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 "llvm/ADT/DenseMap.h"
17 #include "llvm/Support/Debug.h"
18 #include "llvm/Support/raw_ostream.h"
22 /// ContractNodes - Turn multiple matcher node patterns like 'MoveChild+Record'
23 /// into single compound nodes like RecordChild.
24 static void ContractNodes(OwningPtr<Matcher> &MatcherPtr) {
25 // If we reached the end of the chain, we're done.
26 Matcher *N = MatcherPtr.get();
29 // If we have a scope node, walk down all of the children.
30 if (ScopeMatcher *Scope = dyn_cast<ScopeMatcher>(N)) {
31 for (unsigned i = 0, e = Scope->getNumChildren(); i != e; ++i) {
32 OwningPtr<Matcher> Child(Scope->takeChild(i));
34 Scope->resetChild(i, Child.take());
39 // If we found a movechild node with a node that comes in a 'foochild' form,
41 if (MoveChildMatcher *MC = dyn_cast<MoveChildMatcher>(N)) {
43 if (RecordMatcher *RM = dyn_cast<RecordMatcher>(MC->getNext()))
44 New = new RecordChildMatcher(MC->getChildNo(), RM->getWhatFor());
46 if (CheckTypeMatcher *CT= dyn_cast<CheckTypeMatcher>(MC->getNext()))
47 New = new CheckChildTypeMatcher(MC->getChildNo(), CT->getType());
50 // Insert the new node.
51 New->setNext(MatcherPtr.take());
52 MatcherPtr.reset(New);
53 // Remove the old one.
54 MC->setNext(MC->getNext()->takeNext());
55 return ContractNodes(MatcherPtr);
59 if (MoveChildMatcher *MC = dyn_cast<MoveChildMatcher>(N))
60 if (MoveParentMatcher *MP =
61 dyn_cast<MoveParentMatcher>(MC->getNext())) {
62 MatcherPtr.reset(MP->takeNext());
63 return ContractNodes(MatcherPtr);
66 ContractNodes(N->getNextPtr());
69 /// SinkPatternPredicates - Pattern predicates can be checked at any level of
70 /// the matching tree. The generator dumps them at the top level of the pattern
71 /// though, which prevents factoring from being able to see past them. This
72 /// optimization sinks them as far down into the pattern as possible.
74 /// Conceptually, we'd like to sink these predicates all the way to the last
75 /// matcher predicate in the series. However, it turns out that some
76 /// ComplexPatterns have side effects on the graph, so we really don't want to
77 /// run a the complex pattern if the pattern predicate will fail. For this
78 /// reason, we refuse to sink the pattern predicate past a ComplexPattern.
80 static void SinkPatternPredicates(OwningPtr<Matcher> &MatcherPtr) {
81 // Recursively scan for a PatternPredicate.
82 // If we reached the end of the chain, we're done.
83 Matcher *N = MatcherPtr.get();
86 // Walk down all members of a scope node.
87 if (ScopeMatcher *Scope = dyn_cast<ScopeMatcher>(N)) {
88 for (unsigned i = 0, e = Scope->getNumChildren(); i != e; ++i) {
89 OwningPtr<Matcher> Child(Scope->takeChild(i));
90 SinkPatternPredicates(Child);
91 Scope->resetChild(i, Child.take());
96 // If this node isn't a CheckPatternPredicateMatcher we keep scanning until
98 CheckPatternPredicateMatcher *CPPM =dyn_cast<CheckPatternPredicateMatcher>(N);
100 return SinkPatternPredicates(N->getNextPtr());
102 // Ok, we found one, lets try to sink it. Check if we can sink it past the
103 // next node in the chain. If not, we won't be able to change anything and
104 // might as well bail.
105 if (!CPPM->getNext()->isSafeToReorderWithPatternPredicate())
108 // Okay, we know we can sink it past at least one node. Unlink it from the
109 // chain and scan for the new insertion point.
110 MatcherPtr.take(); // Don't delete CPPM.
111 MatcherPtr.reset(CPPM->takeNext());
113 N = MatcherPtr.get();
114 while (N->getNext()->isSafeToReorderWithPatternPredicate())
117 // At this point, we want to insert CPPM after N.
118 CPPM->setNext(N->takeNext());
122 /// FactorNodes - Turn matches like this:
124 /// OPC_CheckType i32
126 /// OPC_CheckType i32
129 /// OPC_CheckType i32
134 static void FactorNodes(OwningPtr<Matcher> &MatcherPtr) {
135 // If we reached the end of the chain, we're done.
136 Matcher *N = MatcherPtr.get();
139 // If this is not a push node, just scan for one.
140 ScopeMatcher *Scope = dyn_cast<ScopeMatcher>(N);
142 return FactorNodes(N->getNextPtr());
144 // Okay, pull together the children of the scope node into a vector so we can
145 // inspect it more easily. While we're at it, bucket them up by the hash
146 // code of their first predicate.
147 SmallVector<Matcher*, 32> OptionsToMatch;
149 for (unsigned i = 0, e = Scope->getNumChildren(); i != e; ++i) {
150 // Factor the subexpression.
151 OwningPtr<Matcher> Child(Scope->takeChild(i));
154 if (Matcher *N = Child.take())
155 OptionsToMatch.push_back(N);
158 SmallVector<Matcher*, 32> NewOptionsToMatch;
160 // Loop over options to match, merging neighboring patterns with identical
161 // starting nodes into a shared matcher.
162 for (unsigned OptionIdx = 0, e = OptionsToMatch.size(); OptionIdx != e;) {
163 // Find the set of matchers that start with this node.
164 Matcher *Optn = OptionsToMatch[OptionIdx++];
166 if (OptionIdx == e) {
167 NewOptionsToMatch.push_back(Optn);
171 // See if the next option starts with the same matcher. If the two
172 // neighbors *do* start with the same matcher, we can factor the matcher out
173 // of at least these two patterns. See what the maximal set we can merge
175 SmallVector<Matcher*, 8> EqualMatchers;
176 EqualMatchers.push_back(Optn);
178 // Factor all of the known-equal matchers after this one into the same
180 while (OptionIdx != e && OptionsToMatch[OptionIdx]->isEqual(Optn))
181 EqualMatchers.push_back(OptionsToMatch[OptionIdx++]);
183 // If we found a non-equal matcher, see if it is contradictory with the
184 // current node. If so, we know that the ordering relation between the
185 // current sets of nodes and this node don't matter. Look past it to see if
186 // we can merge anything else into this matching group.
187 unsigned Scan = OptionIdx;
189 while (Scan != e && Optn->isContradictory(OptionsToMatch[Scan]))
192 // Ok, we found something that isn't known to be contradictory. If it is
193 // equal, we can merge it into the set of nodes to factor, if not, we have
194 // to cease factoring.
195 if (Scan == e || !Optn->isEqual(OptionsToMatch[Scan])) break;
197 // If is equal after all, add the option to EqualMatchers and remove it
198 // from OptionsToMatch.
199 EqualMatchers.push_back(OptionsToMatch[Scan]);
200 OptionsToMatch.erase(OptionsToMatch.begin()+Scan);
205 DEBUG(errs() << "Couldn't merge this:\n ";
206 Optn->printOne(errs());
207 errs() << "into this:\n ";
208 OptionsToMatch[OptionIdx]->printOne(errs());
209 if (OptionIdx+1 != e)
210 OptionsToMatch[OptionIdx+1]->printOne(errs());
212 OptionsToMatch[OptionIdx+2]->printOne(errs());
216 // If we only found one option starting with this matcher, no factoring is
218 if (EqualMatchers.size() == 1) {
219 NewOptionsToMatch.push_back(EqualMatchers[0]);
223 // Factor these checks by pulling the first node off each entry and
224 // discarding it. Take the first one off the first entry to reuse.
225 Matcher *Shared = Optn;
226 Optn = Optn->takeNext();
227 EqualMatchers[0] = Optn;
229 // Remove and delete the first node from the other matchers we're factoring.
230 for (unsigned i = 1, e = EqualMatchers.size(); i != e; ++i) {
231 Matcher *Tmp = EqualMatchers[i]->takeNext();
232 delete EqualMatchers[i];
233 EqualMatchers[i] = Tmp;
236 Shared->setNext(new ScopeMatcher(&EqualMatchers[0], EqualMatchers.size()));
238 // Recursively factor the newly created node.
239 FactorNodes(Shared->getNextPtr());
241 NewOptionsToMatch.push_back(Shared);
244 // Reassemble a new Scope node.
245 assert(!NewOptionsToMatch.empty() && "where'd all our children go?");
246 if (NewOptionsToMatch.size() == 1)
247 MatcherPtr.reset(NewOptionsToMatch[0]);
249 Scope->setNumChildren(NewOptionsToMatch.size());
250 for (unsigned i = 0, e = NewOptionsToMatch.size(); i != e; ++i)
251 Scope->resetChild(i, NewOptionsToMatch[i]);
255 Matcher *llvm::OptimizeMatcher(Matcher *TheMatcher) {
256 OwningPtr<Matcher> MatcherPtr(TheMatcher);
257 ContractNodes(MatcherPtr);
258 SinkPatternPredicates(MatcherPtr);
259 FactorNodes(MatcherPtr);
260 return MatcherPtr.take();