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