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 24 namespace llvm { 25 26 class MachineBasicBlock; 27 class MachineFunction; 28 class MachineInstr; 29 class MachineOperand; 30 class MachineRegisterInfo; 31 class RegisterClassInfo; 32 class TargetInstrInfo; 33 class TargetRegisterClass; 34 class TargetRegisterInfo; 35 36 class 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<unsigned, MachineOperand *> RegRefs; 57 58 using RegRefIter = 59 std::multimap<unsigned, 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, 100 RegRefIter RegRefEnd, 101 unsigned NewReg); 102 unsigned findSuitableFreeRegister(RegRefIter RegRefBegin, 103 RegRefIter RegRefEnd, 104 unsigned AntiDepReg, 105 unsigned LastNewReg, 106 const TargetRegisterClass *RC, 107 SmallVectorImpl<unsigned> &Forbid); 108 }; 109 110 } // end namespace llvm 111 112 #endif // LLVM_LIB_CODEGEN_CRITICALANTIDEPBREAKER_H 113