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/DenseMapInfo.h"
17 #include "llvm/ADT/ilist_iterator.h"
18 #include "llvm/CodeGen/MachineBasicBlock.h"
19 #include "llvm/CodeGen/MachineBlockFrequencyInfo.h"
20 #include "llvm/CodeGen/MachineFunction.h"
21 #include "llvm/CodeGen/MachineInstr.h"
22 #include "llvm/CodeGen/MachineInstrBundleIterator.h"
23 #include "llvm/CodeGen/TargetInstrInfo.h"
24 #include "llvm/CodeGen/TargetSubtargetInfo.h"
25 #include "llvm/MC/MCInstrDesc.h"
26 #include "llvm/Support/CommandLine.h"
27
28 using namespace llvm;
29 cl::opt<double> CopyWeight("regalloc-copy-weight", cl::init(0.2), cl::Hidden);
30 cl::opt<double> LoadWeight("regalloc-load-weight", cl::init(4.0), cl::Hidden);
31 cl::opt<double> StoreWeight("regalloc-store-weight", cl::init(1.0), cl::Hidden);
32 cl::opt<double> CheapRematWeight("regalloc-cheap-remat-weight", cl::init(0.2),
33 cl::Hidden);
34 cl::opt<double> ExpensiveRematWeight("regalloc-expensive-remat-weight",
35 cl::init(1.0), cl::Hidden);
36 #define DEBUG_TYPE "regalloc-score"
37
operator +=(const RegAllocScore & Other)38 RegAllocScore &RegAllocScore::operator+=(const RegAllocScore &Other) {
39 CopyCounts += Other.copyCounts();
40 LoadCounts += Other.loadCounts();
41 StoreCounts += Other.storeCounts();
42 LoadStoreCounts += Other.loadStoreCounts();
43 CheapRematCounts += Other.cheapRematCounts();
44 ExpensiveRematCounts += Other.expensiveRematCounts();
45 return *this;
46 }
47
operator ==(const RegAllocScore & Other) const48 bool RegAllocScore::operator==(const RegAllocScore &Other) const {
49 return copyCounts() == Other.copyCounts() &&
50 loadCounts() == Other.loadCounts() &&
51 storeCounts() == Other.storeCounts() &&
52 loadStoreCounts() == Other.loadStoreCounts() &&
53 cheapRematCounts() == Other.cheapRematCounts() &&
54 expensiveRematCounts() == Other.expensiveRematCounts();
55 }
56
operator !=(const RegAllocScore & Other) const57 bool RegAllocScore::operator!=(const RegAllocScore &Other) const {
58 return !(*this == Other);
59 }
60
getScore() const61 double RegAllocScore::getScore() const {
62 double Ret = 0.0;
63 Ret += CopyWeight * copyCounts();
64 Ret += LoadWeight * loadCounts();
65 Ret += StoreWeight * storeCounts();
66 Ret += (LoadWeight + StoreWeight) * loadStoreCounts();
67 Ret += CheapRematWeight * cheapRematCounts();
68 Ret += ExpensiveRematWeight * expensiveRematCounts();
69
70 return Ret;
71 }
72
73 RegAllocScore
calculateRegAllocScore(const MachineFunction & MF,const MachineBlockFrequencyInfo & MBFI)74 llvm::calculateRegAllocScore(const MachineFunction &MF,
75 const MachineBlockFrequencyInfo &MBFI) {
76 return calculateRegAllocScore(
77 MF,
78 [&](const MachineBasicBlock &MBB) {
79 return MBFI.getBlockFreqRelativeToEntryBlock(&MBB);
80 },
81 [&](const MachineInstr &MI) {
82 return MF.getSubtarget().getInstrInfo()->isTriviallyReMaterializable(
83 MI);
84 });
85 }
86
calculateRegAllocScore(const MachineFunction & MF,llvm::function_ref<double (const MachineBasicBlock &)> GetBBFreq,llvm::function_ref<bool (const MachineInstr &)> IsTriviallyRematerializable)87 RegAllocScore llvm::calculateRegAllocScore(
88 const MachineFunction &MF,
89 llvm::function_ref<double(const MachineBasicBlock &)> GetBBFreq,
90 llvm::function_ref<bool(const MachineInstr &)>
91 IsTriviallyRematerializable) {
92 RegAllocScore Total;
93
94 for (const MachineBasicBlock &MBB : MF) {
95 double BlockFreqRelativeToEntrypoint = GetBBFreq(MBB);
96 RegAllocScore MBBScore;
97
98 for (const MachineInstr &MI : MBB) {
99 if (MI.isDebugInstr() || MI.isKill() || MI.isInlineAsm()) {
100 continue;
101 }
102 if (MI.isCopy()) {
103 MBBScore.onCopy(BlockFreqRelativeToEntrypoint);
104 } else if (IsTriviallyRematerializable(MI)) {
105 if (MI.getDesc().isAsCheapAsAMove()) {
106 MBBScore.onCheapRemat(BlockFreqRelativeToEntrypoint);
107 } else {
108 MBBScore.onExpensiveRemat(BlockFreqRelativeToEntrypoint);
109 }
110 } else if (MI.mayLoad() && MI.mayStore()) {
111 MBBScore.onLoadStore(BlockFreqRelativeToEntrypoint);
112 } else if (MI.mayLoad()) {
113 MBBScore.onLoad(BlockFreqRelativeToEntrypoint);
114 } else if (MI.mayStore()) {
115 MBBScore.onStore(BlockFreqRelativeToEntrypoint);
116 }
117 }
118 Total += MBBScore;
119 }
120 return Total;
121 }
122