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());
48 if (CheckTypeMatcher *CT= dyn_cast<CheckTypeMatcher>(MC->getNext()))
49 New = new CheckChildTypeMatcher(MC->getChildNo(), CT->getType());
52 // Insert the new node.
53 New->setNext(MatcherPtr.take());
54 MatcherPtr.reset(New);
55 // Remove the old one.
56 MC->setNext(MC->getNext()->takeNext());
57 return ContractNodes(MatcherPtr, CGP);
61 // Zap movechild -> moveparent.
62 if (MoveChildMatcher *MC = dyn_cast<MoveChildMatcher>(N))
63 if (MoveParentMatcher *MP =
64 dyn_cast<MoveParentMatcher>(MC->getNext())) {
65 MatcherPtr.reset(MP->takeNext());
66 return ContractNodes(MatcherPtr, CGP);
69 // FIXME: Handle OPC_MarkFlagResults.
71 // Turn EmitNode->CompleteMatch into MorphNodeTo if we can.
72 if (EmitNodeMatcher *EN = dyn_cast<EmitNodeMatcher>(N))
73 if (CompleteMatchMatcher *CM =
74 dyn_cast<CompleteMatchMatcher>(EN->getNext())) {
75 // We can only use MorphNodeTo if the result values match up.
76 unsigned RootResultFirst = EN->getFirstResultSlot();
77 bool ResultsMatch = true;
78 for (unsigned i = 0, e = CM->getNumResults(); i != e; ++i)
79 if (CM->getResult(i) != RootResultFirst+i)
82 // If the selected node defines a subset of the flag/chain results, we
83 // can't use MorphNodeTo. For example, we can't use MorphNodeTo if the
84 // matched pattern has a chain but the root node doesn't.
85 const PatternToMatch &Pattern = CM->getPattern();
87 if (!EN->hasChain() &&
88 Pattern.getSrcPattern()->NodeHasProperty(SDNPHasChain, CGP))
91 // If the matched node has a flag and the output root doesn't, we can't
94 // NOTE: Strictly speaking, we don't have to check for the flag here
95 // because the code in the pattern generator doesn't handle it right. We
96 // do it anyway for thoroughness.
97 if (!EN->hasOutFlag() &&
98 Pattern.getSrcPattern()->NodeHasProperty(SDNPOutFlag, CGP))
102 // If the root result node defines more results than the source root node
103 // *and* has a chain or flag input, then we can't match it because it
104 // would end up replacing the extra result with the chain/flag.
106 if ((EN->hasFlag() || EN->hasChain()) &&
107 EN->getNumNonChainFlagVTs() > ... need to get no results reliably ...)
112 const SmallVectorImpl<MVT::SimpleValueType> &VTs = EN->getVTList();
113 const SmallVectorImpl<unsigned> &Operands = EN->getOperandList();
114 MatcherPtr.reset(new MorphNodeToMatcher(EN->getOpcodeName(),
115 VTs.data(), VTs.size(),
116 Operands.data(),Operands.size(),
117 EN->hasChain(), EN->hasInFlag(),
120 EN->getNumFixedArityOperands(),
125 // FIXME2: Kill off all the SelectionDAG::MorphNodeTo and getMachineNode
129 ContractNodes(N->getNextPtr(), CGP);
132 /// SinkPatternPredicates - Pattern predicates can be checked at any level of
133 /// the matching tree. The generator dumps them at the top level of the pattern
134 /// though, which prevents factoring from being able to see past them. This
135 /// optimization sinks them as far down into the pattern as possible.
137 /// Conceptually, we'd like to sink these predicates all the way to the last
138 /// matcher predicate in the series. However, it turns out that some
139 /// ComplexPatterns have side effects on the graph, so we really don't want to
140 /// run a the complex pattern if the pattern predicate will fail. For this
141 /// reason, we refuse to sink the pattern predicate past a ComplexPattern.
143 static void SinkPatternPredicates(OwningPtr<Matcher> &MatcherPtr) {
144 // Recursively scan for a PatternPredicate.
145 // If we reached the end of the chain, we're done.
146 Matcher *N = MatcherPtr.get();
149 // Walk down all members of a scope node.
150 if (ScopeMatcher *Scope = dyn_cast<ScopeMatcher>(N)) {
151 for (unsigned i = 0, e = Scope->getNumChildren(); i != e; ++i) {
152 OwningPtr<Matcher> Child(Scope->takeChild(i));
153 SinkPatternPredicates(Child);
154 Scope->resetChild(i, Child.take());
159 // If this node isn't a CheckPatternPredicateMatcher we keep scanning until
161 CheckPatternPredicateMatcher *CPPM =dyn_cast<CheckPatternPredicateMatcher>(N);
163 return SinkPatternPredicates(N->getNextPtr());
165 // Ok, we found one, lets try to sink it. Check if we can sink it past the
166 // next node in the chain. If not, we won't be able to change anything and
167 // might as well bail.
168 if (!CPPM->getNext()->isSafeToReorderWithPatternPredicate())
171 // Okay, we know we can sink it past at least one node. Unlink it from the
172 // chain and scan for the new insertion point.
173 MatcherPtr.take(); // Don't delete CPPM.
174 MatcherPtr.reset(CPPM->takeNext());
176 N = MatcherPtr.get();
177 while (N->getNext()->isSafeToReorderWithPatternPredicate())
180 // At this point, we want to insert CPPM after N.
181 CPPM->setNext(N->takeNext());
185 /// FactorNodes - Turn matches like this:
187 /// OPC_CheckType i32
189 /// OPC_CheckType i32
192 /// OPC_CheckType i32
197 static void FactorNodes(OwningPtr<Matcher> &MatcherPtr) {
198 // If we reached the end of the chain, we're done.
199 Matcher *N = MatcherPtr.get();
202 // If this is not a push node, just scan for one.
203 ScopeMatcher *Scope = dyn_cast<ScopeMatcher>(N);
205 return FactorNodes(N->getNextPtr());
207 // Okay, pull together the children of the scope node into a vector so we can
208 // inspect it more easily. While we're at it, bucket them up by the hash
209 // code of their first predicate.
210 SmallVector<Matcher*, 32> OptionsToMatch;
212 for (unsigned i = 0, e = Scope->getNumChildren(); i != e; ++i) {
213 // Factor the subexpression.
214 OwningPtr<Matcher> Child(Scope->takeChild(i));
217 if (Matcher *N = Child.take())
218 OptionsToMatch.push_back(N);
221 SmallVector<Matcher*, 32> NewOptionsToMatch;
223 // Loop over options to match, merging neighboring patterns with identical
224 // starting nodes into a shared matcher.
225 for (unsigned OptionIdx = 0, e = OptionsToMatch.size(); OptionIdx != e;) {
226 // Find the set of matchers that start with this node.
227 Matcher *Optn = OptionsToMatch[OptionIdx++];
229 if (OptionIdx == e) {
230 NewOptionsToMatch.push_back(Optn);
234 // See if the next option starts with the same matcher. If the two
235 // neighbors *do* start with the same matcher, we can factor the matcher out
236 // of at least these two patterns. See what the maximal set we can merge
238 SmallVector<Matcher*, 8> EqualMatchers;
239 EqualMatchers.push_back(Optn);
241 // Factor all of the known-equal matchers after this one into the same
243 while (OptionIdx != e && OptionsToMatch[OptionIdx]->isEqual(Optn))
244 EqualMatchers.push_back(OptionsToMatch[OptionIdx++]);
246 // If we found a non-equal matcher, see if it is contradictory with the
247 // current node. If so, we know that the ordering relation between the
248 // current sets of nodes and this node don't matter. Look past it to see if
249 // we can merge anything else into this matching group.
250 unsigned Scan = OptionIdx;
252 while (Scan != e && Optn->isContradictory(OptionsToMatch[Scan]))
255 // Ok, we found something that isn't known to be contradictory. If it is
256 // equal, we can merge it into the set of nodes to factor, if not, we have
257 // to cease factoring.
258 if (Scan == e || !Optn->isEqual(OptionsToMatch[Scan])) break;
260 // If is equal after all, add the option to EqualMatchers and remove it
261 // from OptionsToMatch.
262 EqualMatchers.push_back(OptionsToMatch[Scan]);
263 OptionsToMatch.erase(OptionsToMatch.begin()+Scan);
268 // Don't print it's obvious nothing extra could be merged anyway.
270 DEBUG(errs() << "Couldn't merge this:\n";
271 Optn->print(errs(), 4);
272 errs() << "into this:\n";
273 OptionsToMatch[Scan]->print(errs(), 4);
275 OptionsToMatch[Scan+1]->printOne(errs());
277 OptionsToMatch[Scan+2]->printOne(errs());
281 // If we only found one option starting with this matcher, no factoring is
283 if (EqualMatchers.size() == 1) {
284 NewOptionsToMatch.push_back(EqualMatchers[0]);
288 // Factor these checks by pulling the first node off each entry and
289 // discarding it. Take the first one off the first entry to reuse.
290 Matcher *Shared = Optn;
291 Optn = Optn->takeNext();
292 EqualMatchers[0] = Optn;
294 // Remove and delete the first node from the other matchers we're factoring.
295 for (unsigned i = 1, e = EqualMatchers.size(); i != e; ++i) {
296 Matcher *Tmp = EqualMatchers[i]->takeNext();
297 delete EqualMatchers[i];
298 EqualMatchers[i] = Tmp;
301 Shared->setNext(new ScopeMatcher(&EqualMatchers[0], EqualMatchers.size()));
303 // Recursively factor the newly created node.
304 FactorNodes(Shared->getNextPtr());
306 NewOptionsToMatch.push_back(Shared);
309 // Reassemble a new Scope node.
310 assert(!NewOptionsToMatch.empty() && "where'd all our children go?");
311 if (NewOptionsToMatch.empty())
313 if (NewOptionsToMatch.size() == 1)
314 MatcherPtr.reset(NewOptionsToMatch[0]);
316 Scope->setNumChildren(NewOptionsToMatch.size());
317 for (unsigned i = 0, e = NewOptionsToMatch.size(); i != e; ++i)
318 Scope->resetChild(i, NewOptionsToMatch[i]);
322 Matcher *llvm::OptimizeMatcher(Matcher *TheMatcher,
323 const CodeGenDAGPatterns &CGP) {
324 OwningPtr<Matcher> MatcherPtr(TheMatcher);
325 ContractNodes(MatcherPtr, CGP);
326 SinkPatternPredicates(MatcherPtr);
327 FactorNodes(MatcherPtr);
328 return MatcherPtr.take();