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 // Turn EmitNode->CompleteMatch into SelectNodeTo if we can.
70 if (EmitNodeMatcher *EN = dyn_cast<EmitNodeMatcher>(N))
71 if (CompleteMatchMatcher *CM =
72 dyn_cast<CompleteMatchMatcher>(EN->getNext())) {
73 // We can only use SelectNodeTo if the result values match up.
74 unsigned RootResultFirst = EN->getFirstResultSlot();
75 bool ResultsMatch = true;
76 for (unsigned i = 0, e = CM->getNumResults(); i != e; ++i)
77 if (CM->getResult(i) != RootResultFirst+i)
80 // If the selected node defines a subset of the flag/chain results, we
81 // can't use SelectNodeTo. For example, we can't use SelectNodeTo if the
82 // matched pattern has a chain but the root node doesn't.
83 const PatternToMatch &Pattern = CM->getPattern();
85 if (!EN->hasChain() &&
86 Pattern.getSrcPattern()->NodeHasProperty(SDNPHasChain, CGP))
89 // If the matched node has a flag and the output root doesn't, we can't
92 // NOTE: Strictly speaking, we don't have to check for the flag here
93 // because the code in the pattern generator doesn't handle it right. We
94 // do it anyway for thoroughness.
96 Pattern.getSrcPattern()->NodeHasProperty(SDNPOutFlag, CGP))
100 // If the root result node defines more results than the source root node
101 // *and* has a chain or flag input, then we can't match it because it
102 // would end up replacing the extra result with the chain/flag.
104 if ((EN->hasFlag() || EN->hasChain()) &&
105 EN->getNumNonChainFlagVTs() > ... need to get no results reliably ...)
110 const SmallVectorImpl<MVT::SimpleValueType> &VTs = EN->getVTList();
111 const SmallVectorImpl<unsigned> &Operands = EN->getOperandList();
112 MatcherPtr.reset(new SelectNodeToMatcher(EN->getOpcodeName(),
114 Operands.data(), Operands.size(),
115 EN->hasChain(), EN->hasFlag(),
117 EN->getNumFixedArityOperands(),
122 // FIXME: Handle OPC_MarkFlagResults.
124 // FIXME2: Kill off all the SelectionDAG::SelectNodeTo and getMachineNode
125 // variants. Call MorphNodeTo instead of SelectNodeTo.
128 ContractNodes(N->getNextPtr(), CGP);
131 /// SinkPatternPredicates - Pattern predicates can be checked at any level of
132 /// the matching tree. The generator dumps them at the top level of the pattern
133 /// though, which prevents factoring from being able to see past them. This
134 /// optimization sinks them as far down into the pattern as possible.
136 /// Conceptually, we'd like to sink these predicates all the way to the last
137 /// matcher predicate in the series. However, it turns out that some
138 /// ComplexPatterns have side effects on the graph, so we really don't want to
139 /// run a the complex pattern if the pattern predicate will fail. For this
140 /// reason, we refuse to sink the pattern predicate past a ComplexPattern.
142 static void SinkPatternPredicates(OwningPtr<Matcher> &MatcherPtr) {
143 // Recursively scan for a PatternPredicate.
144 // If we reached the end of the chain, we're done.
145 Matcher *N = MatcherPtr.get();
148 // Walk down all members of a scope node.
149 if (ScopeMatcher *Scope = dyn_cast<ScopeMatcher>(N)) {
150 for (unsigned i = 0, e = Scope->getNumChildren(); i != e; ++i) {
151 OwningPtr<Matcher> Child(Scope->takeChild(i));
152 SinkPatternPredicates(Child);
153 Scope->resetChild(i, Child.take());
158 // If this node isn't a CheckPatternPredicateMatcher we keep scanning until
160 CheckPatternPredicateMatcher *CPPM =dyn_cast<CheckPatternPredicateMatcher>(N);
162 return SinkPatternPredicates(N->getNextPtr());
164 // Ok, we found one, lets try to sink it. Check if we can sink it past the
165 // next node in the chain. If not, we won't be able to change anything and
166 // might as well bail.
167 if (!CPPM->getNext()->isSafeToReorderWithPatternPredicate())
170 // Okay, we know we can sink it past at least one node. Unlink it from the
171 // chain and scan for the new insertion point.
172 MatcherPtr.take(); // Don't delete CPPM.
173 MatcherPtr.reset(CPPM->takeNext());
175 N = MatcherPtr.get();
176 while (N->getNext()->isSafeToReorderWithPatternPredicate())
179 // At this point, we want to insert CPPM after N.
180 CPPM->setNext(N->takeNext());
184 /// FactorNodes - Turn matches like this:
186 /// OPC_CheckType i32
188 /// OPC_CheckType i32
191 /// OPC_CheckType i32
196 static void FactorNodes(OwningPtr<Matcher> &MatcherPtr) {
197 // If we reached the end of the chain, we're done.
198 Matcher *N = MatcherPtr.get();
201 // If this is not a push node, just scan for one.
202 ScopeMatcher *Scope = dyn_cast<ScopeMatcher>(N);
204 return FactorNodes(N->getNextPtr());
206 // Okay, pull together the children of the scope node into a vector so we can
207 // inspect it more easily. While we're at it, bucket them up by the hash
208 // code of their first predicate.
209 SmallVector<Matcher*, 32> OptionsToMatch;
211 for (unsigned i = 0, e = Scope->getNumChildren(); i != e; ++i) {
212 // Factor the subexpression.
213 OwningPtr<Matcher> Child(Scope->takeChild(i));
216 if (Matcher *N = Child.take())
217 OptionsToMatch.push_back(N);
220 SmallVector<Matcher*, 32> NewOptionsToMatch;
222 // Loop over options to match, merging neighboring patterns with identical
223 // starting nodes into a shared matcher.
224 for (unsigned OptionIdx = 0, e = OptionsToMatch.size(); OptionIdx != e;) {
225 // Find the set of matchers that start with this node.
226 Matcher *Optn = OptionsToMatch[OptionIdx++];
228 if (OptionIdx == e) {
229 NewOptionsToMatch.push_back(Optn);
233 // See if the next option starts with the same matcher. If the two
234 // neighbors *do* start with the same matcher, we can factor the matcher out
235 // of at least these two patterns. See what the maximal set we can merge
237 SmallVector<Matcher*, 8> EqualMatchers;
238 EqualMatchers.push_back(Optn);
240 // Factor all of the known-equal matchers after this one into the same
242 while (OptionIdx != e && OptionsToMatch[OptionIdx]->isEqual(Optn))
243 EqualMatchers.push_back(OptionsToMatch[OptionIdx++]);
245 // If we found a non-equal matcher, see if it is contradictory with the
246 // current node. If so, we know that the ordering relation between the
247 // current sets of nodes and this node don't matter. Look past it to see if
248 // we can merge anything else into this matching group.
249 unsigned Scan = OptionIdx;
251 while (Scan != e && Optn->isContradictory(OptionsToMatch[Scan]))
254 // Ok, we found something that isn't known to be contradictory. If it is
255 // equal, we can merge it into the set of nodes to factor, if not, we have
256 // to cease factoring.
257 if (Scan == e || !Optn->isEqual(OptionsToMatch[Scan])) break;
259 // If is equal after all, add the option to EqualMatchers and remove it
260 // from OptionsToMatch.
261 EqualMatchers.push_back(OptionsToMatch[Scan]);
262 OptionsToMatch.erase(OptionsToMatch.begin()+Scan);
267 // Don't print it's obvious nothing extra could be merged anyway.
269 DEBUG(errs() << "Couldn't merge this:\n";
270 Optn->print(errs(), 4);
271 errs() << "into this:\n";
272 OptionsToMatch[Scan]->print(errs(), 4);
274 OptionsToMatch[Scan+1]->printOne(errs());
276 OptionsToMatch[Scan+2]->printOne(errs());
280 // If we only found one option starting with this matcher, no factoring is
282 if (EqualMatchers.size() == 1) {
283 NewOptionsToMatch.push_back(EqualMatchers[0]);
287 // Factor these checks by pulling the first node off each entry and
288 // discarding it. Take the first one off the first entry to reuse.
289 Matcher *Shared = Optn;
290 Optn = Optn->takeNext();
291 EqualMatchers[0] = Optn;
293 // Remove and delete the first node from the other matchers we're factoring.
294 for (unsigned i = 1, e = EqualMatchers.size(); i != e; ++i) {
295 Matcher *Tmp = EqualMatchers[i]->takeNext();
296 delete EqualMatchers[i];
297 EqualMatchers[i] = Tmp;
300 Shared->setNext(new ScopeMatcher(&EqualMatchers[0], EqualMatchers.size()));
302 // Recursively factor the newly created node.
303 FactorNodes(Shared->getNextPtr());
305 NewOptionsToMatch.push_back(Shared);
308 // Reassemble a new Scope node.
309 assert(!NewOptionsToMatch.empty() && "where'd all our children go?");
310 if (NewOptionsToMatch.empty())
312 if (NewOptionsToMatch.size() == 1)
313 MatcherPtr.reset(NewOptionsToMatch[0]);
315 Scope->setNumChildren(NewOptionsToMatch.size());
316 for (unsigned i = 0, e = NewOptionsToMatch.size(); i != e; ++i)
317 Scope->resetChild(i, NewOptionsToMatch[i]);
321 Matcher *llvm::OptimizeMatcher(Matcher *TheMatcher,
322 const CodeGenDAGPatterns &CGP) {
323 OwningPtr<Matcher> MatcherPtr(TheMatcher);
324 ContractNodes(MatcherPtr, CGP);
325 SinkPatternPredicates(MatcherPtr);
326 FactorNodes(MatcherPtr);
327 return MatcherPtr.take();