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/*
* Copyright 2013 Google Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
* in compliance with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software distributed under the License
* is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
* or implied. See the License for the specific language governing permissions and limitations under
* the License.
*/
package com.google.gwt.dev.jjs.impl.codesplitter;
import com.google.gwt.core.ext.TreeLogger;
import com.google.gwt.dev.jjs.ast.JDeclaredType;
import com.google.gwt.dev.jjs.ast.JField;
import com.google.gwt.dev.jjs.ast.JMethod;
import com.google.gwt.dev.jjs.ast.JNode;
import com.google.gwt.dev.jjs.ast.JReferenceType;
import com.google.gwt.dev.jjs.ast.JRunAsync;
import com.google.gwt.dev.jjs.impl.ControlFlowAnalyzer;
import com.google.gwt.thirdparty.guava.common.collect.LinkedHashMultiset;
import com.google.gwt.thirdparty.guava.common.collect.Lists;
import com.google.gwt.thirdparty.guava.common.collect.Maps;
import com.google.gwt.thirdparty.guava.common.collect.Multiset;
import java.util.BitSet;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.PriorityQueue;
/**
* Maps an atom to a set of runAsyncs that can be live (NOT necessary exclusively) when that
* runAsync is activated. The runAsyncs are represented by a bit set where S[i] is set if the atom
* needs to be live when runAsync i is live.
*
* In this class "payload size" is the size of the atoms that will be loaded (beyond the set of
* atoms already loaded in the initial sequence) as part of a particular exclusive fragment.
*
* "Subset" refers to an arbitrary combination of runAsync ids.
*/
class LiveAtomsByRunAsyncSets {
LiveAtomsByRunAsyncSets(TreeLogger logger) {
this.logger = logger;
}
private static class SubsetWithSize implements Comparable {
private final int size;
private final BitSet subset;
public SubsetWithSize(BitSet subset, int size) {
this.subset = subset;
this.size = size;
}
@Override
public int compareTo(SubsetWithSize o) {
return Integer.valueOf(o.size).compareTo(Integer.valueOf(size));
}
}
private static final int AVERAGE_METHOD_SIZE = 40;
private static final int AVERAGE_NAME_SIZE = 2;
private static final int FUNCTION_DEFINITION_CONSTANT_SIZE = "function".length() + "()".length();
private static BitSet computeComplement(BitSet bitSet, int count) {
BitSet notMergedSubset = (BitSet) bitSet.clone();
notMergedSubset.flip(0, count);
return notMergedSubset;
}
private static BitSet computeIntersection(BitSet thisSet, BitSet thatSet) {
BitSet intersectionBitSet = (BitSet) thisSet.clone();
intersectionBitSet.and(thatSet);
return intersectionBitSet;
}
private static int getSizeEstimate(JDeclaredType type) {
int defineClassSize = AVERAGE_NAME_SIZE + 50;
int methodsSize = (3 + AVERAGE_NAME_SIZE) * type.getMethods().size();
return defineClassSize + methodsSize;
}
private static int getSizeEstimate(JField field) {
return AVERAGE_NAME_SIZE;
}
private static int getSizeEstimate(JMethod method) {
int methodSize = FUNCTION_DEFINITION_CONSTANT_SIZE + (AVERAGE_NAME_SIZE + /* , */1
+ AVERAGE_METHOD_SIZE) * method.getParams().size();
return methodSize;
}
private static int getSizeEstimate(Object obj) {
if (obj instanceof JField) {
return getSizeEstimate((JField) obj);
} else if (obj instanceof JMethod) {
return getSizeEstimate((JMethod) obj);
} else if (obj instanceof String) {
return getSizeEstimate((String) obj);
} else if (obj instanceof JDeclaredType) {
return getSizeEstimate((JDeclaredType) obj);
}
throw new UnsupportedOperationException(
"estimateSize unsupported for type " + obj.getClass().getName());
}
private static int getSizeEstimate(String string) {
return string.length();
}
private static boolean isSubset(BitSet smallerSet, BitSet biggerSet) {
return computeIntersection(smallerSet, biggerSet).equals(smallerSet);
}
private final Map idForRunAsync = Maps.newHashMap();
private Map liveSubsetForField = Maps.newLinkedHashMap();
private Map liveSubsetForMethod = Maps.newLinkedHashMap();
private Map liveSubsetForString = Maps.newLinkedHashMap();
private Map liveSubsetForType = Maps.newLinkedHashMap();
private int nextRunAsyncId = 0;
private final Multiset payloadSizeBySubset = LinkedHashMultiset.create();
private final Map runAsyncForId = Maps.newHashMap();
private final TreeLogger logger;
private Collection> groupedRunAsyncs;
public int getRunAsyncCount() {
return idForRunAsync.size();
}
/**
* Returns a list of lists of runAsyncs where {@code pairCount} lists are the result of greedily
* accumulating the pairs of runAsyncs that together result in the largest payload, while
* referencing each runAsync only once.
*/
public Collection> mergeSimilarPairs(int pairCount) {
Collection> fragmentRunAsyncLists = Lists.newArrayList();
BitSet mergedSubset = new BitSet();
PriorityQueue subsetsDescending = computeSubsetsDescending();
// Exclude the groupings prespecified by the user.
// TODO(rluble): we could do better and treat a prespecified grouping as one runAsync for
// merging purpose. For now prespecified groupings are excluded from merge by similarity.
// will be treated better in v3.
for (Collection runAsyncGroup : groupedRunAsyncs) {
if (runAsyncGroup.size() <= 1) {
continue;
}
// Premptively add them to the output.
fragmentRunAsyncLists.add(runAsyncGroup);
// And mark them as used.
mergedSubset.or(asBitSet(runAsyncGroup));
}
// While there are still combinations to examine
while (fragmentRunAsyncLists.size() < pairCount && !subsetsDescending.isEmpty()) {
BitSet largestSubset = subsetsDescending.poll().subset;
// If one of the runAsyncs in the current set of runAsyncs has already been used.
if (largestSubset.intersects(mergedSubset)) {
// Then throw this set out.
continue;
}
logger.log(TreeLogger.Type.DEBUG, "Merging " + largestSubset);
fragmentRunAsyncLists.add(asRunAsyncList(largestSubset));
// Remember that the runAsyncs have already been used.
mergedSubset.or(largestSubset);
}
// Get the ones that are not merged
BitSet notMergedSubset = computeComplement(mergedSubset, getRunAsyncCount());
fragmentRunAsyncLists.addAll(CodeSplitters.getListOfLists(asRunAsyncList(notMergedSubset)));
return fragmentRunAsyncLists;
}
/**
* Modifies a provided list of lists of runAsyncs (each of which represents a fragment) by
* combining sets of runAsyncs whose output size is too small.
*/
public Collection> mergeSmallFragments(
Collection> fragmentRunAsyncLists, int minSize) {
List smallFragmentRunAsyncs = Lists.newArrayList();
Iterator> fragmentIterator = fragmentRunAsyncLists.iterator();
while (fragmentIterator.hasNext()) {
Collection fragmentRunAsyncs = fragmentIterator.next();
if (isFragmentTooSmall(fragmentRunAsyncs, minSize)) {
smallFragmentRunAsyncs.addAll(fragmentRunAsyncs);
fragmentIterator.remove();
}
}
if (!smallFragmentRunAsyncs.isEmpty() && !isFragmentTooSmall(smallFragmentRunAsyncs, minSize)) {
// Keep the fragment combining all the small fragments.
fragmentRunAsyncLists.add(smallFragmentRunAsyncs);
logger.log(TreeLogger.Type.DEBUG, "Merging small fragments " + smallFragmentRunAsyncs +
" together ");
} else if (!smallFragmentRunAsyncs.isEmpty()) {
// This fragment was still small so it is not added to fragmentRunAsyncLists and consequently
// its contents will end up in the leftovers.
logger.log(TreeLogger.Type.DEBUG, "Merging small fragments " + smallFragmentRunAsyncs +
" into leftovers ");
}
return fragmentRunAsyncLists;
}
/**
* Iteratively expand the initial sequence CFA with each runAsync, record the resulting live
* atoms and finally compute the payload size for each subset.
*/
public void recordLiveSubsetsAndEstimateTheirSizes(
ControlFlowAnalyzer initialSequenceCfa, Collection> groupedRunAsyncs) {
this.groupedRunAsyncs = groupedRunAsyncs;
for (Collection runAsyncGroup : groupedRunAsyncs) {
for (JRunAsync runAsync : runAsyncGroup) {
ControlFlowAnalyzer withRunAsyncCfa = new ControlFlowAnalyzer(initialSequenceCfa);
withRunAsyncCfa.traverseFromRunAsync(runAsync);
recordLiveSubset(withRunAsyncCfa, runAsync);
}
}
accumulatePayloadSizes();
}
private void accumulatePayloadSizes(Map liveSubsetsByAtom) {
for (Map.Entry entry : liveSubsetsByAtom.entrySet()) {
BitSet liveSubset = entry.getValue();
T atom = entry.getKey();
// TODO(rluble): Underestimates the size of fragments resulting of merging more than 2
// fragments. With the current strategy it can only happen for the set of very small fragments
// and that is OK.
if (liveSubset.cardinality() > 2) {
continue;
}
payloadSizeBySubset.add(liveSubset, getSizeEstimate(atom));
}
}
private void addRunAsync(JRunAsync runAsync) {
int runAsyncId = nextRunAsyncId++;
idForRunAsync.put(runAsync, runAsyncId);
runAsyncForId.put(runAsyncId, runAsync);
}
private BitSet asBitSet(Collection runAsyncs) {
BitSet result = new BitSet();
for (JRunAsync runAsync : runAsyncs) {
result.set(getIdForRunAsync(runAsync));
}
return result;
}
private List asRunAsyncList(BitSet subset) {
int runAsyncId = -1;
List runAsyncs = Lists.newArrayList();
while ((runAsyncId = subset.nextSetBit(runAsyncId + 1)) != -1) {
runAsyncs.add(runAsyncForId.get(runAsyncId));
}
return runAsyncs;
}
private PriorityQueue computeSubsetsDescending() {
PriorityQueue subsetsDescending = new PriorityQueue();
for (BitSet subset : payloadSizeBySubset.elementSet()) {
if (subset.cardinality() != 2) {
continue;
}
subsetsDescending.add(new SubsetWithSize(subset, payloadSizeBySubset.count(subset)));
}
return subsetsDescending;
}
/**
* Accumulate payload sizes.
*/
private void accumulatePayloadSizes() {
accumulatePayloadSizes(liveSubsetForField);
accumulatePayloadSizes(liveSubsetForMethod);
accumulatePayloadSizes(liveSubsetForString);
accumulatePayloadSizes(liveSubsetForType);
}
private int getIdForRunAsync(JRunAsync runAsync) {
return idForRunAsync.get(runAsync);
}
private boolean isFragmentTooSmall(Collection fragmentRunAsyncs, int minSize) {
BitSet fragmentSubset = asBitSet(fragmentRunAsyncs);
int size = 0;
// TODO(rluble): This might be quite inefficient as it compare to all possible (non trivially
// empty) subsets (bounded by the number of atoms). But is only run at most #runAsyncs times to
// determine whether to merge small fragments.
for (BitSet subset : payloadSizeBySubset.elementSet()) {
if (isSubset(subset, fragmentSubset)) {
size += payloadSizeBySubset.count(subset);
if (size >= minSize) {
return false;
}
}
}
return true;
}
private ControlFlowAnalyzer recordLiveSubset(ControlFlowAnalyzer cfa, JRunAsync runAsync) {
addRunAsync(runAsync);
for (JNode node : cfa.getLiveFieldsAndMethods()) {
if (node instanceof JField) {
setLive(liveSubsetForField, (JField) node, runAsync);
}
if (node instanceof JMethod) {
setLive(liveSubsetForMethod, (JMethod) node, runAsync);
}
}
for (JField field : cfa.getFieldsWritten()) {
setLive(liveSubsetForField, field, runAsync);
}
for (String string : cfa.getLiveStrings()) {
setLive(liveSubsetForString, string, runAsync);
}
for (JReferenceType type : cfa.getInstantiatedTypes()) {
if (type instanceof JDeclaredType) {
setLive(liveSubsetForType, (JDeclaredType) type, runAsync);
}
}
return cfa;
}
private boolean setLive(Map liveSubsetsByAtom, T atom, JRunAsync runAsync) {
int runAsyncId = idForRunAsync.get(runAsync);
BitSet liveSubset = liveSubsetsByAtom.get(atom);
if (liveSubset == null) {
liveSubset = new BitSet();
liveSubset.set(runAsyncId);
liveSubsetsByAtom.put(atom, liveSubset);
return true;
} else {
if (liveSubset.get(runAsyncId)) {
return false;
} else {
liveSubset.set(runAsyncId);
return true;
}
}
}
}
