| commit | 4dc50a3924e7a5be979c4efd1437d55dad4531b2 | [log] [tgz] |
|---|---|---|
| author | Denis Vnukov <vnukov@google.com> | Fri Feb 09 07:43:50 2018 -0800 |
| committer | Denis Vnukov <vnukov@google.com> | Fri Feb 09 07:43:50 2018 -0800 |
| tree | babf046afee83c9fd5861b06d085f10904fa2a0a | |
| parent | 63a2d9ca01aff532fe5c3b2b1c1c96f26076034c [diff] |
Flipping if statement in case fall-through successor always throws (#2).
In case an if instruction has fall-through successor which always throws an
exception while the other ('true-target') successor does not, it is very
likely that this if instruction serves as a safeguard for assertion-like
test, for example for null checks.
In this case we assume that always throwing branch is executed very rarely
and 'true-target' branch is what is executed more frequently since it
represents no error scenario.
For such if instructions we flip the branches and invert the test, so the
non-error branch becomes a fall-through successor. This helps improve
performance on ART.
Note that we also do NOT flip the successors if the method code has any
positions and any of throwing instructions in fall-through successor
does not have a position. This should guarantee we don't introduce wrong
debug information by moving such an instruction to wrong place.
Bug:
Change-Id: I1243c1ff8e092c39211a0a8228ad23c76448e06c
The R8 repo contains two tools:
D8 is a replacement for the DX dexer and R8 is a replacement for the Proguard shrinking and minification tool.
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.
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.
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.
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.
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.
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.