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//===---------------- lib/CodeGen/CalcSpillWeights.h ------------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_CODEGEN_CALCSPILLWEIGHTS_H
#define LLVM_CODEGEN_CALCSPILLWEIGHTS_H
#include "llvm/ADT/DenseMap.h"
#include "llvm/CodeGen/SlotIndexes.h"
namespace llvm {
class LiveInterval;
class LiveIntervals;
class MachineLoopInfo;
/// normalizeSpillWeight - The spill weight of a live interval is computed as:
///
/// (sum(use freq) + sum(def freq)) / (K + size)
///
/// @param UseDefFreq Expected number of executed use and def instructions
/// per function call. Derived from block frequencies.
/// @param Size Size of live interval as returnexd by getSize()
///
static inline float normalizeSpillWeight(float UseDefFreq, unsigned Size) {
// The constant 25 instructions is added to avoid depending too much on
// accidental SlotIndex gaps for small intervals. The effect is that small
// intervals have a spill weight that is mostly proportional to the number
// of uses, while large intervals get a spill weight that is closer to a use
// density.
return UseDefFreq / (Size + 25*SlotIndex::InstrDist);
}
/// VirtRegAuxInfo - Calculate auxiliary information for a virtual
/// register such as its spill weight and allocation hint.
class VirtRegAuxInfo {
MachineFunction &MF;
LiveIntervals &LIS;
const MachineLoopInfo &Loops;
DenseMap<unsigned, float> Hint;
public:
VirtRegAuxInfo(MachineFunction &mf, LiveIntervals &lis,
const MachineLoopInfo &loops) :
MF(mf), LIS(lis), Loops(loops) {}
/// CalculateWeightAndHint - (re)compute li's spill weight and allocation
/// hint.
void CalculateWeightAndHint(LiveInterval &li);
};
/// CalculateSpillWeights - Compute spill weights for all virtual register
/// live intervals.
class CalculateSpillWeights : public MachineFunctionPass {
public:
static char ID;
CalculateSpillWeights() : MachineFunctionPass(ID) {
initializeCalculateSpillWeightsPass(*PassRegistry::getPassRegistry());
}
virtual void getAnalysisUsage(AnalysisUsage &au) const;
virtual bool runOnMachineFunction(MachineFunction &fn);
private:
/// Returns true if the given live interval is zero length.
bool isZeroLengthInterval(LiveInterval *li) const;
};
}
#endif // LLVM_CODEGEN_CALCSPILLWEIGHTS_H
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