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1 : //===- RegAllocPBQP.h -------------------------------------------*- C++ -*-===//
2 : //
3 : // The LLVM Compiler Infrastructure
4 : //
5 : // This file is distributed under the University of Illinois Open Source
6 : // License. See LICENSE.TXT for details.
7 : //
8 : //===----------------------------------------------------------------------===//
9 : //
10 : // This file defines the PBQPBuilder interface, for classes which build PBQP
11 : // instances to represent register allocation problems, and the RegAllocPBQP
12 : // interface.
13 : //
14 : //===----------------------------------------------------------------------===//
15 :
16 : #ifndef LLVM_CODEGEN_REGALLOCPBQP_H
17 : #define LLVM_CODEGEN_REGALLOCPBQP_H
18 :
19 : #include "llvm/ADT/DenseMap.h"
20 : #include "llvm/ADT/Hashing.h"
21 : #include "llvm/CodeGen/PBQP/CostAllocator.h"
22 : #include "llvm/CodeGen/PBQP/Graph.h"
23 : #include "llvm/CodeGen/PBQP/Math.h"
24 : #include "llvm/CodeGen/PBQP/ReductionRules.h"
25 : #include "llvm/CodeGen/PBQP/Solution.h"
26 : #include "llvm/Support/ErrorHandling.h"
27 : #include <algorithm>
28 : #include <cassert>
29 : #include <cstddef>
30 : #include <limits>
31 : #include <memory>
32 : #include <set>
33 : #include <vector>
34 :
35 : namespace llvm {
36 :
37 : class FunctionPass;
38 : class LiveIntervals;
39 : class MachineBlockFrequencyInfo;
40 : class MachineFunction;
41 : class raw_ostream;
42 :
43 : namespace PBQP {
44 : namespace RegAlloc {
45 :
46 : /// Spill option index.
47 : inline unsigned getSpillOptionIdx() { return 0; }
48 :
49 : /// Metadata to speed allocatability test.
50 : ///
51 : /// Keeps track of the number of infinities in each row and column.
52 : class MatrixMetadata {
53 : public:
54 76 : MatrixMetadata(const Matrix& M)
55 2126 : : UnsafeRows(new bool[M.getRows() - 1]()),
56 2156 : UnsafeCols(new bool[M.getCols() - 1]()) {
57 2080 : unsigned* ColCounts = new unsigned[M.getCols() - 1]();
58 :
59 2126 : for (unsigned i = 1; i < M.getRows(); ++i) {
60 2050 : unsigned RowCount = 0;
61 62130 : for (unsigned j = 1; j < M.getCols(); ++j) {
62 60080 : if (M[i][j] == std::numeric_limits<PBQPNum>::infinity()) {
63 1870 : ++RowCount;
64 1870 : ++ColCounts[j - 1];
65 3740 : UnsafeRows[i - 1] = true;
66 1870 : UnsafeCols[j - 1] = true;
67 : }
68 : }
69 2122 : WorstRow = std::max(WorstRow, RowCount);
70 : }
71 : unsigned WorstColCountForCurRow =
72 76 : *std::max_element(ColCounts, ColCounts + M.getCols() - 1);
73 76 : WorstCol = std::max(WorstCol, WorstColCountForCurRow);
74 76 : delete[] ColCounts;
75 76 : }
76 :
77 : MatrixMetadata(const MatrixMetadata &) = delete;
78 : MatrixMetadata &operator=(const MatrixMetadata &) = delete;
79 :
80 0 : unsigned getWorstRow() const { return WorstRow; }
81 0 : unsigned getWorstCol() const { return WorstCol; }
82 : const bool* getUnsafeRows() const { return UnsafeRows.get(); }
83 : const bool* getUnsafeCols() const { return UnsafeCols.get(); }
84 :
85 : private:
86 : unsigned WorstRow = 0;
87 : unsigned WorstCol = 0;
88 : std::unique_ptr<bool[]> UnsafeRows;
89 : std::unique_ptr<bool[]> UnsafeCols;
90 : };
91 :
92 : /// Holds a vector of the allowed physical regs for a vreg.
93 28 : class AllowedRegVector {
94 : friend hash_code hash_value(const AllowedRegVector &);
95 :
96 : public:
97 : AllowedRegVector() = default;
98 56 : AllowedRegVector(AllowedRegVector &&) = default;
99 :
100 153 : AllowedRegVector(const std::vector<unsigned> &OptVec)
101 306 : : NumOpts(OptVec.size()), Opts(new unsigned[NumOpts]) {
102 153 : std::copy(OptVec.begin(), OptVec.end(), Opts.get());
103 153 : }
104 :
105 0 : unsigned size() const { return NumOpts; }
106 84180 : unsigned operator[](size_t I) const { return Opts[I]; }
107 :
108 153 : bool operator==(const AllowedRegVector &Other) const {
109 153 : if (NumOpts != Other.NumOpts)
110 : return false;
111 153 : return std::equal(Opts.get(), Opts.get() + NumOpts, Other.Opts.get());
112 : }
113 :
114 : bool operator!=(const AllowedRegVector &Other) const {
115 : return !(*this == Other);
116 : }
117 :
118 : private:
119 : unsigned NumOpts = 0;
120 : std::unique_ptr<unsigned[]> Opts;
121 : };
122 :
123 201 : inline hash_code hash_value(const AllowedRegVector &OptRegs) {
124 : unsigned *OStart = OptRegs.Opts.get();
125 201 : unsigned *OEnd = OptRegs.Opts.get() + OptRegs.NumOpts;
126 201 : return hash_combine(OptRegs.NumOpts,
127 201 : hash_combine_range(OStart, OEnd));
128 : }
129 :
130 : /// Holds graph-level metadata relevant to PBQP RA problems.
131 : class GraphMetadata {
132 : private:
133 : using AllowedRegVecPool = ValuePool<AllowedRegVector>;
134 :
135 : public:
136 : using AllowedRegVecRef = AllowedRegVecPool::PoolRef;
137 :
138 : GraphMetadata(MachineFunction &MF,
139 : LiveIntervals &LIS,
140 : MachineBlockFrequencyInfo &MBFI)
141 8 : : MF(MF), LIS(LIS), MBFI(MBFI) {}
142 :
143 : MachineFunction &MF;
144 : LiveIntervals &LIS;
145 : MachineBlockFrequencyInfo &MBFI;
146 :
147 : void setNodeIdForVReg(unsigned VReg, GraphBase::NodeId NId) {
148 153 : VRegToNodeId[VReg] = NId;
149 : }
150 :
151 : GraphBase::NodeId getNodeIdForVReg(unsigned VReg) const {
152 138 : auto VRegItr = VRegToNodeId.find(VReg);
153 138 : if (VRegItr == VRegToNodeId.end())
154 : return GraphBase::invalidNodeId();
155 138 : return VRegItr->second;
156 : }
157 :
158 153 : AllowedRegVecRef getAllowedRegs(AllowedRegVector Allowed) {
159 306 : return AllowedRegVecs.getValue(std::move(Allowed));
160 : }
161 :
162 : private:
163 : DenseMap<unsigned, GraphBase::NodeId> VRegToNodeId;
164 : AllowedRegVecPool AllowedRegVecs;
165 : };
166 :
167 : /// Holds solver state and other metadata relevant to each PBQP RA node.
168 0 : class NodeMetadata {
169 : public:
170 : using AllowedRegVector = RegAlloc::AllowedRegVector;
171 :
172 : // The node's reduction state. The order in this enum is important,
173 : // as it is assumed nodes can only progress up (i.e. towards being
174 : // optimally reducible) when reducing the graph.
175 : using ReductionState = enum {
176 : Unprocessed,
177 : NotProvablyAllocatable,
178 : ConservativelyAllocatable,
179 : OptimallyReducible
180 : };
181 :
182 306 : NodeMetadata() = default;
183 :
184 : NodeMetadata(const NodeMetadata &Other)
185 : : RS(Other.RS), NumOpts(Other.NumOpts), DeniedOpts(Other.DeniedOpts),
186 : OptUnsafeEdges(new unsigned[NumOpts]), VReg(Other.VReg),
187 : AllowedRegs(Other.AllowedRegs)
188 : #ifndef NDEBUG
189 : , everConservativelyAllocatable(Other.everConservativelyAllocatable)
190 : #endif
191 : {
192 : if (NumOpts > 0) {
193 : std::copy(&Other.OptUnsafeEdges[0], &Other.OptUnsafeEdges[NumOpts],
194 : &OptUnsafeEdges[0]);
195 : }
196 : }
197 :
198 : NodeMetadata(NodeMetadata &&) = default;
199 : NodeMetadata& operator=(NodeMetadata &&) = default;
200 :
201 153 : void setVReg(unsigned VReg) { this->VReg = VReg; }
202 0 : unsigned getVReg() const { return VReg; }
203 :
204 : void setAllowedRegs(GraphMetadata::AllowedRegVecRef AllowedRegs) {
205 : this->AllowedRegs = std::move(AllowedRegs);
206 : }
207 : const AllowedRegVector& getAllowedRegs() const { return *AllowedRegs; }
208 :
209 153 : void setup(const Vector& Costs) {
210 153 : NumOpts = Costs.getLength() - 1;
211 4257 : OptUnsafeEdges = std::unique_ptr<unsigned[]>(new unsigned[NumOpts]());
212 153 : }
213 :
214 0 : ReductionState getReductionState() const { return RS; }
215 0 : void setReductionState(ReductionState RS) {
216 : assert(RS >= this->RS && "A node's reduction state can not be downgraded");
217 240 : this->RS = RS;
218 :
219 : #ifndef NDEBUG
220 : // Remember this state to assert later that a non-infinite register
221 : // option was available.
222 : if (RS == ConservativelyAllocatable)
223 : everConservativelyAllocatable = true;
224 : #endif
225 0 : }
226 :
227 1192 : void handleAddEdge(const MatrixMetadata& MD, bool Transpose) {
228 1192 : DeniedOpts += Transpose ? MD.getWorstRow() : MD.getWorstCol();
229 : const bool* UnsafeOpts =
230 1192 : Transpose ? MD.getUnsafeCols() : MD.getUnsafeRows();
231 30926 : for (unsigned i = 0; i < NumOpts; ++i)
232 59468 : OptUnsafeEdges[i] += UnsafeOpts[i];
233 1192 : }
234 :
235 631 : void handleRemoveEdge(const MatrixMetadata& MD, bool Transpose) {
236 631 : DeniedOpts -= Transpose ? MD.getWorstRow() : MD.getWorstCol();
237 : const bool* UnsafeOpts =
238 631 : Transpose ? MD.getUnsafeCols() : MD.getUnsafeRows();
239 16501 : for (unsigned i = 0; i < NumOpts; ++i)
240 31740 : OptUnsafeEdges[i] -= UnsafeOpts[i];
241 631 : }
242 :
243 261 : bool isConservativelyAllocatable() const {
244 261 : return (DeniedOpts < NumOpts) ||
245 138 : (std::find(&OptUnsafeEdges[0], &OptUnsafeEdges[NumOpts], 0) !=
246 261 : &OptUnsafeEdges[NumOpts]);
247 : }
248 :
249 : #ifndef NDEBUG
250 : bool wasConservativelyAllocatable() const {
251 : return everConservativelyAllocatable;
252 : }
253 : #endif
254 :
255 : private:
256 : ReductionState RS = Unprocessed;
257 : unsigned NumOpts = 0;
258 : unsigned DeniedOpts = 0;
259 : std::unique_ptr<unsigned[]> OptUnsafeEdges;
260 : unsigned VReg = 0;
261 : GraphMetadata::AllowedRegVecRef AllowedRegs;
262 :
263 : #ifndef NDEBUG
264 : bool everConservativelyAllocatable = false;
265 : #endif
266 : };
267 :
268 : class RegAllocSolverImpl {
269 : private:
270 : using RAMatrix = MDMatrix<MatrixMetadata>;
271 :
272 : public:
273 : using RawVector = PBQP::Vector;
274 : using RawMatrix = PBQP::Matrix;
275 : using Vector = PBQP::Vector;
276 : using Matrix = RAMatrix;
277 : using CostAllocator = PBQP::PoolCostAllocator<Vector, Matrix>;
278 :
279 : using NodeId = GraphBase::NodeId;
280 : using EdgeId = GraphBase::EdgeId;
281 :
282 : using NodeMetadata = RegAlloc::NodeMetadata;
283 : struct EdgeMetadata {};
284 : using GraphMetadata = RegAlloc::GraphMetadata;
285 :
286 : using Graph = PBQP::Graph<RegAllocSolverImpl>;
287 :
288 8 : RegAllocSolverImpl(Graph &G) : G(G) {}
289 :
290 8 : Solution solve() {
291 8 : G.setSolver(*this);
292 : Solution S;
293 8 : setup();
294 16 : S = backpropagate(G, reduce());
295 8 : G.unsetSolver();
296 8 : return S;
297 : }
298 :
299 0 : void handleAddNode(NodeId NId) {
300 : assert(G.getNodeCosts(NId).getLength() > 1 &&
301 : "PBQP Graph should not contain single or zero-option nodes");
302 153 : G.getNodeMetadata(NId).setup(G.getNodeCosts(NId));
303 0 : }
304 :
305 : void handleRemoveNode(NodeId NId) {}
306 0 : void handleSetNodeCosts(NodeId NId, const Vector& newCosts) {}
307 :
308 0 : void handleAddEdge(EdgeId EId) {
309 0 : handleReconnectEdge(EId, G.getEdgeNode1Id(EId));
310 0 : handleReconnectEdge(EId, G.getEdgeNode2Id(EId));
311 0 : }
312 :
313 561 : void handleDisconnectEdge(EdgeId EId, NodeId NId) {
314 561 : NodeMetadata& NMd = G.getNodeMetadata(NId);
315 : const MatrixMetadata& MMd = G.getEdgeCosts(EId).getMetadata();
316 561 : NMd.handleRemoveEdge(MMd, NId == G.getEdgeNode2Id(EId));
317 561 : promote(NId, NMd);
318 561 : }
319 :
320 0 : void handleReconnectEdge(EdgeId EId, NodeId NId) {
321 0 : NodeMetadata& NMd = G.getNodeMetadata(NId);
322 : const MatrixMetadata& MMd = G.getEdgeCosts(EId).getMetadata();
323 0 : NMd.handleAddEdge(MMd, NId == G.getEdgeNode2Id(EId));
324 0 : }
325 :
326 35 : void handleUpdateCosts(EdgeId EId, const Matrix& NewCosts) {
327 35 : NodeId N1Id = G.getEdgeNode1Id(EId);
328 : NodeId N2Id = G.getEdgeNode2Id(EId);
329 : NodeMetadata& N1Md = G.getNodeMetadata(N1Id);
330 : NodeMetadata& N2Md = G.getNodeMetadata(N2Id);
331 : bool Transpose = N1Id != G.getEdgeNode1Id(EId);
332 :
333 : // Metadata are computed incrementally. First, update them
334 : // by removing the old cost.
335 : const MatrixMetadata& OldMMd = G.getEdgeCosts(EId).getMetadata();
336 35 : N1Md.handleRemoveEdge(OldMMd, Transpose);
337 35 : N2Md.handleRemoveEdge(OldMMd, !Transpose);
338 :
339 : // And update now the metadata with the new cost.
340 : const MatrixMetadata& MMd = NewCosts.getMetadata();
341 35 : N1Md.handleAddEdge(MMd, Transpose);
342 35 : N2Md.handleAddEdge(MMd, !Transpose);
343 :
344 : // As the metadata may have changed with the update, the nodes may have
345 : // become ConservativelyAllocatable or OptimallyReducible.
346 35 : promote(N1Id, N1Md);
347 35 : promote(N2Id, N2Md);
348 35 : }
349 :
350 : private:
351 631 : void promote(NodeId NId, NodeMetadata& NMd) {
352 1262 : if (G.getNodeDegree(NId) == 3) {
353 : // This node is becoming optimally reducible.
354 75 : moveToOptimallyReducibleNodes(NId);
355 556 : } else if (NMd.getReductionState() ==
356 683 : NodeMetadata::NotProvablyAllocatable &&
357 127 : NMd.isConservativelyAllocatable()) {
358 : // This node just became conservatively allocatable.
359 12 : moveToConservativelyAllocatableNodes(NId);
360 : }
361 631 : }
362 :
363 240 : void removeFromCurrentSet(NodeId NId) {
364 480 : switch (G.getNodeMetadata(NId).getReductionState()) {
365 : case NodeMetadata::Unprocessed: break;
366 19 : case NodeMetadata::OptimallyReducible:
367 : assert(OptimallyReducibleNodes.find(NId) !=
368 : OptimallyReducibleNodes.end() &&
369 : "Node not in optimally reducible set.");
370 : OptimallyReducibleNodes.erase(NId);
371 : break;
372 56 : case NodeMetadata::ConservativelyAllocatable:
373 : assert(ConservativelyAllocatableNodes.find(NId) !=
374 : ConservativelyAllocatableNodes.end() &&
375 : "Node not in conservatively allocatable set.");
376 : ConservativelyAllocatableNodes.erase(NId);
377 : break;
378 12 : case NodeMetadata::NotProvablyAllocatable:
379 : assert(NotProvablyAllocatableNodes.find(NId) !=
380 : NotProvablyAllocatableNodes.end() &&
381 : "Node not in not-provably-allocatable set.");
382 : NotProvablyAllocatableNodes.erase(NId);
383 : break;
384 : }
385 240 : }
386 :
387 94 : void moveToOptimallyReducibleNodes(NodeId NId) {
388 94 : removeFromCurrentSet(NId);
389 : OptimallyReducibleNodes.insert(NId);
390 94 : G.getNodeMetadata(NId).setReductionState(
391 : NodeMetadata::OptimallyReducible);
392 94 : }
393 :
394 124 : void moveToConservativelyAllocatableNodes(NodeId NId) {
395 124 : removeFromCurrentSet(NId);
396 : ConservativelyAllocatableNodes.insert(NId);
397 124 : G.getNodeMetadata(NId).setReductionState(
398 : NodeMetadata::ConservativelyAllocatable);
399 124 : }
400 :
401 22 : void moveToNotProvablyAllocatableNodes(NodeId NId) {
402 22 : removeFromCurrentSet(NId);
403 : NotProvablyAllocatableNodes.insert(NId);
404 22 : G.getNodeMetadata(NId).setReductionState(
405 : NodeMetadata::NotProvablyAllocatable);
406 22 : }
407 :
408 8 : void setup() {
409 : // Set up worklists.
410 161 : for (auto NId : G.nodeIds()) {
411 306 : if (G.getNodeDegree(NId) < 3)
412 19 : moveToOptimallyReducibleNodes(NId);
413 134 : else if (G.getNodeMetadata(NId).isConservativelyAllocatable())
414 112 : moveToConservativelyAllocatableNodes(NId);
415 : else
416 22 : moveToNotProvablyAllocatableNodes(NId);
417 : }
418 8 : }
419 :
420 : // Compute a reduction order for the graph by iteratively applying PBQP
421 : // reduction rules. Locally optimal rules are applied whenever possible (R0,
422 : // R1, R2). If no locally-optimal rules apply then any conservatively
423 : // allocatable node is reduced. Finally, if no conservatively allocatable
424 : // node exists then the node with the lowest spill-cost:degree ratio is
425 : // selected.
426 8 : std::vector<GraphBase::NodeId> reduce() {
427 : assert(!G.empty() && "Cannot reduce empty graph.");
428 :
429 : using NodeId = GraphBase::NodeId;
430 : std::vector<NodeId> NodeStack;
431 :
432 : // Consume worklists.
433 : while (true) {
434 161 : if (!OptimallyReducibleNodes.empty()) {
435 : NodeSet::iterator NItr = OptimallyReducibleNodes.begin();
436 75 : NodeId NId = *NItr;
437 : OptimallyReducibleNodes.erase(NItr);
438 75 : NodeStack.push_back(NId);
439 150 : switch (G.getNodeDegree(NId)) {
440 : case 0:
441 : break;
442 17 : case 1:
443 17 : applyR1(G, NId);
444 17 : break;
445 35 : case 2:
446 35 : applyR2(G, NId);
447 35 : break;
448 0 : default: llvm_unreachable("Not an optimally reducible node.");
449 : }
450 86 : } else if (!ConservativelyAllocatableNodes.empty()) {
451 : // Conservatively allocatable nodes will never spill. For now just
452 : // take the first node in the set and push it on the stack. When we
453 : // start optimizing more heavily for register preferencing, it may
454 : // would be better to push nodes with lower 'expected' or worst-case
455 : // register costs first (since early nodes are the most
456 : // constrained).
457 : NodeSet::iterator NItr = ConservativelyAllocatableNodes.begin();
458 68 : NodeId NId = *NItr;
459 : ConservativelyAllocatableNodes.erase(NItr);
460 68 : NodeStack.push_back(NId);
461 68 : G.disconnectAllNeighborsFromNode(NId);
462 18 : } else if (!NotProvablyAllocatableNodes.empty()) {
463 : NodeSet::iterator NItr =
464 : std::min_element(NotProvablyAllocatableNodes.begin(),
465 : NotProvablyAllocatableNodes.end(),
466 10 : SpillCostComparator(G));
467 10 : NodeId NId = *NItr;
468 : NotProvablyAllocatableNodes.erase(NItr);
469 10 : NodeStack.push_back(NId);
470 10 : G.disconnectAllNeighborsFromNode(NId);
471 : } else
472 : break;
473 : }
474 :
475 8 : return NodeStack;
476 : }
477 :
478 : class SpillCostComparator {
479 : public:
480 : SpillCostComparator(const Graph& G) : G(G) {}
481 :
482 105 : bool operator()(NodeId N1Id, NodeId N2Id) {
483 210 : PBQPNum N1SC = G.getNodeCosts(N1Id)[0];
484 105 : PBQPNum N2SC = G.getNodeCosts(N2Id)[0];
485 105 : if (N1SC == N2SC)
486 0 : return G.getNodeDegree(N1Id) < G.getNodeDegree(N2Id);
487 105 : return N1SC < N2SC;
488 : }
489 :
490 : private:
491 : const Graph& G;
492 : };
493 :
494 : Graph& G;
495 : using NodeSet = std::set<NodeId>;
496 : NodeSet OptimallyReducibleNodes;
497 : NodeSet ConservativelyAllocatableNodes;
498 : NodeSet NotProvablyAllocatableNodes;
499 : };
500 :
501 8 : class PBQPRAGraph : public PBQP::Graph<RegAllocSolverImpl> {
502 : private:
503 : using BaseT = PBQP::Graph<RegAllocSolverImpl>;
504 :
505 : public:
506 8 : PBQPRAGraph(GraphMetadata Metadata) : BaseT(std::move(Metadata)) {}
507 :
508 : /// Dump this graph to dbgs().
509 : void dump() const;
510 :
511 : /// Dump this graph to an output stream.
512 : /// @param OS Output stream to print on.
513 : void dump(raw_ostream &OS) const;
514 :
515 : /// Print a representation of this graph in DOT format.
516 : /// @param OS Output stream to print on.
517 : void printDot(raw_ostream &OS) const;
518 : };
519 :
520 8 : inline Solution solve(PBQPRAGraph& G) {
521 8 : if (G.empty())
522 0 : return Solution();
523 8 : RegAllocSolverImpl RegAllocSolver(G);
524 8 : return RegAllocSolver.solve();
525 : }
526 :
527 : } // end namespace RegAlloc
528 : } // end namespace PBQP
529 :
530 : /// Create a PBQP register allocator instance.
531 : FunctionPass *
532 : createPBQPRegisterAllocator(char *customPassID = nullptr);
533 :
534 : } // end namespace llvm
535 :
536 : #endif // LLVM_CODEGEN_REGALLOCPBQP_H
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