From 4e0a5cb6209952ff9d83b9aa41d68c133ea4a964 Mon Sep 17 00:00:00 2001
From: Googler <noreply@google.com>
Date: Sun, 9 Apr 2017 17:58:18 -0400
Subject: Optimize TransitiveInfoMap memory consumption.

Instead of using ImmutableMap, we share the keys between all provider maps with an identical key set.

PiperOrigin-RevId: 155432135
---
 .../TransitiveInfoProviderMapOffsetBased.java      | 127 +++++++++++++++++++++
 1 file changed, 127 insertions(+)
 create mode 100644 src/main/java/com/google/devtools/build/lib/analysis/TransitiveInfoProviderMapOffsetBased.java

(limited to 'src/main/java/com/google/devtools/build/lib/analysis/TransitiveInfoProviderMapOffsetBased.java')

diff --git a/src/main/java/com/google/devtools/build/lib/analysis/TransitiveInfoProviderMapOffsetBased.java b/src/main/java/com/google/devtools/build/lib/analysis/TransitiveInfoProviderMapOffsetBased.java
new file mode 100644
index 0000000000..a36a3e14be
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/analysis/TransitiveInfoProviderMapOffsetBased.java
@@ -0,0 +1,127 @@
+// Copyright 2017 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.analysis;
+
+import com.google.common.collect.ImmutableMap;
+import com.google.common.collect.Interner;
+import com.google.devtools.build.lib.concurrent.BlazeInterners;
+import java.util.Arrays;
+import java.util.Map.Entry;
+import javax.annotation.Nullable;
+import javax.annotation.concurrent.Immutable;
+
+/**
+ * Provides a mapping between a TransitiveInfoProvider class and an instance.
+ *
+ * <p>This class implements a map where it is expected that a lot of the key sets will be the same.
+ * These key sets are shared and an offset table of indices is computed. Each provider map instance
+ * thus contains only a reference to the shared offset table, and a plain array of providers.
+ */
+@Immutable
+final class TransitiveInfoProviderMapOffsetBased implements TransitiveInfoProviderMap {
+  private static final Interner<OffsetTable> offsetTables = BlazeInterners.newWeakInterner();
+
+  private final OffsetTable offsetTable;
+  private final TransitiveInfoProvider[] providers;
+
+  private static final class OffsetTable {
+    private final Class<? extends TransitiveInfoProvider>[] providerClasses;
+    // Keep a map around to speed up get lookups for larger maps.
+    // We make this value lazy to avoid computing for values that end up being thrown away
+    // during interning anyway (the majority).
+    private volatile ImmutableMap<Class<? extends TransitiveInfoProvider>, Integer> indexMap;
+
+    OffsetTable(Class<? extends TransitiveInfoProvider>[] providerClasses) {
+      this.providerClasses = providerClasses;
+    }
+
+    private ImmutableMap<Class<? extends TransitiveInfoProvider>, Integer> getIndexMap() {
+      if (indexMap == null) {
+        synchronized (this) {
+          if (indexMap == null) {
+            ImmutableMap.Builder<Class<? extends TransitiveInfoProvider>, Integer> builder =
+                ImmutableMap.builder();
+            for (int i = 0; i < providerClasses.length; ++i) {
+              builder.put(providerClasses[i], i);
+            }
+            this.indexMap = builder.build();
+          }
+        }
+      }
+      return indexMap;
+    }
+
+    int getOffsetForClass(Class effectiveClass) {
+      return getIndexMap().getOrDefault(effectiveClass, -1);
+    }
+
+    @Override
+    public boolean equals(Object o) {
+      if (this == o) {
+        return true;
+      }
+      if (!(o instanceof OffsetTable)) {
+        return false;
+      }
+      OffsetTable that = (OffsetTable) o;
+      return Arrays.equals(this.providerClasses, that.providerClasses);
+    }
+
+    @Override
+    public int hashCode() {
+      return Arrays.hashCode(providerClasses);
+    }
+  }
+
+  TransitiveInfoProviderMapOffsetBased(
+      ImmutableMap<Class<? extends TransitiveInfoProvider>, TransitiveInfoProvider> map) {
+    int count = map.size();
+    Class<? extends TransitiveInfoProvider>[] providerClasses = new Class[count];
+    this.providers = new TransitiveInfoProvider[count];
+    int i = 0;
+    for (Entry<Class<? extends TransitiveInfoProvider>, TransitiveInfoProvider> entry :
+        map.entrySet()) {
+      providerClasses[i] = entry.getKey();
+      providers[i] = entry.getValue();
+      ++i;
+    }
+    OffsetTable offsetTable = new OffsetTable(providerClasses);
+    this.offsetTable = offsetTables.intern(offsetTable);
+  }
+
+  /** Returns the instance for the provided providerClass, or <tt>null</tt> if not present. */
+  @Override
+  @Nullable
+  public <P extends TransitiveInfoProvider> P getProvider(Class<P> providerClass) {
+    Class effectiveClass = TransitiveInfoProviderEffectiveClassHelper.get(providerClass);
+    int offset = offsetTable.getOffsetForClass(effectiveClass);
+    return offset >= 0 ? (P) providers[offset] : null;
+  }
+
+  @Override
+  public int getProviderCount() {
+    return providers.length;
+  }
+
+  @Override
+  public Class<? extends TransitiveInfoProvider> getProviderClassAt(int i) {
+    return offsetTable.providerClasses[i];
+  }
+
+  @Override
+  public TransitiveInfoProvider getProviderAt(int i) {
+    return providers[i];
+  }
+}
-- 
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