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
17namespace 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    /// CalculateWeightAndHint - (re)compute li's spill weight and allocation
53    /// hint.
54    void CalculateWeightAndHint(LiveInterval &li);
55  };
56
57  /// CalculateSpillWeights - Compute spill weights for all virtual register
58  /// live intervals.
59  class CalculateSpillWeights : public MachineFunctionPass {
60  public:
61    static char ID;
62
63    CalculateSpillWeights() : MachineFunctionPass(ID) {
64      initializeCalculateSpillWeightsPass(*PassRegistry::getPassRegistry());
65    }
66
67    virtual void getAnalysisUsage(AnalysisUsage &au) const;
68
69    virtual bool runOnMachineFunction(MachineFunction &fn);
70
71  private:
72    /// Returns true if the given live interval is zero length.
73    bool isZeroLengthInterval(LiveInterval *li) const;
74  };
75
76}
77
78#endif // LLVM_CODEGEN_CALCSPILLWEIGHTS_H
79