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