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 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