Add combine option for multiple profile file stats

Add the --combine option to produce a single aggregated statistics output for
multiple profile files. Outputs neither Skylark histograms nor the task chart.

--
MOS_MIGRATED_REVID=105051164

11 files changed, 732 insertions, 208 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/profiler/output/HtmlCreator.java b/src/main/java/com/google/devtools/build/lib/profiler/output/HtmlCreator.java
index ab703ac2fd..885c965ee4 100644
--- a/src/main/java/com/google/devtools/build/lib/profiler/output/HtmlCreator.java
+++ b/src/main/java/com/google/devtools/build/lib/profiler/output/HtmlCreator.java
@@ -21,6 +21,7 @@ import com.google.devtools.build.lib.profiler.chart.Chart;
 import com.google.devtools.build.lib.profiler.chart.ChartCreator;
 import com.google.devtools.build.lib.profiler.chart.DetailedChartCreator;
 import com.google.devtools.build.lib.profiler.chart.HtmlChartVisitor;
+import com.google.devtools.build.lib.profiler.statistics.MultiProfileStatistics;
 import com.google.devtools.build.lib.profiler.statistics.PhaseStatistics;
 import com.google.devtools.build.lib.profiler.statistics.PhaseSummaryStatistics;
 import com.google.devtools.build.lib.profiler.statistics.SkylarkStatistics;
@@ -40,6 +41,7 @@ public final class HtmlCreator extends HtmlPrinter {
   private final Optional<Chart> chart;
   private final HtmlChartVisitor chartVisitor;
   private final Optional<SkylarkHtml> skylarkStats;
+  private final Optional<MultiProfilePhaseHtml> multiFileStats;
   private final String title;
   private final PhaseHtml phases;
 
@@ -48,25 +50,21 @@ public final class HtmlCreator extends HtmlPrinter {
       String title,
       Optional<Chart> chart,
       Optional<SkylarkHtml> skylarkStats,
-      int htmlPixelsPerSecond,
-      PhaseHtml phases) {
+      Optional<MultiProfilePhaseHtml> multiFileStats,
+      PhaseHtml phases,
+      int htmlPixelsPerSecond) {
     super(out);
     this.title = title;
     this.chart = chart;
     this.skylarkStats = skylarkStats;
     this.phases = phases;
+    this.multiFileStats = multiFileStats;
     chartVisitor = new HtmlChartVisitor(out, htmlPixelsPerSecond);
   }
 
-  public HtmlCreator(
-      PrintStream out,
-      String title,
-      Optional<SkylarkHtml> skylarkStats,
-      int htmlPixelsPerSecond,
-      PhaseHtml phases) {
-    this(out, title, Optional.<Chart>absent(), skylarkStats, htmlPixelsPerSecond, phases);
-  }
-
+  /**
+   * Output the HTML depending on which statistics should be printed.
+   */
   private void print() {
     htmlFrontMatter();
     if (chart.isPresent()) {
@@ -77,22 +75,34 @@ public final class HtmlCreator extends HtmlPrinter {
     element("h2", "Statistics");
     phases.print();
 
+    if (multiFileStats.isPresent()) {
+      multiFileStats.get().printHtmlBody();
+    }
     if (skylarkStats.isPresent()) {
       skylarkStats.get().printHtmlBody();
     }
     htmlBackMatter();
   }
 
+  /**
+   * Print opening tags, CSS and JavaScript
+   */
   private void htmlFrontMatter() {
     lnOpen("html");
     lnOpen("head");
     lnElement("title", title);
+
+    printVisualizationJs();
+
     if (chart.isPresent()) {
       chartVisitor.printCss(chart.get().getSortedTypes());
     }
 
     phases.printCss();
 
+    if (multiFileStats.isPresent()) {
+      multiFileStats.get().printHtmlHead();
+    }
     if (skylarkStats.isPresent()) {
       skylarkStats.get().printHtmlHead();
     }
@@ -108,6 +118,30 @@ public final class HtmlCreator extends HtmlPrinter {
   }
 
   /**
+   * Print code for loading the Google Visualization JS library.
+   *
+   * <p>Used for the charts and tables for {@link SkylarkHtml} and {@link MultiProfilePhaseHtml}.
+   * Also adds a callback on load of the library which draws the charts and tables.
+   */
+  private void printVisualizationJs() {
+    lnElement("script", "type", "text/javascript", "src", "https://www.google.com/jsapi");
+    lnOpen("script", "type", "text/javascript");
+    lnPrint("google.load(\"visualization\", \"1.1\", {packages:[\"corechart\",\"table\"]});");
+    lnPrint("google.setOnLoadCallback(drawVisualization);");
+    lnPrint("function drawVisualization() {");
+    down();
+    if (skylarkStats.isPresent()) {
+      skylarkStats.get().printVisualizationCallbackJs();
+    }
+    if (multiFileStats.isPresent()) {
+      multiFileStats.get().printVisualizationCallbackJs();
+    }
+    up();
+    lnPrint("}");
+    lnClose(); // script
+  }
+
+  /**
    * Writes the HTML profiling information.
    *
    * @throws IOException
@@ -140,8 +174,49 @@ public final class HtmlCreator extends HtmlPrinter {
         }
         chart = Optional.of(chartCreator.create());
       }
-      new HtmlCreator(out, info.comment, chart, skylarkStats, htmlPixelsPerSecond, phaseHtml)
+      new HtmlCreator(
+              out,
+              info.comment,
+              chart,
+              skylarkStats,
+              Optional.<MultiProfilePhaseHtml>absent(),
+              phaseHtml,
+              htmlPixelsPerSecond)
           .print();
     }
   }
+
+  /**
+   * Writes the HTML profiling information for multiple files.
+   *
+   * <p>Does not print a {@link Chart} or even multiple charts and no Skylark histograms.
+   */
+  public static void create(
+      PrintStream out,
+      MultiProfileStatistics statistics,
+      boolean detailed,
+      int htmlPixelsPerSecond,
+      int vfsStatsLimit) {
+    PhaseHtml phaseHtml =
+        new PhaseHtml(
+            out,
+            statistics.getSummaryStatistics(),
+            statistics.getSummaryPhaseStatistics(),
+            vfsStatsLimit);
+    Optional<SkylarkHtml> skylarkStats;
+    if (detailed) {
+      skylarkStats = Optional.of(new SkylarkHtml(out, statistics.getSkylarkStatistics(), false));
+    } else {
+      skylarkStats = Optional.absent();
+    }
+    new HtmlCreator(
+            out,
+            "Statistics from multiple profile files",
+            Optional.<Chart>absent(),
+            skylarkStats,
+            Optional.of(new MultiProfilePhaseHtml(out, statistics)),
+            phaseHtml,
+            htmlPixelsPerSecond)
+        .print();
+  }
 }
diff --git a/src/main/java/com/google/devtools/build/lib/profiler/output/MultiProfilePhaseHtml.java b/src/main/java/com/google/devtools/build/lib/profiler/output/MultiProfilePhaseHtml.java
new file mode 100644
index 0000000000..cbde62b4b4
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/profiler/output/MultiProfilePhaseHtml.java
@@ -0,0 +1,110 @@
+// Copyright 2015 The Bazel Authors. All rights reserved.
+//
+// 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.devtools.build.lib.profiler.output;
+
+import com.google.devtools.build.lib.profiler.ProfilePhase;
+import com.google.devtools.build.lib.profiler.ProfilerTask;
+import com.google.devtools.build.lib.profiler.statistics.MultiProfileStatistics;
+import com.google.devtools.build.lib.profiler.statistics.PhaseStatistics;
+import com.google.devtools.build.lib.util.TimeUtilities;
+import com.google.devtools.build.lib.vfs.Path;
+
+import java.io.PrintStream;
+import java.util.EnumMap;
+
+/**
+ * Formats the per file phase statistics from {@link MultiProfileStatistics} into HTML tables.
+ */
+public final class MultiProfilePhaseHtml extends HtmlPrinter {
+
+  private final MultiProfileStatistics statistics;
+
+  public MultiProfilePhaseHtml(PrintStream out, MultiProfileStatistics statistics) {
+    super(out);
+    this.statistics = statistics;
+  }
+
+  /**
+   * Prints CSS definitions and JavaScript code.
+   */
+  void printHtmlHead() {
+    lnOpen("style", "type", "text/css", "<!--");
+    lnPrint("div.profiles-table {");
+    lnPrint("  width: 95%; margin: 0 auto; height: auto;");
+    lnPrint("}");
+    lnPrint("-->");
+    close(); // style
+  }
+
+  /**
+   * Prints the table data and JS for each phase and file.
+   *
+   * <p>Code must be added to the callback that is run when the Visualization library has loaded.
+   */
+  public void printVisualizationCallbackJs() {
+    lnPrint("var multiData;");
+    lnPrint("var statsDiv;");
+    lnPrint("var profileTable;");
+    for (ProfilePhase phase : statistics.getSummaryStatistics()) {
+      lnPrintf("statsDiv = document.getElementById('profile_file_stats_%s');", phase.nick);
+      lnPrint("multiData = new google.visualization.DataTable();");
+      lnPrint("multiData.addColumn('string', 'File');");
+      lnPrint("multiData.addColumn('number', 'total');");
+      PhaseStatistics summaryPhaseStatistics = statistics.getSummaryPhaseStatistics(phase);
+      for (ProfilerTask taskType : summaryPhaseStatistics) {
+        lnPrintf("multiData.addColumn('number', '%s %%');", taskType.name());
+      }
+      lnPrint("multiData.addRows([");
+      down();
+      for (Path file : statistics) {
+        EnumMap<ProfilePhase, PhaseStatistics> phases = statistics.getPhaseStatistics(file);
+        PhaseStatistics phaseStatistics = phases.get(phase);
+        lnPrintf("['%s', ", file);
+        long phaseDuration = phaseStatistics.getPhaseDurationNanos();
+        printf("{v:%d, f:'%s'}, ", phaseDuration, TimeUtilities.prettyTime(phaseDuration));
+        for (ProfilerTask taskType : summaryPhaseStatistics) {
+          if (phaseStatistics.wasExecuted(taskType)) {
+            double relative = phaseStatistics.getTotalRelativeDuration(taskType);
+            printf("{v:%.4f, f:'%.3f %%'}, ", relative, relative * 100);
+          } else {
+            print("0, ");
+          }
+        }
+        print("],");
+      }
+      lnPrint("]);");
+      up();
+      lnPrint("profileTable = new google.visualization.Table(statsDiv);");
+      lnPrint("profileTable.draw(multiData, {showRowNumber: true, width: '100%%'});");
+    }
+  }
+
+  /**
+   * Prints divs for the tables of statistics for profile files and their phases.
+   */
+  void printHtmlBody() {
+    lnPrint("<a name='profile_file_stats'/>");
+    lnElement("h3", "Profile File Statistics");
+    lnOpen("div", "class", "profiles-tables", "id", "profile_file_stats");
+    for (ProfilePhase phase : statistics.getSummaryStatistics()) {
+      lnOpen("div");
+      lnElement("h4", phase.nick);
+      lnElement("div", "class", "profiles-table", "id", "profile_file_stats_" + phase.nick);
+      lnClose();
+    }
+    lnClose(); // div
+  }
+}
+
+
diff --git a/src/main/java/com/google/devtools/build/lib/profiler/output/PhaseHtml.java b/src/main/java/com/google/devtools/build/lib/profiler/output/PhaseHtml.java
index 231143177d..039ea28de7 100644
--- a/src/main/java/com/google/devtools/build/lib/profiler/output/PhaseHtml.java
+++ b/src/main/java/com/google/devtools/build/lib/profiler/output/PhaseHtml.java
@@ -25,7 +25,6 @@ import com.google.devtools.build.lib.util.TimeUtilities;
 import java.io.PrintStream;
 import java.util.Arrays;
 import java.util.EnumMap;
-import java.util.Map.Entry;
 
 /**
  * Output {@link PhaseSummaryStatistics}, {@link PhaseStatistics} and {@link PhaseVfsStatistics}
@@ -88,7 +87,7 @@ public final class PhaseHtml extends HtmlPrinter {
     for (ProfilePhase phase :
         Arrays.asList(ProfilePhase.INIT, ProfilePhase.LOAD, ProfilePhase.ANALYZE)) {
       PhaseStatistics statistics = phaseStatistics.get(phase);
-      if (!statistics.wasExecuted()) {
+      if (statistics == null || !statistics.wasExecuted()) {
         continue;
       }
       printPhaseStatistics(statistics);
@@ -159,7 +158,7 @@ public final class PhaseHtml extends HtmlPrinter {
 
     for (ProfilerTask type : stats) {
       int numPrinted = 0;
-      for (Entry<Stat, String> stat : stats.getSortedStatistics(type)) {
+      for (Stat stat : stats.getSortedStatistics(type)) {
         lnOpen("tr");
         if (vfsStatsLimit != -1 && numPrinted++ == vfsStatsLimit) {
           open("td", "class", "center", "colspan", "4");
@@ -169,9 +168,9 @@ public final class PhaseHtml extends HtmlPrinter {
           break;
         }
         element("td", type.name());
-        element("td", stat.getKey().count);
-        element("td", TimeUtilities.prettyTime(stat.getKey().duration));
-        element("td", "class", "left", stat.getValue());
+        element("td", stat.getCount());
+        element("td", TimeUtilities.prettyTime(stat.getDuration()));
+        element("td", "class", "left", stat.path);
         close(); // tr
       }
     }
diff --git a/src/main/java/com/google/devtools/build/lib/profiler/output/PhaseText.java b/src/main/java/com/google/devtools/build/lib/profiler/output/PhaseText.java
index e246eb1c71..f3b71098bf 100644
--- a/src/main/java/com/google/devtools/build/lib/profiler/output/PhaseText.java
+++ b/src/main/java/com/google/devtools/build/lib/profiler/output/PhaseText.java
@@ -26,7 +26,6 @@ import com.google.devtools.build.lib.util.TimeUtilities;
 import java.io.PrintStream;
 import java.util.Arrays;
 import java.util.EnumMap;
-import java.util.Map.Entry;
 
 /**
  * Output {@link PhaseSummaryStatistics}, {@link PhaseStatistics} and {@link PhaseVfsStatistics}
@@ -206,7 +205,7 @@ public final class PhaseText extends TextPrinter {
 
     for (ProfilerTask type : stats) {
       int numPrinted = 0;
-      for (Entry<Stat, String> stat : stats.getSortedStatistics(type)) {
+      for (Stat stat : stats.getSortedStatistics(type)) {
         if (vfsStatsLimit != -1 && numPrinted++ == vfsStatsLimit) {
           lnPrintf("... %d more ...", stats.getStatisticsCount(type) - vfsStatsLimit);
           break;
@@ -214,9 +213,9 @@ public final class PhaseText extends TextPrinter {
         lnPrintf(
             "%15s %10d %10s %s",
             type.name(),
-            stat.getKey().count,
-            TimeUtilities.prettyTime(stat.getKey().duration),
-            stat.getValue());
+            stat.getCount(),
+            TimeUtilities.prettyTime(stat.getDuration()),
+            stat.path);
       }
     }
   }
diff --git a/src/main/java/com/google/devtools/build/lib/profiler/output/SkylarkHtml.java b/src/main/java/com/google/devtools/build/lib/profiler/output/SkylarkHtml.java
index c0e9ee14fa..769e4e3b7f 100644
--- a/src/main/java/com/google/devtools/build/lib/profiler/output/SkylarkHtml.java
+++ b/src/main/java/com/google/devtools/build/lib/profiler/output/SkylarkHtml.java
@@ -33,6 +33,8 @@ public final class SkylarkHtml extends HtmlPrinter {
    * How many characters from the end of the location of a Skylark function to display.
    */
   private static final int NUM_LOCATION_CHARS_UNABBREVIATED = 40;
+  private static final String JS_DATA_VAR = "skylarkData";
+  private static final String JS_TABLE_VAR = JS_DATA_VAR + "Table";
 
   private final SkylarkStatistics stats;
   private final boolean printHistograms;
@@ -64,48 +66,11 @@ public final class SkylarkHtml extends HtmlPrinter {
     lnPrint("-->");
     close(); // style
 
-    lnElement("script", "type", "text/javascript", "src", "https://www.google.com/jsapi");
     lnOpen("script", "type", "text/javascript");
-    lnPrint("google.load(\"visualization\", \"1.1\", {packages:[\"corechart\",\"table\"]});");
-    lnPrint("google.setOnLoadCallback(drawVisualization);");
-
-    String dataVar = "data";
-    String tableVar = dataVar + "Table";
-    lnPrintf("var %s = {};\n", dataVar);
-    lnPrintf("var %s = {};\n", tableVar);
+    lnPrintf("var %s = {};\n", JS_DATA_VAR);
+    lnPrintf("var %s = {};\n", JS_TABLE_VAR);
     lnPrint("var histogramData;");
 
-    lnPrint("function drawVisualization() {");
-    down();
-    printStatsJs(
-        stats.getUserFunctionStatistics(),
-        stats.getUserFunctionSelfStatistics(),
-        "user",
-        dataVar,
-        tableVar,
-        stats.getUserTotalNanos());
-    printStatsJs(
-        stats.getBuiltinFunctionStatistics(),
-        stats.getBuiltinFunctionSelfStatistics(),
-        "builtin",
-        dataVar,
-        tableVar,
-        stats.getBuiltinTotalNanos());
-
-    if (printHistograms) {
-      printHistogramData();
-
-      lnPrint("document.querySelector('#user-close').onclick = function() {");
-      lnPrint("  document.querySelector('#user-histogram').style.display = 'none';");
-      lnPrint("};");
-      lnPrint("document.querySelector('#builtin-close').onclick = function() {");
-      lnPrint("  document.querySelector('#builtin-histogram').style.display = 'none';");
-      lnPrint("};");
-    }
-
-    up();
-    lnPrint("};");
-
     if (printHistograms) {
       lnPrint("var options = {");
       down();
@@ -122,11 +87,11 @@ public final class SkylarkHtml extends HtmlPrinter {
     down();
     lnPrint("return function() {");
     down();
-    printf("var selection = %s[category].getSelection();", tableVar);
+    printf("var selection = %s[category].getSelection();", JS_TABLE_VAR);
     lnPrint("if (selection.length < 1) return;");
     lnPrint("var item = selection[0];");
-    lnPrintf("var loc = %s[category].getValue(item.row, 0);", dataVar);
-    lnPrintf("var func = %s[category].getValue(item.row, 1);", dataVar);
+    lnPrintf("var loc = %s[category].getValue(item.row, 0);", JS_DATA_VAR);
+    lnPrintf("var func = %s[category].getValue(item.row, 1);", JS_DATA_VAR);
     lnPrint("var histogramDiv = document.getElementById(category+'-histogram');");
     if (printHistograms) {
       lnPrint("var key = loc + '#' + func;");
@@ -151,6 +116,34 @@ public final class SkylarkHtml extends HtmlPrinter {
     lnClose(); // script
   }
 
+  /**
+   * Prints the data for the tables of Skylark function statistics and - if needed - the
+   * histogram data.
+   */
+  void printVisualizationCallbackJs() {
+    printStatsJs(
+        stats.getUserFunctionStatistics(),
+        stats.getUserFunctionSelfStatistics(),
+        "user",
+        stats.getUserTotalNanos());
+    printStatsJs(
+        stats.getBuiltinFunctionStatistics(),
+        stats.getBuiltinFunctionSelfStatistics(),
+        "builtin",
+        stats.getBuiltinTotalNanos());
+
+    if (printHistograms) {
+      printHistogramData();
+
+      lnPrint("document.querySelector('#user-close').onclick = function() {");
+      lnPrint("  document.querySelector('#user-histogram').style.display = 'none';");
+      lnPrint("};");
+      lnPrint("document.querySelector('#builtin-close').onclick = function() {");
+      lnPrint("  document.querySelector('#builtin-histogram').style.display = 'none';");
+      lnPrint("};");
+    }
+  }
+
   private void printHistogramData() {
     lnPrint("histogramData = {");
     down();
@@ -182,10 +175,8 @@ public final class SkylarkHtml extends HtmlPrinter {
       Map<String, TasksStatistics> taskStatistics,
       Map<String, TasksStatistics> taskSelfStatistics,
       String category,
-      String dataVar,
-      String tableVar,
       long totalNanos) {
-    String tmpVar = category + dataVar;
+    String tmpVar = category + JS_DATA_VAR;
     lnPrintf("var statsDiv = document.getElementById('%s_function_stats');", category);
     if (taskStatistics.isEmpty()) {
       lnPrint(
@@ -239,18 +230,18 @@ public final class SkylarkHtml extends HtmlPrinter {
       }
       lnPrint("]);");
       up();
-      lnPrintf("%s.%s = %s;", dataVar, category, tmpVar);
-      lnPrintf("%s.%s = new google.visualization.Table(statsDiv);", tableVar, category);
+      lnPrintf("%s.%s = %s;", JS_DATA_VAR, category, tmpVar);
+      lnPrintf("%s.%s = new google.visualization.Table(statsDiv);", JS_TABLE_VAR, category);
       lnPrintf(
           "google.visualization.events.addListener(%s.%s, 'select', selectHandler('%s'));",
-          tableVar,
+          JS_TABLE_VAR,
           category,
           category);
       lnPrintf(
           "%s.%s.draw(%s.%s, {showRowNumber: true, width: '100%%', height: '100%%'});",
-          tableVar,
+          JS_TABLE_VAR,
           category,
-          dataVar,
+          JS_DATA_VAR,
           category);
     }
   }
diff --git a/src/main/java/com/google/devtools/build/lib/profiler/statistics/MultiProfileStatistics.java b/src/main/java/com/google/devtools/build/lib/profiler/statistics/MultiProfileStatistics.java
new file mode 100644
index 0000000000..a4e8959f44
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/profiler/statistics/MultiProfileStatistics.java
@@ -0,0 +1,124 @@
+// Copyright 2015 The Bazel Authors. All rights reserved.
+//
+// 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.devtools.build.lib.profiler.statistics;
+
+import com.google.devtools.build.lib.profiler.ProfileInfo;
+import com.google.devtools.build.lib.profiler.ProfileInfo.InfoListener;
+import com.google.devtools.build.lib.profiler.ProfilePhase;
+import com.google.devtools.build.lib.vfs.Path;
+
+import java.io.IOException;
+import java.util.EnumMap;
+import java.util.HashMap;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+
+/**
+ * Builds and aggregates statistics for multiple profile files.
+ */
+public final class MultiProfileStatistics implements Iterable<Path> {
+  private final PhaseSummaryStatistics summaryStatistics;
+  private final EnumMap<ProfilePhase, PhaseStatistics> summaryPhaseStatistics;
+  private final Map<Path, EnumMap<ProfilePhase, PhaseStatistics>> filePhaseStatistics;
+  private final SkylarkStatistics skylarkStatistics;
+
+  private int missingActionsCount;
+  private boolean generateVfsStatistics;
+
+  public MultiProfileStatistics(
+      Path workingDirectory,
+      String workSpaceName,
+      List<String> files,
+      InfoListener listener,
+      boolean generateVfsStatistics) {
+    summaryStatistics = new PhaseSummaryStatistics();
+    summaryPhaseStatistics = new EnumMap<>(ProfilePhase.class);
+    filePhaseStatistics = new HashMap<>();
+    skylarkStatistics = new SkylarkStatistics();
+    this.generateVfsStatistics = generateVfsStatistics;
+    for (String file : files) {
+      loadProfileFile(workingDirectory, workSpaceName, file, listener);
+    }
+  }
+
+  public PhaseSummaryStatistics getSummaryStatistics() {
+    return summaryStatistics;
+  }
+
+  public EnumMap<ProfilePhase, PhaseStatistics> getSummaryPhaseStatistics() {
+    return summaryPhaseStatistics;
+  }
+
+  public PhaseStatistics getSummaryPhaseStatistics(ProfilePhase phase) {
+    return summaryPhaseStatistics.get(phase);
+  }
+
+  public SkylarkStatistics getSkylarkStatistics() {
+    return skylarkStatistics;
+  }
+
+  public int getMissingActionsCount() {
+    return missingActionsCount;
+  }
+
+  public EnumMap<ProfilePhase, PhaseStatistics> getPhaseStatistics(Path file) {
+    return filePhaseStatistics.get(file);
+  }
+
+  @Override
+  public Iterator<Path> iterator() {
+    return filePhaseStatistics.keySet().iterator();
+  }
+
+  /**
+   * Loads a single profile file and adds the statistics to the previously collected ones.
+   */
+  private void loadProfileFile(
+      Path workingDirectory, String workSpaceName, String file, InfoListener listener) {
+    ProfileInfo info;
+    Path profileFile = workingDirectory.getRelative(file);
+    try {
+      info = ProfileInfo.loadProfileVerbosely(profileFile, listener);
+      ProfileInfo.aggregateProfile(info, listener);
+    } catch (IOException e) {
+      listener.warn("Ignoring file " + file + " - cannot load: " + e.getMessage());
+      return;
+    }
+
+    summaryStatistics.addProfileInfo(info);
+
+    EnumMap<ProfilePhase, PhaseStatistics> fileStatistics = new EnumMap<>(ProfilePhase.class);
+    filePhaseStatistics.put(profileFile, fileStatistics);
+
+    for (ProfilePhase phase : ProfilePhase.values()) {
+      PhaseStatistics filePhaseStat =
+          new PhaseStatistics(phase, info, workSpaceName, generateVfsStatistics);
+      fileStatistics.put(phase, filePhaseStat);
+
+      PhaseStatistics summaryPhaseStats;
+      if (summaryPhaseStatistics.containsKey(phase)) {
+        summaryPhaseStats = summaryPhaseStatistics.get(phase);
+      } else {
+        summaryPhaseStats = new PhaseStatistics(phase, generateVfsStatistics);
+        summaryPhaseStatistics.put(phase, summaryPhaseStats);
+      }
+      summaryPhaseStats.add(filePhaseStat);
+    }
+
+    skylarkStatistics.addProfileInfo(info);
+
+    missingActionsCount += info.getMissingActionsCount();
+  }
+}
diff --git a/src/main/java/com/google/devtools/build/lib/profiler/statistics/PhaseStatistics.java b/src/main/java/com/google/devtools/build/lib/profiler/statistics/PhaseStatistics.java
index 3f6e326adf..96602a9d39 100644
--- a/src/main/java/com/google/devtools/build/lib/profiler/statistics/PhaseStatistics.java
+++ b/src/main/java/com/google/devtools/build/lib/profiler/statistics/PhaseStatistics.java
@@ -13,6 +13,7 @@
 // limitations under the License.
 package com.google.devtools.build.lib.profiler.statistics;
 
+import com.google.common.base.Preconditions;
 import com.google.common.base.Predicate;
 import com.google.common.collect.Iterators;
 import com.google.devtools.build.lib.profiler.ProfileInfo;
@@ -31,39 +32,92 @@ import java.util.List;
 public final class PhaseStatistics implements Iterable<ProfilerTask> {
 
   private final ProfilePhase phase;
-  private final long phaseDurationNanos;
-  private final long totalDurationNanos;
-  private final EnumMap<ProfilerTask, AggregateAttr> aggregateTaskStatistics;
+  private long phaseDurationNanos;
+  private long totalDurationNanos;
+  private final EnumMap<ProfilerTask, Long> taskDurations;
+  private final EnumMap<ProfilerTask, Long> taskCounts;
   private final PhaseVfsStatistics vfsStatistics;
-  private final boolean wasExecuted;
+  private boolean wasExecuted;
+  private int count;
 
-  public PhaseStatistics(ProfilePhase phase, ProfileInfo info, String workSpaceName) {
+  public PhaseStatistics(ProfilePhase phase, boolean generateVfsStatistics) {
     this.phase = phase;
-    this.aggregateTaskStatistics = new EnumMap<>(ProfilerTask.class);
-    Task phaseTask = info.getPhaseTask(phase);
-    vfsStatistics = new PhaseVfsStatistics(workSpaceName, phase, info);
-    if (phaseTask == null) {
-      wasExecuted = false;
-      totalDurationNanos = 0;
-      phaseDurationNanos = 0;
+    this.taskDurations = new EnumMap<>(ProfilerTask.class);
+    this.taskCounts = new EnumMap<>(ProfilerTask.class);
+    if (generateVfsStatistics) {
+      vfsStatistics = new PhaseVfsStatistics(phase);
     } else {
+      vfsStatistics = null;
+    }
+  }
+
+  public PhaseStatistics(ProfilePhase phase, ProfileInfo info, String workSpaceName, boolean vfs) {
+    this(phase, vfs);
+    addProfileInfo(workSpaceName, info);
+  }
+
+  /**
+   * Add statistics from {@link ProfileInfo} to the ones already accumulated for this phase.
+   */
+  public void addProfileInfo(String workSpaceName, ProfileInfo info) {
+    Task phaseTask = info.getPhaseTask(phase);
+    if (phaseTask != null) {
+      if (vfsStatistics != null) {
+        vfsStatistics.addProfileInfo(workSpaceName, info);
+      }
       wasExecuted = true;
-      phaseDurationNanos = info.getPhaseDuration(phaseTask);
+      long infoPhaseDuration = info.getPhaseDuration(phaseTask);
+      phaseDurationNanos += infoPhaseDuration;
       List<Task> taskList = info.getTasksForPhase(phaseTask);
-      long duration = phaseDurationNanos;
+      long duration = infoPhaseDuration;
       for (Task task : taskList) {
         // Tasks on the phaseTask thread already accounted for in the phaseDuration.
         if (task.threadId != phaseTask.threadId) {
           duration += task.durationNanos;
         }
       }
-      totalDurationNanos = duration;
+      totalDurationNanos += duration;
       for (ProfilerTask type : ProfilerTask.values()) {
-        aggregateTaskStatistics.put(type, info.getStatsForType(type, taskList));
+        AggregateAttr attr = info.getStatsForType(type, taskList);
+        long totalTime = Math.max(0, attr.totalTime);
+        long count = Math.max(0, attr.count);
+        add(taskCounts, type, count);
+        add(taskDurations, type, totalTime);
       }
+      count++;
     }
   }
 
+  /**
+   * Add statistics accumulated in another PhaseStatistics object to this one.
+   */
+  public void add(PhaseStatistics other) {
+    Preconditions.checkArgument(
+        phase == other.phase, "Should not combine statistics from different phases");
+    if (other.wasExecuted) {
+      if (vfsStatistics != null && other.vfsStatistics != null) {
+        vfsStatistics.add(other.vfsStatistics);
+      }
+      wasExecuted = true;
+      phaseDurationNanos += other.phaseDurationNanos;
+      totalDurationNanos += other.totalDurationNanos;
+      for (ProfilerTask type : other) {
+        long otherCount = other.getCount(type);
+        long otherDuration = other.getTotalDurationNanos(type);
+        add(taskCounts, type, otherCount);
+        add(taskDurations, type, otherDuration);
+      }
+      count++;
+    }
+  }
+
+  /**
+   * @return how many executions of this phase were accumulated
+   */
+  public int getPhaseCount() {
+    return count;
+  }
+
   public ProfilePhase getProfilePhase() {
     return phase;
   }
@@ -76,7 +130,7 @@ public final class PhaseStatistics implements Iterable<ProfilerTask> {
    * @return true if no {@link ProfilerTask}s have been executed in this phase, false otherwise
    */
   public boolean isEmpty() {
-    return aggregateTaskStatistics.isEmpty();
+    return taskCounts.isEmpty();
   }
 
   /**
@@ -98,14 +152,19 @@ public final class PhaseStatistics implements Iterable<ProfilerTask> {
    * @return true if a task of the given {@link ProfilerTask} type was executed in this phase
    */
   public boolean wasExecuted(ProfilerTask taskType) {
-    return aggregateTaskStatistics.get(taskType).count != 0;
+    Long count = taskCounts.get(taskType);
+    return count != null && count != 0;
   }
 
   /**
    * @return the sum of all task durations of the given type
    */
   public long getTotalDurationNanos(ProfilerTask taskType) {
-    return aggregateTaskStatistics.get(taskType).totalTime;
+    Long duration = taskDurations.get(taskType);
+    if (duration == null) {
+      return 0;
+    }
+    return duration;
   }
 
   /**
@@ -113,8 +172,9 @@ public final class PhaseStatistics implements Iterable<ProfilerTask> {
    */
   public double getMeanDuration(ProfilerTask taskType) {
     if (wasExecuted(taskType)) {
-      AggregateAttr stats = aggregateTaskStatistics.get(taskType);
-      return (double) stats.totalTime / stats.count;
+      double duration = taskDurations.get(taskType);
+      long count = taskCounts.get(taskType);
+      return duration / count;
     }
     return 0;
   }
@@ -124,17 +184,30 @@ public final class PhaseStatistics implements Iterable<ProfilerTask> {
    *    phase duration
    */
   public double getTotalRelativeDuration(ProfilerTask taskType) {
-    if (wasExecuted(taskType)) {
-      return (double) aggregateTaskStatistics.get(taskType).totalTime / totalDurationNanos;
+    Long duration = taskDurations.get(taskType);
+    if (duration == null || duration == 0) {
+      return 0;
     }
-    return 0;
+    // sanity check for broken profile files
+    Preconditions.checkState(
+        totalDurationNanos != 0,
+        "Profiler tasks of type %s have non-zero duration %s in phase %s but the phase itself has"
+        + " zero duration. Most likely the profile file is broken.",
+        taskType,
+        duration,
+        phase);
+    return (double) duration / totalDurationNanos;
   }
 
   /**
    * @return how many tasks of the given type were executed in this phase
    */
-  public int getCount(ProfilerTask taskType) {
-    return aggregateTaskStatistics.get(taskType).count;
+  public long getCount(ProfilerTask taskType) {
+    Long count = taskCounts.get(taskType);
+    if (count == null) {
+      return 0;
+    }
+    return count;
   }
 
   /**
@@ -144,14 +217,26 @@ public final class PhaseStatistics implements Iterable<ProfilerTask> {
   @Override
   public Iterator<ProfilerTask> iterator() {
     return Iterators.filter(
-        aggregateTaskStatistics.keySet().iterator(),
+        taskCounts.keySet().iterator(),
         new Predicate<ProfilerTask>() {
           @Override
           public boolean apply(ProfilerTask taskType) {
-
-            return getTotalDurationNanos(taskType) != 0 && getCount(taskType) != 0;
+            return getTotalDurationNanos(taskType) > 0 && wasExecuted(taskType);
           }
         });
   }
+
+  /**
+   * Helper method to sum up long values within an {@link EnumMap}.
+   */
+  private static <T extends Enum<T>> void add(EnumMap<T, Long> map, T key, long value) {
+    long previous;
+    if (map.containsKey(key)) {
+      previous = map.get(key);
+    } else {
+      previous = 0;
+    }
+    map.put(key, previous + value);
+  }
 }
 
diff --git a/src/main/java/com/google/devtools/build/lib/profiler/statistics/PhaseSummaryStatistics.java b/src/main/java/com/google/devtools/build/lib/profiler/statistics/PhaseSummaryStatistics.java
index 965cd78828..59032b13ef 100644
--- a/src/main/java/com/google/devtools/build/lib/profiler/statistics/PhaseSummaryStatistics.java
+++ b/src/main/java/com/google/devtools/build/lib/profiler/statistics/PhaseSummaryStatistics.java
@@ -26,21 +26,31 @@ import java.util.NoSuchElementException;
  */
 public final class PhaseSummaryStatistics implements Iterable<ProfilePhase> {
 
-  private final long totalDurationNanos;
+  private long totalDurationNanos;
   private final EnumMap<ProfilePhase, Long> durations;
 
-  public PhaseSummaryStatistics(ProfileInfo info) {
+  public PhaseSummaryStatistics() {
     durations = new EnumMap<>(ProfilePhase.class);
-    long totalDuration = 0;
+    totalDurationNanos = 0;
+  }
+
+  public PhaseSummaryStatistics(ProfileInfo info) {
+    this();
+    addProfileInfo(info);
+  }
+
+  /**
+   * Add a summary of the {@link ProfilePhase}s durations from a {@link ProfileInfo}.
+   */
+  public void addProfileInfo(ProfileInfo info) {
     for (ProfilePhase phase : ProfilePhase.values()) {
       ProfileInfo.Task phaseTask = info.getPhaseTask(phase);
       if (phaseTask != null) {
         long phaseDuration = info.getPhaseDuration(phaseTask);
-        totalDuration += phaseDuration;
+        totalDurationNanos += phaseDuration;
         durations.put(phase, phaseDuration);
       }
     }
-    totalDurationNanos = totalDuration;
   }
 
   /**
diff --git a/src/main/java/com/google/devtools/build/lib/profiler/statistics/PhaseVfsStatistics.java b/src/main/java/com/google/devtools/build/lib/profiler/statistics/PhaseVfsStatistics.java
index 4c52c47eb5..58d454f368 100644
--- a/src/main/java/com/google/devtools/build/lib/profiler/statistics/PhaseVfsStatistics.java
+++ b/src/main/java/com/google/devtools/build/lib/profiler/statistics/PhaseVfsStatistics.java
@@ -13,10 +13,12 @@
 // limitations under the License.
 package com.google.devtools.build.lib.profiler.statistics;
 
-import com.google.common.collect.Maps;
-import com.google.common.collect.Multimaps;
-import com.google.common.collect.Ordering;
-import com.google.common.collect.TreeMultimap;
+import com.google.common.base.Supplier;
+import com.google.common.collect.ComparisonChain;
+import com.google.common.collect.ImmutableSortedSet;
+import com.google.common.collect.Table;
+import com.google.common.collect.Table.Cell;
+import com.google.common.collect.Tables;
 import com.google.devtools.build.lib.profiler.ProfileInfo;
 import com.google.devtools.build.lib.profiler.ProfileInfo.Task;
 import com.google.devtools.build.lib.profiler.ProfilePhase;
@@ -28,7 +30,8 @@ import java.util.HashMap;
 import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
-import java.util.Map.Entry;
+import java.util.Objects;
+import java.util.SortedSet;
 
 /**
  * Compute and store statistics of all {@link ProfilerTask}s that begin with VFS_ in sorted order.
@@ -36,34 +39,98 @@ import java.util.Map.Entry;
 public final class PhaseVfsStatistics implements Iterable<ProfilerTask> {
 
   /**
-   * Pair of duration and count for sorting by duration first and count in case of tie
+   * Duration, count and path for sorting by duration first and count in case of tie. Path for
+   * easy returning of a {@link SortedSet}.
    */
-  public static class Stat implements Comparable<Stat> {
-    public long duration;
-    public long count;
+  public static final class Stat implements Comparable<Stat> {
+    private long duration;
+    private long count;
+    public final String path;
 
+    public Stat(String path) {
+      this.path = path;
+    }
+
+    public Stat(Stat other) {
+      this.duration = other.duration;
+      this.count = other.count;
+      this.path = other.path;
+    }
+
+    public long getDuration() {
+      return duration;
+    }
+
+    public long getCount() {
+      return count;
+    }
+
+    private void add(Stat other) {
+      this.duration += other.duration;
+      this.count += other.count;
+    }
+
+    private void add(long duration) {
+      this.duration += duration;
+      this.count++;
+    }
+
+    /**
+     * Order first by duration, then count, then path
+     */
     @Override
     public int compareTo(Stat o) {
-      return this.duration == o.duration
-          ? Long.compare(this.count, o.count)
-          : Long.compare(this.duration, o.duration);
+      return ComparisonChain.start()
+          .compare(duration, o.duration)
+          .compare(count, o.count)
+          .compare(path, o.path)
+          .result();
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+      if (obj instanceof Stat) {
+        return compareTo((Stat) obj) == 0;
+      }
+      return false;
+    }
+
+    @Override
+    public int hashCode() {
+      return Objects.hash(duration, count, path);
     }
   }
 
   private final ProfilePhase phase;
-  private final EnumMap<ProfilerTask, TreeMultimap<Stat, String>> sortedStatistics;
-  private final String workSpaceName;
+  private final Table<ProfilerTask, String, Stat> statistics;
 
-  public PhaseVfsStatistics(final String workSpaceName, ProfilePhase phase, ProfileInfo info) {
-    this.workSpaceName = workSpaceName;
+  public PhaseVfsStatistics(ProfilePhase phase) {
     this.phase = phase;
-    this.sortedStatistics = Maps.newEnumMap(ProfilerTask.class);
+    this.statistics =
+        Tables.newCustomTable(
+            new EnumMap<ProfilerTask, Map<String, Stat>>(ProfilerTask.class),
+            new Supplier<Map<String, Stat>>() {
+              @Override
+              public Map<String, Stat> get() {
+                return new HashMap<>();
+              }
+            });
+  }
+
+  public PhaseVfsStatistics(final String workSpaceName, ProfilePhase phase, ProfileInfo info) {
+    this(phase);
+    addProfileInfo(workSpaceName, info);
+  }
 
+  /**
+   * Accumulate statistics from another {@link ProfileInfo} in this object.
+   */
+  public void addProfileInfo(final String workSpaceName, ProfileInfo info) {
     Task phaseTask = info.getPhaseTask(phase);
     if (phaseTask == null) {
       return;
     }
-    collectVfsEntries(info.getTasksForPhase(phaseTask));
+    collectVfsEntries(workSpaceName, info.getTasksForPhase(phaseTask));
   }
 
   public ProfilePhase getProfilePhase() {
@@ -71,63 +138,66 @@ public final class PhaseVfsStatistics implements Iterable<ProfilerTask> {
   }
 
   public boolean isEmpty() {
-    return sortedStatistics.isEmpty();
+    return statistics.isEmpty();
   }
 
-  public Iterable<Entry<Stat, String>> getSortedStatistics(ProfilerTask taskType) {
-    return sortedStatistics.get(taskType).entries();
+  /**
+   * Builds a new {@link ImmutableSortedSet} of the path statistics for the given
+   * {@link ProfilerTask}.
+   *
+   * <p>{@link Stat}s are sorted by their natural order.
+   */
+  public ImmutableSortedSet<Stat> getSortedStatistics(ProfilerTask taskType) {
+    return ImmutableSortedSet.copyOf(statistics.row(taskType).values());
   }
 
   public int getStatisticsCount(ProfilerTask taskType) {
-    return sortedStatistics.get(taskType).size();
+    return statistics.row(taskType).size();
   }
 
   @Override
   public Iterator<ProfilerTask> iterator() {
-    return sortedStatistics.keySet().iterator();
+    return statistics.rowKeySet().iterator();
   }
 
   /**
-   * Group into VFS operations and build maps from path to duration.
+   * Add statistics from another PhaseVfsStatistics aggregation to this one.
    */
-  private void collectVfsEntries(List<Task> taskList) {
-    EnumMap<ProfilerTask, Map<String, Stat>> stats = Maps.newEnumMap(ProfilerTask.class);
+  public void add(PhaseVfsStatistics other) {
+    for (Cell<ProfilerTask, String, Stat> cell : other.statistics.cellSet()) {
+      Stat stat = statistics.get(cell.getRowKey(), cell.getColumnKey());
+      if (stat == null) {
+        stat = new Stat(cell.getValue());
+        statistics.put(cell.getRowKey(), stat.path, stat);
+      } else {
+        stat.add(cell.getValue());
+      }
+    }
+  }
+
+  /**
+   * Add the VFS operations from the list of tasks to the {@link #statistics} table
+   */
+  private void collectVfsEntries(String workSpaceName, List<Task> taskList) {
     for (Task task : taskList) {
-      collectVfsEntries(Arrays.asList(task.subtasks));
+      collectVfsEntries(workSpaceName, Arrays.asList(task.subtasks));
       if (!task.type.name().startsWith("VFS_")) {
         continue;
       }
 
-      Map<String, Stat> statsForType = stats.get(task.type);
-      if (statsForType == null) {
-        statsForType = new HashMap<>();
-        stats.put(task.type, statsForType);
-      }
-
-      String path = currentPathMapping(task.getDescription());
+      String path = pathMapping(workSpaceName, task.getDescription());
 
-      Stat stat = statsForType.get(path);
+      Stat stat = statistics.get(task.type, path);
       if (stat == null) {
-        stat = new Stat();
+        stat = new Stat(path);
+        statistics.put(task.type, path, stat);
       }
 
-      stat.duration += task.durationNanos;
-      stat.count++;
-      statsForType.put(path, stat);
-    }
-    // Reverse the maps to get maps from duration to path. We use a TreeMultimap to sort by
-    // duration and because durations are not unique.
-    for (ProfilerTask type : stats.keySet()) {
-      Map<String, Stat> statsForType = stats.get(type);
-      TreeMultimap<Stat, String> sortedStats =
-          TreeMultimap.create(Ordering.natural().reverse(), Ordering.natural());
-
-      Multimaps.invertFrom(Multimaps.forMap(statsForType), sortedStats);
-      sortedStatistics.put(type, sortedStats);
+      stat.add(task.durationNanos);
     }
   }
 
-  private String currentPathMapping(String input) {
+  private String pathMapping(String workSpaceName, String input) {
     if (workSpaceName.isEmpty()) {
       return input;
     } else {
diff --git a/src/main/java/com/google/devtools/build/lib/runtime/commands/ProfileCommand.java b/src/main/java/com/google/devtools/build/lib/runtime/commands/ProfileCommand.java
index 30eeb76111..b21d7ca20d 100644
--- a/src/main/java/com/google/devtools/build/lib/runtime/commands/ProfileCommand.java
+++ b/src/main/java/com/google/devtools/build/lib/runtime/commands/ProfileCommand.java
@@ -26,6 +26,7 @@ import com.google.devtools.build.lib.profiler.ProfilerTask;
 import com.google.devtools.build.lib.profiler.output.HtmlCreator;
 import com.google.devtools.build.lib.profiler.output.PhaseText;
 import com.google.devtools.build.lib.profiler.statistics.CriticalPathStatistics;
+import com.google.devtools.build.lib.profiler.statistics.MultiProfileStatistics;
 import com.google.devtools.build.lib.profiler.statistics.PhaseStatistics;
 import com.google.devtools.build.lib.profiler.statistics.PhaseSummaryStatistics;
 import com.google.devtools.build.lib.runtime.BlazeCommand;
@@ -42,6 +43,7 @@ import com.google.devtools.common.options.OptionsBase;
 import com.google.devtools.common.options.OptionsParser;
 import com.google.devtools.common.options.OptionsProvider;
 
+import java.io.BufferedOutputStream;
 import java.io.IOException;
 import java.io.PrintStream;
 import java.util.EnumMap;
@@ -75,6 +77,16 @@ public final class ProfileCommand implements BlazeCommand {
     )
     public boolean chart;
 
+    @Option(
+      name = "combine",
+      defaultValue = "null",
+      help =
+          "If present, the statistics of all given profile files will be combined and output"
+              + " in text/--html format to the file named in the argument. Does not output HTML"
+              + " task charts."
+    )
+    public String combine;
+
     @Option(name = "dump",
         abbrev='d',
         converter = DumpConverter.class,
@@ -178,65 +190,102 @@ public final class ProfileCommand implements BlazeCommand {
       env.getReporter().handle(Event.warn(
           null, "This information is intended for consumption by Blaze developers"
               + " only, and may change at any time.  Script against it at your own risk"));
-
-      for (String name : options.getResidue()) {
-        Path profileFile = runtime.getWorkingDirectory().getRelative(name);
-        try {
-          ProfileInfo info = ProfileInfo.loadProfileVerbosely(
-              profileFile, getInfoListener(env));
-
-          if (opts.dumpMode == null || !opts.dumpMode.contains("unsorted")) {
-            ProfileInfo.aggregateProfile(info, getInfoListener(env));
-          }
-
-          if (opts.taskTree != null) {
-            printTaskTree(out, name, info, opts.taskTree, opts.taskTreeThreshold);
-            continue;
-          }
-
-          if (opts.dumpMode != null) {
-            dumpProfile(info, out, opts.dumpMode);
-            continue;
-          }
-
-          PhaseSummaryStatistics phaseSummaryStatistics = new PhaseSummaryStatistics(info);
-          EnumMap<ProfilePhase, PhaseStatistics> phaseStatistics =
-              new EnumMap<>(ProfilePhase.class);
-          for (ProfilePhase phase : ProfilePhase.values()) {
-            phaseStatistics.put(
-                phase, new PhaseStatistics(phase, info, runtime.getWorkspaceName()));
-          }
-
+      if (opts.combine != null && opts.dumpMode == null) {
+        MultiProfileStatistics statistics =
+            new MultiProfileStatistics(
+                runtime.getWorkingDirectory(),
+                runtime.getWorkspaceName(),
+                options.getResidue(),
+                getInfoListener(env),
+                opts.vfsStatsLimit > 0);
+        Path outputFile = runtime.getWorkingDirectory().getRelative(opts.combine);
+        try (PrintStream output =
+                new PrintStream(new BufferedOutputStream(outputFile.getOutputStream()))) {
           if (opts.html) {
-            Path htmlFile =
-                profileFile.getParentDirectory().getChild(profileFile.getBaseName() + ".html");
-
-            env.getReporter().handle(Event.info("Creating HTML output in " + htmlFile));
-
+            env.getReporter().handle(Event.info("Creating HTML output in " + outputFile));
             HtmlCreator.create(
-                info,
-                htmlFile,
-                phaseSummaryStatistics,
-                phaseStatistics,
-                opts.htmlDetails,
-                opts.htmlPixelsPerSecond,
-                opts.vfsStatsLimit,
-                opts.chart,
-                opts.htmlHistograms);
+                output, statistics, opts.htmlDetails, opts.htmlPixelsPerSecond, opts.vfsStatsLimit);
           } else {
-            CriticalPathStatistics critPathStats = new CriticalPathStatistics(info);
+            env.getReporter().handle(Event.info("Creating text output in " + outputFile));
             new PhaseText(
-                    out,
-                    phaseSummaryStatistics,
-                    phaseStatistics,
-                    Optional.of(critPathStats),
-                    info.getMissingActionsCount(),
+                    output,
+                    statistics.getSummaryStatistics(),
+                    statistics.getSummaryPhaseStatistics(),
+                    Optional.<CriticalPathStatistics>absent(),
+                    statistics.getMissingActionsCount(),
                     opts.vfsStatsLimit)
                 .print();
           }
         } catch (IOException e) {
-          env.getReporter().handle(Event.error(
-              null, "Failed to process file " + name + ": " + e.getMessage()));
+          env
+              .getReporter()
+              .handle(
+                  Event.error(
+                      "Failed to write to output file " + outputFile + ":" + e.getMessage()));
+        }
+      } else {
+        for (String name : options.getResidue()) {
+          Path profileFile = runtime.getWorkingDirectory().getRelative(name);
+          try {
+            ProfileInfo info = ProfileInfo.loadProfileVerbosely(profileFile, getInfoListener(env));
+
+            if (opts.dumpMode == null || !opts.dumpMode.contains("unsorted")) {
+              ProfileInfo.aggregateProfile(info, getInfoListener(env));
+            }
+
+            if (opts.taskTree != null) {
+              printTaskTree(out, name, info, opts.taskTree, opts.taskTreeThreshold);
+              continue;
+            }
+
+            if (opts.dumpMode != null) {
+              dumpProfile(info, out, opts.dumpMode);
+              continue;
+            }
+
+            PhaseSummaryStatistics phaseSummaryStatistics = new PhaseSummaryStatistics(info);
+            EnumMap<ProfilePhase, PhaseStatistics> phaseStatistics =
+                new EnumMap<>(ProfilePhase.class);
+            for (ProfilePhase phase : ProfilePhase.values()) {
+              phaseStatistics.put(
+                  phase,
+                  new PhaseStatistics(
+                      phase, info, runtime.getWorkspaceName(), opts.vfsStatsLimit > 0));
+            }
+
+            if (opts.html) {
+              Path htmlFile =
+                  profileFile.getParentDirectory().getChild(profileFile.getBaseName() + ".html");
+
+              env.getReporter().handle(Event.info("Creating HTML output in " + htmlFile));
+
+              HtmlCreator.create(
+                  info,
+                  htmlFile,
+                  phaseSummaryStatistics,
+                  phaseStatistics,
+                  opts.htmlDetails,
+                  opts.htmlPixelsPerSecond,
+                  opts.vfsStatsLimit,
+                  opts.chart,
+                  opts.htmlHistograms);
+            } else {
+              CriticalPathStatistics critPathStats = new CriticalPathStatistics(info);
+              new PhaseText(
+                      out,
+                      phaseSummaryStatistics,
+                      phaseStatistics,
+                      Optional.of(critPathStats),
+                      info.getMissingActionsCount(),
+                      opts.vfsStatsLimit)
+                  .print();
+            }
+          } catch (IOException e) {
+            System.out.println(e);
+            env
+                .getReporter()
+                .handle(Event.error("Failed to analyze profile file(s): " + e.getMessage()));
+          }
         }
       }
     }
diff --git a/src/main/java/com/google/devtools/build/lib/util/TimeUtilities.java b/src/main/java/com/google/devtools/build/lib/util/TimeUtilities.java
index 13de97cc82..2a1fbebc72 100644
--- a/src/main/java/com/google/devtools/build/lib/util/TimeUtilities.java
+++ b/src/main/java/com/google/devtools/build/lib/util/TimeUtilities.java
@@ -14,6 +14,8 @@
 
 package com.google.devtools.build.lib.util;
 
+import java.util.concurrent.TimeUnit;
+
 /**
  * Various utility methods operating on time values.
  */
@@ -38,4 +40,14 @@ public class TimeUtilities {
     }
     return String.format("%.3f s", ms / 1000.0);
   }
+
+  /**
+   * Convert nanoseconds to milliseconds.
+   *
+   * <p>This is different from the methods in {@link TimeUnit} in that it returns and accepts a
+   * double.
+   */
+  public static double nanosToMillis(double timeNanos) {
+    return timeNanos / 1000000;
+  }
 }