Details | Last modification | View Log | RSS feed
Rev | Author | Line No. | Line |
---|---|---|---|
14 | pmbaty | 1 | //===- llvm/CodeGen/AntiDepBreaker.h - Anti-Dependence Breaking -*- 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 AntiDepBreaker class, which implements |
||
10 | // anti-dependence breaking heuristics for post-register-allocation scheduling. |
||
11 | // |
||
12 | //===----------------------------------------------------------------------===// |
||
13 | |||
14 | #ifndef LLVM_CODEGEN_ANTIDEPBREAKER_H |
||
15 | #define LLVM_CODEGEN_ANTIDEPBREAKER_H |
||
16 | |||
17 | #include "llvm/ADT/iterator_range.h" |
||
18 | #include "llvm/CodeGen/MachineBasicBlock.h" |
||
19 | #include "llvm/CodeGen/MachineInstr.h" |
||
20 | #include "llvm/CodeGen/TargetSubtargetInfo.h" |
||
21 | #include "llvm/Support/Compiler.h" |
||
22 | #include <cassert> |
||
23 | #include <utility> |
||
24 | #include <vector> |
||
25 | |||
26 | namespace llvm { |
||
27 | |||
28 | class RegisterClassInfo; |
||
29 | |||
30 | /// This class works in conjunction with the post-RA scheduler to rename |
||
31 | /// registers to break register anti-dependencies (WAR hazards). |
||
32 | class AntiDepBreaker { |
||
33 | public: |
||
34 | using DbgValueVector = |
||
35 | std::vector<std::pair<MachineInstr *, MachineInstr *>>; |
||
36 | |||
37 | virtual ~AntiDepBreaker(); |
||
38 | |||
39 | /// Initialize anti-dep breaking for a new basic block. |
||
40 | virtual void StartBlock(MachineBasicBlock *BB) = 0; |
||
41 | |||
42 | /// Identifiy anti-dependencies within a basic-block region and break them by |
||
43 | /// renaming registers. Return the number of anti-dependencies broken. |
||
44 | virtual unsigned BreakAntiDependencies(const std::vector<SUnit> &SUnits, |
||
45 | MachineBasicBlock::iterator Begin, |
||
46 | MachineBasicBlock::iterator End, |
||
47 | unsigned InsertPosIndex, |
||
48 | DbgValueVector &DbgValues) = 0; |
||
49 | |||
50 | /// Update liveness information to account for the current |
||
51 | /// instruction, which will not be scheduled. |
||
52 | virtual void Observe(MachineInstr &MI, unsigned Count, |
||
53 | unsigned InsertPosIndex) = 0; |
||
54 | |||
55 | /// Finish anti-dep breaking for a basic block. |
||
56 | virtual void FinishBlock() = 0; |
||
57 | |||
58 | /// Update DBG_VALUE or DBG_PHI if dependency breaker is updating |
||
59 | /// other machine instruction to use NewReg. |
||
60 | void UpdateDbgValue(MachineInstr &MI, unsigned OldReg, unsigned NewReg) { |
||
61 | if (MI.isDebugValue()) { |
||
62 | if (MI.getDebugOperand(0).isReg() && |
||
63 | MI.getDebugOperand(0).getReg() == OldReg) |
||
64 | MI.getDebugOperand(0).setReg(NewReg); |
||
65 | } else if (MI.isDebugPHI()) { |
||
66 | if (MI.getOperand(0).isReg() && |
||
67 | MI.getOperand(0).getReg() == OldReg) |
||
68 | MI.getOperand(0).setReg(NewReg); |
||
69 | } else { |
||
70 | llvm_unreachable("MI is not DBG_VALUE / DBG_PHI!"); |
||
71 | } |
||
72 | } |
||
73 | |||
74 | /// Update all DBG_VALUE instructions that may be affected by the dependency |
||
75 | /// breaker's update of ParentMI to use NewReg. |
||
76 | void UpdateDbgValues(const DbgValueVector &DbgValues, MachineInstr *ParentMI, |
||
77 | unsigned OldReg, unsigned NewReg) { |
||
78 | // The following code is dependent on the order in which the DbgValues are |
||
79 | // constructed in ScheduleDAGInstrs::buildSchedGraph. |
||
80 | MachineInstr *PrevDbgMI = nullptr; |
||
81 | for (const auto &DV : make_range(DbgValues.crbegin(), DbgValues.crend())) { |
||
82 | MachineInstr *PrevMI = DV.second; |
||
83 | if ((PrevMI == ParentMI) || (PrevMI == PrevDbgMI)) { |
||
84 | MachineInstr *DbgMI = DV.first; |
||
85 | UpdateDbgValue(*DbgMI, OldReg, NewReg); |
||
86 | PrevDbgMI = DbgMI; |
||
87 | } else if (PrevDbgMI) { |
||
88 | break; // If no match and already found a DBG_VALUE, we're done. |
||
89 | } |
||
90 | } |
||
91 | } |
||
92 | }; |
||
93 | |||
94 | AntiDepBreaker *createAggressiveAntiDepBreaker( |
||
95 | MachineFunction &MFi, const RegisterClassInfo &RCI, |
||
96 | TargetSubtargetInfo::RegClassVector &CriticalPathRCs); |
||
97 | |||
98 | AntiDepBreaker *createCriticalAntiDepBreaker(MachineFunction &MFi, |
||
99 | const RegisterClassInfo &RCI); |
||
100 | |||
101 | } // end namespace llvm |
||
102 | |||
103 | #endif // LLVM_CODEGEN_ANTIDEPBREAKER_H |