1 //===- llvm/CodeGen/CriticalAntiDepBreaker.h - Anti-Dep Support -*- C++ -*-===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 // 10 // This file implements the CriticalAntiDepBreaker class, which 11 // implements register anti-dependence breaking along a blocks 12 // critical path during post-RA scheduler. 13 // 14 //===----------------------------------------------------------------------===// 15 16 #ifndef LLVM_LIB_CODEGEN_CRITICALANTIDEPBREAKER_H 17 #define LLVM_LIB_CODEGEN_CRITICALANTIDEPBREAKER_H 18 19 #include "AntiDepBreaker.h" 20 #include "llvm/ADT/BitVector.h" 21 #include "llvm/Support/Compiler.h" 22 #include <map> 23 #include <vector> 24 25 namespace llvm { 26 27 class MachineBasicBlock; 28 class MachineFunction; 29 class MachineInstr; 30 class MachineOperand; 31 class MachineRegisterInfo; 32 class RegisterClassInfo; 33 class TargetInstrInfo; 34 class TargetRegisterClass; 35 class TargetRegisterInfo; 36 37 class 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<unsigned, MachineOperand *> RegRefs; 58 59 using RegRefIter = 60 std::multimap<unsigned, 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, 101 RegRefIter RegRefEnd, 102 unsigned NewReg); 103 unsigned findSuitableFreeRegister(RegRefIter RegRefBegin, 104 RegRefIter RegRefEnd, 105 unsigned AntiDepReg, 106 unsigned LastNewReg, 107 const TargetRegisterClass *RC, 108 SmallVectorImpl<unsigned> &Forbid); 109 }; 110 111 } // end namespace llvm 112 113 #endif // LLVM_LIB_CODEGEN_CRITICALANTIDEPBREAKER_H 114