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//===- RegAllocScore.cpp - evaluate regalloc policy quality ---------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
/// Calculate a measure of the register allocation policy quality. This is used
/// to construct a reward for the training of the ML-driven allocation policy.
/// Currently, the score is the sum of the machine basic block frequency-weighed
/// number of loads, stores, copies, and remat instructions, each factored with
/// a relative weight.
//===----------------------------------------------------------------------===//
#include "RegAllocScore.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/TargetInstrInfo.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/Format.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetMachine.h"
#include <cassert>
#include <cstdint>
#include <numeric>
#include <vector>
using namespace llvm;
cl::opt<double> CopyWeight("regalloc-copy-weight", cl::init(0.2), cl::Hidden);
cl::opt<double> LoadWeight("regalloc-load-weight", cl::init(4.0), cl::Hidden);
cl::opt<double> StoreWeight("regalloc-store-weight", cl::init(1.0), cl::Hidden);
cl::opt<double> CheapRematWeight("regalloc-cheap-remat-weight", cl::init(0.2),
cl::Hidden);
cl::opt<double> ExpensiveRematWeight("regalloc-expensive-remat-weight",
cl::init(1.0), cl::Hidden);
#define DEBUG_TYPE "regalloc-score"
RegAllocScore &RegAllocScore::operator+=(const RegAllocScore &Other) {
CopyCounts += Other.copyCounts();
LoadCounts += Other.loadCounts();
StoreCounts += Other.storeCounts();
LoadStoreCounts += Other.loadStoreCounts();
CheapRematCounts += Other.cheapRematCounts();
ExpensiveRematCounts += Other.expensiveRematCounts();
return *this;
}
bool RegAllocScore::operator==(const RegAllocScore &Other) const {
return copyCounts() == Other.copyCounts() &&
loadCounts() == Other.loadCounts() &&
storeCounts() == Other.storeCounts() &&
loadStoreCounts() == Other.loadStoreCounts() &&
cheapRematCounts() == Other.cheapRematCounts() &&
expensiveRematCounts() == Other.expensiveRematCounts();
}
bool RegAllocScore::operator!=(const RegAllocScore &Other) const {
return !(*this == Other);
}
double RegAllocScore::getScore() const {
double Ret = 0.0;
Ret += CopyWeight * copyCounts();
Ret += LoadWeight * loadCounts();
Ret += StoreWeight * storeCounts();
Ret += (LoadWeight + StoreWeight) * loadStoreCounts();
Ret += CheapRematWeight * cheapRematCounts();
Ret += ExpensiveRematWeight * expensiveRematCounts();
return Ret;
}
RegAllocScore
llvm::calculateRegAllocScore(const MachineFunction &MF,
const MachineBlockFrequencyInfo &MBFI,
AAResults &AAResults) {
return calculateRegAllocScore(
MF,
[&](const MachineBasicBlock &MBB) {
return MBFI.getBlockFreqRelativeToEntryBlock(&MBB);
},
[&](const MachineInstr &MI) {
return MF.getSubtarget().getInstrInfo()->isTriviallyReMaterializable(
MI, &AAResults);
});
}
RegAllocScore llvm::calculateRegAllocScore(
const MachineFunction &MF,
llvm::function_ref<double(const MachineBasicBlock &)> GetBBFreq,
llvm::function_ref<bool(const MachineInstr &)>
IsTriviallyRematerializable) {
RegAllocScore Total;
for (const MachineBasicBlock &MBB : MF) {
double BlockFreqRelativeToEntrypoint = GetBBFreq(MBB);
RegAllocScore MBBScore;
for (const MachineInstr &MI : MBB) {
if (MI.isDebugInstr() || MI.isKill() || MI.isInlineAsm()) {
continue;
}
if (MI.isCopy()) {
MBBScore.onCopy(BlockFreqRelativeToEntrypoint);
} else if (IsTriviallyRematerializable(MI)) {
if (MI.getDesc().isAsCheapAsAMove()) {
MBBScore.onCheapRemat(BlockFreqRelativeToEntrypoint);
} else {
MBBScore.onExpensiveRemat(BlockFreqRelativeToEntrypoint);
}
} else if (MI.mayLoad() && MI.mayStore()) {
MBBScore.onLoadStore(BlockFreqRelativeToEntrypoint);
} else if (MI.mayLoad()) {
MBBScore.onLoad(BlockFreqRelativeToEntrypoint);
} else if (MI.mayStore()) {
MBBScore.onStore(BlockFreqRelativeToEntrypoint);
}
}
Total += MBBScore;
}
return Total;
}
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