1//===- RegisterCoalescer.h - Register Coalescing Interface ------*- C++ -*-===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file contains the abstract interface for register coalescers,
10// allowing them to interact with and query register allocators.
11//
12//===----------------------------------------------------------------------===//
13
14#ifndef LLVM_LIB_CODEGEN_REGISTERCOALESCER_H
15#define LLVM_LIB_CODEGEN_REGISTERCOALESCER_H
16
17#include "llvm/CodeGen/MachinePassManager.h"
18#include "llvm/CodeGen/Register.h"
19
20namespace llvm {
21
22class MachineInstr;
23class TargetRegisterClass;
24class TargetRegisterInfo;
25
26/// A helper class for register coalescers. When deciding if
27/// two registers can be coalesced, CoalescerPair can determine if a copy
28/// instruction would become an identity copy after coalescing.
29class CoalescerPair {
30 const TargetRegisterInfo &TRI;
31
32 /// The register that will be left after coalescing. It can be a
33 /// virtual or physical register.
34 Register DstReg;
35
36 /// The virtual register that will be coalesced into dstReg.
37 Register SrcReg;
38
39 /// The sub-register index of the old DstReg in the new coalesced register.
40 unsigned DstIdx = 0;
41
42 /// The sub-register index of the old SrcReg in the new coalesced register.
43 unsigned SrcIdx = 0;
44
45 /// True when the original copy was a partial subregister copy.
46 bool Partial = false;
47
48 /// True when both regs are virtual and newRC is constrained.
49 bool CrossClass = false;
50
51 /// True when DstReg and SrcReg are reversed from the original
52 /// copy instruction.
53 bool Flipped = false;
54
55 /// The register class of the coalesced register, or NULL if DstReg
56 /// is a physreg. This register class may be a super-register of both
57 /// SrcReg and DstReg.
58 const TargetRegisterClass *NewRC = nullptr;
59
60public:
61 CoalescerPair(const TargetRegisterInfo &tri) : TRI(tri) {}
62
63 /// Create a CoalescerPair representing a virtreg-to-physreg copy.
64 /// No need to call setRegisters().
65 CoalescerPair(Register VirtReg, MCRegister PhysReg,
66 const TargetRegisterInfo &tri)
67 : TRI(tri), DstReg(PhysReg), SrcReg(VirtReg) {}
68
69 /// Set registers to match the copy instruction MI. Return
70 /// false if MI is not a coalescable copy instruction.
71 bool setRegisters(const MachineInstr *);
72
73 /// Swap SrcReg and DstReg. Return false if swapping is impossible
74 /// because DstReg is a physical register, or SubIdx is set.
75 bool flip();
76
77 /// Return true if MI is a copy instruction that will become
78 /// an identity copy after coalescing.
79 bool isCoalescable(const MachineInstr *) const;
80
81 /// Return true if DstReg is a physical register.
82 bool isPhys() const { return !NewRC; }
83
84 /// Return true if the original copy instruction did not copy
85 /// the full register, but was a subreg operation.
86 bool isPartial() const { return Partial; }
87
88 /// Return true if DstReg is virtual and NewRC is a smaller
89 /// register class than DstReg's.
90 bool isCrossClass() const { return CrossClass; }
91
92 /// Return true when getSrcReg is the register being defined by
93 /// the original copy instruction.
94 bool isFlipped() const { return Flipped; }
95
96 /// Return the register (virtual or physical) that will remain
97 /// after coalescing.
98 Register getDstReg() const { return DstReg; }
99
100 /// Return the virtual register that will be coalesced away.
101 Register getSrcReg() const { return SrcReg; }
102
103 /// Return the subregister index that DstReg will be coalesced into, or 0.
104 unsigned getDstIdx() const { return DstIdx; }
105
106 /// Return the subregister index that SrcReg will be coalesced into, or 0.
107 unsigned getSrcIdx() const { return SrcIdx; }
108
109 /// Return the register class of the coalesced register.
110 const TargetRegisterClass *getNewRC() const { return NewRC; }
111};
112
113} // end namespace llvm
114
115#endif // LLVM_LIB_CODEGEN_REGISTERCOALESCER_H
116