Compiler Explorer

This doc describes how to run a local instance of Compiler Explorer (https://godbolt.org/) with local compilers built from an Android source tree.

Prerequisites

• Compiler Explorer depends on Node.js. You can download it through Node Version Manager (NVM) or through your favorite package manager.
• You need a full Android source tree to build compilers.

Instructions

1. Set a directory to install Compiler Explorer.

   export COMPILER_EXPLORER_DIR=/tmp/compiler-explorer
   

2. Create the directory.

   mkdir -p $COMPILER_EXPLORER_DIR
   

3. Check out Compiler Explorer.

   cd $COMPILER_EXPLORER_DIR
   git clone https://github.com/compiler-explorer/compiler-explorer.git
   

4. Go to a full Android source tree, and initialize the environment as usual.

   cd <path-to-android-source-tree>
   source build/envsetup.sh
   lunch aosp_cf_x86_64_phone-trunk_staging-userdebug
   

   Note: You may use a different lunch target, as long as it can build the host binaries in the later steps.

5. Configure Compiler Explorer.

   cp art/tools/compiler-explorer/config/* $COMPILER_EXPLORER_DIR/compiler-explorer/etc/config
   # Replace {{compilersDir}} in the config files with the actual path.
   find $COMPILER_EXPLORER_DIR/compiler-explorer/etc/config -type f -name '*local*' | \
     xargs sed -i 's?{{compilersDir}}?'$COMPILER_EXPLORER_DIR/compilers'?'
   

6. Build Compiler Explorer.

   (cd $COMPILER_EXPLORER_DIR/compiler-explorer && make prebuild)
   

7. Build and copy compilers except dex2oat.

   m r8 smali-baksmali
   rm -rf $COMPILER_EXPLORER_DIR/compilers
   mkdir $COMPILER_EXPLORER_DIR/compilers
   cp -r prebuilts/jdk/jdk21/linux-x86 $COMPILER_EXPLORER_DIR/compilers/java-local
   cp -r external/kotlinc $COMPILER_EXPLORER_DIR/compilers/kotlinc-local
   mkdir $COMPILER_EXPLORER_DIR/compilers/d8-local
   cp out/host/linux-x86/framework/r8.jar $COMPILER_EXPLORER_DIR/compilers/d8-local
   chmod +x $COMPILER_EXPLORER_DIR/compilers/d8-local/r8.jar
   mkdir $COMPILER_EXPLORER_DIR/compilers/baksmali-local
   cp out/host/linux-x86/framework/smali-baksmali.jar $COMPILER_EXPLORER_DIR/compilers/baksmali-local
   

   Note: smali-baksmali is for decompiling dex code. You don't need it if you only want to see native code generated by dex2oat.

8. Build and copy dex2oat.

   m dist out/dist/art_release.zip
   rm -rf $COMPILER_EXPLORER_DIR/compilers/dex2oat-local
   unzip -d $COMPILER_EXPLORER_DIR/compilers/dex2oat-local out/dist/art_release.zip
   

   Note: You may choose to do this on master-art instead of on a full Android source tree if you wish.

9. Generate boot images (optional but recommended).

   declare -a instruction_sets=("arm" "arm64" "x86" "x86_64" "riscv64")
   m generate-boot-image
   rm -rf $COMPILER_EXPLORER_DIR/compilers/dex2oat-local/app
   mkdir -p $COMPILER_EXPLORER_DIR/compilers/dex2oat-local/app/apex/com.android.art/javalib
   cp $COMPILER_EXPLORER_DIR/compilers/dex2oat-local/bootjars/* \
       $COMPILER_EXPLORER_DIR/compilers/dex2oat-local/app/apex/com.android.art/javalib
   mkdir -p $COMPILER_EXPLORER_DIR/compilers/dex2oat-local/app/system/framework
   for instruction_set in "${instruction_sets[@]}"; do
     $ANDROID_HOST_OUT/bin/generate-boot-image64 \
         --output-dir=$COMPILER_EXPLORER_DIR/compilers/dex2oat-local/app/system/framework \
         --compiler-filter=speed \
         --use-profile=false \
         --dex2oat-bin=$COMPILER_EXPLORER_DIR/compilers/dex2oat-local/x86_64/bin/dex2oat64 \
         --android-root=$COMPILER_EXPLORER_DIR/compilers/dex2oat-local/app \
         --core-only=true \
         --instruction-set=$instruction_set \
         -- \
         --runtime-arg \
         -Xgc:CMC
   done
   

   Note: You may change instruction_sets on the first line to only include the instruction sets that you need, to speed up boot image generation.

   Note: Although this step is not required, having boot images makes dex2oat generate better code.

10. Start Compiler Explorer server.

    (cd $COMPILER_EXPLORER_DIR/compiler-explorer && make run-only)
    

    Once you see Listening on http://localhost:10240/, you can open a browser with that address to access Compiler Explorer.

When you iterate, press Ctrl+C to stop the server, and then repeat the last three steps.