1 //===- DDG.cpp - Data Dependence Graph -------------------------------------==//
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
7 //===----------------------------------------------------------------------===//
9 // The implementation for the data dependence graph.
10 //===----------------------------------------------------------------------===//
11 #include "llvm/Analysis/DDG.h"
12 #include "llvm/ADT/SCCIterator.h"
13 #include "llvm/Analysis/LoopInfo.h"
14 #include "llvm/Analysis/LoopIterator.h"
15 #include "llvm/Support/CommandLine.h"
19 static cl::opt<bool> SimplifyDDG(
20 "ddg-simplify", cl::init(true), cl::Hidden, cl::ZeroOrMore,
22 "Simplify DDG by merging nodes that have less interesting edges."));
25 CreatePiBlocks("ddg-pi-blocks", cl::init(true), cl::Hidden, cl::ZeroOrMore,
26 cl::desc("Create pi-block nodes."));
28 #define DEBUG_TYPE "ddg"
30 template class llvm::DGEdge<DDGNode, DDGEdge>;
31 template class llvm::DGNode<DDGNode, DDGEdge>;
32 template class llvm::DirectedGraph<DDGNode, DDGEdge>;
34 //===--------------------------------------------------------------------===//
35 // DDGNode implementation
36 //===--------------------------------------------------------------------===//
37 DDGNode::~DDGNode() {}
39 bool DDGNode::collectInstructions(
40 llvm::function_ref<bool(Instruction *)> const &Pred,
41 InstructionListType &IList) const {
42 assert(IList.empty() && "Expected the IList to be empty on entry.");
43 if (isa<SimpleDDGNode>(this)) {
44 for (Instruction *I : cast<const SimpleDDGNode>(this)->getInstructions())
47 } else if (isa<PiBlockDDGNode>(this)) {
48 for (const DDGNode *PN : cast<const PiBlockDDGNode>(this)->getNodes()) {
49 assert(!isa<PiBlockDDGNode>(PN) && "Nested PiBlocks are not supported.");
50 SmallVector<Instruction *, 8> TmpIList;
51 PN->collectInstructions(Pred, TmpIList);
52 IList.insert(IList.end(), TmpIList.begin(), TmpIList.end());
55 llvm_unreachable("unimplemented type of node");
56 return !IList.empty();
59 raw_ostream &llvm::operator<<(raw_ostream &OS, const DDGNode::NodeKind K) {
62 case DDGNode::NodeKind::SingleInstruction:
63 Out = "single-instruction";
65 case DDGNode::NodeKind::MultiInstruction:
66 Out = "multi-instruction";
68 case DDGNode::NodeKind::PiBlock:
71 case DDGNode::NodeKind::Root:
74 case DDGNode::NodeKind::Unknown:
82 raw_ostream &llvm::operator<<(raw_ostream &OS, const DDGNode &N) {
83 OS << "Node Address:" << &N << ":" << N.getKind() << "\n";
84 if (isa<SimpleDDGNode>(N)) {
85 OS << " Instructions:\n";
86 for (const Instruction *I : cast<const SimpleDDGNode>(N).getInstructions())
87 OS.indent(2) << *I << "\n";
88 } else if (isa<PiBlockDDGNode>(&N)) {
89 OS << "--- start of nodes in pi-block ---\n";
90 auto &Nodes = cast<const PiBlockDDGNode>(&N)->getNodes();
92 for (const DDGNode *N : Nodes)
93 OS << *N << (++Count == Nodes.size() ? "" : "\n");
94 OS << "--- end of nodes in pi-block ---\n";
95 } else if (!isa<RootDDGNode>(N))
96 llvm_unreachable("unimplemented type of node");
98 OS << (N.getEdges().empty() ? " Edges:none!\n" : " Edges:\n");
99 for (auto &E : N.getEdges())
104 //===--------------------------------------------------------------------===//
105 // SimpleDDGNode implementation
106 //===--------------------------------------------------------------------===//
108 SimpleDDGNode::SimpleDDGNode(Instruction &I)
109 : DDGNode(NodeKind::SingleInstruction), InstList() {
110 assert(InstList.empty() && "Expected empty list.");
111 InstList.push_back(&I);
114 SimpleDDGNode::SimpleDDGNode(const SimpleDDGNode &N)
115 : DDGNode(N), InstList(N.InstList) {
116 assert(((getKind() == NodeKind::SingleInstruction && InstList.size() == 1) ||
117 (getKind() == NodeKind::MultiInstruction && InstList.size() > 1)) &&
118 "constructing from invalid simple node.");
121 SimpleDDGNode::SimpleDDGNode(SimpleDDGNode &&N)
122 : DDGNode(std::move(N)), InstList(std::move(N.InstList)) {
123 assert(((getKind() == NodeKind::SingleInstruction && InstList.size() == 1) ||
124 (getKind() == NodeKind::MultiInstruction && InstList.size() > 1)) &&
125 "constructing from invalid simple node.");
128 SimpleDDGNode::~SimpleDDGNode() { InstList.clear(); }
130 //===--------------------------------------------------------------------===//
131 // PiBlockDDGNode implementation
132 //===--------------------------------------------------------------------===//
134 PiBlockDDGNode::PiBlockDDGNode(const PiNodeList &List)
135 : DDGNode(NodeKind::PiBlock), NodeList(List) {
136 assert(!NodeList.empty() && "pi-block node constructed with an empty list.");
139 PiBlockDDGNode::PiBlockDDGNode(const PiBlockDDGNode &N)
140 : DDGNode(N), NodeList(N.NodeList) {
141 assert(getKind() == NodeKind::PiBlock && !NodeList.empty() &&
142 "constructing from invalid pi-block node.");
145 PiBlockDDGNode::PiBlockDDGNode(PiBlockDDGNode &&N)
146 : DDGNode(std::move(N)), NodeList(std::move(N.NodeList)) {
147 assert(getKind() == NodeKind::PiBlock && !NodeList.empty() &&
148 "constructing from invalid pi-block node.");
151 PiBlockDDGNode::~PiBlockDDGNode() { NodeList.clear(); }
153 //===--------------------------------------------------------------------===//
154 // DDGEdge implementation
155 //===--------------------------------------------------------------------===//
157 raw_ostream &llvm::operator<<(raw_ostream &OS, const DDGEdge::EdgeKind K) {
160 case DDGEdge::EdgeKind::RegisterDefUse:
163 case DDGEdge::EdgeKind::MemoryDependence:
166 case DDGEdge::EdgeKind::Rooted:
169 case DDGEdge::EdgeKind::Unknown:
177 raw_ostream &llvm::operator<<(raw_ostream &OS, const DDGEdge &E) {
178 OS << "[" << E.getKind() << "] to " << &E.getTargetNode() << "\n";
182 //===--------------------------------------------------------------------===//
183 // DataDependenceGraph implementation
184 //===--------------------------------------------------------------------===//
185 using BasicBlockListType = SmallVector<BasicBlock *, 8>;
187 DataDependenceGraph::DataDependenceGraph(Function &F, DependenceInfo &D)
188 : DependenceGraphInfo(F.getName().str(), D) {
189 // Put the basic blocks in program order for correct dependence
191 BasicBlockListType BBList;
192 for (auto &SCC : make_range(scc_begin(&F), scc_end(&F)))
193 for (BasicBlock * BB : SCC)
194 BBList.push_back(BB);
195 std::reverse(BBList.begin(), BBList.end());
196 DDGBuilder(*this, D, BBList).populate();
199 DataDependenceGraph::DataDependenceGraph(Loop &L, LoopInfo &LI,
201 : DependenceGraphInfo(Twine(L.getHeader()->getParent()->getName() + "." +
202 L.getHeader()->getName())
205 // Put the basic blocks in program order for correct dependence
207 LoopBlocksDFS DFS(&L);
209 BasicBlockListType BBList;
210 for (BasicBlock *BB : make_range(DFS.beginRPO(), DFS.endRPO()))
211 BBList.push_back(BB);
212 DDGBuilder(*this, D, BBList).populate();
215 DataDependenceGraph::~DataDependenceGraph() {
216 for (auto *N : Nodes) {
223 bool DataDependenceGraph::addNode(DDGNode &N) {
224 if (!DDGBase::addNode(N))
227 // In general, if the root node is already created and linked, it is not safe
228 // to add new nodes since they may be unreachable by the root. However,
229 // pi-block nodes need to be added after the root node is linked, and they are
230 // always reachable by the root, because they represent components that are
231 // already reachable by root.
232 auto *Pi = dyn_cast<PiBlockDDGNode>(&N);
233 assert((!Root || Pi) &&
234 "Root node is already added. No more nodes can be added.");
236 if (isa<RootDDGNode>(N))
240 for (DDGNode *NI : Pi->getNodes())
241 PiBlockMap.insert(std::make_pair(NI, Pi));
246 const PiBlockDDGNode *DataDependenceGraph::getPiBlock(const NodeType &N) const {
247 if (PiBlockMap.find(&N) == PiBlockMap.end())
249 auto *Pi = PiBlockMap.find(&N)->second;
250 assert(PiBlockMap.find(Pi) == PiBlockMap.end() &&
251 "Nested pi-blocks detected.");
255 raw_ostream &llvm::operator<<(raw_ostream &OS, const DataDependenceGraph &G) {
256 for (DDGNode *Node : G)
257 // Avoid printing nodes that are part of a pi-block twice. They will get
258 // printed when the pi-block is printed.
259 if (!G.getPiBlock(*Node))
265 //===--------------------------------------------------------------------===//
266 // DDGBuilder implementation
267 //===--------------------------------------------------------------------===//
269 bool DDGBuilder::areNodesMergeable(const DDGNode &Src,
270 const DDGNode &Tgt) const {
271 // Only merge two nodes if they are both simple nodes and the consecutive
272 // instructions after merging belong to the same BB.
273 const auto *SimpleSrc = dyn_cast<const SimpleDDGNode>(&Src);
274 const auto *SimpleTgt = dyn_cast<const SimpleDDGNode>(&Tgt);
275 if (!SimpleSrc || !SimpleTgt)
278 return SimpleSrc->getLastInstruction()->getParent() ==
279 SimpleTgt->getFirstInstruction()->getParent();
282 void DDGBuilder::mergeNodes(DDGNode &A, DDGNode &B) {
283 DDGEdge &EdgeToFold = A.back();
284 assert(A.getEdges().size() == 1 && EdgeToFold.getTargetNode() == B &&
285 "Expected A to have a single edge to B.");
286 assert(isa<SimpleDDGNode>(&A) && isa<SimpleDDGNode>(&B) &&
287 "Expected simple nodes");
289 // Copy instructions from B to the end of A.
290 cast<SimpleDDGNode>(&A)->appendInstructions(*cast<SimpleDDGNode>(&B));
292 // Move to A any outgoing edges from B.
293 for (DDGEdge *BE : B)
294 Graph.connect(A, BE->getTargetNode(), *BE);
296 A.removeEdge(EdgeToFold);
297 destroyEdge(EdgeToFold);
302 bool DDGBuilder::shouldSimplify() const { return SimplifyDDG; }
304 bool DDGBuilder::shouldCreatePiBlocks() const { return CreatePiBlocks; }
306 //===--------------------------------------------------------------------===//
307 // DDG Analysis Passes
308 //===--------------------------------------------------------------------===//
310 /// DDG as a loop pass.
311 DDGAnalysis::Result DDGAnalysis::run(Loop &L, LoopAnalysisManager &AM,
312 LoopStandardAnalysisResults &AR) {
313 Function *F = L.getHeader()->getParent();
314 DependenceInfo DI(F, &AR.AA, &AR.SE, &AR.LI);
315 return std::make_unique<DataDependenceGraph>(L, AR.LI, DI);
317 AnalysisKey DDGAnalysis::Key;
319 PreservedAnalyses DDGAnalysisPrinterPass::run(Loop &L, LoopAnalysisManager &AM,
320 LoopStandardAnalysisResults &AR,
322 OS << "'DDG' for loop '" << L.getHeader()->getName() << "':\n";
323 OS << *AM.getResult<DDGAnalysis>(L, AR);
324 return PreservedAnalyses::all();