diff --git a/WHATSNEW b/WHATSNEW
index 5d8c24796..e947a0f61 100644
--- a/WHATSNEW
+++ b/WHATSNEW
@@ -196,6 +196,10 @@ Fixed bugs:
 
 Other changes:
 --------------
+
+* Various small optimizations speed up common tasks such as <javac> on large
+  filesets, reducing both I/O and CPU usage.
+
 * Profiling logger has been added with basic profiling capabilities.
 
 * <script> now has basic support for JavaFX scripts
diff --git a/src/main/org/apache/tools/ant/DirectoryScanner.java b/src/main/org/apache/tools/ant/DirectoryScanner.java
index 663fd7b2d..98f0c6722 100644
--- a/src/main/org/apache/tools/ant/DirectoryScanner.java
+++ b/src/main/org/apache/tools/ant/DirectoryScanner.java
@@ -1065,28 +1065,25 @@ public class DirectoryScanner
     protected void scandir(File dir, String vpath, boolean fast) {
         if (dir == null) {
             throw new BuildException("dir must not be null.");
-        } else if (!dir.exists()) {
-            throw new BuildException(dir + " doesn't exist.");
-        } else if (!dir.isDirectory()) {
-            throw new BuildException(dir + " is not a directory.");
         }
+        String[] newfiles = dir.list();
+        if (newfiles == null) {
+            if (!dir.exists()) {
+                throw new BuildException(dir + " doesn't exist.");
+            } else if (!dir.isDirectory()) {
+                throw new BuildException(dir + " is not a directory.");
+            } else {
+                throw new BuildException("IO error scanning directory '"
+                                         + dir.getAbsolutePath() + "'");
+            }
+        }
+        scandir(dir, vpath, fast, newfiles);
+    }
+    private void scandir(File dir, String vpath, boolean fast, String[] newfiles) {
         // avoid double scanning of directories, can only happen in fast mode
         if (fast && hasBeenScanned(vpath)) {
             return;
         }
-        String[] newfiles = dir.list();
-
-        if (newfiles == null) {
-            /*
-             * two reasons are mentioned in the API docs for File.list
-             * (1) dir is not a directory. This is impossible as
-             *     we wouldn't get here in this case.
-             * (2) an IO error occurred (why doesn't it throw an exception
-             *     then???)
-             */
-            throw new BuildException("IO error scanning directory '"
-                                     + dir.getAbsolutePath() + "'");
-        }
         if (!followSymlinks) {
             Vector noLinks = new Vector();
             for (int i = 0; i < newfiles.length; i++) {
@@ -1112,25 +1109,26 @@ public class DirectoryScanner
         for (int i = 0; i < newfiles.length; i++) {
             String name = vpath + newfiles[i];
             File file = new File(dir, newfiles[i]);
-            if (file.isDirectory()) {
+            String[] children = file.list();
+            if (children == null) { // probably file
+                if (isIncluded(name)) {
+                    accountForIncludedFile(name, file);
+                } else {
+                    everythingIncluded = false;
+                    filesNotIncluded.addElement(name);
+                }
+            } else { // dir
                 if (isIncluded(name)) {
-                    accountForIncludedDir(name, file, fast);
+                    accountForIncludedDir(name, file, fast, children);
                 } else {
                     everythingIncluded = false;
                     dirsNotIncluded.addElement(name);
                     if (fast && couldHoldIncluded(name)) {
-                        scandir(file, name + File.separator, fast);
+                        scandir(file, name + File.separator, fast, children);
                     }
                 }
                 if (!fast) {
-                    scandir(file, name + File.separator, fast);
-                }
-            } else if (file.isFile()) {
-                if (isIncluded(name)) {
-                    accountForIncludedFile(name, file);
-                } else {
-                    everythingIncluded = false;
-                    filesNotIncluded.addElement(name);
+                    scandir(file, name + File.separator, fast, children);
                 }
             }
         }
@@ -1158,6 +1156,12 @@ public class DirectoryScanner
             scandir(file, name + File.separator, fast);
         }
     }
+    private void accountForIncludedDir(String name, File file, boolean fast, String[] children) {
+        processIncluded(name, file, dirsIncluded, dirsExcluded, dirsDeselected);
+        if (fast && couldHoldIncluded(name) && !contentsExcluded(name)) {
+            scandir(file, name + File.separator, fast, children);
+        }
+    }
 
     private void processIncluded(String name, File file, Vector inc, Vector exc, Vector des) {
 
diff --git a/src/main/org/apache/tools/ant/taskdefs/Rmic.java b/src/main/org/apache/tools/ant/taskdefs/Rmic.java
index 0c7e9b1f3..471916306 100644
--- a/src/main/org/apache/tools/ant/taskdefs/Rmic.java
+++ b/src/main/org/apache/tools/ant/taskdefs/Rmic.java
@@ -524,9 +524,15 @@ public class Rmic extends MatchingTask {
                 scanDir(baseDir, files, adapter.getMapper());
             } else {
                 // otherwise perform a timestamp comparison - at least
-                scanDir(baseDir, new String[] {
-                        classname.replace('.', File.separatorChar)
-                        + ".class" }, adapter.getMapper());
+                String path = classname.replace('.', File.separatorChar) + ".class";
+                File f = new File(baseDir, path);
+                if (f.isFile()) {
+                    scanDir(baseDir, new String[] { path }, adapter.getMapper());
+                } else {
+                    // Does not exist, so checking whether it is up to date makes no sense.
+                    // Compilation will fail later anyway, but tests expect a certain output.
+                    compileList.add(classname);
+                }
             }
             int fileCount = compileList.size();
             if (fileCount > 0) {
diff --git a/src/main/org/apache/tools/ant/taskdefs/optional/depend/Depend.java b/src/main/org/apache/tools/ant/taskdefs/optional/depend/Depend.java
index 14293a433..56b7c21aa 100644
--- a/src/main/org/apache/tools/ant/taskdefs/optional/depend/Depend.java
+++ b/src/main/org/apache/tools/ant/taskdefs/optional/depend/Depend.java
@@ -773,18 +773,21 @@ public class Depend extends MatchingTask {
      * Find the source file for a given class
      *
      * @param classname the classname in slash format.
+     * @param sourceFileKnownToExist if not null, a file already known to exist (saves call to .exists())
      */
-    private File findSourceFile(String classname) {
-        String sourceFilename = classname + ".java";
+    private File findSourceFile(String classname, File sourceFileKnownToExist) {
+        String sourceFilename;
         int innerIndex = classname.indexOf("$");
         if (innerIndex != -1) {
             sourceFilename = classname.substring(0, innerIndex) + ".java";
+        } else {
+            sourceFilename = classname + ".java";
         }
 
         // search the various source path entries
         for (int i = 0; i < srcPathList.length; ++i) {
             File sourceFile = new File(srcPathList[i], sourceFilename);
-            if (sourceFile.exists()) {
+            if (sourceFile.equals(sourceFileKnownToExist) || sourceFile.exists()) {
                 return sourceFile;
             }
         }
@@ -812,11 +815,10 @@ public class Depend extends MatchingTask {
         int length = filesInDir.length;
 
         int rootLength = root.getPath().length();
+        File sourceFileKnownToExist = null; // speed optimization
         for (int i = 0; i < length; ++i) {
             File file = new File(dir, filesInDir[i]);
-            if (file.isDirectory()) {
-                addClassFiles(classFileList, file, root);
-            } else if (file.getName().endsWith(".class")) {
+            if (filesInDir[i].endsWith(".class")) {
                 ClassFileInfo info = new ClassFileInfo();
                 info.absoluteFile = file;
                 String relativeName = file.getPath().substring(
@@ -824,8 +826,10 @@ public class Depend extends MatchingTask {
                     file.getPath().length() - ".class".length());
                 info.className
                     = ClassFileUtils.convertSlashName(relativeName);
-                info.sourceFile = findSourceFile(relativeName);
+                info.sourceFile = sourceFileKnownToExist = findSourceFile(relativeName, sourceFileKnownToExist);
                 classFileList.addElement(info);
+            } else {
+                addClassFiles(classFileList, file, root);
             }
         }
     }
diff --git a/src/main/org/apache/tools/ant/types/selectors/SelectorUtils.java b/src/main/org/apache/tools/ant/types/selectors/SelectorUtils.java
index f028c7953..91c368514 100644
--- a/src/main/org/apache/tools/ant/types/selectors/SelectorUtils.java
+++ b/src/main/org/apache/tools/ant/types/selectors/SelectorUtils.java
@@ -615,16 +615,16 @@ public final class SelectorUtils {
      */
     public static boolean isOutOfDate(Resource src, Resource target,
                                       long granularity) {
-        if (!src.isExists()) {
+        long sourceLastModified = src.getLastModified();
+        if (sourceLastModified == 0L) {
+            // Does not exist. Quicker than checking exists() again.
             return false;
         }
-        if (!target.isExists()) {
+        long targetLastModified = target.getLastModified();
+        if (targetLastModified == 0L) {
             return true;
         }
-        if ((src.getLastModified() - granularity) > target.getLastModified()) {
-            return true;
-        }
-        return false;
+        return (sourceLastModified - granularity) > targetLastModified;
     }
 
     /**
diff --git a/src/main/org/apache/tools/ant/util/ResourceUtils.java b/src/main/org/apache/tools/ant/util/ResourceUtils.java
index 4c085bb8d..860262e36 100644
--- a/src/main/org/apache/tools/ant/util/ResourceUtils.java
+++ b/src/main/org/apache/tools/ant/util/ResourceUtils.java
@@ -61,17 +61,6 @@ import org.apache.tools.ant.types.selectors.SelectorUtils;
  */
 public class ResourceUtils {
 
-    private static final class Outdated implements ResourceSelector {
-        private Resource control;
-        private long granularity;
-        private Outdated(Resource control, long granularity) {
-            this.control = control;
-            this.granularity = granularity;
-        }
-        public boolean isSelected(Resource r) {
-            return SelectorUtils.isOutOfDate(control, r, granularity);
-        }
-    }
     /** Utilities used for file operations */
     private static final FileUtils FILE_UTILS = FileUtils.getFileUtils();
 
@@ -144,7 +133,7 @@ public class ResourceUtils {
                                                             ResourceCollection source,
                                                             FileNameMapper mapper,
                                                             ResourceFactory targets,
-                                                            long granularity) {
+                                                            final long granularity) {
         if (source.size() == 0) {
             logTo.log("No sources found.", Project.MSG_VERBOSE);
             return Resources.NONE;
@@ -154,7 +143,7 @@ public class ResourceUtils {
 
         Union result = new Union();
         for (Iterator iter = source.iterator(); iter.hasNext();) {
-            Resource sr = (Resource) iter.next();
+            final Resource sr = (Resource) iter.next();
             String srName = sr.getName();
             srName = srName == null
                 ? srName : srName.replace('/', File.separatorChar);
@@ -178,8 +167,16 @@ public class ResourceUtils {
             }
             //find the out-of-date targets:
             Restrict r = new Restrict();
-            r.add(new And(new ResourceSelector[] {Type.FILE, new Or(
-                new ResourceSelector[] {NOT_EXISTS, new Outdated(sr, granularity)})}));
+            r.add(new ResourceSelector() {
+                public boolean isSelected(Resource target) {
+                    /* Extra I/O, probably wasted:
+                    if (target.isDirectory()) {
+                        return false;
+                    }
+                     */
+                    return SelectorUtils.isOutOfDate(sr, target, granularity);
+                }
+            });
             r.add(targetColl);
             if (r.size() > 0) {
                 result.add(sr);
diff --git a/src/main/org/apache/tools/ant/util/SourceFileScanner.java b/src/main/org/apache/tools/ant/util/SourceFileScanner.java
index fd3d8a988..e98698709 100644
--- a/src/main/org/apache/tools/ant/util/SourceFileScanner.java
+++ b/src/main/org/apache/tools/ant/util/SourceFileScanner.java
@@ -91,9 +91,12 @@ public class SourceFileScanner implements ResourceFactory {
         this.destDir = destDir;
         Vector v = new Vector();
         for (int i = 0; i < files.length; i++) {
-            File src = FILE_UTILS.resolveFile(srcDir, files[i]);
-            v.addElement(new Resource(files[i], src.exists(),
-                                      src.lastModified(), src.isDirectory()));
+            final String name = files[i];
+            v.addElement(new FileResource(srcDir, name) {
+                public String getName() {
+                    return name;
+                }
+            });
         }
         Resource[] sourceresources = new Resource[v.size()];
         v.copyInto(sourceresources);