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/ilist_iterator.h"
  17 #include "llvm/CodeGen/MachineBasicBlock.h"
  18 #include "llvm/CodeGen/MachineBlockFrequencyInfo.h"
  19 #include "llvm/CodeGen/MachineFunction.h"
  20 #include "llvm/CodeGen/MachineInstr.h"
  21 #include "llvm/CodeGen/MachineInstrBundleIterator.h"
  22 #include "llvm/CodeGen/TargetInstrInfo.h"
  23 #include "llvm/CodeGen/TargetSubtargetInfo.h"
  24 #include "llvm/MC/MCInstrDesc.h"
  25 #include "llvm/Support/CommandLine.h"
  26
  27 using namespace llvm;
  28 cl::opt<double> CopyWeight("regalloc-copy-weight", cl::init(0.2), cl::Hidden);
  29 cl::opt<double> LoadWeight("regalloc-load-weight", cl::init(4.0), cl::Hidden);
  30 cl::opt<double> StoreWeight("regalloc-store-weight", cl::init(1.0), cl::Hidden);
  31 cl::opt<double> CheapRematWeight("regalloc-cheap-remat-weight", cl::init(0.2),
  32                                  cl::Hidden);
  33 cl::opt<double> ExpensiveRematWeight("regalloc-expensive-remat-weight",
  34                                      cl::init(1.0), cl::Hidden);
  35 #define DEBUG_TYPE "regalloc-score"
  36
  37 RegAllocScore &RegAllocScore::operator+=(const RegAllocScore &Other) {
  38   CopyCounts += Other.copyCounts();
  39   LoadCounts += Other.loadCounts();
  40   StoreCounts += Other.storeCounts();
  41   LoadStoreCounts += Other.loadStoreCounts();
  42   CheapRematCounts += Other.cheapRematCounts();
  43   ExpensiveRematCounts += Other.expensiveRematCounts();
  44   return *this;
  45 }
  46
  47 bool RegAllocScore::operator==(const RegAllocScore &Other) const {
  48   return copyCounts() == Other.copyCounts() &&
  49          loadCounts() == Other.loadCounts() &&
  50          storeCounts() == Other.storeCounts() &&
  51          loadStoreCounts() == Other.loadStoreCounts() &&
  52          cheapRematCounts() == Other.cheapRematCounts() &&
  53          expensiveRematCounts() == Other.expensiveRematCounts();
  54 }
  55
  56 bool RegAllocScore::operator!=(const RegAllocScore &Other) const {
  57   return !(*this == Other);
  58 }
  59
  60 double RegAllocScore::getScore() const {
  61   double Ret = 0.0;
  62   Ret += CopyWeight * copyCounts();
  63   Ret += LoadWeight * loadCounts();
  64   Ret += StoreWeight * storeCounts();
  65   Ret += (LoadWeight + StoreWeight) * loadStoreCounts();
  66   Ret += CheapRematWeight * cheapRematCounts();
  67   Ret += ExpensiveRematWeight * expensiveRematCounts();
  68
  69   return Ret;
  70 }
  71
  72 RegAllocScore
  73 llvm::calculateRegAllocScore(const MachineFunction &MF,
  74                              const MachineBlockFrequencyInfo &MBFI) {
  75   return calculateRegAllocScore(
  76       MF,
  77       [&](const MachineBasicBlock &MBB) {
  78         return MBFI.getBlockFreqRelativeToEntryBlock(&MBB);
  79       },
  80       [&](const MachineInstr &MI) {
  81         return MF.getSubtarget().getInstrInfo()->isTriviallyReMaterializable(
  82             MI);
  83       });
  84 }
  85
  86 RegAllocScore llvm::calculateRegAllocScore(
  87     const MachineFunction &MF,
  88     llvm::function_ref<double(const MachineBasicBlock &)> GetBBFreq,
  89     llvm::function_ref<bool(const MachineInstr &)>
  90         IsTriviallyRematerializable) {
  91   RegAllocScore Total;
  92
  93   for (const MachineBasicBlock &MBB : MF) {
  94     double BlockFreqRelativeToEntrypoint = GetBBFreq(MBB);
  95     RegAllocScore MBBScore;
  96
  97     for (const MachineInstr &MI : MBB) {
  98       if (MI.isDebugInstr() || MI.isKill() || MI.isInlineAsm()) {
  99         continue;
 100       }
 101       if (MI.isCopy()) {
 102         MBBScore.onCopy(BlockFreqRelativeToEntrypoint);
 103       } else if (IsTriviallyRematerializable(MI)) {
 104         if (MI.getDesc().isAsCheapAsAMove()) {
 105           MBBScore.onCheapRemat(BlockFreqRelativeToEntrypoint);
 106         } else {
 107           MBBScore.onExpensiveRemat(BlockFreqRelativeToEntrypoint);
 108         }
 109       } else if (MI.mayLoad() && MI.mayStore()) {
 110         MBBScore.onLoadStore(BlockFreqRelativeToEntrypoint);
 111       } else if (MI.mayLoad()) {
 112         MBBScore.onLoad(BlockFreqRelativeToEntrypoint);
 113       } else if (MI.mayStore()) {
 114         MBBScore.onStore(BlockFreqRelativeToEntrypoint);
 115       }
 116     }
 117     Total += MBBScore;
 118   }
 119   return Total;
 120 }