| //===-- llvm/CodeGen/LiveVariables.h - Live Variable Analysis ---*- C++ -*-===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file was developed by the LLVM research group and is distributed under |
| // the University of Illinois Open Source License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This 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. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #ifndef LLVM_CODEGEN_LIVEVARIABLES_H |
| #define LLVM_CODEGEN_LIVEVARIABLES_H |
| |
| #include "llvm/CodeGen/MachineFunctionPass.h" |
| #include <map> |
| |
| class MRegisterInfo; |
| |
| class LiveVariables : public MachineFunctionPass { |
| public: |
| struct VarInfo { |
| /// DefBlock - The basic block which defines this value... |
| MachineBasicBlock *DefBlock; |
| MachineInstr *DefInst; |
| |
| /// AliveBlocks - Set of blocks of which this value is alive completely |
| /// through. This is a bit set which uses the basic block number as an |
| /// index. |
| /// |
| std::vector<bool> AliveBlocks; |
| |
| /// Kills - List of MachineBasicblock's which contain the last use of this |
| /// virtual register (kill it). This also includes the specific instruction |
| /// which kills the value. |
| /// |
| std::vector<std::pair<MachineBasicBlock*, MachineInstr*> > Kills; |
| |
| VarInfo() : DefBlock(0), DefInst(0) {} |
| |
| /// removeKill - Delete a kill corresponding to the specified machine instr |
| void removeKill(MachineInstr *MI) { |
| for (unsigned i = 0; ; ++i) { |
| assert(i < Kills.size() && "Machine instr is not a kill!"); |
| if (Kills[i].second == MI) { |
| Kills.erase(Kills.begin()+i); |
| return; |
| } |
| } |
| } |
| }; |
| |
| private: |
| /// VirtRegInfo - This list is a mapping from virtual register number to |
| /// variable information. FirstVirtualRegister is subtracted from the virtual |
| /// register number before indexing into this list. |
| /// |
| std::vector<VarInfo> VirtRegInfo; |
| |
| /// RegistersKilled - This multimap keeps track of all of the registers that |
| /// are dead immediately after an instruction reads its operands. If an |
| /// instruction does not have an entry in this map, it kills no registers. |
| /// |
| std::multimap<MachineInstr*, unsigned> RegistersKilled; |
| |
| /// RegistersDead - This multimap keeps track of all of the registers that are |
| /// dead immediately after an instruction executes, which are not dead after |
| /// the operands are evaluated. In practice, this only contains registers |
| /// which are defined by an instruction, but never used. |
| /// |
| std::multimap<MachineInstr*, unsigned> RegistersDead; |
| |
| /// AllocatablePhysicalRegisters - This vector keeps track of which registers |
| /// are actually register allocatable by the target machine. We can not track |
| /// liveness for values that are not in this set. |
| /// |
| std::vector<bool> AllocatablePhysicalRegisters; |
| |
| private: // Intermediate data structures |
| |
| /// BBMap - Maps LLVM basic blocks to their corresponding machine basic block. |
| /// This also provides a numbering of the basic blocks in the function. |
| std::map<const BasicBlock*, std::pair<MachineBasicBlock*, unsigned> > BBMap; |
| |
| const MRegisterInfo *RegInfo; |
| |
| MachineInstr **PhysRegInfo; |
| bool *PhysRegUsed; |
| |
| public: |
| |
| virtual bool runOnMachineFunction(MachineFunction &MF); |
| |
| /// getMachineBasicBlockIndex - Turn a MachineBasicBlock into an index number |
| /// suitable for use with VarInfo's. |
| /// |
| const std::pair<MachineBasicBlock*, unsigned> |
| &getMachineBasicBlockInfo(MachineBasicBlock *MBB) const; |
| const std::pair<MachineBasicBlock*, unsigned> |
| &getBasicBlockInfo(const BasicBlock *BB) const { |
| return BBMap.find(BB)->second; |
| } |
| |
| |
| /// killed_iterator - Iterate over registers killed by a machine instruction |
| /// |
| typedef std::multimap<MachineInstr*, unsigned>::iterator killed_iterator; |
| |
| /// killed_begin/end - Get access to the range of registers killed by a |
| /// machine instruction. |
| killed_iterator killed_begin(MachineInstr *MI) { |
| return RegistersKilled.lower_bound(MI); |
| } |
| killed_iterator killed_end(MachineInstr *MI) { |
| return RegistersKilled.upper_bound(MI); |
| } |
| std::pair<killed_iterator, killed_iterator> |
| killed_range(MachineInstr *MI) { |
| return RegistersKilled.equal_range(MI); |
| } |
| |
| killed_iterator dead_begin(MachineInstr *MI) { |
| return RegistersDead.lower_bound(MI); |
| } |
| killed_iterator dead_end(MachineInstr *MI) { |
| return RegistersDead.upper_bound(MI); |
| } |
| std::pair<killed_iterator, killed_iterator> |
| dead_range(MachineInstr *MI) { |
| return RegistersDead.equal_range(MI); |
| } |
| |
| //===--------------------------------------------------------------------===// |
| // API to update live variable information |
| |
| /// addVirtualRegisterKilled - Add information about the fact that the |
| /// specified register is killed after being used by the specified |
| /// instruction. |
| /// |
| void addVirtualRegisterKilled(unsigned IncomingReg, MachineBasicBlock *MBB, |
| MachineInstr *MI) { |
| RegistersKilled.insert(std::make_pair(MI, IncomingReg)); |
| getVarInfo(IncomingReg).Kills.push_back(std::make_pair(MBB, MI)); |
| } |
| |
| /// removeVirtualRegistersKilled - Remove all of the specified killed |
| /// registers from the live variable information. |
| void removeVirtualRegistersKilled(killed_iterator B, killed_iterator E) { |
| for (killed_iterator I = B; I != E; ++I) // Remove VarInfo entries... |
| getVarInfo(I->second).removeKill(I->first); |
| RegistersKilled.erase(B, E); |
| } |
| |
| /// addVirtualRegisterDead - Add information about the fact that the specified |
| /// register is dead after being used by the specified instruction. |
| /// |
| void addVirtualRegisterDead(unsigned IncomingReg, MachineBasicBlock *MBB, |
| MachineInstr *MI) { |
| RegistersDead.insert(std::make_pair(MI, IncomingReg)); |
| getVarInfo(IncomingReg).Kills.push_back(std::make_pair(MBB, MI)); |
| } |
| |
| /// removeVirtualRegistersKilled - Remove all of the specified killed |
| /// registers from the live variable information. |
| void removeVirtualRegistersDead(killed_iterator B, killed_iterator E) { |
| for (killed_iterator I = B; I != E; ++I) // Remove VarInfo entries... |
| getVarInfo(I->second).removeKill(I->first); |
| RegistersDead.erase(B, E); |
| } |
| |
| virtual void getAnalysisUsage(AnalysisUsage &AU) const { |
| AU.setPreservesAll(); |
| } |
| |
| virtual void releaseMemory() { |
| VirtRegInfo.clear(); |
| RegistersKilled.clear(); |
| RegistersDead.clear(); |
| BBMap.clear(); |
| } |
| |
| /// getVarInfo - Return the VarInfo structure for the specified VIRTUAL |
| /// register. |
| VarInfo &getVarInfo(unsigned RegIdx); |
| |
| void MarkVirtRegAliveInBlock(VarInfo &VRInfo, const BasicBlock *BB); |
| void HandleVirtRegUse(VarInfo &VRInfo, MachineBasicBlock *MBB, |
| MachineInstr *MI); |
| void HandlePhysRegUse(unsigned Reg, MachineInstr *MI); |
| void HandlePhysRegDef(unsigned Reg, MachineInstr *MI); |
| }; |
| |
| #endif |