DAGISelMatcherOpt.cpp revision 204642
1//===- DAGISelMatcherOpt.cpp - Optimize a DAG Matcher ---------------------===// 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 implements the DAG Matcher optimizer. 11// 12//===----------------------------------------------------------------------===// 13 14#define DEBUG_TYPE "isel-opt" 15#include "DAGISelMatcher.h" 16#include "CodeGenDAGPatterns.h" 17#include "llvm/ADT/DenseSet.h" 18#include "llvm/ADT/StringSet.h" 19#include "llvm/Support/Debug.h" 20#include "llvm/Support/raw_ostream.h" 21#include <vector> 22using namespace llvm; 23 24/// ContractNodes - Turn multiple matcher node patterns like 'MoveChild+Record' 25/// into single compound nodes like RecordChild. 26static void ContractNodes(OwningPtr<Matcher> &MatcherPtr, 27 const CodeGenDAGPatterns &CGP) { 28 // If we reached the end of the chain, we're done. 29 Matcher *N = MatcherPtr.get(); 30 if (N == 0) return; 31 32 // If we have a scope node, walk down all of the children. 33 if (ScopeMatcher *Scope = dyn_cast<ScopeMatcher>(N)) { 34 for (unsigned i = 0, e = Scope->getNumChildren(); i != e; ++i) { 35 OwningPtr<Matcher> Child(Scope->takeChild(i)); 36 ContractNodes(Child, CGP); 37 Scope->resetChild(i, Child.take()); 38 } 39 return; 40 } 41 42 // If we found a movechild node with a node that comes in a 'foochild' form, 43 // transform it. 44 if (MoveChildMatcher *MC = dyn_cast<MoveChildMatcher>(N)) { 45 Matcher *New = 0; 46 if (RecordMatcher *RM = dyn_cast<RecordMatcher>(MC->getNext())) 47 New = new RecordChildMatcher(MC->getChildNo(), RM->getWhatFor(), 48 RM->getResultNo()); 49 50 if (CheckTypeMatcher *CT= dyn_cast<CheckTypeMatcher>(MC->getNext())) 51 New = new CheckChildTypeMatcher(MC->getChildNo(), CT->getType()); 52 53 if (New) { 54 // Insert the new node. 55 New->setNext(MatcherPtr.take()); 56 MatcherPtr.reset(New); 57 // Remove the old one. 58 MC->setNext(MC->getNext()->takeNext()); 59 return ContractNodes(MatcherPtr, CGP); 60 } 61 } 62 63 // Zap movechild -> moveparent. 64 if (MoveChildMatcher *MC = dyn_cast<MoveChildMatcher>(N)) 65 if (MoveParentMatcher *MP = 66 dyn_cast<MoveParentMatcher>(MC->getNext())) { 67 MatcherPtr.reset(MP->takeNext()); 68 return ContractNodes(MatcherPtr, CGP); 69 } 70 71 // Turn EmitNode->MarkFlagResults->CompleteMatch into 72 // MarkFlagResults->EmitNode->CompleteMatch when we can to encourage 73 // MorphNodeTo formation. This is safe because MarkFlagResults never refers 74 // to the root of the pattern. 75 if (isa<EmitNodeMatcher>(N) && isa<MarkFlagResultsMatcher>(N->getNext()) && 76 isa<CompleteMatchMatcher>(N->getNext()->getNext())) { 77 // Unlink the two nodes from the list. 78 Matcher *EmitNode = MatcherPtr.take(); 79 Matcher *MFR = EmitNode->takeNext(); 80 Matcher *Tail = MFR->takeNext(); 81 82 // Relink them. 83 MatcherPtr.reset(MFR); 84 MFR->setNext(EmitNode); 85 EmitNode->setNext(Tail); 86 return ContractNodes(MatcherPtr, CGP); 87 } 88 89 // Turn EmitNode->CompleteMatch into MorphNodeTo if we can. 90 if (EmitNodeMatcher *EN = dyn_cast<EmitNodeMatcher>(N)) 91 if (CompleteMatchMatcher *CM = 92 dyn_cast<CompleteMatchMatcher>(EN->getNext())) { 93 // We can only use MorphNodeTo if the result values match up. 94 unsigned RootResultFirst = EN->getFirstResultSlot(); 95 bool ResultsMatch = true; 96 for (unsigned i = 0, e = CM->getNumResults(); i != e; ++i) 97 if (CM->getResult(i) != RootResultFirst+i) 98 ResultsMatch = false; 99 100 // If the selected node defines a subset of the flag/chain results, we 101 // can't use MorphNodeTo. For example, we can't use MorphNodeTo if the 102 // matched pattern has a chain but the root node doesn't. 103 const PatternToMatch &Pattern = CM->getPattern(); 104 105 if (!EN->hasChain() && 106 Pattern.getSrcPattern()->NodeHasProperty(SDNPHasChain, CGP)) 107 ResultsMatch = false; 108 109 // If the matched node has a flag and the output root doesn't, we can't 110 // use MorphNodeTo. 111 // 112 // NOTE: Strictly speaking, we don't have to check for the flag here 113 // because the code in the pattern generator doesn't handle it right. We 114 // do it anyway for thoroughness. 115 if (!EN->hasOutFlag() && 116 Pattern.getSrcPattern()->NodeHasProperty(SDNPOutFlag, CGP)) 117 ResultsMatch = false; 118 119 120 // If the root result node defines more results than the source root node 121 // *and* has a chain or flag input, then we can't match it because it 122 // would end up replacing the extra result with the chain/flag. 123#if 0 124 if ((EN->hasFlag() || EN->hasChain()) && 125 EN->getNumNonChainFlagVTs() > ... need to get no results reliably ...) 126 ResultMatch = false; 127#endif 128 129 if (ResultsMatch) { 130 const SmallVectorImpl<MVT::SimpleValueType> &VTs = EN->getVTList(); 131 const SmallVectorImpl<unsigned> &Operands = EN->getOperandList(); 132 MatcherPtr.reset(new MorphNodeToMatcher(EN->getOpcodeName(), 133 VTs.data(), VTs.size(), 134 Operands.data(),Operands.size(), 135 EN->hasChain(), EN->hasInFlag(), 136 EN->hasOutFlag(), 137 EN->hasMemRefs(), 138 EN->getNumFixedArityOperands(), 139 Pattern)); 140 return; 141 } 142 143 // FIXME2: Kill off all the SelectionDAG::SelectNodeTo and getMachineNode 144 // variants. 145 } 146 147 ContractNodes(N->getNextPtr(), CGP); 148 149 150 // If we have a CheckType/CheckChildType/Record node followed by a 151 // CheckOpcode, invert the two nodes. We prefer to do structural checks 152 // before type checks, as this opens opportunities for factoring on targets 153 // like X86 where many operations are valid on multiple types. 154 if ((isa<CheckTypeMatcher>(N) || isa<CheckChildTypeMatcher>(N) || 155 isa<RecordMatcher>(N)) && 156 isa<CheckOpcodeMatcher>(N->getNext())) { 157 // Unlink the two nodes from the list. 158 Matcher *CheckType = MatcherPtr.take(); 159 Matcher *CheckOpcode = CheckType->takeNext(); 160 Matcher *Tail = CheckOpcode->takeNext(); 161 162 // Relink them. 163 MatcherPtr.reset(CheckOpcode); 164 CheckOpcode->setNext(CheckType); 165 CheckType->setNext(Tail); 166 return ContractNodes(MatcherPtr, CGP); 167 } 168} 169 170/// SinkPatternPredicates - Pattern predicates can be checked at any level of 171/// the matching tree. The generator dumps them at the top level of the pattern 172/// though, which prevents factoring from being able to see past them. This 173/// optimization sinks them as far down into the pattern as possible. 174/// 175/// Conceptually, we'd like to sink these predicates all the way to the last 176/// matcher predicate in the series. However, it turns out that some 177/// ComplexPatterns have side effects on the graph, so we really don't want to 178/// run a the complex pattern if the pattern predicate will fail. For this 179/// reason, we refuse to sink the pattern predicate past a ComplexPattern. 180/// 181static void SinkPatternPredicates(OwningPtr<Matcher> &MatcherPtr) { 182 // Recursively scan for a PatternPredicate. 183 // If we reached the end of the chain, we're done. 184 Matcher *N = MatcherPtr.get(); 185 if (N == 0) return; 186 187 // Walk down all members of a scope node. 188 if (ScopeMatcher *Scope = dyn_cast<ScopeMatcher>(N)) { 189 for (unsigned i = 0, e = Scope->getNumChildren(); i != e; ++i) { 190 OwningPtr<Matcher> Child(Scope->takeChild(i)); 191 SinkPatternPredicates(Child); 192 Scope->resetChild(i, Child.take()); 193 } 194 return; 195 } 196 197 // If this node isn't a CheckPatternPredicateMatcher we keep scanning until 198 // we find one. 199 CheckPatternPredicateMatcher *CPPM =dyn_cast<CheckPatternPredicateMatcher>(N); 200 if (CPPM == 0) 201 return SinkPatternPredicates(N->getNextPtr()); 202 203 // Ok, we found one, lets try to sink it. Check if we can sink it past the 204 // next node in the chain. If not, we won't be able to change anything and 205 // might as well bail. 206 if (!CPPM->getNext()->isSafeToReorderWithPatternPredicate()) 207 return; 208 209 // Okay, we know we can sink it past at least one node. Unlink it from the 210 // chain and scan for the new insertion point. 211 MatcherPtr.take(); // Don't delete CPPM. 212 MatcherPtr.reset(CPPM->takeNext()); 213 214 N = MatcherPtr.get(); 215 while (N->getNext()->isSafeToReorderWithPatternPredicate()) 216 N = N->getNext(); 217 218 // At this point, we want to insert CPPM after N. 219 CPPM->setNext(N->takeNext()); 220 N->setNext(CPPM); 221} 222 223/// FactorNodes - Turn matches like this: 224/// Scope 225/// OPC_CheckType i32 226/// ABC 227/// OPC_CheckType i32 228/// XYZ 229/// into: 230/// OPC_CheckType i32 231/// Scope 232/// ABC 233/// XYZ 234/// 235static void FactorNodes(OwningPtr<Matcher> &MatcherPtr) { 236 // If we reached the end of the chain, we're done. 237 Matcher *N = MatcherPtr.get(); 238 if (N == 0) return; 239 240 // If this is not a push node, just scan for one. 241 ScopeMatcher *Scope = dyn_cast<ScopeMatcher>(N); 242 if (Scope == 0) 243 return FactorNodes(N->getNextPtr()); 244 245 // Okay, pull together the children of the scope node into a vector so we can 246 // inspect it more easily. While we're at it, bucket them up by the hash 247 // code of their first predicate. 248 SmallVector<Matcher*, 32> OptionsToMatch; 249 250 for (unsigned i = 0, e = Scope->getNumChildren(); i != e; ++i) { 251 // Factor the subexpression. 252 OwningPtr<Matcher> Child(Scope->takeChild(i)); 253 FactorNodes(Child); 254 255 if (Matcher *N = Child.take()) 256 OptionsToMatch.push_back(N); 257 } 258 259 SmallVector<Matcher*, 32> NewOptionsToMatch; 260 261 // Loop over options to match, merging neighboring patterns with identical 262 // starting nodes into a shared matcher. 263 for (unsigned OptionIdx = 0, e = OptionsToMatch.size(); OptionIdx != e;) { 264 // Find the set of matchers that start with this node. 265 Matcher *Optn = OptionsToMatch[OptionIdx++]; 266 267 if (OptionIdx == e) { 268 NewOptionsToMatch.push_back(Optn); 269 continue; 270 } 271 272 // See if the next option starts with the same matcher. If the two 273 // neighbors *do* start with the same matcher, we can factor the matcher out 274 // of at least these two patterns. See what the maximal set we can merge 275 // together is. 276 SmallVector<Matcher*, 8> EqualMatchers; 277 EqualMatchers.push_back(Optn); 278 279 // Factor all of the known-equal matchers after this one into the same 280 // group. 281 while (OptionIdx != e && OptionsToMatch[OptionIdx]->isEqual(Optn)) 282 EqualMatchers.push_back(OptionsToMatch[OptionIdx++]); 283 284 // If we found a non-equal matcher, see if it is contradictory with the 285 // current node. If so, we know that the ordering relation between the 286 // current sets of nodes and this node don't matter. Look past it to see if 287 // we can merge anything else into this matching group. 288 unsigned Scan = OptionIdx; 289 while (1) { 290 while (Scan != e && Optn->isContradictory(OptionsToMatch[Scan])) 291 ++Scan; 292 293 // Ok, we found something that isn't known to be contradictory. If it is 294 // equal, we can merge it into the set of nodes to factor, if not, we have 295 // to cease factoring. 296 if (Scan == e || !Optn->isEqual(OptionsToMatch[Scan])) break; 297 298 // If is equal after all, add the option to EqualMatchers and remove it 299 // from OptionsToMatch. 300 EqualMatchers.push_back(OptionsToMatch[Scan]); 301 OptionsToMatch.erase(OptionsToMatch.begin()+Scan); 302 --e; 303 } 304 305 if (Scan != e && 306 // Don't print it's obvious nothing extra could be merged anyway. 307 Scan+1 != e) { 308 DEBUG(errs() << "Couldn't merge this:\n"; 309 Optn->print(errs(), 4); 310 errs() << "into this:\n"; 311 OptionsToMatch[Scan]->print(errs(), 4); 312 if (Scan+1 != e) 313 OptionsToMatch[Scan+1]->printOne(errs()); 314 if (Scan+2 < e) 315 OptionsToMatch[Scan+2]->printOne(errs()); 316 errs() << "\n"); 317 } 318 319 // If we only found one option starting with this matcher, no factoring is 320 // possible. 321 if (EqualMatchers.size() == 1) { 322 NewOptionsToMatch.push_back(EqualMatchers[0]); 323 continue; 324 } 325 326 // Factor these checks by pulling the first node off each entry and 327 // discarding it. Take the first one off the first entry to reuse. 328 Matcher *Shared = Optn; 329 Optn = Optn->takeNext(); 330 EqualMatchers[0] = Optn; 331 332 // Remove and delete the first node from the other matchers we're factoring. 333 for (unsigned i = 1, e = EqualMatchers.size(); i != e; ++i) { 334 Matcher *Tmp = EqualMatchers[i]->takeNext(); 335 delete EqualMatchers[i]; 336 EqualMatchers[i] = Tmp; 337 } 338 339 Shared->setNext(new ScopeMatcher(&EqualMatchers[0], EqualMatchers.size())); 340 341 // Recursively factor the newly created node. 342 FactorNodes(Shared->getNextPtr()); 343 344 NewOptionsToMatch.push_back(Shared); 345 } 346 347 // If we're down to a single pattern to match, then we don't need this scope 348 // anymore. 349 if (NewOptionsToMatch.size() == 1) { 350 MatcherPtr.reset(NewOptionsToMatch[0]); 351 return; 352 } 353 354 if (NewOptionsToMatch.empty()) { 355 MatcherPtr.reset(0); 356 return; 357 } 358 359 // If our factoring failed (didn't achieve anything) see if we can simplify in 360 // other ways. 361 362 // Check to see if all of the leading entries are now opcode checks. If so, 363 // we can convert this Scope to be a OpcodeSwitch instead. 364 bool AllOpcodeChecks = true, AllTypeChecks = true; 365 for (unsigned i = 0, e = NewOptionsToMatch.size(); i != e; ++i) { 366 if (!isa<CheckOpcodeMatcher>(NewOptionsToMatch[i])) { 367#if 0 368 if (i > 3 && AllOpcodeChecks) { 369 errs() << "FAILING OPC #" << i << "\n"; 370 NewOptionsToMatch[i]->dump(); 371 } 372#endif 373 AllOpcodeChecks = false; 374 } 375 376 if (!isa<CheckTypeMatcher>(NewOptionsToMatch[i]) || 377 // iPTR checks could alias any other case without us knowing, don't 378 // bother with them. 379 cast<CheckTypeMatcher>(NewOptionsToMatch[i])->getType() == MVT::iPTR) { 380#if 0 381 if (i > 3 && AllTypeChecks) { 382 errs() << "FAILING TYPE #" << i << "\n"; 383 NewOptionsToMatch[i]->dump(); 384 } 385#endif 386 AllTypeChecks = false; 387 } 388 } 389 // TODO: Can also do CheckChildNType. 390 391 // If all the options are CheckOpcode's, we can form the SwitchOpcode, woot. 392 if (AllOpcodeChecks) { 393 StringSet<> Opcodes; 394 SmallVector<std::pair<const SDNodeInfo*, Matcher*>, 8> Cases; 395 for (unsigned i = 0, e = NewOptionsToMatch.size(); i != e; ++i) { 396 CheckOpcodeMatcher *COM = cast<CheckOpcodeMatcher>(NewOptionsToMatch[i]); 397 assert(Opcodes.insert(COM->getOpcode().getEnumName()) && 398 "Duplicate opcodes not factored?"); 399 Cases.push_back(std::make_pair(&COM->getOpcode(), COM->getNext())); 400 } 401 402 MatcherPtr.reset(new SwitchOpcodeMatcher(&Cases[0], Cases.size())); 403 return; 404 } 405 406 // If all the options are CheckType's, we can form the SwitchType, woot. 407 if (AllTypeChecks) { 408 DenseSet<unsigned> Types; 409 SmallVector<std::pair<MVT::SimpleValueType, Matcher*>, 8> Cases; 410 for (unsigned i = 0, e = NewOptionsToMatch.size(); i != e; ++i) { 411 CheckTypeMatcher *CTM = cast<CheckTypeMatcher>(NewOptionsToMatch[i]); 412 assert(Types.insert(CTM->getType()).second && 413 "Duplicate types not factored?"); 414 Cases.push_back(std::make_pair(CTM->getType(), CTM->getNext())); 415 } 416 417 MatcherPtr.reset(new SwitchTypeMatcher(&Cases[0], Cases.size())); 418 return; 419 } 420 421 422 // Reassemble the Scope node with the adjusted children. 423 Scope->setNumChildren(NewOptionsToMatch.size()); 424 for (unsigned i = 0, e = NewOptionsToMatch.size(); i != e; ++i) 425 Scope->resetChild(i, NewOptionsToMatch[i]); 426} 427 428Matcher *llvm::OptimizeMatcher(Matcher *TheMatcher, 429 const CodeGenDAGPatterns &CGP) { 430 OwningPtr<Matcher> MatcherPtr(TheMatcher); 431 ContractNodes(MatcherPtr, CGP); 432 SinkPatternPredicates(MatcherPtr); 433 FactorNodes(MatcherPtr); 434 return MatcherPtr.take(); 435} 436