Make it possible to put the Crosstool proto in BUILD files.

This is needed so that Bazel can access Android NDK if it's outside of the workspace. The current limitation is that we Bazel can pretend that there is a BUILD file there, but cannot do the same with a CROSSTOOL file. We could fix that limitation, but given that Crosstool is the only conceivable use case, let's fix it by changing the Blaze-Crosstool interface.

--
MOS_MIGRATED_REVID=95517408

9 files changed, 283 insertions, 66 deletions

diff --git a/src/main/java/com/google/devtools/build/docgen/RuleDocumentationAttribute.java b/src/main/java/com/google/devtools/build/docgen/RuleDocumentationAttribute.java
index 0d6f5d691a..c68dae2dbc 100644
--- a/src/main/java/com/google/devtools/build/docgen/RuleDocumentationAttribute.java
+++ b/src/main/java/com/google/devtools/build/docgen/RuleDocumentationAttribute.java
@@ -45,6 +45,8 @@ class RuleDocumentationAttribute implements Comparable<RuleDocumentationAttribut
       .put(Type.TRISTATE, "Integer")
       .put(Type.LABEL, "<a href=\"build-ref.html#labels\">Label</a>")
       .put(Type.LABEL_LIST, "List of <a href=\"build-ref.html#labels\">labels</a>")
+      .put(Type.LABEL_DICT_UNARY,
+          "Dictionary mapping strings to <a href=\"build-ref.html#labels\">labels</a>")
       .put(Type.LABEL_LIST_DICT,
           "Dictionary mapping strings to lists of <a href=\"build-ref.html#labels\">labels</a>")
       .put(Type.NODEP_LABEL, "<a href=\"build-ref.html#name\">Name</a>")
diff --git a/src/main/java/com/google/devtools/build/lib/packages/PackageSerializer.java b/src/main/java/com/google/devtools/build/lib/packages/PackageSerializer.java
index 75067b726d..16b318cb62 100644
--- a/src/main/java/com/google/devtools/build/lib/packages/PackageSerializer.java
+++ b/src/main/java/com/google/devtools/build/lib/packages/PackageSerializer.java
@@ -19,6 +19,7 @@ import static com.google.devtools.build.lib.packages.Type.FILESET_ENTRY_LIST;
 import static com.google.devtools.build.lib.packages.Type.INTEGER;
 import static com.google.devtools.build.lib.packages.Type.INTEGER_LIST;
 import static com.google.devtools.build.lib.packages.Type.LABEL;
+import static com.google.devtools.build.lib.packages.Type.LABEL_DICT_UNARY;
 import static com.google.devtools.build.lib.packages.Type.LABEL_LIST;
 import static com.google.devtools.build.lib.packages.Type.LABEL_LIST_DICT;
 import static com.google.devtools.build.lib.packages.Type.LICENSE;
@@ -252,6 +253,17 @@ public class PackageSerializer {
           attrPb.addStringListDictValue(entry);
         }
       }
+    } else if (type == LABEL_DICT_UNARY) {
+      for (Object value : values) {
+        Map<String, Label> dict = (Map<String, Label>) value;
+        for (Map.Entry<String, Label> dictEntry : dict.entrySet()) {
+          Build.LabelDictUnaryEntry entry = Build.LabelDictUnaryEntry.newBuilder()
+              .setKey(dictEntry.getKey())
+              .setValue(dictEntry.getValue().toString())
+              .build();
+          attrPb.addLabelDictUnaryValue(entry);
+        }
+      }
     } else if (type == LABEL_LIST_DICT) {
       for (Object value : values) {
         Map<String, List<Label>> dict = (Map<String, List<Label>>) value;
diff --git a/src/main/java/com/google/devtools/build/lib/packages/ProtoUtils.java b/src/main/java/com/google/devtools/build/lib/packages/ProtoUtils.java
index 7b6eaf1efa..653e283e84 100644
--- a/src/main/java/com/google/devtools/build/lib/packages/ProtoUtils.java
+++ b/src/main/java/com/google/devtools/build/lib/packages/ProtoUtils.java
@@ -20,6 +20,7 @@ import static com.google.devtools.build.lib.packages.Type.FILESET_ENTRY_LIST;
 import static com.google.devtools.build.lib.packages.Type.INTEGER;
 import static com.google.devtools.build.lib.packages.Type.INTEGER_LIST;
 import static com.google.devtools.build.lib.packages.Type.LABEL;
+import static com.google.devtools.build.lib.packages.Type.LABEL_DICT_UNARY;
 import static com.google.devtools.build.lib.packages.Type.LABEL_LIST;
 import static com.google.devtools.build.lib.packages.Type.LABEL_LIST_DICT;
 import static com.google.devtools.build.lib.packages.Type.LICENSE;
@@ -65,6 +66,7 @@ public class ProtoUtils {
           .put(LICENSE, Discriminator.LICENSE)
           .put(STRING_DICT, Discriminator.STRING_DICT)
           .put(FILESET_ENTRY_LIST, Discriminator.FILESET_ENTRY_LIST)
+          .put(LABEL_DICT_UNARY, Discriminator.LABEL_DICT_UNARY)
           .put(LABEL_LIST_DICT, Discriminator.LABEL_LIST_DICT)
           .put(STRING_LIST_DICT, Discriminator.STRING_LIST_DICT)
           .put(BOOLEAN, Discriminator.BOOLEAN)
diff --git a/src/main/java/com/google/devtools/build/lib/packages/Type.java b/src/main/java/com/google/devtools/build/lib/packages/Type.java
index b1ca03e8a0..96191626dc 100644
--- a/src/main/java/com/google/devtools/build/lib/packages/Type.java
+++ b/src/main/java/com/google/devtools/build/lib/packages/Type.java
@@ -336,6 +336,11 @@ public abstract class Type<T> {
       DictType.create(STRING, LABEL_LIST);
 
   /**
+   * The type of a dictionary of {@linkplain #LABEL labels}.
+   */
+  public static final DictType<String, Label> LABEL_DICT_UNARY = DictType.create(STRING, LABEL);
+
+  /**
    * The type of a list of {@linkplain #FILESET_ENTRY FilesetEntries}.
    */
   public static final ListType<FilesetEntry> FILESET_ENTRY_LIST = ListType.create(FILESET_ENTRY);
@@ -1003,7 +1008,7 @@ public abstract class Type<T> {
    * Returns whether the specified type is a label type or not.
    */
   public static boolean isLabelType(Type<?> type) {
-    return type == LABEL || type == LABEL_LIST
+    return type == LABEL || type == LABEL_LIST || type == LABEL_DICT_UNARY
         || type == NODEP_LABEL || type == NODEP_LABEL_LIST
         || type == LABEL_LIST_DICT || type == FILESET_ENTRY_LIST;
   }
diff --git a/src/main/java/com/google/devtools/build/lib/rules/cpp/CcToolchainSuite.java b/src/main/java/com/google/devtools/build/lib/rules/cpp/CcToolchainSuite.java
new file mode 100644
index 0000000000..17d14feb37
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/rules/cpp/CcToolchainSuite.java
@@ -0,0 +1,39 @@
+// Copyright 2015 Google Inc. 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.rules.cpp;
+
+import com.google.devtools.build.lib.actions.Artifact;
+import com.google.devtools.build.lib.analysis.ConfiguredTarget;
+import com.google.devtools.build.lib.analysis.RuleConfiguredTargetBuilder;
+import com.google.devtools.build.lib.analysis.RuleContext;
+import com.google.devtools.build.lib.collect.nestedset.NestedSetBuilder;
+import com.google.devtools.build.lib.collect.nestedset.Order;
+import com.google.devtools.build.lib.rules.RuleConfiguredTargetFactory;
+
+/**
+ * Implementation of the {@code cc_toolchain_suite} rule.
+ *
+ * <p>This is currently a no-op because the logic that transforms this rule into something that can
+ * be understood by the {@code cc_*} rules is in
+ * {@link com.google.devtools.build.lib.rules.cpp.CppConfigurationLoader}.
+ */
+public class CcToolchainSuite implements RuleConfiguredTargetFactory {
+
+  @Override
+  public ConfiguredTarget create(RuleContext ruleContext) throws InterruptedException {
+    return new RuleConfiguredTargetBuilder(ruleContext)
+        .setFilesToBuild(NestedSetBuilder.<Artifact>emptySet(Order.STABLE_ORDER))
+        .build();
+  }
+}
diff --git a/src/main/java/com/google/devtools/build/lib/rules/cpp/CcToolchainSuiteRule.java b/src/main/java/com/google/devtools/build/lib/rules/cpp/CcToolchainSuiteRule.java
new file mode 100644
index 0000000000..9bc59c9d24
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/rules/cpp/CcToolchainSuiteRule.java
@@ -0,0 +1,50 @@
+// Copyright 2015 Google Inc. 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.rules.cpp;
+
+import static com.google.devtools.build.lib.packages.Attribute.attr;
+
+import com.google.devtools.build.lib.analysis.BaseRuleClasses;
+import com.google.devtools.build.lib.analysis.RuleDefinition;
+import com.google.devtools.build.lib.analysis.RuleDefinitionEnvironment;
+import com.google.devtools.build.lib.packages.RuleClass;
+import com.google.devtools.build.lib.packages.RuleClass.Builder;
+import com.google.devtools.build.lib.packages.Type;
+
+/**
+ * Definition of the {@code cc_toolchain_sute} rule.
+ */
+public final class CcToolchainSuiteRule implements RuleDefinition {
+
+  @Override
+  public RuleClass build(Builder builder, RuleDefinitionEnvironment environment) {
+    return builder
+        .setUndocumented()
+        .add(attr("toolchains", Type.LABEL_DICT_UNARY)
+            .mandatory()
+            .nonconfigurable("Used during configuration creation"))
+        .add(attr("proto", Type.STRING)
+            .nonconfigurable("Used during configuration creation"))
+        .build();
+  }
+
+  @Override
+  public Metadata getMetadata() {
+    return RuleDefinition.Metadata.builder()
+        .name("cc_toolchain_suite")
+        .ancestors(BaseRuleClasses.BaseRule.class)
+        .factoryClass(CcToolchainSuite.class)
+        .build();
+  }
+}
diff --git a/src/main/java/com/google/devtools/build/lib/rules/cpp/CppConfigurationLoader.java b/src/main/java/com/google/devtools/build/lib/rules/cpp/CppConfigurationLoader.java
index bf26f630f8..9d4818ef24 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/cpp/CppConfigurationLoader.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/cpp/CppConfigurationLoader.java
@@ -28,8 +28,10 @@ import com.google.devtools.build.lib.packages.InputFile;
 import com.google.devtools.build.lib.packages.NoSuchPackageException;
 import com.google.devtools.build.lib.packages.NoSuchTargetException;
 import com.google.devtools.build.lib.packages.NoSuchThingException;
+import com.google.devtools.build.lib.packages.NonconfigurableAttributeMapper;
 import com.google.devtools.build.lib.packages.Rule;
 import com.google.devtools.build.lib.packages.Target;
+import com.google.devtools.build.lib.packages.Type;
 import com.google.devtools.build.lib.syntax.Label;
 import com.google.devtools.build.lib.syntax.Label.SyntaxException;
 import com.google.devtools.build.lib.vfs.Path;
@@ -108,13 +110,14 @@ public class CppConfigurationLoader implements ConfigurationFragmentFactory {
     if (directories == null) {
       return null;
     }
-    Label crosstoolTop = RedirectChaser.followRedirects(env,
+    Label crosstoolTopLabel = RedirectChaser.followRedirects(env,
         options.get(CppOptions.class).crosstoolTop, "crosstool_top");
-    if (crosstoolTop == null) {
+    if (crosstoolTopLabel == null) {
       return null;
     }
+
     CrosstoolConfigurationLoader.CrosstoolFile file =
-        CrosstoolConfigurationLoader.readCrosstool(env, crosstoolTop);
+        CrosstoolConfigurationLoader.readCrosstool(env, crosstoolTopLabel);
     if (file == null) {
       return null;
     }
@@ -150,12 +153,33 @@ public class CppConfigurationLoader implements ConfigurationFragmentFactory {
     }
 
     Label ccToolchainLabel;
+    Target crosstoolTop;
+
     try {
-      ccToolchainLabel = crosstoolTop.getRelative("cc-compiler-" + toolchain.getTargetCpu());
-    } catch (Label.SyntaxException e) {
-      throw new InvalidConfigurationException(String.format(
-          "'%s' is not a valid CPU. It should only consist of characters valid in labels",
-          toolchain.getTargetCpu()));
+      crosstoolTop = env.getTarget(crosstoolTopLabel);
+    } catch (NoSuchThingException e) {
+      throw new IllegalStateException(e);  // Should have been found out during redirect chasing
+    }
+
+    if (crosstoolTop instanceof Rule
+        && ((Rule) crosstoolTop).getRuleClass().equals("cc_toolchain_suite")) {
+      Rule ccToolchainSuite = (Rule) crosstoolTop;
+      ccToolchainLabel = NonconfigurableAttributeMapper.of(ccToolchainSuite)
+          .get("toolchains", Type.LABEL_DICT_UNARY)
+          .get(toolchain.getTargetCpu());
+      if (ccToolchainLabel == null) {
+        throw new InvalidConfigurationException(String.format(
+            "cc_toolchain_suite '%s' does not contain a toolchain for CPU '%s'",
+            crosstoolTopLabel, toolchain.getTargetCpu()));
+      }
+    } else {
+      try {
+        ccToolchainLabel = crosstoolTopLabel.getRelative("cc-compiler-" + toolchain.getTargetCpu());
+      } catch (Label.SyntaxException e) {
+        throw new InvalidConfigurationException(String.format(
+            "'%s' is not a valid CPU. It should only consist of characters valid in labels",
+            toolchain.getTargetCpu()));
+      }
     }
 
     Target ccToolchain;
@@ -176,6 +200,6 @@ public class CppConfigurationLoader implements ConfigurationFragmentFactory {
     }
 
     return new CppConfigurationParameters(toolchain, file.getMd5(), options,
-        fdoZip, directories.getExecRoot(), crosstoolTop, ccToolchainLabel);
+        fdoZip, directories.getExecRoot(), crosstoolTopLabel, ccToolchainLabel);
   }
 }
diff --git a/src/main/java/com/google/devtools/build/lib/rules/cpp/CrosstoolConfigurationLoader.java b/src/main/java/com/google/devtools/build/lib/rules/cpp/CrosstoolConfigurationLoader.java
index a113f5f126..e5957581ae 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/cpp/CrosstoolConfigurationLoader.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/cpp/CrosstoolConfigurationLoader.java
@@ -14,24 +14,30 @@
 
 package com.google.devtools.build.lib.rules.cpp;
 
+import static java.nio.charset.StandardCharsets.UTF_8;
+
 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.base.Function;
+import com.google.common.cache.Cache;
 import com.google.common.cache.CacheBuilder;
-import com.google.common.cache.CacheLoader;
-import com.google.common.cache.LoadingCache;
 import com.google.common.io.BaseEncoding;
 import com.google.devtools.build.lib.analysis.RedirectChaser;
 import com.google.devtools.build.lib.analysis.config.BuildOptions;
 import com.google.devtools.build.lib.analysis.config.ConfigurationEnvironment;
 import com.google.devtools.build.lib.analysis.config.InvalidConfigurationException;
 import com.google.devtools.build.lib.packages.NoSuchThingException;
+import com.google.devtools.build.lib.packages.NonconfigurableAttributeMapper;
 import com.google.devtools.build.lib.packages.Package;
+import com.google.devtools.build.lib.packages.Rule;
+import com.google.devtools.build.lib.packages.Target;
+import com.google.devtools.build.lib.packages.Type;
 import com.google.devtools.build.lib.syntax.Label;
 import com.google.devtools.build.lib.syntax.Label.SyntaxException;
-import com.google.devtools.build.lib.util.Pair;
+import com.google.devtools.build.lib.util.Fingerprint;
 import com.google.devtools.build.lib.vfs.FileSystemUtils;
 import com.google.devtools.build.lib.vfs.Path;
 import com.google.devtools.build.lib.view.config.crosstool.CrosstoolConfig;
+import com.google.devtools.build.lib.view.config.crosstool.CrosstoolConfig.CrosstoolRelease;
 import com.google.protobuf.TextFormat;
 import com.google.protobuf.TextFormat.ParseException;
 import com.google.protobuf.UninitializedMessageException;
@@ -39,6 +45,7 @@ import com.google.protobuf.UninitializedMessageException;
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.Collection;
+import java.util.concurrent.Callable;
 import java.util.concurrent.ExecutionException;
 
 import javax.annotation.Nullable;
@@ -46,6 +53,10 @@ import javax.annotation.Nullable;
 /**
  * A loader that reads Crosstool configuration files and creates CToolchain
  * instances from them.
+ *
+ * <p>Note that this class contains a cache for the text format -> proto objects mapping of
+ * Crosstool protos that is completely independent from Skyframe or anything else. This should be
+ * done in a saner way.
  */
 public class CrosstoolConfigurationLoader {
   private static final String CROSSTOOL_CONFIGURATION_FILENAME = "CROSSTOOL";
@@ -54,53 +65,27 @@ public class CrosstoolConfigurationLoader {
    * Cache for storing result of toReleaseConfiguration function based on path and md5 sum of
    * input file. We can use md5 because result of this function depends only on the file content.
    */
-  private static final LoadingCache<Pair<Path, String>, CrosstoolConfig.CrosstoolRelease> 
-      crosstoolReleaseCache = CacheBuilder.newBuilder().concurrencyLevel(4).maximumSize(100).build(
-        new CacheLoader<Pair<Path, String>, CrosstoolConfig.CrosstoolRelease>() {
-          @Override
-          public CrosstoolConfig.CrosstoolRelease load(Pair<Path, String> key) throws IOException {
-            char[] data = FileSystemUtils.readContentAsLatin1(key.first);
-            return toReleaseConfiguration(key.first.getPathString(), new String(data));
-          }
-        });
-
+  private static final Cache<String, CrosstoolRelease> crosstoolReleaseCache =
+      CacheBuilder.newBuilder().concurrencyLevel(4).maximumSize(100).build();
   /**
    * A class that holds the results of reading a CROSSTOOL file.
    */
   public static class CrosstoolFile {
-    private final Label crosstoolTop;
-    private Path crosstoolPath;
-    private CrosstoolConfig.CrosstoolRelease crosstool;
-    private String md5;
-
-    CrosstoolFile(Label crosstoolTop) {
-      this.crosstoolTop = crosstoolTop;
-    }
-
-    void setCrosstoolPath(Path crosstoolPath) {
-      this.crosstoolPath = crosstoolPath;
-    }
+    private final String location;
+    private final CrosstoolConfig.CrosstoolRelease crosstool;
+    private final String md5;
 
-    void setCrosstool(CrosstoolConfig.CrosstoolRelease crosstool) {
+    CrosstoolFile(String location, CrosstoolConfig.CrosstoolRelease crosstool, String md5) {
+      this.location = location;
       this.crosstool = crosstool;
-    }
-
-    void setMd5(String md5) {
       this.md5 = md5;
     }
 
     /**
-     * Returns the crosstool top as resolved.
-     */
-    public Label getCrosstoolTop() {
-      return crosstoolTop;
-    }
-
-    /**
-     * Returns the absolute path from which the CROSSTOOL file was read.
+     * Returns a user-friendly location of the CROSSTOOL proto for error messages.
      */
-    public Path getCrosstoolPath() {
-      return crosstoolPath;
+    public String getLocation() {
+      return location;
     }
 
     /**
@@ -145,27 +130,115 @@ public class CrosstoolConfigurationLoader {
     }
   }
 
-  private static boolean findCrosstoolConfiguration(
-      ConfigurationEnvironment env,
-      CrosstoolConfigurationLoader.CrosstoolFile file)
+  /**
+   * This class is the in-memory representation of a text-formatted Crosstool proto file.
+   *
+   * <p>This layer of abstraction is here so that we can load these protos either from BUILD files
+   * or from CROSSTOOL files.
+   *
+   * <p>An implementation of this class should override {@link #getContents()} and call
+   * the constructor with the MD5 checksum of what that method will return and a human-readable name
+   * used in error messages.
+   */
+  private abstract static class CrosstoolProto {
+    private final byte[] md5;
+    private final String name;
+
+    private CrosstoolProto(byte[] md5, String name) {
+      this.md5 = md5;
+      this.name = name;
+    }
+
+    /**
+     * The binary MD5 checksum of the proto.
+     */
+    public byte[] getMd5() {
+      return md5;
+    }
+
+    /**
+     * A user-friendly string describing the location of the proto.
+     */
+    public String getName() {
+      return name;
+    }
+
+    /**
+     * The proto itself.
+     */
+    public abstract String getContents() throws IOException;
+  }
+
+  private static CrosstoolProto getCrosstoolProtofromBuildFile(
+      ConfigurationEnvironment env, Label crosstoolTop) {
+    Target target;
+    try {
+      target = env.getTarget(crosstoolTop);
+    } catch (NoSuchThingException e) {
+      throw new IllegalStateException(e);  // Should have beeen evaluated by RedirectChaser
+    }
+
+    if (!(target instanceof Rule)) {
+      return null;
+    }
+
+    Rule rule = (Rule) target;
+    if (!(rule.getRuleClass().equals("cc_toolchain_suite"))
+        || !rule.isAttributeValueExplicitlySpecified("proto")) {
+      return null;
+    }
+
+    final String contents = NonconfigurableAttributeMapper.of(rule).get("proto", Type.STRING);
+    byte[] md5 = new Fingerprint().addBytes(contents.getBytes(UTF_8)).digestAndReset();
+    return new CrosstoolProto(md5, "cc_toolchain_suite rule " + crosstoolTop.toString()) {
+
+      @Override
+      public String getContents() throws IOException {
+        return contents;
+      }
+    };
+  }
+
+  private static CrosstoolProto getCrosstoolProtoFromCrosstoolFile(
+      ConfigurationEnvironment env, Label crosstoolTop)
       throws IOException, InvalidConfigurationException {
-    Label crosstoolTop = file.getCrosstoolTop();
-    Path path = null;
+    final Path path;
     try {
       Package containingPackage = env.getTarget(crosstoolTop.getLocalTargetLabel("BUILD"))
           .getPackage();
       if (containingPackage == null) {
-        return false;
+        return null;
       }
       path = env.getPath(containingPackage, CROSSTOOL_CONFIGURATION_FILENAME);
     } catch (SyntaxException e) {
       throw new InvalidConfigurationException(e);
     } catch (NoSuchThingException e) {
       // Handled later
+      return null;
     }
 
-    // If we can't find a file, fall back to the provided alternative.
     if (path == null || !path.exists()) {
+      return null;
+    }
+
+    return new CrosstoolProto(path.getMD5Digest(), "CROSSTOOL file " + path.getPathString()) {
+      @Override
+      public String getContents() throws IOException {
+        return new String(FileSystemUtils.readContentAsLatin1(path.getInputStream()));
+      }
+    };
+  }
+
+  private static CrosstoolFile findCrosstoolConfiguration(
+      ConfigurationEnvironment env, Label crosstoolTop)
+      throws IOException, InvalidConfigurationException {
+
+    CrosstoolProto crosstoolProto = getCrosstoolProtofromBuildFile(env, crosstoolTop);
+    if (crosstoolProto == null) {
+      crosstoolProto = getCrosstoolProtoFromCrosstoolFile(env, crosstoolTop);
+    }
+
+    if (crosstoolProto == null) {
       throw new InvalidConfigurationException("The crosstool_top you specified was resolved to '" +
           crosstoolTop + "', which does not contain a CROSSTOOL file. " +
           "You can use a crosstool from the depot by specifying its label.");
@@ -173,18 +246,22 @@ public class CrosstoolConfigurationLoader {
       // Do this before we read the data, so if it changes, we get a different MD5 the next time.
       // Alternatively, we could calculate the MD5 of the contents, which we also read, but this
       // is faster if the file comes from a file system with md5 support.
-      file.setCrosstoolPath(path);
-      String md5 = BaseEncoding.base16().lowerCase().encode(path.getMD5Digest());
+      final CrosstoolProto finalProto = crosstoolProto;
+      String md5 = BaseEncoding.base16().lowerCase().encode(finalProto.getMd5());
       CrosstoolConfig.CrosstoolRelease release;
       try {
-        release = crosstoolReleaseCache.get(new Pair<Path, String>(path, md5));
-        file.setCrosstool(release);
-        file.setMd5(md5);
+        release = crosstoolReleaseCache.get(md5, new Callable<CrosstoolRelease>() {
+          @Override
+          public CrosstoolRelease call() throws Exception {
+            return toReleaseConfiguration(finalProto.getName(), finalProto.getContents());
+          }
+        });
       } catch (ExecutionException e) {
         throw new InvalidConfigurationException(e);
       }
+
+      return new CrosstoolFile(finalProto.getName(), release, md5);
     }
-    return true;
   }
 
   /**
@@ -197,11 +274,8 @@ public class CrosstoolConfigurationLoader {
     if (crosstoolTop == null) {
       return null;
     }
-    CrosstoolConfigurationLoader.CrosstoolFile file =
-        new CrosstoolConfigurationLoader.CrosstoolFile(crosstoolTop);
     try {
-      boolean allDependenciesPresent = findCrosstoolConfiguration(env, file);
-      return allDependenciesPresent ? file : null;
+      return findCrosstoolConfiguration(env, crosstoolTop);
     } catch (IOException e) {
       throw new InvalidConfigurationException(e);
     }
diff --git a/src/main/protobuf/build.proto b/src/main/protobuf/build.proto
index a84df42b43..6780d4d844 100644
--- a/src/main/protobuf/build.proto
+++ b/src/main/protobuf/build.proto
@@ -38,6 +38,11 @@ message StringDictUnaryEntry {
   required string value = 2;
 }
 
+message LabelDictUnaryEntry {
+  required string key = 1;
+  required string value = 2;
+}
+
 message LabelListDictEntry {
   required string key = 1;
   repeated string value = 2;
@@ -112,6 +117,7 @@ message Attribute {
     INTEGER_LIST = 16;       // int_list_value
     STRING_DICT_UNARY = 17;  // string_dict_unary_value
     UNKNOWN = 18;            // unknown type, use only for build extensions
+    LABEL_DICT_UNARY = 19;   // label_dict_unary_value
   }
 
   // Values for the TriState field type.
@@ -186,6 +192,9 @@ message Attribute {
 
   // If this is a string dict unary, each entry will be stored here.
   repeated StringDictUnaryEntry string_dict_unary_value = 18;
+
+  // If this is a label dict unary, each entry will be stored here.
+  repeated LabelDictUnaryEntry label_dict_unary_value = 19;
 }
 
 // A rule from a BUILD file (e.g., cc_library, java_binary).  The rule class