1 //===---------------- lib/CodeGen/CalcSpillWeights.h ------------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
11 #ifndef LLVM_CODEGEN_CALCSPILLWEIGHTS_H
12 #define LLVM_CODEGEN_CALCSPILLWEIGHTS_H
14 #include "llvm/ADT/DenseMap.h"
15 #include "llvm/CodeGen/SlotIndexes.h"
21 class MachineBlockFrequencyInfo;
22 class MachineLoopInfo;
24 /// normalizeSpillWeight - The spill weight of a live interval is computed as:
26 /// (sum(use freq) + sum(def freq)) / (K + size)
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()
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
38 return UseDefFreq / (Size + 25*SlotIndex::InstrDist);
41 /// VirtRegAuxInfo - Calculate auxiliary information for a virtual
42 /// register such as its spill weight and allocation hint.
43 class VirtRegAuxInfo {
46 const MachineLoopInfo &Loops;
47 const MachineBlockFrequencyInfo &MBFI;
48 DenseMap<unsigned, float> Hint;
50 VirtRegAuxInfo(MachineFunction &mf, LiveIntervals &lis,
51 const MachineLoopInfo &loops,
52 const MachineBlockFrequencyInfo &mbfi)
53 : MF(mf), LIS(lis), Loops(loops), MBFI(mbfi) {}
55 /// CalculateWeightAndHint - (re)compute li's spill weight and allocation
57 void CalculateWeightAndHint(LiveInterval &li);
60 /// CalculateSpillWeights - Compute spill weights for all virtual register
62 class CalculateSpillWeights : public MachineFunctionPass {
66 CalculateSpillWeights() : MachineFunctionPass(ID) {
67 initializeCalculateSpillWeightsPass(*PassRegistry::getPassRegistry());
70 virtual void getAnalysisUsage(AnalysisUsage &au) const;
72 virtual bool runOnMachineFunction(MachineFunction &fn);
75 /// Returns true if the given live interval is zero length.
76 bool isZeroLengthInterval(LiveInterval *li) const;
81 #endif // LLVM_CODEGEN_CALCSPILLWEIGHTS_H