1//===-- RegisterCoalescer.h - Register Coalescing Interface -----*- 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 contains the abstract interface for register coalescers,
11// allowing them to interact with and query register allocators.
12//
13//===----------------------------------------------------------------------===//
14
15#ifndef LLVM_CODEGEN_REGISTER_COALESCER_H
16#define LLVM_CODEGEN_REGISTER_COALESCER_H
17
18namespace llvm {
19
20  class MachineInstr;
21  class TargetRegisterInfo;
22  class TargetRegisterClass;
23  class TargetInstrInfo;
24
25  /// CoalescerPair - A helper class for register coalescers. When deciding if
26  /// two registers can be coalesced, CoalescerPair can determine if a copy
27  /// instruction would become an identity copy after coalescing.
28  class CoalescerPair {
29    const TargetRegisterInfo &TRI;
30
31    /// DstReg - The register that will be left after coalescing. It can be a
32    /// virtual or physical register.
33    unsigned DstReg;
34
35    /// SrcReg - the virtual register that will be coalesced into dstReg.
36    unsigned SrcReg;
37
38    /// DstIdx - The sub-register index of the old DstReg in the new coalesced
39    /// register.
40    unsigned DstIdx;
41
42    /// SrcIdx - The sub-register index of the old SrcReg in the new coalesced
43    /// register.
44    unsigned SrcIdx;
45
46    /// Partial - True when the original copy was a partial subregister copy.
47    bool Partial;
48
49    /// CrossClass - True when both regs are virtual, and newRC is constrained.
50    bool CrossClass;
51
52    /// Flipped - True when DstReg and SrcReg are reversed from the original
53    /// copy instruction.
54    bool Flipped;
55
56    /// NewRC - The register class of the coalesced register, or NULL if DstReg
57    /// is a physreg. This register class may be a super-register of both
58    /// SrcReg and DstReg.
59    const TargetRegisterClass *NewRC;
60
61  public:
62    CoalescerPair(const TargetRegisterInfo &tri)
63      : TRI(tri), DstReg(0), SrcReg(0), DstIdx(0), SrcIdx(0),
64        Partial(false), CrossClass(false), Flipped(false), NewRC(nullptr) {}
65
66    /// Create a CoalescerPair representing a virtreg-to-physreg copy.
67    /// No need to call setRegisters().
68    CoalescerPair(unsigned VirtReg, unsigned PhysReg,
69                  const TargetRegisterInfo &tri)
70      : TRI(tri), DstReg(PhysReg), SrcReg(VirtReg), DstIdx(0), SrcIdx(0),
71        Partial(false), CrossClass(false), Flipped(false), NewRC(nullptr) {}
72
73    /// setRegisters - set registers to match the copy instruction MI. Return
74    /// false if MI is not a coalescable copy instruction.
75    bool setRegisters(const MachineInstr*);
76
77    /// flip - Swap SrcReg and DstReg. Return false if swapping is impossible
78    /// because DstReg is a physical register, or SubIdx is set.
79    bool flip();
80
81    /// isCoalescable - Return true if MI is a copy instruction that will become
82    /// an identity copy after coalescing.
83    bool isCoalescable(const MachineInstr*) const;
84
85    /// isPhys - Return true if DstReg is a physical register.
86    bool isPhys() const { return !NewRC; }
87
88    /// isPartial - Return true if the original copy instruction did not copy
89    /// the full register, but was a subreg operation.
90    bool isPartial() const { return Partial; }
91
92    /// isCrossClass - Return true if DstReg is virtual and NewRC is a smaller
93    /// register class than DstReg's.
94    bool isCrossClass() const { return CrossClass; }
95
96    /// isFlipped - Return true when getSrcReg is the register being defined by
97    /// the original copy instruction.
98    bool isFlipped() const { return Flipped; }
99
100    /// getDstReg - Return the register (virtual or physical) that will remain
101    /// after coalescing.
102    unsigned getDstReg() const { return DstReg; }
103
104    /// getSrcReg - Return the virtual register that will be coalesced away.
105    unsigned getSrcReg() const { return SrcReg; }
106
107    /// getDstIdx - Return the subregister index that DstReg will be coalesced
108    /// into, or 0.
109    unsigned getDstIdx() const { return DstIdx; }
110
111    /// getSrcIdx - Return the subregister index that SrcReg will be coalesced
112    /// into, or 0.
113    unsigned getSrcIdx() const { return SrcIdx; }
114
115    /// getNewRC - Return the register class of the coalesced register.
116    const TargetRegisterClass *getNewRC() const { return NewRC; }
117  };
118} // End llvm namespace
119
120#endif
121