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 11 #ifndef LLVM_CODEGEN_CALCSPILLWEIGHTS_H 12 #define LLVM_CODEGEN_CALCSPILLWEIGHTS_H 13 14 #include "llvm/ADT/DenseMap.h" 15 #include "llvm/CodeGen/SlotIndexes.h" 16 17 namespace llvm { 18 19 class LiveInterval; 20 class LiveIntervals; 21 class MachineBlockFrequencyInfo; 22 class MachineLoopInfo; 23 24 /// \brief Normalize the spill weight of a live interval 25 /// 26 /// The spill weight of a live interval is computed as: 27 /// 28 /// (sum(use freq) + sum(def freq)) / (K + size) 29 /// 30 /// @param UseDefFreq Expected number of executed use and def instructions 31 /// per function call. Derived from block frequencies. 32 /// @param Size Size of live interval as returnexd by getSize() 33 /// @param NumInstr Number of instructions using this live interval 34 /// 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 typedef float (*NormalizingFn)(float, unsigned, unsigned); 50 51 private: 52 MachineFunction &MF; 53 LiveIntervals &LIS; 54 const MachineLoopInfo &Loops; 55 const MachineBlockFrequencyInfo &MBFI; 56 DenseMap<unsigned, float> Hint; 57 NormalizingFn normalize; 58 59 public: 60 VirtRegAuxInfo(MachineFunction &mf, LiveIntervals &lis, 61 const MachineLoopInfo &loops, 62 const MachineBlockFrequencyInfo &mbfi, 63 NormalizingFn norm = normalizeSpillWeight) 64 : MF(mf), LIS(lis), Loops(loops), MBFI(mbfi), normalize(norm) {} 65 66 /// \brief (re)compute li's spill weight and allocation hint. 67 void calculateSpillWeightAndHint(LiveInterval &li); 68 }; 69 70 /// \brief Compute spill weights and allocation hints for all virtual register 71 /// live intervals. 72 void calculateSpillWeightsAndHints(LiveIntervals &LIS, MachineFunction &MF, 73 const MachineLoopInfo &MLI, 74 const MachineBlockFrequencyInfo &MBFI, 75 VirtRegAuxInfo::NormalizingFn norm = 76 normalizeSpillWeight); 77 } 78 79 #endif // LLVM_CODEGEN_CALCSPILLWEIGHTS_H 80
