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 TargetInstrInfo &TII;
30    const TargetRegisterInfo &TRI;
31
32    /// DstReg - The register that will be left after coalescing. It can be a
33    /// virtual or physical register.
34    unsigned DstReg;
35
36    /// SrcReg - the virtual register that will be coalesced into dstReg.
37    unsigned SrcReg;
38
39    /// subReg_ - The subregister index of srcReg in DstReg. It is possible the
40    /// coalesce SrcReg into a subreg of the larger DstReg when DstReg is a
41    /// virtual register.
42    unsigned SubIdx;
43
44    /// Partial - True when the original copy was a partial subregister copy.
45    bool Partial;
46
47    /// CrossClass - True when both regs are virtual, and newRC is constrained.
48    bool CrossClass;
49
50    /// Flipped - True when DstReg and SrcReg are reversed from the oriignal
51    /// copy instruction.
52    bool Flipped;
53
54    /// NewRC - The register class of the coalesced register, or NULL if DstReg
55    /// is a physreg.
56    const TargetRegisterClass *NewRC;
57
58  public:
59    CoalescerPair(const TargetInstrInfo &tii, const TargetRegisterInfo &tri)
60      : TII(tii), TRI(tri), DstReg(0), SrcReg(0), SubIdx(0),
61        Partial(false), CrossClass(false), Flipped(false), NewRC(0) {}
62
63    /// setRegisters - set registers to match the copy instruction MI. Return
64    /// false if MI is not a coalescable copy instruction.
65    bool setRegisters(const MachineInstr*);
66
67    /// flip - Swap SrcReg and DstReg. Return false if swapping is impossible
68    /// because DstReg is a physical register, or SubIdx is set.
69    bool flip();
70
71    /// isCoalescable - Return true if MI is a copy instruction that will become
72    /// an identity copy after coalescing.
73    bool isCoalescable(const MachineInstr*) const;
74
75    /// isPhys - Return true if DstReg is a physical register.
76    bool isPhys() const { return !NewRC; }
77
78    /// isPartial - Return true if the original copy instruction did not copy
79    /// the full register, but was a subreg operation.
80    bool isPartial() const { return Partial; }
81
82    /// isCrossClass - Return true if DstReg is virtual and NewRC is a smaller
83    /// register class than DstReg's.
84    bool isCrossClass() const { return CrossClass; }
85
86    /// isFlipped - Return true when getSrcReg is the register being defined by
87    /// the original copy instruction.
88    bool isFlipped() const { return Flipped; }
89
90    /// getDstReg - Return the register (virtual or physical) that will remain
91    /// after coalescing.
92    unsigned getDstReg() const { return DstReg; }
93
94    /// getSrcReg - Return the virtual register that will be coalesced away.
95    unsigned getSrcReg() const { return SrcReg; }
96
97    /// getSubIdx - Return the subregister index in DstReg that SrcReg will be
98    /// coalesced into, or 0.
99    unsigned getSubIdx() const { return SubIdx; }
100
101    /// getNewRC - Return the register class of the coalesced register.
102    const TargetRegisterClass *getNewRC() const { return NewRC; }
103  };
104} // End llvm namespace
105
106#endif
107