Optimizing class inliner to favor kotlin j-/k-style lambdas.

We add an analysis of how method parameters are being used. Currently
we only identify parameters that are not used, and parameters that
are only used for calling a method on it exactly one time.

(Note that the latter pattern is typical for lambdas passed into a
method which calls them in some context.)

With this information we extend class inliner to allow the eligible
instance to be passed as an argument to a method (extra method below)
and we know that the corresponding parameter is used in one of the
two supported special ways. If it is, we:

 ** if the eligible instance is passed to an unused parameter of the
    extra method and the eligible instance can be inlined without this
    use, we just replace this use with null and proceed with eligible
    instance inlining

 ** if the eligible instance is passed to a parameter of the extra
    method with one call on it, we look if this call will become an
    eligible use after the extra method is inlined, and if it is we
    try to force-inline extra method and proceed with eligible
    instance inlining after that. (Note that extra method size
    contributes to combined inlined instructions size).

NOTE: unfortunately I had to restructure ClassInliner since it was
getting more complicated, this will make review more difficult. Those
are mostly class and method moves/renames and trivial changes.

We have just few instances where new patterns were applied on gmscore,
totalling to about 1K size reduce.

Bug: 80135467
Change-Id: I8fc747b80bd4846a1227c6bdbb064b563dd89419
17 files changed
tree: ee5d63f5a240fd61b307045b7c7f46fe38e6a12b
  1. .gitignore
  2. AUTHORS
  3. CONTRIBUTING.md
  4. LIBRARY-LICENSE
  5. LICENSE
  6. README.md
  7. build.gradle
  8. buildSrc/
  9. codereview.settings
  10. copyAdditionalJctfCommonFiles.gradle
  11. library-licensing/
  12. scripts/
  13. src/
  14. tests/
  15. third_party/
  16. tools/
README.md

D8 dexer and R8 shrinker

The R8 repo contains two tools:

  • D8 is a dexer that converts java byte code to dex code.
  • R8 is a java program shrinking and minification tool that converts java byte code to optimized dex code.

D8 is a replacement for the DX dexer and R8 is a replacement for the Proguard shrinking and minification tool.

Downloading and building

The R8 project uses depot_tools from the chromium project to manage dependencies. Install depot_tools and add it to your path before proceeding.

The R8 project uses Java 8 language features and requires a Java 8 compiler and runtime system.

Typical steps to download and build:

$ git clone https://r8.googlesource.com/r8
$ cd r8
$ tools/gradle.py d8 r8

The tools/gradle.py script will bootstrap using depot_tools to download a version of gradle to use for building on the first run. This will produce two jar files: build/libs/d8.jar and build/libs/r8.jar.

Running D8

The D8 dexer has a simple command-line interface with only a few options.

The most important option is whether to build in debug or release mode. Debug is the default mode and includes debugging information in the resulting dex files. Debugging information contains information about local variables used when debugging dex code. This information is not useful when shipping final Android apps to users and therefore, final builds should use the --release flag to remove this debugging information to produce smaller dex files.

Typical invocations of D8 to produce dex file(s) in the out directoy:

Debug mode build:

$ java -jar build/libs/d8.jar --output out input.jar

Release mode build:

$ java -jar build/libs/d8.jar --release --output out input.jar

The full set of D8 options can be obtained by running the command line tool with the --help option.

Running R8

R8 is a Proguard replacement for whole-program optimization, shrinking and minification. R8 uses the Proguard keep rule format for specifying the entry points for an application.

Typical invocations of R8 to produce optimized dex file(s) in the out directory:

$ java -jar build/libs/r8.jar --release --output out --pg-conf proguard.cfg input.jar

The full set of R8 options can be obtained by running the command line tool with the --help option.

Testing

Typical steps to run tests:

$ tools/test.py --no_internal

The tools/test.py script will use depot_tools to download a lot of tests and test dependencies on the first run. This includes prebuilt version of the art runtime on which to validate the produced dex code.

Contributing

In order to contribute to D8/R8 you have to sign the Contributor License Agreement. If your contribution is owned by your employer you need the Corporate Contributor License Agreement.

Once the license agreement is in place, you can upload your patches using ‘git cl’ which is available in depot_tools. Once you have a change that you are happy with you should make sure that it passes all tests and then upload the change to our code review tool using:

$ git cl upload

On your first upload you will be asked to acquire credentials. Follow the instructions given by git cl upload.

On successful uploads a link to the code review is printed in the output of the upload command. In the code review tool you can assign reviewers and mark the change ready for review. At that point the code review tool will send emails to reviewers.

Getting help

For questions, reach out to us at r8-dev@googlegroups.com.

For D8, find known issues in the D8 issue tracker or file a new D8 bug report.

For R8, find known issues in the R8 issue tracker or file a new R8 bug report.