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/CodeGen/MachineBasicBlock.h"
17#include "llvm/CodeGen/MachineBlockFrequencyInfo.h"
18#include "llvm/CodeGen/MachineFunction.h"
19#include "llvm/CodeGen/MachineInstr.h"
20#include "llvm/CodeGen/TargetInstrInfo.h"
21#include "llvm/CodeGen/TargetSubtargetInfo.h"
22#include "llvm/MC/MCInstrDesc.h"
23#include "llvm/Support/CommandLine.h"
24
25using namespace llvm;
26
27static cl::opt<double> CopyWeight("regalloc-copy-weight", cl::init(Val: 0.2),
28 cl::Hidden);
29static cl::opt<double> LoadWeight("regalloc-load-weight", cl::init(Val: 4.0),
30 cl::Hidden);
31static cl::opt<double> StoreWeight("regalloc-store-weight", cl::init(Val: 1.0),
32 cl::Hidden);
33static cl::opt<double> CheapRematWeight("regalloc-cheap-remat-weight",
34 cl::init(Val: 0.2), cl::Hidden);
35static cl::opt<double> ExpensiveRematWeight("regalloc-expensive-remat-weight",
36 cl::init(Val: 1.0), cl::Hidden);
37
38#define DEBUG_TYPE "regalloc-score"
39
40RegAllocScore &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
50bool 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
59bool RegAllocScore::operator!=(const RegAllocScore &Other) const {
60 return !(*this == Other);
61}
62
63double 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
75RegAllocScore
76llvm::calculateRegAllocScore(const MachineFunction &MF,
77 const MachineBlockFrequencyInfo &MBFI) {
78 return calculateRegAllocScore(
79 MF,
80 GetBBFreq: [&](const MachineBasicBlock &MBB) {
81 return MBFI.getBlockFreqRelativeToEntryBlock(MBB: &MBB);
82 },
83 IsTriviallyRematerializable: [&](const MachineInstr &MI) {
84 return MF.getSubtarget().getInstrInfo()->isReMaterializable(MI);
85 });
86}
87
88RegAllocScore llvm::calculateRegAllocScore(
89 const MachineFunction &MF,
90 llvm::function_ref<double(const MachineBasicBlock &)> GetBBFreq,
91 llvm::function_ref<bool(const MachineInstr &)>
92 IsTriviallyRematerializable) {
93 RegAllocScore Total;
94
95 for (const MachineBasicBlock &MBB : MF) {
96 double BlockFreqRelativeToEntrypoint = GetBBFreq(MBB);
97 RegAllocScore MBBScore;
98
99 for (const MachineInstr &MI : MBB) {
100 if (MI.isDebugInstr() || MI.isKill() || MI.isInlineAsm()) {
101 continue;
102 }
103 if (MI.isCopy()) {
104 MBBScore.onCopy(Freq: BlockFreqRelativeToEntrypoint);
105 } else if (IsTriviallyRematerializable(MI)) {
106 if (MI.getDesc().isAsCheapAsAMove()) {
107 MBBScore.onCheapRemat(Freq: BlockFreqRelativeToEntrypoint);
108 } else {
109 MBBScore.onExpensiveRemat(Freq: BlockFreqRelativeToEntrypoint);
110 }
111 } else if (MI.mayLoad() && MI.mayStore()) {
112 MBBScore.onLoadStore(Freq: BlockFreqRelativeToEntrypoint);
113 } else if (MI.mayLoad()) {
114 MBBScore.onLoad(Freq: BlockFreqRelativeToEntrypoint);
115 } else if (MI.mayStore()) {
116 MBBScore.onStore(Freq: BlockFreqRelativeToEntrypoint);
117 }
118 }
119 Total += MBBScore;
120 }
121 return Total;
122}
123