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/Support/Debug.h"
19 #include "llvm/Support/raw_ostream.h"
23 /// ContractNodes - Turn multiple matcher node patterns like 'MoveChild+Record'
24 /// into single compound nodes like RecordChild.
25 static void ContractNodes(OwningPtr<Matcher> &MatcherPtr,
26 const CodeGenDAGPatterns &CGP) {
27 // If we reached the end of the chain, we're done.
28 Matcher *N = MatcherPtr.get();
31 // If we have a scope node, walk down all of the children.
32 if (ScopeMatcher *Scope = dyn_cast<ScopeMatcher>(N)) {
33 for (unsigned i = 0, e = Scope->getNumChildren(); i != e; ++i) {
34 OwningPtr<Matcher> Child(Scope->takeChild(i));
35 ContractNodes(Child, CGP);
36 Scope->resetChild(i, Child.take());
41 // If we found a movechild node with a node that comes in a 'foochild' form,
43 if (MoveChildMatcher *MC = dyn_cast<MoveChildMatcher>(N)) {
45 if (RecordMatcher *RM = dyn_cast<RecordMatcher>(MC->getNext()))
46 New = new RecordChildMatcher(MC->getChildNo(), RM->getWhatFor(),
49 if (CheckTypeMatcher *CT= dyn_cast<CheckTypeMatcher>(MC->getNext()))
50 New = new CheckChildTypeMatcher(MC->getChildNo(), CT->getType());
53 // Insert the new node.
54 New->setNext(MatcherPtr.take());
55 MatcherPtr.reset(New);
56 // Remove the old one.
57 MC->setNext(MC->getNext()->takeNext());
58 return ContractNodes(MatcherPtr, CGP);
62 // Zap movechild -> moveparent.
63 if (MoveChildMatcher *MC = dyn_cast<MoveChildMatcher>(N))
64 if (MoveParentMatcher *MP =
65 dyn_cast<MoveParentMatcher>(MC->getNext())) {
66 MatcherPtr.reset(MP->takeNext());
67 return ContractNodes(MatcherPtr, CGP);
70 // Turn EmitNode->MarkFlagResults->CompleteMatch into
71 // MarkFlagResults->EmitNode->CompleteMatch when we can to encourage
72 // MorphNodeTo formation. This is safe because MarkFlagResults never refers
73 // to the root of the pattern.
74 if (isa<EmitNodeMatcher>(N) && isa<MarkFlagResultsMatcher>(N->getNext()) &&
75 isa<CompleteMatchMatcher>(N->getNext()->getNext())) {
76 // Unlink the two nodes from the list.
77 Matcher *EmitNode = MatcherPtr.take();
78 Matcher *MFR = EmitNode->takeNext();
79 Matcher *Tail = MFR->takeNext();
82 MatcherPtr.reset(MFR);
83 MFR->setNext(EmitNode);
84 EmitNode->setNext(Tail);
85 return ContractNodes(MatcherPtr, CGP);
88 // Turn EmitNode->CompleteMatch into MorphNodeTo if we can.
89 if (EmitNodeMatcher *EN = dyn_cast<EmitNodeMatcher>(N))
90 if (CompleteMatchMatcher *CM =
91 dyn_cast<CompleteMatchMatcher>(EN->getNext())) {
92 // We can only use MorphNodeTo if the result values match up.
93 unsigned RootResultFirst = EN->getFirstResultSlot();
94 bool ResultsMatch = true;
95 for (unsigned i = 0, e = CM->getNumResults(); i != e; ++i)
96 if (CM->getResult(i) != RootResultFirst+i)
99 // If the selected node defines a subset of the flag/chain results, we
100 // can't use MorphNodeTo. For example, we can't use MorphNodeTo if the
101 // matched pattern has a chain but the root node doesn't.
102 const PatternToMatch &Pattern = CM->getPattern();
104 if (!EN->hasChain() &&
105 Pattern.getSrcPattern()->NodeHasProperty(SDNPHasChain, CGP))
106 ResultsMatch = false;
108 // If the matched node has a flag and the output root doesn't, we can't
111 // NOTE: Strictly speaking, we don't have to check for the flag here
112 // because the code in the pattern generator doesn't handle it right. We
113 // do it anyway for thoroughness.
114 if (!EN->hasOutFlag() &&
115 Pattern.getSrcPattern()->NodeHasProperty(SDNPOutFlag, CGP))
116 ResultsMatch = false;
119 // If the root result node defines more results than the source root node
120 // *and* has a chain or flag input, then we can't match it because it
121 // would end up replacing the extra result with the chain/flag.
123 if ((EN->hasFlag() || EN->hasChain()) &&
124 EN->getNumNonChainFlagVTs() > ... need to get no results reliably ...)
129 const SmallVectorImpl<MVT::SimpleValueType> &VTs = EN->getVTList();
130 const SmallVectorImpl<unsigned> &Operands = EN->getOperandList();
131 MatcherPtr.reset(new MorphNodeToMatcher(EN->getOpcodeName(),
132 VTs.data(), VTs.size(),
133 Operands.data(),Operands.size(),
134 EN->hasChain(), EN->hasInFlag(),
137 EN->getNumFixedArityOperands(),
142 // FIXME2: Kill off all the SelectionDAG::MorphNodeTo and getMachineNode
146 ContractNodes(N->getNextPtr(), CGP);
149 // If we have a CheckType/CheckChildType/Record node followed by a
150 // CheckOpcode, invert the two nodes. We prefer to do structural checks
151 // before type checks, as this opens opportunities for factoring on targets
152 // like X86 where many operations are valid on multiple types.
153 if ((isa<CheckTypeMatcher>(N) || isa<CheckChildTypeMatcher>(N) ||
154 isa<RecordMatcher>(N)) &&
155 isa<CheckOpcodeMatcher>(N->getNext())) {
156 // Unlink the two nodes from the list.
157 Matcher *CheckType = MatcherPtr.take();
158 Matcher *CheckOpcode = CheckType->takeNext();
159 Matcher *Tail = CheckOpcode->takeNext();
162 MatcherPtr.reset(CheckOpcode);
163 CheckOpcode->setNext(CheckType);
164 CheckType->setNext(Tail);
165 return ContractNodes(MatcherPtr, CGP);
169 /// SinkPatternPredicates - Pattern predicates can be checked at any level of
170 /// the matching tree. The generator dumps them at the top level of the pattern
171 /// though, which prevents factoring from being able to see past them. This
172 /// optimization sinks them as far down into the pattern as possible.
174 /// Conceptually, we'd like to sink these predicates all the way to the last
175 /// matcher predicate in the series. However, it turns out that some
176 /// ComplexPatterns have side effects on the graph, so we really don't want to
177 /// run a the complex pattern if the pattern predicate will fail. For this
178 /// reason, we refuse to sink the pattern predicate past a ComplexPattern.
180 static void SinkPatternPredicates(OwningPtr<Matcher> &MatcherPtr) {
181 // Recursively scan for a PatternPredicate.
182 // If we reached the end of the chain, we're done.
183 Matcher *N = MatcherPtr.get();
186 // Walk down all members of a scope node.
187 if (ScopeMatcher *Scope = dyn_cast<ScopeMatcher>(N)) {
188 for (unsigned i = 0, e = Scope->getNumChildren(); i != e; ++i) {
189 OwningPtr<Matcher> Child(Scope->takeChild(i));
190 SinkPatternPredicates(Child);
191 Scope->resetChild(i, Child.take());
196 // If this node isn't a CheckPatternPredicateMatcher we keep scanning until
198 CheckPatternPredicateMatcher *CPPM =dyn_cast<CheckPatternPredicateMatcher>(N);
200 return SinkPatternPredicates(N->getNextPtr());
202 // Ok, we found one, lets try to sink it. Check if we can sink it past the
203 // next node in the chain. If not, we won't be able to change anything and
204 // might as well bail.
205 if (!CPPM->getNext()->isSafeToReorderWithPatternPredicate())
208 // Okay, we know we can sink it past at least one node. Unlink it from the
209 // chain and scan for the new insertion point.
210 MatcherPtr.take(); // Don't delete CPPM.
211 MatcherPtr.reset(CPPM->takeNext());
213 N = MatcherPtr.get();
214 while (N->getNext()->isSafeToReorderWithPatternPredicate())
217 // At this point, we want to insert CPPM after N.
218 CPPM->setNext(N->takeNext());
222 /// FactorNodes - Turn matches like this:
224 /// OPC_CheckType i32
226 /// OPC_CheckType i32
229 /// OPC_CheckType i32
234 static void FactorNodes(OwningPtr<Matcher> &MatcherPtr) {
235 // If we reached the end of the chain, we're done.
236 Matcher *N = MatcherPtr.get();
239 // If this is not a push node, just scan for one.
240 ScopeMatcher *Scope = dyn_cast<ScopeMatcher>(N);
242 return FactorNodes(N->getNextPtr());
244 // Okay, pull together the children of the scope node into a vector so we can
245 // inspect it more easily. While we're at it, bucket them up by the hash
246 // code of their first predicate.
247 SmallVector<Matcher*, 32> OptionsToMatch;
249 for (unsigned i = 0, e = Scope->getNumChildren(); i != e; ++i) {
250 // Factor the subexpression.
251 OwningPtr<Matcher> Child(Scope->takeChild(i));
254 if (Matcher *N = Child.take())
255 OptionsToMatch.push_back(N);
258 SmallVector<Matcher*, 32> NewOptionsToMatch;
260 // Loop over options to match, merging neighboring patterns with identical
261 // starting nodes into a shared matcher.
262 for (unsigned OptionIdx = 0, e = OptionsToMatch.size(); OptionIdx != e;) {
263 // Find the set of matchers that start with this node.
264 Matcher *Optn = OptionsToMatch[OptionIdx++];
266 if (OptionIdx == e) {
267 NewOptionsToMatch.push_back(Optn);
271 // See if the next option starts with the same matcher. If the two
272 // neighbors *do* start with the same matcher, we can factor the matcher out
273 // of at least these two patterns. See what the maximal set we can merge
275 SmallVector<Matcher*, 8> EqualMatchers;
276 EqualMatchers.push_back(Optn);
278 // Factor all of the known-equal matchers after this one into the same
280 while (OptionIdx != e && OptionsToMatch[OptionIdx]->isEqual(Optn))
281 EqualMatchers.push_back(OptionsToMatch[OptionIdx++]);
283 // If we found a non-equal matcher, see if it is contradictory with the
284 // current node. If so, we know that the ordering relation between the
285 // current sets of nodes and this node don't matter. Look past it to see if
286 // we can merge anything else into this matching group.
287 unsigned Scan = OptionIdx;
289 while (Scan != e && Optn->isContradictory(OptionsToMatch[Scan]))
292 // Ok, we found something that isn't known to be contradictory. If it is
293 // equal, we can merge it into the set of nodes to factor, if not, we have
294 // to cease factoring.
295 if (Scan == e || !Optn->isEqual(OptionsToMatch[Scan])) break;
297 // If is equal after all, add the option to EqualMatchers and remove it
298 // from OptionsToMatch.
299 EqualMatchers.push_back(OptionsToMatch[Scan]);
300 OptionsToMatch.erase(OptionsToMatch.begin()+Scan);
305 // Don't print it's obvious nothing extra could be merged anyway.
307 DEBUG(errs() << "Couldn't merge this:\n";
308 Optn->print(errs(), 4);
309 errs() << "into this:\n";
310 OptionsToMatch[Scan]->print(errs(), 4);
312 OptionsToMatch[Scan+1]->printOne(errs());
314 OptionsToMatch[Scan+2]->printOne(errs());
318 // If we only found one option starting with this matcher, no factoring is
320 if (EqualMatchers.size() == 1) {
321 NewOptionsToMatch.push_back(EqualMatchers[0]);
325 // Factor these checks by pulling the first node off each entry and
326 // discarding it. Take the first one off the first entry to reuse.
327 Matcher *Shared = Optn;
328 Optn = Optn->takeNext();
329 EqualMatchers[0] = Optn;
331 // Remove and delete the first node from the other matchers we're factoring.
332 for (unsigned i = 1, e = EqualMatchers.size(); i != e; ++i) {
333 Matcher *Tmp = EqualMatchers[i]->takeNext();
334 delete EqualMatchers[i];
335 EqualMatchers[i] = Tmp;
338 Shared->setNext(new ScopeMatcher(&EqualMatchers[0], EqualMatchers.size()));
340 // Recursively factor the newly created node.
341 FactorNodes(Shared->getNextPtr());
343 NewOptionsToMatch.push_back(Shared);
346 // Reassemble a new Scope node.
347 assert(!NewOptionsToMatch.empty() && "where'd all our children go?");
348 if (NewOptionsToMatch.empty())
350 if (NewOptionsToMatch.size() == 1)
351 MatcherPtr.reset(NewOptionsToMatch[0]);
353 Scope->setNumChildren(NewOptionsToMatch.size());
354 for (unsigned i = 0, e = NewOptionsToMatch.size(); i != e; ++i)
355 Scope->resetChild(i, NewOptionsToMatch[i]);
359 Matcher *llvm::OptimizeMatcher(Matcher *TheMatcher,
360 const CodeGenDAGPatterns &CGP) {
361 OwningPtr<Matcher> MatcherPtr(TheMatcher);
362 ContractNodes(MatcherPtr, CGP);
363 SinkPatternPredicates(MatcherPtr);
364 FactorNodes(MatcherPtr);
365 return MatcherPtr.take();