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 // FIXME: Handle OPC_MarkFlagResults.
72 // Turn EmitNode->CompleteMatch into MorphNodeTo if we can.
73 if (EmitNodeMatcher *EN = dyn_cast<EmitNodeMatcher>(N))
74 if (CompleteMatchMatcher *CM =
75 dyn_cast<CompleteMatchMatcher>(EN->getNext())) {
76 // We can only use MorphNodeTo if the result values match up.
77 unsigned RootResultFirst = EN->getFirstResultSlot();
78 bool ResultsMatch = true;
79 for (unsigned i = 0, e = CM->getNumResults(); i != e; ++i)
80 if (CM->getResult(i) != RootResultFirst+i)
83 // If the selected node defines a subset of the flag/chain results, we
84 // can't use MorphNodeTo. For example, we can't use MorphNodeTo if the
85 // matched pattern has a chain but the root node doesn't.
86 const PatternToMatch &Pattern = CM->getPattern();
88 if (!EN->hasChain() &&
89 Pattern.getSrcPattern()->NodeHasProperty(SDNPHasChain, CGP))
92 // If the matched node has a flag and the output root doesn't, we can't
95 // NOTE: Strictly speaking, we don't have to check for the flag here
96 // because the code in the pattern generator doesn't handle it right. We
97 // do it anyway for thoroughness.
98 if (!EN->hasOutFlag() &&
99 Pattern.getSrcPattern()->NodeHasProperty(SDNPOutFlag, CGP))
100 ResultsMatch = false;
103 // If the root result node defines more results than the source root node
104 // *and* has a chain or flag input, then we can't match it because it
105 // would end up replacing the extra result with the chain/flag.
107 if ((EN->hasFlag() || EN->hasChain()) &&
108 EN->getNumNonChainFlagVTs() > ... need to get no results reliably ...)
113 const SmallVectorImpl<MVT::SimpleValueType> &VTs = EN->getVTList();
114 const SmallVectorImpl<unsigned> &Operands = EN->getOperandList();
115 MatcherPtr.reset(new MorphNodeToMatcher(EN->getOpcodeName(),
116 VTs.data(), VTs.size(),
117 Operands.data(),Operands.size(),
118 EN->hasChain(), EN->hasInFlag(),
121 EN->getNumFixedArityOperands(),
126 // FIXME2: Kill off all the SelectionDAG::MorphNodeTo and getMachineNode
130 ContractNodes(N->getNextPtr(), CGP);
133 // If we have a CheckType/CheckChildType/Record node followed by a
134 // CheckOpcode, invert the two nodes. We prefer to do structural checks
135 // before type checks, as this opens opportunities for factoring on targets
136 // like X86 where many operations are valid on multiple types.
137 if ((isa<CheckTypeMatcher>(N) || isa<CheckChildTypeMatcher>(N) ||
138 isa<RecordMatcher>(N)) &&
139 isa<CheckOpcodeMatcher>(N->getNext())) {
140 // Unlink the two nodes from the list.
141 Matcher *CheckType = MatcherPtr.take();
142 Matcher *CheckOpcode = CheckType->takeNext();
143 Matcher *Tail = CheckOpcode->takeNext();
146 MatcherPtr.reset(CheckOpcode);
147 CheckOpcode->setNext(CheckType);
148 CheckType->setNext(Tail);
149 return ContractNodes(MatcherPtr, CGP);
153 /// SinkPatternPredicates - Pattern predicates can be checked at any level of
154 /// the matching tree. The generator dumps them at the top level of the pattern
155 /// though, which prevents factoring from being able to see past them. This
156 /// optimization sinks them as far down into the pattern as possible.
158 /// Conceptually, we'd like to sink these predicates all the way to the last
159 /// matcher predicate in the series. However, it turns out that some
160 /// ComplexPatterns have side effects on the graph, so we really don't want to
161 /// run a the complex pattern if the pattern predicate will fail. For this
162 /// reason, we refuse to sink the pattern predicate past a ComplexPattern.
164 static void SinkPatternPredicates(OwningPtr<Matcher> &MatcherPtr) {
165 // Recursively scan for a PatternPredicate.
166 // If we reached the end of the chain, we're done.
167 Matcher *N = MatcherPtr.get();
170 // Walk down all members of a scope node.
171 if (ScopeMatcher *Scope = dyn_cast<ScopeMatcher>(N)) {
172 for (unsigned i = 0, e = Scope->getNumChildren(); i != e; ++i) {
173 OwningPtr<Matcher> Child(Scope->takeChild(i));
174 SinkPatternPredicates(Child);
175 Scope->resetChild(i, Child.take());
180 // If this node isn't a CheckPatternPredicateMatcher we keep scanning until
182 CheckPatternPredicateMatcher *CPPM =dyn_cast<CheckPatternPredicateMatcher>(N);
184 return SinkPatternPredicates(N->getNextPtr());
186 // Ok, we found one, lets try to sink it. Check if we can sink it past the
187 // next node in the chain. If not, we won't be able to change anything and
188 // might as well bail.
189 if (!CPPM->getNext()->isSafeToReorderWithPatternPredicate())
192 // Okay, we know we can sink it past at least one node. Unlink it from the
193 // chain and scan for the new insertion point.
194 MatcherPtr.take(); // Don't delete CPPM.
195 MatcherPtr.reset(CPPM->takeNext());
197 N = MatcherPtr.get();
198 while (N->getNext()->isSafeToReorderWithPatternPredicate())
201 // At this point, we want to insert CPPM after N.
202 CPPM->setNext(N->takeNext());
206 /// FactorNodes - Turn matches like this:
208 /// OPC_CheckType i32
210 /// OPC_CheckType i32
213 /// OPC_CheckType i32
218 static void FactorNodes(OwningPtr<Matcher> &MatcherPtr) {
219 // If we reached the end of the chain, we're done.
220 Matcher *N = MatcherPtr.get();
223 // If this is not a push node, just scan for one.
224 ScopeMatcher *Scope = dyn_cast<ScopeMatcher>(N);
226 return FactorNodes(N->getNextPtr());
228 // Okay, pull together the children of the scope node into a vector so we can
229 // inspect it more easily. While we're at it, bucket them up by the hash
230 // code of their first predicate.
231 SmallVector<Matcher*, 32> OptionsToMatch;
233 for (unsigned i = 0, e = Scope->getNumChildren(); i != e; ++i) {
234 // Factor the subexpression.
235 OwningPtr<Matcher> Child(Scope->takeChild(i));
238 if (Matcher *N = Child.take())
239 OptionsToMatch.push_back(N);
242 SmallVector<Matcher*, 32> NewOptionsToMatch;
244 // Loop over options to match, merging neighboring patterns with identical
245 // starting nodes into a shared matcher.
246 for (unsigned OptionIdx = 0, e = OptionsToMatch.size(); OptionIdx != e;) {
247 // Find the set of matchers that start with this node.
248 Matcher *Optn = OptionsToMatch[OptionIdx++];
250 if (OptionIdx == e) {
251 NewOptionsToMatch.push_back(Optn);
255 // See if the next option starts with the same matcher. If the two
256 // neighbors *do* start with the same matcher, we can factor the matcher out
257 // of at least these two patterns. See what the maximal set we can merge
259 SmallVector<Matcher*, 8> EqualMatchers;
260 EqualMatchers.push_back(Optn);
262 // Factor all of the known-equal matchers after this one into the same
264 while (OptionIdx != e && OptionsToMatch[OptionIdx]->isEqual(Optn))
265 EqualMatchers.push_back(OptionsToMatch[OptionIdx++]);
267 // If we found a non-equal matcher, see if it is contradictory with the
268 // current node. If so, we know that the ordering relation between the
269 // current sets of nodes and this node don't matter. Look past it to see if
270 // we can merge anything else into this matching group.
271 unsigned Scan = OptionIdx;
273 while (Scan != e && Optn->isContradictory(OptionsToMatch[Scan]))
276 // Ok, we found something that isn't known to be contradictory. If it is
277 // equal, we can merge it into the set of nodes to factor, if not, we have
278 // to cease factoring.
279 if (Scan == e || !Optn->isEqual(OptionsToMatch[Scan])) break;
281 // If is equal after all, add the option to EqualMatchers and remove it
282 // from OptionsToMatch.
283 EqualMatchers.push_back(OptionsToMatch[Scan]);
284 OptionsToMatch.erase(OptionsToMatch.begin()+Scan);
289 // Don't print it's obvious nothing extra could be merged anyway.
291 DEBUG(errs() << "Couldn't merge this:\n";
292 Optn->print(errs(), 4);
293 errs() << "into this:\n";
294 OptionsToMatch[Scan]->print(errs(), 4);
296 OptionsToMatch[Scan+1]->printOne(errs());
298 OptionsToMatch[Scan+2]->printOne(errs());
302 // If we only found one option starting with this matcher, no factoring is
304 if (EqualMatchers.size() == 1) {
305 NewOptionsToMatch.push_back(EqualMatchers[0]);
309 // Factor these checks by pulling the first node off each entry and
310 // discarding it. Take the first one off the first entry to reuse.
311 Matcher *Shared = Optn;
312 Optn = Optn->takeNext();
313 EqualMatchers[0] = Optn;
315 // Remove and delete the first node from the other matchers we're factoring.
316 for (unsigned i = 1, e = EqualMatchers.size(); i != e; ++i) {
317 Matcher *Tmp = EqualMatchers[i]->takeNext();
318 delete EqualMatchers[i];
319 EqualMatchers[i] = Tmp;
322 Shared->setNext(new ScopeMatcher(&EqualMatchers[0], EqualMatchers.size()));
324 // Recursively factor the newly created node.
325 FactorNodes(Shared->getNextPtr());
327 NewOptionsToMatch.push_back(Shared);
330 // Reassemble a new Scope node.
331 assert(!NewOptionsToMatch.empty() && "where'd all our children go?");
332 if (NewOptionsToMatch.empty())
334 if (NewOptionsToMatch.size() == 1)
335 MatcherPtr.reset(NewOptionsToMatch[0]);
337 Scope->setNumChildren(NewOptionsToMatch.size());
338 for (unsigned i = 0, e = NewOptionsToMatch.size(); i != e; ++i)
339 Scope->resetChild(i, NewOptionsToMatch[i]);
343 Matcher *llvm::OptimizeMatcher(Matcher *TheMatcher,
344 const CodeGenDAGPatterns &CGP) {
345 OwningPtr<Matcher> MatcherPtr(TheMatcher);
346 ContractNodes(MatcherPtr, CGP);
347 SinkPatternPredicates(MatcherPtr);
348 FactorNodes(MatcherPtr);
349 return MatcherPtr.take();