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 /// normalizeSpillWeight - The spill weight of a live interval is computed as: 25 /// 26 /// (sum(use freq) + sum(def freq)) / (K + size) 27 /// 28 /// @param UseDefFreq Expected number of executed use and def instructions 29 /// per function call. Derived from block frequencies. 30 /// @param Size Size of live interval as returnexd by getSize() 31 /// 32 static inline float normalizeSpillWeight(float UseDefFreq, unsigned Size) { 33 // The constant 25 instructions is added to avoid depending too much on 34 // accidental SlotIndex gaps for small intervals. The effect is that small 35 // intervals have a spill weight that is mostly proportional to the number 36 // of uses, while large intervals get a spill weight that is closer to a use 37 // density. 38 return UseDefFreq / (Size + 25*SlotIndex::InstrDist); 39 } 40 41 /// VirtRegAuxInfo - Calculate auxiliary information for a virtual 42 /// register such as its spill weight and allocation hint. 43 class VirtRegAuxInfo { 44 MachineFunction &MF; 45 LiveIntervals &LIS; 46 const MachineLoopInfo &Loops; 47 const MachineBlockFrequencyInfo &MBFI; 48 DenseMap<unsigned, float> Hint; 49 public: 50 VirtRegAuxInfo(MachineFunction &mf, LiveIntervals &lis, 51 const MachineLoopInfo &loops, 52 const MachineBlockFrequencyInfo &mbfi) 53 : MF(mf), LIS(lis), Loops(loops), MBFI(mbfi) {} 54 55 /// CalculateWeightAndHint - (re)compute li's spill weight and allocation 56 /// hint. 57 void CalculateWeightAndHint(LiveInterval &li); 58 }; 59 60 /// CalculateSpillWeights - Compute spill weights for all virtual register 61 /// live intervals. 62 class CalculateSpillWeights : public MachineFunctionPass { 63 public: 64 static char ID; 65 66 CalculateSpillWeights() : MachineFunctionPass(ID) { 67 initializeCalculateSpillWeightsPass(*PassRegistry::getPassRegistry()); 68 } 69 70 virtual void getAnalysisUsage(AnalysisUsage &au) const; 71 72 virtual bool runOnMachineFunction(MachineFunction &fn); 73 74 private: 75 /// Returns true if the given live interval is zero length. 76 bool isZeroLengthInterval(LiveInterval *li) const; 77 }; 78 79 } 80 81 #endif // LLVM_CODEGEN_CALCSPILLWEIGHTS_H 82
