1 //===- DAGISelMatcherOpt.cpp - Optimize a DAG Matcher ---------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements the DAG Matcher optimizer.
12 //===----------------------------------------------------------------------===//
14 #define DEBUG_TYPE "isel-opt"
15 #include "DAGISelMatcher.h"
16 #include "CodeGenDAGPatterns.h"
17 #include "llvm/ADT/DenseMap.h"
18 #include "llvm/ADT/StringSet.h"
19 #include "llvm/Support/Debug.h"
20 #include "llvm/Support/raw_ostream.h"
24 /// ContractNodes - Turn multiple matcher node patterns like 'MoveChild+Record'
25 /// into single compound nodes like RecordChild.
26 static 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();
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());
42 // If we found a movechild node with a node that comes in a 'foochild' form,
44 if (MoveChildMatcher *MC = dyn_cast<MoveChildMatcher>(N)) {
46 if (RecordMatcher *RM = dyn_cast<RecordMatcher>(MC->getNext()))
47 New = new RecordChildMatcher(MC->getChildNo(), RM->getWhatFor(),
50 if (CheckTypeMatcher *CT= dyn_cast<CheckTypeMatcher>(MC->getNext()))
51 New = new CheckChildTypeMatcher(MC->getChildNo(), CT->getType());
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);
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);
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();
83 MatcherPtr.reset(MFR);
84 MFR->setNext(EmitNode);
85 EmitNode->setNext(Tail);
86 return ContractNodes(MatcherPtr, CGP);
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)
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();
105 if (!EN->hasChain() &&
106 Pattern.getSrcPattern()->NodeHasProperty(SDNPHasChain, CGP))
107 ResultsMatch = false;
109 // If the matched node has a flag and the output root doesn't, we can't
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;
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.
124 if ((EN->hasFlag() || EN->hasChain()) &&
125 EN->getNumNonChainFlagVTs() > ... need to get no results reliably ...)
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(),
138 EN->getNumFixedArityOperands(),
143 // FIXME2: Kill off all the SelectionDAG::MorphNodeTo and getMachineNode
147 ContractNodes(N->getNextPtr(), CGP);
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();
163 MatcherPtr.reset(CheckOpcode);
164 CheckOpcode->setNext(CheckType);
165 CheckType->setNext(Tail);
166 return ContractNodes(MatcherPtr, CGP);
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.
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.
181 static 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();
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());
197 // If this node isn't a CheckPatternPredicateMatcher we keep scanning until
199 CheckPatternPredicateMatcher *CPPM =dyn_cast<CheckPatternPredicateMatcher>(N);
201 return SinkPatternPredicates(N->getNextPtr());
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())
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());
214 N = MatcherPtr.get();
215 while (N->getNext()->isSafeToReorderWithPatternPredicate())
218 // At this point, we want to insert CPPM after N.
219 CPPM->setNext(N->takeNext());
223 /// FactorNodes - Turn matches like this:
225 /// OPC_CheckType i32
227 /// OPC_CheckType i32
230 /// OPC_CheckType i32
235 static void FactorNodes(OwningPtr<Matcher> &MatcherPtr) {
236 // If we reached the end of the chain, we're done.
237 Matcher *N = MatcherPtr.get();
240 // If this is not a push node, just scan for one.
241 ScopeMatcher *Scope = dyn_cast<ScopeMatcher>(N);
243 return FactorNodes(N->getNextPtr());
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;
250 for (unsigned i = 0, e = Scope->getNumChildren(); i != e; ++i) {
251 // Factor the subexpression.
252 OwningPtr<Matcher> Child(Scope->takeChild(i));
255 if (Matcher *N = Child.take())
256 OptionsToMatch.push_back(N);
259 SmallVector<Matcher*, 32> NewOptionsToMatch;
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++];
267 if (OptionIdx == e) {
268 NewOptionsToMatch.push_back(Optn);
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
276 SmallVector<Matcher*, 8> EqualMatchers;
277 EqualMatchers.push_back(Optn);
279 // Factor all of the known-equal matchers after this one into the same
281 while (OptionIdx != e && OptionsToMatch[OptionIdx]->isEqual(Optn))
282 EqualMatchers.push_back(OptionsToMatch[OptionIdx++]);
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;
290 while (Scan != e && Optn->isContradictory(OptionsToMatch[Scan]))
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;
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);
306 // Don't print it's obvious nothing extra could be merged anyway.
308 DEBUG(errs() << "Couldn't merge this:\n";
309 Optn->print(errs(), 4);
310 errs() << "into this:\n";
311 OptionsToMatch[Scan]->print(errs(), 4);
313 OptionsToMatch[Scan+1]->printOne(errs());
315 OptionsToMatch[Scan+2]->printOne(errs());
319 // If we only found one option starting with this matcher, no factoring is
321 if (EqualMatchers.size() == 1) {
322 NewOptionsToMatch.push_back(EqualMatchers[0]);
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;
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;
339 Shared->setNext(new ScopeMatcher(&EqualMatchers[0], EqualMatchers.size()));
341 // Recursively factor the newly created node.
342 FactorNodes(Shared->getNextPtr());
344 NewOptionsToMatch.push_back(Shared);
347 // If we're down to a single pattern to match, then we don't need this scope
349 if (NewOptionsToMatch.size() == 1) {
350 MatcherPtr.reset(NewOptionsToMatch[0]);
354 // If our factoring failed (didn't achieve anything) see if we can simplify in
357 // Check to see if all of the leading entries are now opcode checks. If so,
358 // we can convert this Scope to be a OpcodeSwitch instead.
359 bool AllOpcodeChecks = true;
360 for (unsigned i = 0, e = NewOptionsToMatch.size(); i != e; ++i) {
361 if (isa<CheckOpcodeMatcher>(NewOptionsToMatch[i])) continue;
365 errs() << "FAILING OPC #" << i << "\n";
366 NewOptionsToMatch[i]->dump();
370 AllOpcodeChecks = false;
374 // If all the options are CheckOpcode's, we can form the SwitchOpcode, woot.
375 if (AllOpcodeChecks) {
377 SmallVector<std::pair<const SDNodeInfo*, Matcher*>, 8> Cases;
378 for (unsigned i = 0, e = NewOptionsToMatch.size(); i != e; ++i) {
379 CheckOpcodeMatcher *COM =cast<CheckOpcodeMatcher>(NewOptionsToMatch[i]);
380 assert(Opcodes.insert(COM->getOpcode().getEnumName()) &&
381 "Duplicate opcodes not factored?");
382 Cases.push_back(std::make_pair(&COM->getOpcode(), COM->getNext()));
385 MatcherPtr.reset(new SwitchOpcodeMatcher(&Cases[0], Cases.size()));
390 // Reassemble a new Scope node.
391 assert(!NewOptionsToMatch.empty() &&
392 "Where'd all our children go? Did we really factor everything??");
393 if (NewOptionsToMatch.empty())
396 Scope->setNumChildren(NewOptionsToMatch.size());
397 for (unsigned i = 0, e = NewOptionsToMatch.size(); i != e; ++i)
398 Scope->resetChild(i, NewOptionsToMatch[i]);
402 Matcher *llvm::OptimizeMatcher(Matcher *TheMatcher,
403 const CodeGenDAGPatterns &CGP) {
404 OwningPtr<Matcher> MatcherPtr(TheMatcher);
405 ContractNodes(MatcherPtr, CGP);
406 SinkPatternPredicates(MatcherPtr);
407 FactorNodes(MatcherPtr);
408 return MatcherPtr.take();