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/CodeGen/SlotIndexes.h" 15 #include "llvm/ADT/DenseMap.h" 16 17 namespace llvm { 18 19 class LiveInterval; 20 class LiveIntervals; 21 class MachineLoopInfo; 22 23 /// normalizeSpillWeight - The spill weight of a live interval is computed as: 24 /// 25 /// (sum(use freq) + sum(def freq)) / (K + size) 26 /// 27 /// @param UseDefFreq Expected number of executed use and def instructions 28 /// per function call. Derived from block frequencies. 29 /// @param Size Size of live interval as returnexd by getSize() 30 /// 31 static inline float normalizeSpillWeight(float UseDefFreq, unsigned Size) { 32 // The constant 25 instructions is added to avoid depending too much on 33 // accidental SlotIndex gaps for small intervals. The effect is that small 34 // intervals have a spill weight that is mostly proportional to the number 35 // of uses, while large intervals get a spill weight that is closer to a use 36 // density. 37 return UseDefFreq / (Size + 25*SlotIndex::InstrDist); 38 } 39 40 /// VirtRegAuxInfo - Calculate auxiliary information for a virtual 41 /// register such as its spill weight and allocation hint. 42 class VirtRegAuxInfo { 43 MachineFunction &MF; 44 LiveIntervals &LIS; 45 const MachineLoopInfo &Loops; 46 DenseMap<unsigned, float> Hint; 47 public: 48 VirtRegAuxInfo(MachineFunction &mf, LiveIntervals &lis, 49 const MachineLoopInfo &loops) : 50 MF(mf), LIS(lis), Loops(loops) {} 51 52 /// CalculateRegClass - recompute the register class for reg from its uses. 53 /// Since the register class can affect the allocation hint, this function 54 /// should be called before CalculateWeightAndHint if both are called. 55 void CalculateRegClass(unsigned reg); 56 57 /// CalculateWeightAndHint - (re)compute li's spill weight and allocation 58 /// hint. 59 void CalculateWeightAndHint(LiveInterval &li); 60 }; 61 62 /// CalculateSpillWeights - Compute spill weights for all virtual register 63 /// live intervals. 64 class CalculateSpillWeights : public MachineFunctionPass { 65 public: 66 static char ID; 67 68 CalculateSpillWeights() : MachineFunctionPass(ID) { 69 initializeCalculateSpillWeightsPass(*PassRegistry::getPassRegistry()); 70 } 71 72 virtual void getAnalysisUsage(AnalysisUsage &au) const; 73 74 virtual bool runOnMachineFunction(MachineFunction &fn); 75 76 private: 77 /// Returns true if the given live interval is zero length. 78 bool isZeroLengthInterval(LiveInterval *li) const; 79 }; 80 81 } 82 83 #endif // LLVM_CODEGEN_CALCSPILLWEIGHTS_H 84
