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eb9f040f0d
Simplify the spill weight calculation a bit by bypassing getApproximateInstructionCount() and using LiveInterval::getSize() directly. This changes the computed spill weights, but only by a constant factor in each function. It should not affect how spill weights compare against each other, and so it shouldn't affect code generation. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@125530 91177308-0d34-0410-b5e6-96231b3b80d8
87 lines
3.0 KiB
C++
87 lines
3.0 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/CodeGen/MachineFunctionPass.h"
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#include "llvm/ADT/DenseMap.h"
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namespace llvm {
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class LiveInterval;
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class LiveIntervals;
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class MachineLoopInfo;
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/// normalizeSpillWeight - 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 magic constant 200 corresponds to approx. 25 instructions since
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// SlotIndexes allocate 8 slots per instruction.
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//
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// The constant is added to avoid depending too much on accidental SlotIndex
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// gaps for small intervals. The effect is that small intervals have a spill
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// weight that is mostly proportional to the number of uses, while large
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// intervals get a spill weight that is closer to a use density.
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//
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return UseDefFreq / (Size + 200);
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}
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/// VirtRegAuxInfo - Calculate auxiliary information for a virtual
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/// register such as its 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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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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mf_(mf), lis_(lis), loops_(loops) {}
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/// CalculateRegClass - recompute the register class for reg from its uses.
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/// Since the register class can affect the allocation hint, this function
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/// should be called before CalculateWeightAndHint if both are called.
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void CalculateRegClass(unsigned reg);
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/// CalculateWeightAndHint - (re)compute li's spill weight and allocation
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/// hint.
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void CalculateWeightAndHint(LiveInterval &li);
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};
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/// CalculateSpillWeights - Compute spill weights for all virtual register
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/// live intervals.
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class CalculateSpillWeights : public MachineFunctionPass {
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public:
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static char ID;
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CalculateSpillWeights() : MachineFunctionPass(ID) {
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initializeCalculateSpillWeightsPass(*PassRegistry::getPassRegistry());
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}
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virtual void getAnalysisUsage(AnalysisUsage &au) const;
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virtual bool runOnMachineFunction(MachineFunction &fn);
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private:
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/// Returns true if the given live interval is zero length.
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bool isZeroLengthInterval(LiveInterval *li) const;
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};
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}
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#endif // LLVM_CODEGEN_CALCSPILLWEIGHTS_H
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