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      1 //===-- llvm/CodeGen/VirtRegMap.h - Virtual Register Map -*- C++ -*--------===//
      2 //
      3 //                     The LLVM Compiler Infrastructure
      4 //
      5 // This file is distributed under the University of Illinois Open Source
      6 // License. See LICENSE.TXT for details.
      7 //
      8 //===----------------------------------------------------------------------===//
      9 //
     10 // This file implements a virtual register map. This maps virtual registers to
     11 // physical registers and virtual registers to stack slots. It is created and
     12 // updated by a register allocator and then used by a machine code rewriter that
     13 // adds spill code and rewrites virtual into physical register references.
     14 //
     15 //===----------------------------------------------------------------------===//
     16 
     17 #ifndef LLVM_CODEGEN_VIRTREGMAP_H
     18 #define LLVM_CODEGEN_VIRTREGMAP_H
     19 
     20 #include "llvm/ADT/IndexedMap.h"
     21 #include "llvm/CodeGen/MachineFunctionPass.h"
     22 #include "llvm/Target/TargetRegisterInfo.h"
     23 
     24 namespace llvm {
     25   class MachineInstr;
     26   class MachineFunction;
     27   class MachineRegisterInfo;
     28   class TargetInstrInfo;
     29   class raw_ostream;
     30   class SlotIndexes;
     31 
     32   class VirtRegMap : public MachineFunctionPass {
     33   public:
     34     enum {
     35       NO_PHYS_REG = 0,
     36       NO_STACK_SLOT = (1L << 30)-1,
     37       MAX_STACK_SLOT = (1L << 18)-1
     38     };
     39 
     40   private:
     41     MachineRegisterInfo *MRI;
     42     const TargetInstrInfo *TII;
     43     const TargetRegisterInfo *TRI;
     44     MachineFunction *MF;
     45 
     46     /// Virt2PhysMap - This is a virtual to physical register
     47     /// mapping. Each virtual register is required to have an entry in
     48     /// it; even spilled virtual registers (the register mapped to a
     49     /// spilled register is the temporary used to load it from the
     50     /// stack).
     51     IndexedMap<unsigned, VirtReg2IndexFunctor> Virt2PhysMap;
     52 
     53     /// Virt2StackSlotMap - This is virtual register to stack slot
     54     /// mapping. Each spilled virtual register has an entry in it
     55     /// which corresponds to the stack slot this register is spilled
     56     /// at.
     57     IndexedMap<int, VirtReg2IndexFunctor> Virt2StackSlotMap;
     58 
     59     /// Virt2SplitMap - This is virtual register to splitted virtual register
     60     /// mapping.
     61     IndexedMap<unsigned, VirtReg2IndexFunctor> Virt2SplitMap;
     62 
     63     /// createSpillSlot - Allocate a spill slot for RC from MFI.
     64     unsigned createSpillSlot(const TargetRegisterClass *RC);
     65 
     66     VirtRegMap(const VirtRegMap&) LLVM_DELETED_FUNCTION;
     67     void operator=(const VirtRegMap&) LLVM_DELETED_FUNCTION;
     68 
     69   public:
     70     static char ID;
     71     VirtRegMap() : MachineFunctionPass(ID), Virt2PhysMap(NO_PHYS_REG),
     72                    Virt2StackSlotMap(NO_STACK_SLOT), Virt2SplitMap(0) { }
     73     virtual bool runOnMachineFunction(MachineFunction &MF);
     74 
     75     virtual void getAnalysisUsage(AnalysisUsage &AU) const {
     76       AU.setPreservesAll();
     77       MachineFunctionPass::getAnalysisUsage(AU);
     78     }
     79 
     80     MachineFunction &getMachineFunction() const {
     81       assert(MF && "getMachineFunction called before runOnMachineFunction");
     82       return *MF;
     83     }
     84 
     85     MachineRegisterInfo &getRegInfo() const { return *MRI; }
     86     const TargetRegisterInfo &getTargetRegInfo() const { return *TRI; }
     87 
     88     void grow();
     89 
     90     /// @brief returns true if the specified virtual register is
     91     /// mapped to a physical register
     92     bool hasPhys(unsigned virtReg) const {
     93       return getPhys(virtReg) != NO_PHYS_REG;
     94     }
     95 
     96     /// @brief returns the physical register mapped to the specified
     97     /// virtual register
     98     unsigned getPhys(unsigned virtReg) const {
     99       assert(TargetRegisterInfo::isVirtualRegister(virtReg));
    100       return Virt2PhysMap[virtReg];
    101     }
    102 
    103     /// @brief creates a mapping for the specified virtual register to
    104     /// the specified physical register
    105     void assignVirt2Phys(unsigned virtReg, unsigned physReg) {
    106       assert(TargetRegisterInfo::isVirtualRegister(virtReg) &&
    107              TargetRegisterInfo::isPhysicalRegister(physReg));
    108       assert(Virt2PhysMap[virtReg] == NO_PHYS_REG &&
    109              "attempt to assign physical register to already mapped "
    110              "virtual register");
    111       Virt2PhysMap[virtReg] = physReg;
    112     }
    113 
    114     /// @brief clears the specified virtual register's, physical
    115     /// register mapping
    116     void clearVirt(unsigned virtReg) {
    117       assert(TargetRegisterInfo::isVirtualRegister(virtReg));
    118       assert(Virt2PhysMap[virtReg] != NO_PHYS_REG &&
    119              "attempt to clear a not assigned virtual register");
    120       Virt2PhysMap[virtReg] = NO_PHYS_REG;
    121     }
    122 
    123     /// @brief clears all virtual to physical register mappings
    124     void clearAllVirt() {
    125       Virt2PhysMap.clear();
    126       grow();
    127     }
    128 
    129     /// @brief returns true if VirtReg is assigned to its preferred physreg.
    130     bool hasPreferredPhys(unsigned VirtReg);
    131 
    132     /// @brief returns true if VirtReg has a known preferred register.
    133     /// This returns false if VirtReg has a preference that is a virtual
    134     /// register that hasn't been assigned yet.
    135     bool hasKnownPreference(unsigned VirtReg);
    136 
    137     /// @brief records virtReg is a split live interval from SReg.
    138     void setIsSplitFromReg(unsigned virtReg, unsigned SReg) {
    139       Virt2SplitMap[virtReg] = SReg;
    140     }
    141 
    142     /// @brief returns the live interval virtReg is split from.
    143     unsigned getPreSplitReg(unsigned virtReg) const {
    144       return Virt2SplitMap[virtReg];
    145     }
    146 
    147     /// getOriginal - Return the original virtual register that VirtReg descends
    148     /// from through splitting.
    149     /// A register that was not created by splitting is its own original.
    150     /// This operation is idempotent.
    151     unsigned getOriginal(unsigned VirtReg) const {
    152       unsigned Orig = getPreSplitReg(VirtReg);
    153       return Orig ? Orig : VirtReg;
    154     }
    155 
    156     /// @brief returns true if the specified virtual register is not
    157     /// mapped to a stack slot or rematerialized.
    158     bool isAssignedReg(unsigned virtReg) const {
    159       if (getStackSlot(virtReg) == NO_STACK_SLOT)
    160         return true;
    161       // Split register can be assigned a physical register as well as a
    162       // stack slot or remat id.
    163       return (Virt2SplitMap[virtReg] && Virt2PhysMap[virtReg] != NO_PHYS_REG);
    164     }
    165 
    166     /// @brief returns the stack slot mapped to the specified virtual
    167     /// register
    168     int getStackSlot(unsigned virtReg) const {
    169       assert(TargetRegisterInfo::isVirtualRegister(virtReg));
    170       return Virt2StackSlotMap[virtReg];
    171     }
    172 
    173     /// @brief create a mapping for the specifed virtual register to
    174     /// the next available stack slot
    175     int assignVirt2StackSlot(unsigned virtReg);
    176     /// @brief create a mapping for the specified virtual register to
    177     /// the specified stack slot
    178     void assignVirt2StackSlot(unsigned virtReg, int frameIndex);
    179 
    180     void print(raw_ostream &OS, const Module* M = 0) const;
    181     void dump() const;
    182   };
    183 
    184   inline raw_ostream &operator<<(raw_ostream &OS, const VirtRegMap &VRM) {
    185     VRM.print(OS);
    186     return OS;
    187   }
    188 } // End llvm namespace
    189 
    190 #endif
    191