Improve artifact->owner label accounting in two ways. First, don't do the full mapping unless requested. This gets rid of any performance issue for the vast majority of builds. Second, if requested, use a custom data structure so that we don't have to create a full HashSet for artifacts whose only owning labels are their own owner labels.

PiperOrigin-RevId: 206610370
diff --git a/src/main/java/com/google/devtools/build/lib/buildtool/ExecutionTool.java b/src/main/java/com/google/devtools/build/lib/buildtool/ExecutionTool.java
index 44a5fd7..9a31023 100644
--- a/src/main/java/com/google/devtools/build/lib/buildtool/ExecutionTool.java
+++ b/src/main/java/com/google/devtools/build/lib/buildtool/ExecutionTool.java
@@ -18,15 +18,14 @@
 import com.google.common.base.Preconditions;
 import com.google.common.base.Predicate;
 import com.google.common.base.Stopwatch;
+import com.google.common.base.Suppliers;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.ImmutableSet;
-import com.google.common.collect.SetMultimap;
 import com.google.devtools.build.lib.actions.Action;
 import com.google.devtools.build.lib.actions.ActionCacheChecker;
 import com.google.devtools.build.lib.actions.ActionGraph;
 import com.google.devtools.build.lib.actions.ActionInputPrefetcher;
-import com.google.devtools.build.lib.actions.Artifact;
 import com.google.devtools.build.lib.actions.ArtifactFactory;
 import com.google.devtools.build.lib.actions.BuildFailedException;
 import com.google.devtools.build.lib.actions.ExecException;
@@ -49,7 +48,6 @@
 import com.google.devtools.build.lib.analysis.config.BuildConfiguration;
 import com.google.devtools.build.lib.buildtool.buildevent.ExecutionPhaseCompleteEvent;
 import com.google.devtools.build.lib.buildtool.buildevent.ExecutionStartingEvent;
-import com.google.devtools.build.lib.cmdline.Label;
 import com.google.devtools.build.lib.cmdline.PackageIdentifier;
 import com.google.devtools.build.lib.events.Event;
 import com.google.devtools.build.lib.events.EventHandler;
@@ -311,16 +309,17 @@
     }
     boolean buildCompleted = false;
     try {
-      SetMultimap<Artifact, Label> topLevelArtifactsToOwnerLabels =
-          TopLevelArtifactHelper.makeTopLevelArtifactsToOwnerLabels(analysisResult, aspects);
       for (ActionContextProvider actionContextProvider : actionContextProviders) {
         try (SilentCloseable c =
             Profiler.instance().profile(actionContextProvider + ".executionPhaseStarting")) {
-          actionContextProvider.executionPhaseStarting(actionGraph, topLevelArtifactsToOwnerLabels);
+          actionContextProvider.executionPhaseStarting(
+              actionGraph,
+              Suppliers.memoize(
+                  () ->
+                      TopLevelArtifactHelper.makeTopLevelArtifactsToOwnerLabels(
+                          analysisResult, aspects)));
         }
       }
-      // Don't retain memory.
-      topLevelArtifactsToOwnerLabels = null;
       executor.executionPhaseStarting();
       skyframeExecutor.drainChangedFiles();
 
@@ -341,7 +340,7 @@
 
       builder.buildArtifacts(
           env.getReporter(),
-          analysisResult.getTopLevelArtifactsToOwnerLabels().keySet(),
+          analysisResult.getTopLevelArtifactsToOwnerLabels().getArtifacts(),
           analysisResult.getParallelTests(),
           analysisResult.getExclusiveTests(),
           analysisResult.getTargetsToBuild(),