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 #include "DAGISelMatcher.h"
15 #include "llvm/ADT/DenseMap.h"
19 static void ContractNodes(OwningPtr<Matcher> &MatcherPtr) {
20 // If we reached the end of the chain, we're done.
21 Matcher *N = MatcherPtr.get();
24 // If we have a scope node, walk down both edges.
25 if (ScopeMatcher *Push = dyn_cast<ScopeMatcher>(N))
26 ContractNodes(Push->getCheckPtr());
28 // If we found a movechild node with a node that comes in a 'foochild' form,
30 if (MoveChildMatcher *MC = dyn_cast<MoveChildMatcher>(N)) {
32 if (RecordMatcher *RM = dyn_cast<RecordMatcher>(MC->getNext()))
33 New = new RecordChildMatcher(MC->getChildNo(), RM->getWhatFor());
35 if (CheckTypeMatcher *CT= dyn_cast<CheckTypeMatcher>(MC->getNext()))
36 New = new CheckChildTypeMatcher(MC->getChildNo(), CT->getType());
39 // Insert the new node.
40 New->setNext(MatcherPtr.take());
41 MatcherPtr.reset(New);
42 // Remove the old one.
43 MC->setNext(MC->getNext()->takeNext());
44 return ContractNodes(MatcherPtr);
48 if (MoveChildMatcher *MC = dyn_cast<MoveChildMatcher>(N))
49 if (MoveParentMatcher *MP =
50 dyn_cast<MoveParentMatcher>(MC->getNext())) {
51 MatcherPtr.reset(MP->takeNext());
52 return ContractNodes(MatcherPtr);
55 ContractNodes(N->getNextPtr());
58 static void FactorNodes(OwningPtr<Matcher> &MatcherPtr) {
59 // If we reached the end of the chain, we're done.
60 Matcher *N = MatcherPtr.get();
63 // If this is not a push node, just scan for one.
64 if (!isa<ScopeMatcher>(N))
65 return FactorNodes(N->getNextPtr());
67 // Okay, pull together the series of linear push nodes into a vector so we can
68 // inspect it more easily. While we're at it, bucket them up by the hash
69 // code of their first predicate.
70 SmallVector<Matcher*, 32> OptionsToMatch;
71 typedef DenseMap<unsigned, std::vector<Matcher*> > HashTableTy;
72 HashTableTy MatchersByHash;
75 for (; ScopeMatcher *PMN = dyn_cast<ScopeMatcher>(CurNode);
76 CurNode = PMN->getNext()) {
77 // Factor the subexpression.
78 FactorNodes(PMN->getCheckPtr());
79 if (Matcher *Check = PMN->getCheck()) {
80 OptionsToMatch.push_back(Check);
81 MatchersByHash[Check->getHash()].push_back(Check);
86 OptionsToMatch.push_back(CurNode);
87 MatchersByHash[CurNode->getHash()].push_back(CurNode);
91 SmallVector<Matcher*, 32> NewOptionsToMatch;
93 // Now that we have bucketed up things by hash code, iterate over sets of
94 // matchers that all start with the same node. We would like to iterate over
95 // the hash table, but it isn't in deterministic order, emulate this by going
96 // about this slightly backwards. After each set of nodes is processed, we
97 // remove them from MatchersByHash.
98 for (unsigned i = 0, e = OptionsToMatch.size();
99 i != e && !MatchersByHash.empty(); ++i) {
100 // Find the set of matchers that start with this node.
101 Matcher *Optn = OptionsToMatch[i];
103 // Find all nodes that hash to the same value. If there is no entry in the
104 // hash table, then we must have previously processed a node equal to this
106 HashTableTy::iterator DMI = MatchersByHash.find(Optn->getHash());
107 if (DMI == MatchersByHash.end()) continue;
109 std::vector<Matcher*> &HashMembers = DMI->second;
110 assert(!HashMembers.empty() && "Should be removed if empty");
112 // Check to see if this node is in HashMembers, if not it was equal to a
113 // previous node and removed.
114 std::vector<Matcher*>::iterator MemberSlot =
115 std::find(HashMembers.begin(), HashMembers.end(), Optn);
116 if (MemberSlot == HashMembers.end()) continue;
118 // If the node *does* exist in HashMembers, then we've confirmed that it
119 // hasn't been processed as equal to a previous node. Process it now, start
120 // by removing it from the list of hash-equal nodes.
121 HashMembers.erase(MemberSlot);
123 // Scan all of the hash members looking for ones that are equal, removing
124 // them from HashMembers, adding them to EqualMatchers.
125 SmallVector<Matcher*, 8> EqualMatchers;
127 // Scan the vector backwards so we're generally removing from the end to
128 // avoid pointless data copying.
129 for (unsigned i = HashMembers.size(); i != 0; --i) {
130 if (!HashMembers[i-1]->isEqual(Optn)) continue;
132 EqualMatchers.push_back(HashMembers[i-1]);
133 HashMembers.erase(HashMembers.begin()+i-1);
135 EqualMatchers.push_back(Optn);
137 // Reverse the vector so that we preserve the match ordering.
138 std::reverse(EqualMatchers.begin(), EqualMatchers.end());
140 // If HashMembers is empty at this point, then we've gotten all nodes with
141 // the same hash, nuke the entry in the hash table.
142 if (HashMembers.empty())
143 MatchersByHash.erase(Optn->getHash());
145 // Okay, we have the list of all matchers that start with the same node as
146 // Optn. If there is more than one in the set, we want to factor them.
147 if (EqualMatchers.size() == 1) {
148 NewOptionsToMatch.push_back(Optn);
152 // Factor these checks by pulling the first node off each entry and
153 // discarding it, replacing it with...
154 // something amazing??
156 // FIXME: Need to change the Scope model.
159 // Reassemble a new Scope node.
163 Matcher *llvm::OptimizeMatcher(Matcher *TheMatcher) {
164 OwningPtr<Matcher> MatcherPtr(TheMatcher);
165 ContractNodes(MatcherPtr);
166 FactorNodes(MatcherPtr);
167 return MatcherPtr.take();