Re-add WalkableGraph#isUpToDate and BuildDriver#alreadyEvaluated

RELNOTES: None
PiperOrigin-RevId: 182389876

5 files changed, 35 insertions, 5 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/query2/SkyQueryEnvironment.java b/src/main/java/com/google/devtools/build/lib/query2/SkyQueryEnvironment.java
index 883047e1a6..03341de629 100644
--- a/src/main/java/com/google/devtools/build/lib/query2/SkyQueryEnvironment.java
+++ b/src/main/java/com/google/devtools/build/lib/query2/SkyQueryEnvironment.java
@@ -249,20 +249,26 @@ public class SkyQueryEnvironment extends AbstractBlazeQueryEnvironment<Target>
       throws QueryException, InterruptedException {
     Set<SkyKey> roots = getGraphRootsFromExpression(expr);
 
-    EvaluationResult<SkyValue> result;
-    try (AutoProfiler p = AutoProfiler.logged("evaluation and walkable graph", logger)) {
-      result = graphFactory.prepareAndGet(roots, loadingPhaseThreads, universeEvalEventHandler);
-    }
+    if (graph == null || !graphFactory.isUpToDate(roots)) {
+      // If this environment is uninitialized or the graph factory needs to evaluate, do so. We
+      // assume here that this environment cannot be initialized-but-stale if the factory is up
+      // to date.
+      EvaluationResult<SkyValue> result;
+      try (AutoProfiler p = AutoProfiler.logged("evaluation and walkable graph", logger)) {
+        result = graphFactory.prepareAndGet(roots, loadingPhaseThreads, universeEvalEventHandler);
+      }
 
-    if (graph == null || graph != result.getWalkableGraph()) {
       checkEvaluationResult(roots, result);
+
       packageSemaphore = makeFreshPackageMultisetSemaphore();
       graph = result.getWalkableGraph();
       blacklistPatternsSupplier = InterruptibleSupplier.Memoize.of(new BlacklistSupplier(graph));
+
       graphBackedRecursivePackageProvider =
           new GraphBackedRecursivePackageProvider(graph, universeTargetPatternKeys, pkgPath);
     }
 
+
     if (executor == null) {
       executor = MoreExecutors.listeningDecorator(
           new ThreadPoolExecutor(
diff --git a/src/main/java/com/google/devtools/build/lib/skyframe/SkyframeExecutor.java b/src/main/java/com/google/devtools/build/lib/skyframe/SkyframeExecutor.java
index 52687e2c43..58f557c96f 100644
--- a/src/main/java/com/google/devtools/build/lib/skyframe/SkyframeExecutor.java
+++ b/src/main/java/com/google/devtools/build/lib/skyframe/SkyframeExecutor.java
@@ -1762,6 +1762,11 @@ public abstract class SkyframeExecutor implements WalkableGraphFactory {
     return evaluationResult;
   }
 
+  @Override
+  public boolean isUpToDate(Set<SkyKey> roots) {
+    return buildDriver.alreadyEvaluated(roots);
+  }
+
   /**
    * Get metadata related to the prepareAndGet() lookup. Resulting data is specific to the
    * underlying evaluation implementation.
diff --git a/src/main/java/com/google/devtools/build/skyframe/BuildDriver.java b/src/main/java/com/google/devtools/build/skyframe/BuildDriver.java
index d1f942e0c7..78c24793c6 100644
--- a/src/main/java/com/google/devtools/build/skyframe/BuildDriver.java
+++ b/src/main/java/com/google/devtools/build/skyframe/BuildDriver.java
@@ -37,6 +37,13 @@ public interface BuildDriver {
   String meta(Iterable<SkyKey> roots, OptionsClassProvider options)
       throws AbruptExitException, InterruptedException;
 
+  /**
+   * Returns true if this {@link BuildDriver} instance has already been used to {@link #evaluate}
+   * the given {@code roots} at the Version that would be passed along to the next call to {@link
+   * MemoizingEvaluator#evaluate} in {@link #evaluate}.
+   */
+  boolean alreadyEvaluated(Iterable<SkyKey> roots);
+
   MemoizingEvaluator getGraphForTesting();
 
   @Nullable
diff --git a/src/main/java/com/google/devtools/build/skyframe/SequentialBuildDriver.java b/src/main/java/com/google/devtools/build/skyframe/SequentialBuildDriver.java
index 51724cdc05..8a42189407 100644
--- a/src/main/java/com/google/devtools/build/skyframe/SequentialBuildDriver.java
+++ b/src/main/java/com/google/devtools/build/skyframe/SequentialBuildDriver.java
@@ -48,6 +48,11 @@ public class SequentialBuildDriver implements BuildDriver {
   }
 
   @Override
+  public boolean alreadyEvaluated(Iterable<SkyKey> roots) {
+    return false;
+  }
+
+  @Override
   public MemoizingEvaluator getGraphForTesting() {
     return memoizingEvaluator;
   }
diff --git a/src/main/java/com/google/devtools/build/skyframe/WalkableGraph.java b/src/main/java/com/google/devtools/build/skyframe/WalkableGraph.java
index a55bbc5415..b5b744f6af 100644
--- a/src/main/java/com/google/devtools/build/skyframe/WalkableGraph.java
+++ b/src/main/java/com/google/devtools/build/skyframe/WalkableGraph.java
@@ -103,6 +103,13 @@ public interface WalkableGraph {
         Set<SkyKey> roots, int numThreads, ExtendedEventHandler eventHandler)
         throws InterruptedException;
 
+    /**
+     * Returns true if this instance has already been used to {@link #prepareAndGet} {@code roots}.
+     * If so, cached results from {@link #prepareAndGet} can be re-used safely, potentially saving
+     * some processing time.
+     */
+    boolean isUpToDate(Set<SkyKey> roots);
+
     /** Returns the {@link SkyKey} that defines this universe. */
     SkyKey getUniverseKey(Collection<String> roots, String offset);
   }