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926576cff3
Based on discussions with Lang Hames and Jakob Stoklund Olesen at the hacker's lab, and in the light of upcoming work on the PBQP register allocator, it was though that CalcSpillWeights does not need to be a pass. This change will enable to customize / tune the spill weight computation depending on the allocator. Update the documentation style while there. No functionnal change. llvm-svn: 194269
71 lines
2.5 KiB
C++
71 lines
2.5 KiB
C++
//===---------------- lib/CodeGen/CalcSpillWeights.h ------------*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_CODEGEN_CALCSPILLWEIGHTS_H
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#define LLVM_CODEGEN_CALCSPILLWEIGHTS_H
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#include "llvm/ADT/DenseMap.h"
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#include "llvm/CodeGen/SlotIndexes.h"
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namespace llvm {
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class LiveInterval;
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class LiveIntervals;
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class MachineBlockFrequencyInfo;
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class MachineLoopInfo;
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/// \brief Normalize the spill weight of a live interval
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///
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/// The spill weight of a live interval is computed as:
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///
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/// (sum(use freq) + sum(def freq)) / (K + size)
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///
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/// @param UseDefFreq Expected number of executed use and def instructions
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/// per function call. Derived from block frequencies.
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/// @param Size Size of live interval as returnexd by getSize()
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///
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static inline float normalizeSpillWeight(float UseDefFreq, unsigned Size) {
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// The constant 25 instructions is added to avoid depending too much on
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// accidental SlotIndex gaps for small intervals. The effect is that small
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// intervals have a spill weight that is mostly proportional to the number
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// of uses, while large intervals get a spill weight that is closer to a use
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// density.
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return UseDefFreq / (Size + 25*SlotIndex::InstrDist);
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}
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/// \brief Calculate auxiliary information for a virtual register such as its
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/// spill weight and allocation hint.
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class VirtRegAuxInfo {
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MachineFunction &MF;
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LiveIntervals &LIS;
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const MachineLoopInfo &Loops;
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const MachineBlockFrequencyInfo &MBFI;
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DenseMap<unsigned, float> Hint;
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public:
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VirtRegAuxInfo(MachineFunction &mf, LiveIntervals &lis,
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const MachineLoopInfo &loops,
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const MachineBlockFrequencyInfo &mbfi)
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: MF(mf), LIS(lis), Loops(loops), MBFI(mbfi) {}
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/// \brief (re)compute li's spill weight and allocation hint.
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void CalculateWeightAndHint(LiveInterval &li);
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};
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/// \brief Compute spill weights and allocation hints for all virtual register
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/// live intervals.
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void calculateSpillWeights(LiveIntervals &LIS,
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MachineFunction &MF,
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const MachineLoopInfo &MLI,
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const MachineBlockFrequencyInfo &MBFI);
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}
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#endif // LLVM_CODEGEN_CALCSPILLWEIGHTS_H
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