) |
| // If vr is not alive in any block, then defaults to dead. |
| VRInfo.Kills.push_back(MI); |
| } |
| |
| /// FindLastPartialDef - Return the last partial def of the specified register. |
| /// Also returns the sub-register that's defined. |
| MachineInstr *LiveVariables::FindLastPartialDef(unsigned Reg, |
| unsigned &PartDefReg) { |
| unsigned LastDefReg = 0; |
| unsigned LastDefDist = 0; |
| MachineInstr *LastDef = NULL; |
| for (const unsigned *SubRegs = TRI->getSubRegisters(Reg); |
| unsigned SubReg = *SubRegs; ++SubRegs) { |
| MachineInstr *Def = PhysRegDef[SubReg]; |
| if (!Def) |
| continue; |
| unsigned Dist = DistanceMap[Def]; |
| if (Dist > LastDefDist) { |
| LastDefReg = SubReg; |
| LastDef = Def; |
| LastDefDist = Dist; |
| } |
| } |
| PartDefReg = LastDefReg; |
| return LastDef; |
| } |
| |
| /// HandlePhysRegUse - Turn previous partial def's into read/mod/writes. Add |
| /// implicit defs to a machine instruction if there was an earlier def of its |
| /// super-register. |
| void LiveVariables::HandlePhysRegUse(unsigned Reg, MachineInstr *MI) { |
| // If there was a previous use or a "full" def all is well. |
| if (!PhysRegDef[Reg] && !PhysRegUse[Reg]) { |
| // Otherwise, the last sub-register def implicitly defines this register. |
| // e.g. |
| // AH = |
| // AL = ... <imp-def EAX>, <imp-kill AH> |
| // = AH |
| // ... |
| // = EAX |
| // All of the sub-registers must have been defined before the use of Reg! |
| unsigned PartDefReg = 0; |
| MachineInstr *LastPartialDef = FindLastPartialDef(Reg, PartDefReg); |
| // If LastPartialDef is NULL, it must be using a livein register. |
| if (LastPartialDef) { |
| LastPartialDef->addOperand(MachineOperand::CreateReg(Reg, true/*IsDef*/, |
| true/*IsImp*/)); |
| PhysRegDef[Reg] = LastPartialDef; |
| SmallSet<unsigned, 8> Processed; |
| for (const unsigned *SubRegs = TRI->getSubRegisters(Reg); |
| unsigned SubReg = *SubRegs; ++SubRegs) { |
| if (Processed.count(SubReg)) |
| continue; |
| if (SubReg == PartDefReg || TRI->isSubRegister(PartDefReg, SubReg)) |
| continue; |
| // This part of Reg was defined before the last partial def. It's killed |
| // here. |
| LastPartialDef->addOperand(MachineOperand::CreateReg(SubReg, |
| false/*IsDef*/, |
| true/*IsImp*/)); |
| PhysRegDef[SubReg] = LastPartialDef; |
| for (const unsigned *SS = TRI->getSubRegisters(SubReg); *SS; ++SS) |
| Processed.insert(*SS); |
| } |
| } |
| } |
| |
| // Remember this use. |
| PhysRegUse[Reg] = MI; |
| for (const unsigned *SubRegs = TRI->getSubRegisters(Reg); |
| unsigned SubReg = *SubRegs; ++SubRegs) |
| PhysRegUse[SubReg] = MI; |
| } |
| |
| /// hasRegisterUseBelow - Return true if the specified register is used after |
| /// the current instruction and before it's next definition. |
| bool LiveVariables::hasRegisterUseBelow(unsigned Reg, |
| MachineBasicBlock::iterator I, |
| MachineBasicBlock *MBB) { |
| if (I == MBB->end()) |
| return false; |
| |
| // First find out if there are any uses / defs below. |
| bool hasDistInfo = true; |
| unsigned CurDist = DistanceMap[I]; |
| SmallVector<MachineInstr*, 4> Uses; |
| SmallVector<MachineInstr*, 4> Defs; |
| for (MachineRegisterInfo::reg_iterator RI = MRI->reg_begin(Reg), |
| RE = MRI->reg_end(); RI != RE; ++RI) { |
| MachineOperand &UDO = RI.getOperand(); |
| MachineInstr *UDMI = &*RI; |
| if (UDMI->getParent() != MBB) |
| continue; |
| DenseMap<MachineInstr*, unsigned>::iterator DI = DistanceMap.find(UDMI); |
| bool isBelow = false; |
| if (DI == DistanceMap.end()) { |
| // Must be below if it hasn't been assigned a distance yet. |
| isBelow = true; |
| hasDistInfo = false; |
| } else if (DI->second > CurDist) |
| isBelow = true; |
| if (isBelow) { |
| if (UDO.isUse()) |
| Uses.push_back(UDMI); |
| if (UDO.isDef()) |
| Defs.push_back(UDMI); |
| } |
| } |
| |
| if (Uses.empty()) |
| // No uses below. |
| return false; |
| else if (!Uses.empty() && Defs.empty()) |
| // There are uses below but no defs below. |
| return true; |
| // There are both uses and defs below. We need to know which comes first. |
| if (!hasDistInfo) { |
| // Complete DistanceMap for this MBB. This information is computed only |
| // once per MBB. |
| ++I; |
| ++CurDist; |
| for (MachineBasicBlock::iterator E = MBB->end(); I != E; ++I, ++CurDist) |
| DistanceMap.insert(std::make_pair(I, CurDist)); |
| } |
| |
| unsigned EarliestUse = DistanceMap[Uses[0]]; |
| for (unsigned i = 1, e = Uses.size(); i != e; ++i) { |
| unsigned Dist = DistanceMap[Uses[i]]; |
| if (Dist < EarliestUse) |
| EarliestUse = Dist; |
| } |
| for (unsigned i = 0, e = Defs.size(); i != e; ++i) { |
| unsigned Dist = DistanceMap[Defs[i]]; |
| if (Dist < EarliestUse) |
| // The register is defined before its first use below. |
| return false; |
| } |
| return true; |
| } |
| |
| bool LiveVariables::HandlePhysRegKill(unsigned Reg, MachineInstr *MI) { |
| if (!PhysRegUse[Reg] && !PhysRegDef[Reg]) |
| return false; |
| |
| MachineInstr *LastRefOrPartRef = PhysRegUse[Reg] |
| ? PhysRegUse[Reg] : PhysRegDef[Reg]; |
| unsigned LastRefOrPartRefDist = DistanceMap[LastRefOrPartRef]; |
| // The whole register is used. |
| // AL = |
| // AH = |
| // |
| // = AX |
| // = AL, AX<imp-use, kill> |
| // AX = |
| // |
| // Or whole register is defined, but not used at all. |
| // AX<dead> = |
| // ... |
| // AX = |
| // |
| // Or whole register is defined, but only partly used. |
| // AX<dead> = AL<imp-def> |
| // = AL<kill> |
| // AX = |
| SmallSet<unsigned, 8> PartUses; |
| for (const unsigned *SubRegs = TRI->getSubRegisters(Reg); |
| unsigned SubReg = *SubRegs; ++SubRegs) { |
| if (MachineInstr *Use = PhysRegUse[SubReg]) { |
| PartUses.insert(SubReg); |
| for (const unsigned *SS = TRI->getSubRegisters(SubReg); *SS; ++SS) |
| PartUses.insert(*SS); |
| unsigned Dist = DistanceMap[Use]; |
| if (Dist > LastRefOrPartRefDist) { |
| LastRefOrPartRefDist = Dist; |
| LastRefOrPartRef = Use; |
| } |
| } |
| } |
| |
| if (LastRefOrPartRef == PhysRegDef[Reg] && LastRefOrPartRef != MI) |
| // If the last reference is the last def, then it's not used at all. |
| // That is, unless we are currently processing the last reference itself. |
| LastRefOrPartRef->addRegisterDead(Reg, TRI, true); |
| |
| // Partial uses. Mark register def dead and add implicit def of |
| // sub-registers which are used. |
| // EAX<dead> = op AL<imp-def> |
| // That is, EAX def is dead but AL def extends pass it. |
| // Enable this after live interval analysis is fixed to improve codegen! |
| else if (!PhysRegUse[Reg]) { |
| PhysRegDef[Reg]->addRegisterDead(Reg, TRI, true); |
| for (const unsigned *SubRegs = TRI->getSubRegisters(Reg); |
| unsigned SubReg = *SubRegs; ++SubRegs) { |
| if (PartUses.count(SubReg)) { |
| bool NeedDef = true; |
| if (PhysRegDef[Reg] == PhysRegDef[SubReg]) { |
| MachineOperand *MO = PhysRegDef[Reg]->findRegisterDefOperand(SubReg); |
| if (MO) { |
| NeedDef = false; |
| assert(!MO->isDead()); |
| } |
| } |
| if (NeedDef) |
| PhysRegDef[Reg]->addOperand(MachineOperand::CreateReg(SubReg, |
| true, true)); |
| LastRefOrPartRef->addRegisterKilled(SubReg, TRI, true); |
| for (const unsigned *SS = TRI->getSubRegisters(SubReg); *SS; ++SS) |
| PartUses.erase(*SS); |
| } |
| } |
| } |
| else |
| LastRefOrPartRef->addRegisterKilled(Reg, TRI, true); |
| return true; |
| } |
| |
| void LiveVariables::HandlePhysRegDef(unsigned Reg, MachineInstr *MI) { |
| // What parts of the register are previously defined? |
| SmallSet<unsigned, 32> Live; |
| if (PhysRegDef[Reg] || PhysRegUse[Reg]) { |
| Live.insert(Reg); |
| for (const unsigned *SS = TRI->getSubRegisters(Reg); *SS; ++SS) |
| Live.insert(*SS); |
| } else { |
| for (const unsigned *SubRegs = TRI->getSubRegisters(Reg); |
| unsigned SubReg = *SubRegs; ++SubRegs) { |
| // If a register isn't itself defined, but all parts that make up of it |
| // are defined, then consider it also defined. |
| // e.g. |
| // AL = |
| // AH = |
| // = AX |
| if (PhysRegDef[SubReg] || PhysRegUse[SubReg]) { |
| Live.insert(SubReg); |
| for (const unsigned *SS = TRI->getSubRegisters(SubReg); *SS; ++SS) |
| Live.insert(*SS); |
| } |
| } |
| } |
| |
| // Start from the largest piece, find the last time any part of the register |
| // is referenced. |
| if (!HandlePhysRegKill(Reg, MI)) { |
| // Only some of the sub-registers are used. |
| for (const unsigned *SubRegs = TRI->getSubRegisters(Reg); |
| unsigned SubReg = *SubRegs; ++SubRegs) { |
| if (!Live.count(SubReg)) |
| // Skip if this sub-register isn't defined. |
| continue; |
| if (HandlePhysRegKill(SubReg, MI)) { |
| Live.erase(SubReg); |
| for (const unsigned *SS = TRI->getSubRegisters(SubReg); *SS; ++SS) |
| Live.erase(*SS); |
| } |
| } |
| assert(Live.empty() && "Not all defined registers are killed / dead?"); |
| } |
| |
| if (MI) { |
| // Does this extend the live range of a super-register? |
| SmallSet<unsigned, 8> Processed; |
| for (const unsigned *SuperRegs = TRI->getSuperRegisters(Reg); |
| unsigned SuperReg = *SuperRegs; ++SuperRegs) { |
| if (Processed.count(SuperReg)) |
| continue; |
| MachineInstr *LastRef = PhysRegUse[SuperReg] |
| ? PhysRegUse[SuperReg] : PhysRegDef[SuperReg]; |
| if (LastRef && LastRef != MI) { |
| // The larger register is previously defined. Now a smaller part is |
| // being re-defined. Treat it as read/mod/write if there are uses |
| // below. |
| // EAX = |
| // AX = EAX<imp-use,kill>, EAX<imp-def> |
| // ... |
| /// = EAX |
| if (hasRegisterUseBelow(SuperReg, MI, MI->getParent())) { |
| MI->addOperand(MachineOperand::CreateReg(SuperReg, false/*IsDef*/, |
| true/*IsImp*/,true/*IsKill*/)); |
| MI->addOperand(MachineOperand::CreateReg(SuperReg, true/*IsDef*/, |
| true/*IsImp*/)); |
| PhysRegDef[SuperReg] = MI; |
| PhysRegUse[SuperReg] = NULL; |
| Processed.insert(SuperReg); |
| for (const unsigned *SS = TRI->getSubRegisters(SuperReg); *SS; ++SS) { |
| PhysRegDef[*SS] = MI; |
| PhysRegUse[*SS] = NULL; |
| Processed.insert(*SS); |
| } |
| } else { |
| // Otherwise, the super register is killed. |
| if (HandlePhysRegKill(SuperReg, MI)) { |
| PhysRegDef[SuperReg] = NULL; |
| PhysRegUse[SuperReg] = NULL; |
| for (const unsigned *SS = TRI->getSubRegisters(SuperReg); *SS; ++SS) { |
| PhysRegDef[*SS] = NULL; |
| PhysRegUse[*SS] = NULL; |
| Processed.insert(*SS); |
| } |
| } |
| } |
| } |
| } |
| |
| // Remember this def. |
| PhysRegDef[Reg] = MI; |
| PhysRegUse[Reg] = NULL; |
| for (const unsigned *SubRegs = TRI->getSubRegisters(Reg); |
| unsigned SubReg = *SubRegs; ++SubRegs) { |
| PhysRegDef[SubReg] = MI; |
| PhysRegUse[SubReg] = NULL; |
| } |
| } |
| } |
| |
| bool LiveVariables::runOnMachineFunction(MachineFunction &mf) { |
| MF = &mf; |
| MRI = &mf.getRegInfo(); |
| TRI = MF->getTarget().getRegisterInfo(); |
| |
| ReservedRegisters = TRI->getReservedRegs(mf); |
| |
| unsigned NumRegs = TRI->getNumRegs(); |
| PhysRegDef = new MachineInstr*[NumRegs]; |
| PhysRegUse = new MachineInstr*[NumRegs]; |
| PHIVarInfo = new SmallVector<unsigned, 4>[MF->getNumBlockIDs()]; |
| std::fill(PhysRegDef, PhysRegDef + NumRegs, (MachineInstr*)0); |
| std::fill(PhysRegUse, PhysRegUse + NumRegs, (MachineInstr*)0); |
| |
| /// Get some space for a respectable number of registers. |
| VirtRegInfo.resize(64); |
| |
| analyzePHINodes(mf); |
| |
| // Calculate live variable information in depth first order on the CFG of the |
| // function. This guarantees that we will see the definition of a virtual |
| // register before its uses due to dominance properties of SSA (except for PHI |
| // nodes, which are treated as a special case). |
| 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) { |
| MachineBasicBlock *MBB = *DFI; |
| |
| // Mark live-in registers as live-in. |
| for (MachineBasicBlock::const_livein_iterator II = MBB->livein_begin(), |
| EE = MBB->livein_end(); II != EE; ++II) { |
| assert(TargetRegisterInfo::isPhysicalRegister(*II) && |
| "Cannot have a live-in virtual register!"); |
| HandlePhysRegDef(*II, 0); |
| } |
| |
| // Loop over all of the instructions, processing them. |
| DistanceMap.clear(); |
| unsigned Dist = 0; |
| for (MachineBasicBlock::iterator I = MBB->begin(), E = MBB->end(); |
| I != E; ++I) { |
| MachineInstr *MI = I; |
| DistanceMap.insert(std::make_pair(MI, Dist++)); |
| |
| // Process all of the operands of the instruction... |
| unsigned NumOperandsToProcess = MI->getNumOperands(); |
| |
| // Unless it is a PHI node. In this case, ONLY process the DEF, not any |
| // of the uses. They will be handled in other basic blocks. |
| if (MI->getOpcode() == TargetInstrInfo::PHI) |
| NumOperandsToProcess = 1; |
| |
| SmallVector<unsigned, 4> UseRegs; |
| SmallVector<unsigned, 4> DefRegs; |
| for (unsigned i = 0; i != NumOperandsToProcess; ++i) { |
| const MachineOperand &MO = MI->getOperand(i); |
| if (!MO.isReg() || MO.getReg() == 0) |
| continue; |
| unsigned MOReg = MO.getReg(); |
| if (MO.isUse()) |
| UseRegs.push_back(MOReg); |
| if (MO.isDef()) |
| DefRegs.push_back(MOReg); |
| } |
| |
| // Process all uses. |
| for (unsigned i = 0, e = UseRegs.size(); i != e; ++i) { |
| unsigned MOReg = UseRegs[i]; |
| if (TargetRegisterInfo::isVirtualRegister(MOReg)) |
| HandleVirtRegUse(MOReg, MBB, MI); |
| else if (!ReservedRegisters[MOReg]) |
| HandlePhysRegUse(MOReg, MI); |
| } |
| |
| // Process all defs. |
| for (unsigned i = 0, e = DefRegs.size(); i != e; ++i) { |
| unsigned MOReg = DefRegs[i]; |
| if (TargetRegisterInfo::isVirtualRegister(MOReg)) |
| HandleVirtRegDef(MOReg, MI); |
| else if (!ReservedRegisters[MOReg]) |
| HandlePhysRegDef(MOReg, MI); |
| } |
| } |
| |
| // Handle any virtual assignments from PHI nodes which might be at the |
| // bottom of this basic block. We check all of our successor blocks to see |
| // if they have PHI nodes, and if so, we simulate an assignment at the end |
| // of the current block. |
| if (!PHIVarInfo[MBB->getNumber()].empty()) { |
| SmallVector<unsigned, 4>& VarInfoVec = PHIVarInfo[MBB->getNumber()]; |
| |
| for (SmallVector<unsigned, 4>::iterator I = VarInfoVec.begin(), |
| E = VarInfoVec.end(); I != E; ++I) |
| // Mark it alive only in the block we are representing. |
| MarkVirtRegAliveInBlock(getVarInfo(*I),MRI->getVRegDef(*I)->getParent(), |
| MBB); |
| } |
| |
| // Finally, if the last instruction in the block is a return, make sure to |
| // mark it as using all of the live-out values in the function. |
| if (!MBB->empty() && MBB->back().getDesc().isReturn()) { |
| MachineInstr *Ret = &MBB->back(); |
| |
| for (MachineRegisterInfo::liveout_iterator |
| I = MF->getRegInfo().liveout_begin(), |
| E = MF->getRegInfo().liveout_end(); I != E; ++I) { |
| assert(TargetRegisterInfo::isPhysicalRegister(*I) && |
| "Cannot have a live-out virtual register!"); |
| HandlePhysRegUse(*I, Ret); |
| |
| // Add live-out registers as implicit uses. |
| if (!Ret->readsRegister(*I)) |
| Ret->addOperand(MachineOperand::CreateReg(*I, false, true)); |
| } |
| } |
| |
| // Loop over PhysRegDef / PhysRegUse, killing any registers that are |
| // available at the end of the basic block. |
| for (unsigned i = 0; i != NumRegs; ++i) |
| if (PhysRegDef[i] || PhysRegUse[i]) |
| HandlePhysRegDef(i, 0); |
| |
| std::fill(PhysRegDef, PhysRegDef + NumRegs, (MachineInstr*)0); |
| std::fill(PhysRegUse, PhysRegUse + NumRegs, (MachineInstr*)0); |
| } |
| |
| // Convert and transfer the dead / killed information we have gathered into |
| // VirtRegInfo onto MI's. |
| for (unsigned i = 0, e1 = VirtRegInfo.size(); i != e1; ++i) |
| for (unsigned j = 0, e2 = VirtRegInfo[i].Kills.size(); j != e2; ++j) |
| if (VirtRegInfo[i].Kills[j] == |
| MRI->getVRegDef(i + TargetRegisterInfo::FirstVirtualRegister)) |
| VirtRegInfo[i] |
| .Kills[j]->addRegisterDead(i + |
| TargetRegisterInfo::FirstVirtualRegister, |
| TRI); |
| else |
| VirtRegInfo[i] |
| .Kills[j]->addRegisterKilled(i + |
| TargetRegisterInfo::FirstVirtualRegister, |
| TRI); |
| |
| // Check to make sure there are no unreachable blocks in the MC CFG for the |
| // function. If so, it is due to a bug in the instruction selector or some |
| // other part of the code generator if this happens. |
| #ifndef NDEBUG |
| for(MachineFunction::iterator i = MF->begin(), e = MF->end(); i != e; ++i) |
| assert(Visited.count(&*i) != 0 && "unreachable basic block found"); |
| #endif |
| |
| delete[] PhysRegDef; |
| delete[] PhysRegUse; |
| delete[] PHIVarInfo; |
| |
| return false; |
| } |
| |
| /// replaceKillInstruction - Update register kill info by replacing a kill |
| /// instruction with a new one. |
| void LiveVariables::replaceKillInstruction(unsigned Reg, MachineInstr *OldMI, |
| MachineInstr *NewMI) { |
| VarInfo &VI = getVarInfo(Reg); |
| std::replace(VI.Kills.begin(), VI.Kills.end(), OldMI, NewMI); |
| } |
| |
| /// removeVirtualRegistersKilled - Remove all killed info for the specified |
| /// instruction. |
| void LiveVariables::removeVirtualRegistersKilled(MachineInstr *MI) { |
| for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) { |
| MachineOperand &MO = MI->getOperand(i); |
| if (MO.isReg() && MO.isKill()) { |
| MO.setIsKill(false); |
| unsigned Reg = MO.getReg(); |
| if (TargetRegisterInfo::isVirtualRegister(Reg)) { |
| bool removed = getVarInfo(Reg).removeKill(MI); |
| assert(removed && "kill not in register's VarInfo?"); |
| removed = true; |
| } |
| } |
| } |
| } |
| |
| /// analyzePHINodes - Gather information about the PHI nodes in here. In |
| /// particular, we want to map the variable information of a virtual register |
| /// which is used in a PHI node. We map that to the BB the vreg is coming from. |
| /// |
| void LiveVariables::analyzePHINodes(const MachineFunction& Fn) { |
| for (MachineFunction::const_iterator I = Fn.begin(), E = Fn.end(); |
| I != E; ++I) |
| for (MachineBasicBlock::const_iterator BBI = I->begin(), BBE = I->end(); |
| BBI != BBE && BBI->getOpcode() == TargetInstrInfo::PHI; ++BBI) |
| for (unsigned i = 1, e = BBI->getNumOperands(); i != e; i += 2) |
| PHIVarInfo[BBI->getOperand(i + 1).getMBB()->getNumber()] |
| .push_back(BBI->getOperand(i).getReg()); |
| } |
