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| 14 | pmbaty | 1 | //===- llvm/CodeGen/AntiDepBreaker.h - Anti-Dependence Breaking -*- C++ -*-===// |
| 2 | // |
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| 3 | // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
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| 4 | // See https://llvm.org/LICENSE.txt for license information. |
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| 5 | // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
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| 6 | // |
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| 7 | //===----------------------------------------------------------------------===// |
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| 8 | // |
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| 9 | // This file implements the AntiDepBreaker class, which implements |
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| 10 | // anti-dependence breaking heuristics for post-register-allocation scheduling. |
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| 11 | // |
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| 12 | //===----------------------------------------------------------------------===// |
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| 13 | |||
| 14 | #ifndef LLVM_CODEGEN_ANTIDEPBREAKER_H |
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| 15 | #define LLVM_CODEGEN_ANTIDEPBREAKER_H |
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| 16 | |||
| 17 | #include "llvm/ADT/iterator_range.h" |
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| 18 | #include "llvm/CodeGen/MachineBasicBlock.h" |
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| 19 | #include "llvm/CodeGen/MachineInstr.h" |
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| 20 | #include "llvm/CodeGen/TargetSubtargetInfo.h" |
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| 21 | #include "llvm/Support/Compiler.h" |
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| 22 | #include <cassert> |
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| 23 | #include <utility> |
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| 24 | #include <vector> |
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| 25 | |||
| 26 | namespace llvm { |
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| 27 | |||
| 28 | class RegisterClassInfo; |
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| 29 | |||
| 30 | /// This class works in conjunction with the post-RA scheduler to rename |
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| 31 | /// registers to break register anti-dependencies (WAR hazards). |
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| 32 | class AntiDepBreaker { |
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| 33 | public: |
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| 34 | using DbgValueVector = |
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| 35 | std::vector<std::pair<MachineInstr *, MachineInstr *>>; |
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| 36 | |||
| 37 | virtual ~AntiDepBreaker(); |
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| 38 | |||
| 39 | /// Initialize anti-dep breaking for a new basic block. |
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| 40 | virtual void StartBlock(MachineBasicBlock *BB) = 0; |
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| 41 | |||
| 42 | /// Identifiy anti-dependencies within a basic-block region and break them by |
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| 43 | /// renaming registers. Return the number of anti-dependencies broken. |
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| 44 | virtual unsigned BreakAntiDependencies(const std::vector<SUnit> &SUnits, |
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| 45 | MachineBasicBlock::iterator Begin, |
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| 46 | MachineBasicBlock::iterator End, |
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| 47 | unsigned InsertPosIndex, |
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| 48 | DbgValueVector &DbgValues) = 0; |
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| 49 | |||
| 50 | /// Update liveness information to account for the current |
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| 51 | /// instruction, which will not be scheduled. |
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| 52 | virtual void Observe(MachineInstr &MI, unsigned Count, |
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| 53 | unsigned InsertPosIndex) = 0; |
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| 54 | |||
| 55 | /// Finish anti-dep breaking for a basic block. |
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| 56 | virtual void FinishBlock() = 0; |
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| 57 | |||
| 58 | /// Update DBG_VALUE or DBG_PHI if dependency breaker is updating |
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| 59 | /// other machine instruction to use NewReg. |
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| 60 | void UpdateDbgValue(MachineInstr &MI, unsigned OldReg, unsigned NewReg) { |
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| 61 | if (MI.isDebugValue()) { |
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| 62 | if (MI.getDebugOperand(0).isReg() && |
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| 63 | MI.getDebugOperand(0).getReg() == OldReg) |
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| 64 | MI.getDebugOperand(0).setReg(NewReg); |
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| 65 | } else if (MI.isDebugPHI()) { |
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| 66 | if (MI.getOperand(0).isReg() && |
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| 67 | MI.getOperand(0).getReg() == OldReg) |
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| 68 | MI.getOperand(0).setReg(NewReg); |
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| 69 | } else { |
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| 70 | llvm_unreachable("MI is not DBG_VALUE / DBG_PHI!"); |
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| 71 | } |
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| 72 | } |
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| 73 | |||
| 74 | /// Update all DBG_VALUE instructions that may be affected by the dependency |
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| 75 | /// breaker's update of ParentMI to use NewReg. |
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| 76 | void UpdateDbgValues(const DbgValueVector &DbgValues, MachineInstr *ParentMI, |
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| 77 | unsigned OldReg, unsigned NewReg) { |
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| 78 | // The following code is dependent on the order in which the DbgValues are |
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| 79 | // constructed in ScheduleDAGInstrs::buildSchedGraph. |
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| 80 | MachineInstr *PrevDbgMI = nullptr; |
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| 81 | for (const auto &DV : make_range(DbgValues.crbegin(), DbgValues.crend())) { |
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| 82 | MachineInstr *PrevMI = DV.second; |
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| 83 | if ((PrevMI == ParentMI) || (PrevMI == PrevDbgMI)) { |
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| 84 | MachineInstr *DbgMI = DV.first; |
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| 85 | UpdateDbgValue(*DbgMI, OldReg, NewReg); |
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| 86 | PrevDbgMI = DbgMI; |
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| 87 | } else if (PrevDbgMI) { |
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| 88 | break; // If no match and already found a DBG_VALUE, we're done. |
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| 89 | } |
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| 90 | } |
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| 91 | } |
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| 92 | }; |
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| 93 | |||
| 94 | AntiDepBreaker *createAggressiveAntiDepBreaker( |
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| 95 | MachineFunction &MFi, const RegisterClassInfo &RCI, |
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| 96 | TargetSubtargetInfo::RegClassVector &CriticalPathRCs); |
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| 97 | |||
| 98 | AntiDepBreaker *createCriticalAntiDepBreaker(MachineFunction &MFi, |
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| 99 | const RegisterClassInfo &RCI); |
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| 100 | |||
| 101 | } // end namespace llvm |
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| 102 | |||
| 103 | #endif // LLVM_CODEGEN_ANTIDEPBREAKER_H |