1 //===- lib/CodeGen/CalcSpillWeights.h ---------------------------*- 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 #ifndef LLVM_CODEGEN_CALCSPILLWEIGHTS_H 11 #define LLVM_CODEGEN_CALCSPILLWEIGHTS_H 12 13 #include "llvm/ADT/DenseMap.h" 14 #include "llvm/CodeGen/SlotIndexes.h" 15 16 namespace llvm { 17 18 class LiveInterval; 19 class LiveIntervals; 20 class MachineBlockFrequencyInfo; 21 class MachineFunction; 22 class MachineLoopInfo; 23 class VirtRegMap; 24 25 /// \brief Normalize the spill weight of a live interval 26 /// 27 /// The spill weight of a live interval is computed as: 28 /// 29 /// (sum(use freq) + sum(def freq)) / (K + size) 30 /// 31 /// @param UseDefFreq Expected number of executed use and def instructions 32 /// per function call. Derived from block frequencies. 33 /// @param Size Size of live interval as returnexd by getSize() 34 /// @param NumInstr Number of instructions using this live interval 35 static inline float normalizeSpillWeight(float UseDefFreq, unsigned Size, 36 unsigned NumInstr) { 37 // The constant 25 instructions is added to avoid depending too much on 38 // accidental SlotIndex gaps for small intervals. The effect is that small 39 // intervals have a spill weight that is mostly proportional to the number 40 // of uses, while large intervals get a spill weight that is closer to a use 41 // density. 42 return UseDefFreq / (Size + 25*SlotIndex::InstrDist); 43 } 44 45 /// \brief Calculate auxiliary information for a virtual register such as its 46 /// spill weight and allocation hint. 47 class VirtRegAuxInfo { 48 public: 49 using NormalizingFn = float (*)(float, unsigned, unsigned); 50 51 private: 52 MachineFunction &MF; 53 LiveIntervals &LIS; 54 VirtRegMap *VRM; 55 const MachineLoopInfo &Loops; 56 const MachineBlockFrequencyInfo &MBFI; 57 DenseMap<unsigned, float> Hint; 58 NormalizingFn normalize; 59 60 public: 61 VirtRegAuxInfo(MachineFunction &mf, LiveIntervals &lis, 62 VirtRegMap *vrm, const MachineLoopInfo &loops, 63 const MachineBlockFrequencyInfo &mbfi, 64 NormalizingFn norm = normalizeSpillWeight) 65 : MF(mf), LIS(lis), VRM(vrm), Loops(loops), MBFI(mbfi), normalize(norm) {} 66 67 /// \brief (re)compute li's spill weight and allocation hint. 68 void calculateSpillWeightAndHint(LiveInterval &li); 69 }; 70 71 /// \brief Compute spill weights and allocation hints for all virtual register 72 /// live intervals. 73 void calculateSpillWeightsAndHints(LiveIntervals &LIS, MachineFunction &MF, 74 VirtRegMap *VRM, 75 const MachineLoopInfo &MLI, 76 const MachineBlockFrequencyInfo &MBFI, 77 VirtRegAuxInfo::NormalizingFn norm = 78 normalizeSpillWeight); 79 80 } // end namespace llvm 81 82 #endif // LLVM_CODEGEN_CALCSPILLWEIGHTS_H 83
