1//===- llvm/CodeGen/CriticalAntiDepBreaker.h - Anti-Dep Support -*- 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 implements the CriticalAntiDepBreaker class, which
10// implements register anti-dependence breaking along a blocks
11// critical path during post-RA scheduler.
12//
13//===----------------------------------------------------------------------===//
14
15#ifndef LLVM_LIB_CODEGEN_CRITICALANTIDEPBREAKER_H
16#define LLVM_LIB_CODEGEN_CRITICALANTIDEPBREAKER_H
17
18#include "llvm/ADT/BitVector.h"
19#include "llvm/CodeGen/AntiDepBreaker.h"
20#include "llvm/Support/Compiler.h"
21#include <map>
22#include <vector>
23
24namespace llvm {
25
26class MachineBasicBlock;
27class MachineFunction;
28class MachineInstr;
29class MachineOperand;
30class MachineRegisterInfo;
31class RegisterClassInfo;
32class TargetInstrInfo;
33class MCRegisterClass;
34using TargetRegisterClass = MCRegisterClass;
35class TargetRegisterInfo;
36
37class LLVM_LIBRARY_VISIBILITY CriticalAntiDepBreaker : public AntiDepBreaker {
38 MachineFunction& MF;
39 MachineRegisterInfo &MRI;
40 const TargetInstrInfo *TII;
41 const TargetRegisterInfo *TRI;
42 const RegisterClassInfo &RegClassInfo;
43
44 /// The set of allocatable registers.
45 /// We'll be ignoring anti-dependencies on non-allocatable registers,
46 /// because they may not be safe to break.
47 const BitVector AllocatableSet;
48
49 /// For live regs that are only used in one register class in a
50 /// live range, the register class. If the register is not live, the
51 /// corresponding value is null. If the register is live but used in
52 /// multiple register classes, the corresponding value is -1 casted to a
53 /// pointer.
54 std::vector<const TargetRegisterClass *> Classes;
55
56 /// Map registers to all their references within a live range.
57 std::multimap<MCRegister, MachineOperand *> RegRefs;
58
59 using RegRefIter =
60 std::multimap<MCRegister, MachineOperand *>::const_iterator;
61
62 /// The index of the most recent kill (proceeding bottom-up),
63 /// or ~0u if the register is not live.
64 std::vector<unsigned> KillIndices;
65
66 /// The index of the most recent complete def (proceeding
67 /// bottom up), or ~0u if the register is live.
68 std::vector<unsigned> DefIndices;
69
70 /// A set of registers which are live and cannot be changed to
71 /// break anti-dependencies.
72 BitVector KeepRegs;
73
74 public:
75 CriticalAntiDepBreaker(MachineFunction& MFi, const RegisterClassInfo &RCI);
76 ~CriticalAntiDepBreaker() override;
77
78 /// Initialize anti-dep breaking for a new basic block.
79 void StartBlock(MachineBasicBlock *BB) override;
80
81 /// Identifiy anti-dependencies along the critical path
82 /// of the ScheduleDAG and break them by renaming registers.
83 unsigned BreakAntiDependencies(const std::vector<SUnit> &SUnits,
84 MachineBasicBlock::iterator Begin,
85 MachineBasicBlock::iterator End,
86 unsigned InsertPosIndex,
87 DbgValueVector &DbgValues) override;
88
89 /// Update liveness information to account for the current
90 /// instruction, which will not be scheduled.
91 void Observe(MachineInstr &MI, unsigned Count,
92 unsigned InsertPosIndex) override;
93
94 /// Finish anti-dep breaking for a basic block.
95 void FinishBlock() override;
96
97 private:
98 void PrescanInstruction(MachineInstr &MI);
99 void ScanInstruction(MachineInstr &MI, unsigned Count);
100 bool isNewRegClobberedByRefs(RegRefIter RegRefBegin, RegRefIter RegRefEnd,
101 MCRegister NewReg);
102 MCRegister
103 findSuitableFreeRegister(RegRefIter RegRefBegin, RegRefIter RegRefEnd,
104 MCRegister AntiDepReg, MCRegister LastNewReg,
105 const TargetRegisterClass *RC,
106 const SmallVectorImpl<Register> &Forbid);
107 };
108
109} // end namespace llvm
110
111#endif // LLVM_LIB_CODEGEN_CRITICALANTIDEPBREAKER_H
112