src/main/java/com/google/devtools/build/lib/rules/android/AndroidSplitTransition.java

// Copyright 2021 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.rules.android;

import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.ImmutableSortedSet;
import com.google.devtools.build.lib.analysis.PlatformOptions;
import com.google.devtools.build.lib.analysis.config.BuildOptions;
import com.google.devtools.build.lib.analysis.config.BuildOptionsView;
import com.google.devtools.build.lib.analysis.config.CoreOptions;
import com.google.devtools.build.lib.analysis.config.FragmentOptions;
import com.google.devtools.build.lib.analysis.config.transitions.SplitTransition;
import com.google.devtools.build.lib.events.EventHandler;
import com.google.devtools.build.lib.rules.android.AndroidConfiguration.ConfigurationDistinguisher;
import com.google.devtools.build.lib.rules.android.AndroidConfiguration.Options;
import com.google.devtools.build.lib.rules.cpp.CppOptions;
import com.google.devtools.build.lib.starlarkbuildapi.android.AndroidSplitTransititionApi;
import net.starlark.java.eval.Printer;

/** Android Split configuration transition for properly handling native dependencies */
final class AndroidSplitTransition implements SplitTransition, AndroidSplitTransititionApi {

  @Override
  public ImmutableSet<Class<? extends FragmentOptions>> requiresOptionFragments() {
    return ImmutableSet.of(
        AndroidConfiguration.Options.class,
        CoreOptions.class,
        CppOptions.class,
        PlatformOptions.class);
  }

  @Override
  public ImmutableMap<String, BuildOptions> split(
      BuildOptionsView buildOptions, EventHandler eventHandler) {

    AndroidConfiguration.Options androidOptions =
        buildOptions.get(AndroidConfiguration.Options.class);
    CppOptions cppOptions = buildOptions.get(CppOptions.class);

    if (!androidOptions.fatApkCpus.isEmpty()) {
      return handleFatApkCpus(buildOptions, androidOptions);
    } else if (!androidOptions.cpu.isEmpty()
        && androidOptions.androidCrosstoolTop != null
        && !androidOptions.androidCrosstoolTop.equals(cppOptions.crosstoolTop)) {
      return handleAndroidCpu(buildOptions, androidOptions);
    } else {
      return handleDefaultSplit(buildOptions, buildOptions.get(CoreOptions.class).cpu);
    }
  }

  /** Returns a single-split transition that uses the "--cpu" and does not change any flags. */
  private ImmutableMap<String, BuildOptions> handleDefaultSplit(
      BuildOptionsView buildOptions, String cpu) {
    return ImmutableMap.of(cpu, buildOptions.underlying());
  }

  /**
   * Returns a single-split transition that sets "--cpu" to the value of "--android_cpu" and sets
   * other C++ flags based on the corresponding Android flags.
   */
  private ImmutableMap<String, BuildOptions> handleAndroidCpu(
      BuildOptionsView buildOptions, Options androidOptions) {
    BuildOptionsView splitOptions = buildOptions.clone();
    splitOptions.get(CoreOptions.class).cpu = androidOptions.cpu;
    setCcFlagsFromAndroid(androidOptions, splitOptions);
    return handleDefaultSplit(splitOptions, androidOptions.cpu);
  }

  /**
   * Returns a multi-split transition that sets "--cpu" with the values of "--fat_apk_cpu" and sets
   * other C++ flags based on the corresponding Android flags.
   */
  private ImmutableMap<String, BuildOptions> handleFatApkCpus(
      BuildOptionsView buildOptions, Options androidOptions) {
    ImmutableMap.Builder<String, BuildOptions> result = ImmutableMap.builder();
    for (String cpu : ImmutableSortedSet.copyOf(androidOptions.fatApkCpus)) {
      BuildOptionsView splitOptions = buildOptions.clone();
      // Disable fat APKs for the child configurations.
      splitOptions.get(Options.class).fatApkCpus = ImmutableList.of();

      // Set the cpu & android_cpu.
      // TODO(bazel-team): --android_cpu doesn't follow --cpu right now; it should.
      splitOptions.get(Options.class).cpu = cpu;
      splitOptions.get(CoreOptions.class).cpu = cpu;
      setCcFlagsFromAndroid(androidOptions, splitOptions);
      result.put(cpu, splitOptions.underlying());

      if (cpu.equals("arm64-v8a") && androidOptions.fatApkHwasan) {
        BuildOptionsView hwasanSplitOptions = splitOptions.clone();

        // A HWASAN build is different from a regular one in these ways:
        // - The native library install directory gets a "-hwasan" suffix
        // - Some compiler/linker command line options are different (defined in the Android C++
        //   toolchain)
        // - The name of the output directory is changed so that HWASAN and non-HWASAN artifacts
        //   do not conflict
        hwasanSplitOptions.get(CppOptions.class).outputDirectoryTag = "hwasan";
        hwasanSplitOptions.get(AndroidConfiguration.Options.class).hwasan = true;

        result.put(cpu + "-hwasan", hwasanSplitOptions.underlying());
      }
    }
    return result.build();
  }

  private void setCcFlagsFromAndroid(
      AndroidConfiguration.Options androidOptions, BuildOptionsView newOptions) {

    // Set the CC options needed to build native code.
    CppOptions newCppOptions = newOptions.get(CppOptions.class);
    newCppOptions.cppCompiler = androidOptions.cppCompiler;
    newCppOptions.libcTopLabel = androidOptions.androidLibcTopLabel;
    newCppOptions.dynamicMode = androidOptions.dynamicMode;

    if (androidOptions.androidCrosstoolTop != null) {
      newCppOptions.crosstoolTop = androidOptions.androidCrosstoolTop;
    }

    newOptions.get(AndroidConfiguration.Options.class).configurationDistinguisher =
        ConfigurationDistinguisher.ANDROID;

    // Ensure platforms aren't set so that platform mapping can take place.
    newOptions.get(PlatformOptions.class).platforms = ImmutableList.of();
  }

  @Override
  public boolean isImmutable() {
    return true;
  }

  @Override
  public void repr(Printer printer) {
    printer.append("android_common.multi_cpu_configuration");
  }
}