LLVM  4.0.0
RegisterCoalescer.h
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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_LIB_CODEGEN_REGISTERCOALESCER_H
16 #define LLVM_LIB_CODEGEN_REGISTERCOALESCER_H
17 
18 namespace llvm {
19 
20  class MachineInstr;
21  class TargetRegisterInfo;
22  class TargetRegisterClass;
23  class TargetInstrInfo;
24 
25  /// 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  /// The register that will be left after coalescing. It can be a
32  /// virtual or physical register.
33  unsigned DstReg;
34 
35  /// The virtual register that will be coalesced into dstReg.
36  unsigned SrcReg;
37 
38  /// The sub-register index of the old DstReg in the new coalesced register.
39  unsigned DstIdx;
40 
41  /// The sub-register index of the old SrcReg in the new coalesced register.
42  unsigned SrcIdx;
43 
44  /// True when the original copy was a partial subregister copy.
45  bool Partial;
46 
47  /// True when both regs are virtual and newRC is constrained.
48  bool CrossClass;
49 
50  /// True when DstReg and SrcReg are reversed from the original
51  /// copy instruction.
52  bool Flipped;
53 
54  /// The register class of the coalesced register, or NULL if DstReg
55  /// is a physreg. This register class may be a super-register of both
56  /// SrcReg and DstReg.
57  const TargetRegisterClass *NewRC;
58 
59  public:
61  : TRI(tri), DstReg(0), SrcReg(0), DstIdx(0), SrcIdx(0),
62  Partial(false), CrossClass(false), Flipped(false), NewRC(nullptr) {}
63 
64  /// Create a CoalescerPair representing a virtreg-to-physreg copy.
65  /// No need to call setRegisters().
66  CoalescerPair(unsigned VirtReg, unsigned PhysReg,
67  const TargetRegisterInfo &tri)
68  : TRI(tri), DstReg(PhysReg), SrcReg(VirtReg), DstIdx(0), SrcIdx(0),
69  Partial(false), CrossClass(false), Flipped(false), NewRC(nullptr) {}
70 
71  /// Set registers to match the copy instruction MI. Return
72  /// false if MI is not a coalescable copy instruction.
73  bool setRegisters(const MachineInstr*);
74 
75  /// Swap SrcReg and DstReg. Return false if swapping is impossible
76  /// because DstReg is a physical register, or SubIdx is set.
77  bool flip();
78 
79  /// Return true if MI is a copy instruction that will become
80  /// an identity copy after coalescing.
81  bool isCoalescable(const MachineInstr*) const;
82 
83  /// Return true if DstReg is a physical register.
84  bool isPhys() const { return !NewRC; }
85 
86  /// Return true if the original copy instruction did not copy
87  /// the full register, but was a subreg operation.
88  bool isPartial() const { return Partial; }
89 
90  /// Return true if DstReg is virtual and NewRC is a smaller
91  /// register class than DstReg's.
92  bool isCrossClass() const { return CrossClass; }
93 
94  /// Return true when getSrcReg is the register being defined by
95  /// the original copy instruction.
96  bool isFlipped() const { return Flipped; }
97 
98  /// Return the register (virtual or physical) that will remain
99  /// after coalescing.
100  unsigned getDstReg() const { return DstReg; }
101 
102  /// Return the virtual register that will be coalesced away.
103  unsigned getSrcReg() const { return SrcReg; }
104 
105  /// Return the subregister index that DstReg will be coalesced into, or 0.
106  unsigned getDstIdx() const { return DstIdx; }
107 
108  /// Return the subregister index that SrcReg will be coalesced into, or 0.
109  unsigned getSrcIdx() const { return SrcIdx; }
110 
111  /// Return the register class of the coalesced register.
112  const TargetRegisterClass *getNewRC() const { return NewRC; }
113  };
114 } // End llvm namespace
115 
116 #endif
unsigned getDstReg() const
Return the register (virtual or physical) that will remain after coalescing.
bool isCrossClass() const
Return true if DstReg is virtual and NewRC is a smaller register class than DstReg's.
bool isFlipped() const
Return true when getSrcReg is the register being defined by the original copy instruction.
A helper class for register coalescers.
Function Alias Analysis false
CoalescerPair(const TargetRegisterInfo &tri)
bool setRegisters(const MachineInstr *)
Set registers to match the copy instruction MI.
const TargetRegisterClass * getNewRC() const
Return the register class of the coalesced register.
TargetRegisterInfo base class - We assume that the target defines a static array of TargetRegisterDes...
bool isPhys() const
Return true if DstReg is a physical register.
bool isCoalescable(const MachineInstr *) const
Return true if MI is a copy instruction that will become an identity copy after coalescing.
unsigned getDstIdx() const
Return the subregister index that DstReg will be coalesced into, or 0.
unsigned getSrcIdx() const
Return the subregister index that SrcReg will be coalesced into, or 0.
Representation of each machine instruction.
Definition: MachineInstr.h:52
CoalescerPair(unsigned VirtReg, unsigned PhysReg, const TargetRegisterInfo &tri)
Create a CoalescerPair representing a virtreg-to-physreg copy.
bool flip()
Swap SrcReg and DstReg.
bool isPartial() const
Return true if the original copy instruction did not copy the full register, but was a subreg operati...
unsigned getSrcReg() const
Return the virtual register that will be coalesced away.