[MLIR][NVVM] Add Op for TMA Store with reduction (#118853)
[llvm-project.git] / lld / COFF / CallGraphSort.cpp
blob9cd60dea6e37776fd381ab16dbd5b54ebf25f029
1 //===- CallGraphSort.cpp --------------------------------------------------===//
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 ///
9 /// This is based on the ELF port, see ELF/CallGraphSort.cpp for the details
10 /// about the algorithm.
11 ///
12 //===----------------------------------------------------------------------===//
14 #include "CallGraphSort.h"
15 #include "COFFLinkerContext.h"
16 #include "InputFiles.h"
17 #include "SymbolTable.h"
18 #include "Symbols.h"
19 #include "lld/Common/ErrorHandler.h"
21 #include <numeric>
23 using namespace llvm;
24 using namespace lld;
25 using namespace lld::coff;
27 namespace {
28 struct Edge {
29 int from;
30 uint64_t weight;
33 struct Cluster {
34 Cluster(int sec, size_t s) : next(sec), prev(sec), size(s) {}
36 double getDensity() const {
37 if (size == 0)
38 return 0;
39 return double(weight) / double(size);
42 int next;
43 int prev;
44 uint64_t size;
45 uint64_t weight = 0;
46 uint64_t initialWeight = 0;
47 Edge bestPred = {-1, 0};
50 class CallGraphSort {
51 public:
52 CallGraphSort(COFFLinkerContext &ctx);
54 DenseMap<const SectionChunk *, int> run();
56 private:
57 std::vector<Cluster> clusters;
58 std::vector<const SectionChunk *> sections;
60 COFFLinkerContext &ctx;
63 // Maximum amount the combined cluster density can be worse than the original
64 // cluster to consider merging.
65 constexpr int MAX_DENSITY_DEGRADATION = 8;
67 // Maximum cluster size in bytes.
68 constexpr uint64_t MAX_CLUSTER_SIZE = 1024 * 1024;
69 } // end anonymous namespace
71 using SectionPair = std::pair<const SectionChunk *, const SectionChunk *>;
73 // Take the edge list in Config->CallGraphProfile, resolve symbol names to
74 // Symbols, and generate a graph between InputSections with the provided
75 // weights.
76 CallGraphSort::CallGraphSort(COFFLinkerContext &ctx) : ctx(ctx) {
77 const MapVector<SectionPair, uint64_t> &profile = ctx.config.callGraphProfile;
78 DenseMap<const SectionChunk *, int> secToCluster;
80 auto getOrCreateNode = [&](const SectionChunk *isec) -> int {
81 auto res = secToCluster.try_emplace(isec, clusters.size());
82 if (res.second) {
83 sections.push_back(isec);
84 clusters.emplace_back(clusters.size(), isec->getSize());
86 return res.first->second;
89 // Create the graph.
90 for (const std::pair<SectionPair, uint64_t> &c : profile) {
91 const auto *fromSec = cast<SectionChunk>(c.first.first->repl);
92 const auto *toSec = cast<SectionChunk>(c.first.second->repl);
93 uint64_t weight = c.second;
95 // Ignore edges between input sections belonging to different output
96 // sections. This is done because otherwise we would end up with clusters
97 // containing input sections that can't actually be placed adjacently in the
98 // output. This messes with the cluster size and density calculations. We
99 // would also end up moving input sections in other output sections without
100 // moving them closer to what calls them.
101 if (ctx.getOutputSection(fromSec) != ctx.getOutputSection(toSec))
102 continue;
104 int from = getOrCreateNode(fromSec);
105 int to = getOrCreateNode(toSec);
107 clusters[to].weight += weight;
109 if (from == to)
110 continue;
112 // Remember the best edge.
113 Cluster &toC = clusters[to];
114 if (toC.bestPred.from == -1 || toC.bestPred.weight < weight) {
115 toC.bestPred.from = from;
116 toC.bestPred.weight = weight;
119 for (Cluster &c : clusters)
120 c.initialWeight = c.weight;
123 // It's bad to merge clusters which would degrade the density too much.
124 static bool isNewDensityBad(Cluster &a, Cluster &b) {
125 double newDensity = double(a.weight + b.weight) / double(a.size + b.size);
126 return newDensity < a.getDensity() / MAX_DENSITY_DEGRADATION;
129 // Find the leader of V's belonged cluster (represented as an equivalence
130 // class). We apply union-find path-halving technique (simple to implement) in
131 // the meantime as it decreases depths and the time complexity.
132 static int getLeader(std::vector<int> &leaders, int v) {
133 while (leaders[v] != v) {
134 leaders[v] = leaders[leaders[v]];
135 v = leaders[v];
137 return v;
140 static void mergeClusters(std::vector<Cluster> &cs, Cluster &into, int intoIdx,
141 Cluster &from, int fromIdx) {
142 int tail1 = into.prev, tail2 = from.prev;
143 into.prev = tail2;
144 cs[tail2].next = intoIdx;
145 from.prev = tail1;
146 cs[tail1].next = fromIdx;
147 into.size += from.size;
148 into.weight += from.weight;
149 from.size = 0;
150 from.weight = 0;
153 // Group InputSections into clusters using the Call-Chain Clustering heuristic
154 // then sort the clusters by density.
155 DenseMap<const SectionChunk *, int> CallGraphSort::run() {
156 std::vector<int> sorted(clusters.size());
157 std::vector<int> leaders(clusters.size());
159 std::iota(leaders.begin(), leaders.end(), 0);
160 std::iota(sorted.begin(), sorted.end(), 0);
161 llvm::stable_sort(sorted, [&](int a, int b) {
162 return clusters[a].getDensity() > clusters[b].getDensity();
165 for (int l : sorted) {
166 // The cluster index is the same as the index of its leader here because
167 // clusters[L] has not been merged into another cluster yet.
168 Cluster &c = clusters[l];
170 // Don't consider merging if the edge is unlikely.
171 if (c.bestPred.from == -1 || c.bestPred.weight * 10 <= c.initialWeight)
172 continue;
174 int predL = getLeader(leaders, c.bestPred.from);
175 if (l == predL)
176 continue;
178 Cluster *predC = &clusters[predL];
179 if (c.size + predC->size > MAX_CLUSTER_SIZE)
180 continue;
182 if (isNewDensityBad(*predC, c))
183 continue;
185 leaders[l] = predL;
186 mergeClusters(clusters, *predC, predL, c, l);
189 // Sort remaining non-empty clusters by density.
190 sorted.clear();
191 for (int i = 0, e = (int)clusters.size(); i != e; ++i)
192 if (clusters[i].size > 0)
193 sorted.push_back(i);
194 llvm::stable_sort(sorted, [&](int a, int b) {
195 return clusters[a].getDensity() > clusters[b].getDensity();
198 DenseMap<const SectionChunk *, int> orderMap;
199 // Sections will be sorted by increasing order. Absent sections will have
200 // priority 0 and be placed at the end of sections.
201 int curOrder = INT_MIN;
202 for (int leader : sorted) {
203 for (int i = leader;;) {
204 orderMap[sections[i]] = curOrder++;
205 i = clusters[i].next;
206 if (i == leader)
207 break;
210 if (!ctx.config.printSymbolOrder.empty()) {
211 std::error_code ec;
212 raw_fd_ostream os(ctx.config.printSymbolOrder, ec, sys::fs::OF_None);
213 if (ec) {
214 Err(ctx) << "cannot open " << ctx.config.printSymbolOrder << ": "
215 << ec.message();
216 return orderMap;
218 // Print the symbols ordered by C3, in the order of increasing curOrder
219 // Instead of sorting all the orderMap, just repeat the loops above.
220 for (int leader : sorted)
221 for (int i = leader;;) {
222 const SectionChunk *sc = sections[i];
224 // Search all the symbols in the file of the section
225 // and find out a DefinedCOFF symbol with name that is within the
226 // section.
227 for (Symbol *sym : sc->file->getSymbols())
228 if (auto *d = dyn_cast_or_null<DefinedCOFF>(sym))
229 // Filter out non-COMDAT symbols and section symbols.
230 if (d->isCOMDAT && !d->getCOFFSymbol().isSection() &&
231 sc == d->getChunk())
232 os << sym->getName() << "\n";
233 i = clusters[i].next;
234 if (i == leader)
235 break;
239 return orderMap;
242 // Sort sections by the profile data provided by /call-graph-ordering-file
244 // This first builds a call graph based on the profile data then merges sections
245 // according to the C³ heuristic. All clusters are then sorted by a density
246 // metric to further improve locality.
247 DenseMap<const SectionChunk *, int>
248 coff::computeCallGraphProfileOrder(COFFLinkerContext &ctx) {
249 return CallGraphSort(ctx).run();