Optimization and optional parallelization of typing minimization

src/main/java/soot/jimple/toolkits/typing/fast/DefaultTypingStrategy.java

@@ -1,5 +1,7 @@
 package soot.jimple.toolkits.typing.fast;
 
+import java.util.ArrayList;
+
 /*-
  * #%L
  * Soot - a J*va Optimization Framework
@@ -29,6 +31,11 @@
 import java.util.List;
 import java.util.ListIterator;
 import java.util.Set;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.stream.IntStream;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 import soot.Local;
 import soot.RefType;
@@ -42,9 +49,13 @@
  * The default typing strategy
  */
 public class DefaultTypingStrategy implements ITypingStrategy {
+  private static final Logger logger = LoggerFactory.getLogger(DefaultTypingStrategy.class);
 
   public static final ITypingStrategy INSTANCE = new DefaultTypingStrategy();
 
+  public static boolean MINIMIZING_ENABLED = true;
+  public static int USE_PARALLEL_MINIMIZE_IF_ENTRIES_MORE_THAN = 1000;
+
   @Override
   public Typing createTyping(Chain<Local> locals) {
     return new Typing(locals);
@@ -81,18 +92,54 @@ public static Set<Local> getObjectLikeTypings(List<Typing> tgs) {
 
   @Override
   public void minimize(List<Typing> tgs, IHierarchy h) {
+    if (!MINIMIZING_ENABLED) {
+      return;
+    }
+
+    if (tgs.size() > USE_PARALLEL_MINIMIZE_IF_ENTRIES_MORE_THAN) {
+      minimizeParallel(tgs, h);
+      return;
+    }
+
+    minimizeSequential(tgs, h);
+  }
+
+  public void minimizeSequential(List<Typing> tgs, IHierarchy h) {
+    // int count = 0;
+    // int tgsSize = tgs.size();
     Set<Local> objectVars = getObjectLikeTypings(tgs);
     OUTER: for (ListIterator<Typing> i = tgs.listIterator(); i.hasNext();) {
       Typing tgi = i.next();
+      // count++;
+      // if (count % 500 == 0) {
+      // logger.info("{} of {} = {}%", count, tgsSize, 100f * count / tgsSize);
+      // }
+      if (tgi == null) {
+        // element is marked to be deleted, here we can finally remove it
+        i.remove();
+        continue;
+      }
 
       // Throw out duplicate typings
-      for (Typing tgj : tgs) {
-        // if compare = 1, then tgi is the more general typing
-        // We shouldn't pick that one as we would then end up
-        // with lots of locals typed to Serializable etc.
-        if (tgi != tgj && compare(tgi, tgj, h, objectVars) == 1) {
+      ListIterator<Typing> j = tgs.listIterator(i.nextIndex());
+      while (j.hasNext()) {
+        Typing tgj = j.next();
+        if (tgj == null) {
+          continue; // element is marked to be deleted
+        }
+        int comp = compare(tgi, tgj, h, objectVars);
+        if (comp == 1) {
+          // if compare = 1, then tgi is the more general typing
+          // We shouldn't pick that one as we would then end up
+          // with lots of locals typed to Serializable etc.
           i.remove();
           continue OUTER;
+        } else if (comp == -1) {
+          // if compare == -1, then tgj is the more general typing
+          // Set it to null as workaround for marking it as deleted.
+          // We can not remove the element here as this would cause a
+          // ConcurrentModificationException in the outer list iterator.
+          j.set(null);
         }
       }
     }
@@ -109,15 +156,17 @@ public int compare(Typing a, Typing b, IHierarchy h, Collection<Local> localsToI
           cmp = 0;
         } else if (h.ancestor(ta, tb)) {
           cmp = 1;
+          if (r == -1) {
+            return 2;
+          }
         } else if (h.ancestor(tb, ta)) {
           cmp = -1;
+          if (r == 1) {
+            return 2;
+          }
         } else {
           return -2;
         }
-
-        if ((cmp == 1 && r == -1) || (cmp == -1 && r == 1)) {
-          return 2;
-        }
         if (r == 0) {
           r = cmp;
         }
@@ -126,6 +175,63 @@ public int compare(Typing a, Typing b, IHierarchy h, Collection<Local> localsToI
     return r;
   }
 
+  public void minimizeParallel(List<Typing> tgs, IHierarchy h) {
+    logger.debug("Performing parallel minimization");
+    Set<Local> objectVars = getObjectLikeTypings(tgs);
+
+    // We don't know what type of list we get, we need a list that is thread safe for get/set
+    // values. (get could return stale values, but this would not cause harm)
+    ArrayList<Typing> workList = new ArrayList<>(tgs);
+    final AtomicInteger processed = new AtomicInteger();
+    final int tgsSize = tgs.size();
+
+    // We iterate over the list using the list item index.
+    // This way we have something like a parallel list iterator.
+    // The only disadvantage is that we can not delete items from the list.
+    // As workaround we replace those entries with a null value (mark them for deletion).
+    IntStream.range(0, tgsSize).parallel().forEach(i -> {
+      int count = processed.incrementAndGet();
+      if (count % 1000 == 0) {
+        logger.debug("minimizing {} = {}%", count, (100f * count) / tgsSize);
+      }
+      Typing tgi = workList.get(i);
+      if (tgi == null) {
+        return;
+      }
+      ListIterator<Typing> j = workList.listIterator(i + 1);
+      while (j.hasNext()) {
+        Typing tgj = j.next();
+        if (tgj == null) {
+          continue;
+        }
+        int comp = compare(tgi, tgj, h, objectVars);
+        if (comp == 1) {
+          // if compare = 1, then tgi is the more general typing
+          // We shouldn't pick that one as we would then end up
+          // with lots of locals typed to Serializable etc.
+          // Set it to null as workaround for marking it as deleted.
+          workList.set(i, null);
+          return;
+        } else if (comp == -1) {
+          // if compare == -1, then tgj is the more general typing
+          // Set it to null as workaround for marking it as deleted.
+          j.set(null);
+        }
+      }
+    });
+    // remove all null entries (entries marked for deletion)
+    for (int i = tgsSize - 1; i >= 0; i--) {
+      if (workList.get(i) == null) {
+        tgs.remove(i);
+      }
+    }
+
+    int diff = tgsSize - tgs.size();
+    if (diff > 0) {
+      logger.debug("Minimizing has removed {} of {} typing", diff, tgsSize);
+    }
+  }
+
   @Override
   public void finalizeTypes(Typing tp) {
     for (Local l : tp.getAllLocals()) {

src/test/java/soot/jimple/toolkits/typing/DefaultTypingStrategyMinimizeParallelTest.java

@@ -0,0 +1,47 @@
+package soot.jimple.toolkits.typing;
+
+/*-
+ * #%L
+ * Soot - a J*va Optimization Framework
+ * %%
+ * Copyright (C) 1997 - 2018 Raja Vallée-Rai and others
+ * %%
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as
+ * published by the Free Software Foundation, either version 2.1 of the
+ * License, or (at your option) any later version.
+ * 
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Lesser Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Lesser Public
+ * License along with this program.  If not, see
+ * <http://www.gnu.org/licenses/lgpl-2.1.html>.
+ * #L%
+ */
+
+import java.util.List;
+
+import soot.jimple.toolkits.typing.fast.BytecodeHierarchy;
+import soot.jimple.toolkits.typing.fast.DefaultTypingStrategy;
+import soot.jimple.toolkits.typing.fast.Typing;
+
+/**
+ * JUnit-Tests for the {@link DefaultTypingStrategy#minimizeParallel(List, soot.jimple.toolkits.typing.fast.IHierarchy)}
+ * method.
+ * 
+ * For each test we generate a simple synthetic class hierarchy and some {@link Typing}s we minimize afterwards and check the
+ * result. The test are the same as in {@link DefaultTypingStrategyMinimizeSequentialTest}.
+ * 
+ * @author Jan Peter Stotz
+ */
+public class DefaultTypingStrategyMinimizeParallelTest extends DefaultTypingStrategyMinimizeSequentialTest {
+
+  @Override
+  protected void executeMinimize(List<Typing> typingList) {
+    new DefaultTypingStrategy().minimizeParallel(typingList, new BytecodeHierarchy());
+  }
+
+}