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;
26LLVM_ABI cl::opt<double> CopyWeight("regalloc-copy-weight", cl::init(Val: 0.2),
27 cl::Hidden);
28LLVM_ABI cl::opt<double> LoadWeight("regalloc-load-weight", cl::init(Val: 4.0),
29 cl::Hidden);
30LLVM_ABI cl::opt<double> StoreWeight("regalloc-store-weight", cl::init(Val: 1.0),
31 cl::Hidden);
32LLVM_ABI cl::opt<double> CheapRematWeight("regalloc-cheap-remat-weight",
33 cl::init(Val: 0.2), cl::Hidden);
34LLVM_ABI cl::opt<double> ExpensiveRematWeight("regalloc-expensive-remat-weight",
35 cl::init(Val: 1.0), cl::Hidden);
36#define DEBUG_TYPE "regalloc-score"
37
38RegAllocScore &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
48bool 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
57bool RegAllocScore::operator!=(const RegAllocScore &Other) const {
58 return !(*this == Other);
59}
60
61double 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
73RegAllocScore
74llvm::calculateRegAllocScore(const MachineFunction &MF,
75 const MachineBlockFrequencyInfo &MBFI) {
76 return calculateRegAllocScore(
77 MF,
78 GetBBFreq: [&](const MachineBasicBlock &MBB) {
79 return MBFI.getBlockFreqRelativeToEntryBlock(MBB: &MBB);
80 },
81 IsTriviallyRematerializable: [&](const MachineInstr &MI) {
82 return MF.getSubtarget().getInstrInfo()->isTriviallyReMaterializable(
83 MI);
84 });
85}
86
87RegAllocScore 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(Freq: BlockFreqRelativeToEntrypoint);
104 } else if (IsTriviallyRematerializable(MI)) {
105 if (MI.getDesc().isAsCheapAsAMove()) {
106 MBBScore.onCheapRemat(Freq: BlockFreqRelativeToEntrypoint);
107 } else {
108 MBBScore.onExpensiveRemat(Freq: BlockFreqRelativeToEntrypoint);
109 }
110 } else if (MI.mayLoad() && MI.mayStore()) {
111 MBBScore.onLoadStore(Freq: BlockFreqRelativeToEntrypoint);
112 } else if (MI.mayLoad()) {
113 MBBScore.onLoad(Freq: BlockFreqRelativeToEntrypoint);
114 } else if (MI.mayStore()) {
115 MBBScore.onStore(Freq: BlockFreqRelativeToEntrypoint);
116 }
117 }
118 Total += MBBScore;
119 }
120 return Total;
121}
122