llvm/lib/CodeGen/RegAllocScore.cpp

   1 //===- RegAllocScore.cpp - evaluate regalloc policy quality ---------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 /// Calculate a measure of the register allocation policy quality. This is used
   9 /// to construct a reward for the training of the ML-driven allocation policy.
  10 /// Currently, the score is the sum of the machine basic block frequency-weighed
  11 /// number of loads, stores, copies, and remat instructions, each factored with
  12 /// a relative weight.
  13 //===----------------------------------------------------------------------===//
  14
  15 #include "RegAllocScore.h"
  16 #include "llvm/ADT/SetVector.h"
  17 #include "llvm/Analysis/AliasAnalysis.h"
  18 #include "llvm/CodeGen/MachineFrameInfo.h"
  19 #include "llvm/CodeGen/MachineRegisterInfo.h"
  20 #include "llvm/CodeGen/TargetInstrInfo.h"
  21 #include "llvm/Support/Debug.h"
  22 #include "llvm/Support/Format.h"
  23 #include "llvm/Support/raw_ostream.h"
  24 #include "llvm/Target/TargetMachine.h"
  25 #include <cassert>
  26 #include <cstdint>
  27 #include <numeric>
  28 #include <vector>
  29
  30 using namespace llvm;
  31 cl::opt<double> CopyWeight("regalloc-copy-weight", cl::init(0.2), cl::Hidden);
  32 cl::opt<double> LoadWeight("regalloc-load-weight", cl::init(4.0), cl::Hidden);
  33 cl::opt<double> StoreWeight("regalloc-store-weight", cl::init(1.0), cl::Hidden);
  34 cl::opt<double> CheapRematWeight("regalloc-cheap-remat-weight", cl::init(0.2),
  35                                  cl::Hidden);
  36 cl::opt<double> ExpensiveRematWeight("regalloc-expensive-remat-weight",
  37                                      cl::init(1.0), cl::Hidden);
  38 #define DEBUG_TYPE "regalloc-score"
  39
  40 RegAllocScore &RegAllocScore::operator+=(const RegAllocScore &Other) {
  41   CopyCounts += Other.copyCounts();
  42   LoadCounts += Other.loadCounts();
  43   StoreCounts += Other.storeCounts();
  44   LoadStoreCounts += Other.loadStoreCounts();
  45   CheapRematCounts += Other.cheapRematCounts();
  46   ExpensiveRematCounts += Other.expensiveRematCounts();
  47   return *this;
  48 }
  49
  50 bool RegAllocScore::operator==(const RegAllocScore &Other) const {
  51   return copyCounts() == Other.copyCounts() &&
  52          loadCounts() == Other.loadCounts() &&
  53          storeCounts() == Other.storeCounts() &&
  54          loadStoreCounts() == Other.loadStoreCounts() &&
  55          cheapRematCounts() == Other.cheapRematCounts() &&
  56          expensiveRematCounts() == Other.expensiveRematCounts();
  57 }
  58
  59 bool RegAllocScore::operator!=(const RegAllocScore &Other) const {
  60   return !(*this == Other);
  61 }
  62
  63 double RegAllocScore::getScore() const {
  64   double Ret = 0.0;
  65   Ret += CopyWeight * copyCounts();
  66   Ret += LoadWeight * loadCounts();
  67   Ret += StoreWeight * storeCounts();
  68   Ret += (LoadWeight + StoreWeight) * loadStoreCounts();
  69   Ret += CheapRematWeight * cheapRematCounts();
  70   Ret += ExpensiveRematWeight * expensiveRematCounts();
  71
  72   return Ret;
  73 }
  74
  75 RegAllocScore
  76 llvm::calculateRegAllocScore(const MachineFunction &MF,
  77                              const MachineBlockFrequencyInfo &MBFI,
  78                              AAResults &AAResults) {
  79   return calculateRegAllocScore(
  80       MF,
  81       [&](const MachineBasicBlock &MBB) {
  82         return MBFI.getBlockFreqRelativeToEntryBlock(&MBB);
  83       },
  84       [&](const MachineInstr &MI) {
  85         return MF.getSubtarget().getInstrInfo()->isTriviallyReMaterializable(
  86             MI, &AAResults);
  87       });
  88 }
  89
  90 RegAllocScore llvm::calculateRegAllocScore(
  91     const MachineFunction &MF,
  92     llvm::function_ref<double(const MachineBasicBlock &)> GetBBFreq,
  93     llvm::function_ref<bool(const MachineInstr &)>
  94         IsTriviallyRematerializable) {
  95   RegAllocScore Total;
  96
  97   for (const MachineBasicBlock &MBB : MF) {
  98     double BlockFreqRelativeToEntrypoint = GetBBFreq(MBB);
  99     RegAllocScore MBBScore;
 100
 101     for (const MachineInstr &MI : MBB) {
 102       if (MI.isDebugInstr() || MI.isKill() || MI.isInlineAsm()) {
 103         continue;
 104       }
 105       if (MI.isCopy()) {
 106         MBBScore.onCopy(BlockFreqRelativeToEntrypoint);
 107       } else if (IsTriviallyRematerializable(MI)) {
 108         if (MI.getDesc().isAsCheapAsAMove()) {
 109           MBBScore.onCheapRemat(BlockFreqRelativeToEntrypoint);
 110         } else {
 111           MBBScore.onExpensiveRemat(BlockFreqRelativeToEntrypoint);
 112         }
 113       } else if (MI.mayLoad() && MI.mayStore()) {
 114         MBBScore.onLoadStore(BlockFreqRelativeToEntrypoint);
 115       } else if (MI.mayLoad()) {
 116         MBBScore.onLoad(BlockFreqRelativeToEntrypoint);
 117       } else if (MI.mayStore()) {
 118         MBBScore.onStore(BlockFreqRelativeToEntrypoint);
 119       }
 120     }
 121     Total += MBBScore;
 122   }
 123   return Total;
 124 }