Updating clang

1. Sync your Chromium tree to the latest revision to pick up any plugin changes

2. Run python tools/clang/scripts/upload_revision.py NNNN with the target LLVM SVN revision number. This creates a roll CL on a new branch, uploads it and starts tryjobs that build the compiler binaries into a staging bucket on Google Cloud Storage (GCS).

3. If the clang upload try bots succeed, copy the binaries from the staging bucket to the production one. For example:

   $ export rev=123456-1
   $ for x in Linux_x64 Mac Win ; do \
       gsutil.py cp -n -a public-read gs://chromium-browser-clang-staging/$x/clang-$rev.tgz \
           gs://chromium-browser-clang/$x/clang-$rev.tgz ; \
       gsutil.py cp -n -a public-read gs://chromium-browser-clang-staging/$x/llvmobjdump-$rev.tgz \
           gs://chromium-browser-clang/$x/llvmobjdump-$rev.tgz ; \
       gsutil.py cp -n -a public-read gs://chromium-browser-clang-staging/$x/llvmcfiverify-$rev.tgz \
           gs://chromium-browser-clang/$x/llvmcfiverify-$rev.tgz ; \
       gsutil.py cp -n -a public-read gs://chromium-browser-clang-staging/$x/translation_unit-$rev.tgz \
           gs://chromium-browser-clang/$x/translation_unit-$rev.tgz ; \
       gsutil.py cp -n -a public-read gs://chromium-browser-clang-staging/$x/llvm-code-coverage-$rev.tgz \
           gs://chromium-browser-clang/$x/llvm-code-coverage-$rev.tgz ; \
       done
   $ gsutil.py cp -n -a public-read gs://chromium-browser-clang-staging/Mac/lld-$rev.tgz \
         gs://chromium-browser-clang/Mac/lld-$rev.tgz
   

4. Run the goma package update script to push these packages to goma. If you do not have the necessary credentials to do the upload, ask clang@chromium.org to find someone who does

5. Run an exhaustive set of try jobs to test the new compiler:

   git cl try && \
   git cl try -m tryserver.chromium.mac -b mac_chromium_asan_rel_ng \
     -b ios-device && \
   git cl try -m tryserver.chromium.linux \
     -b linux_chromium_chromeos_asan_rel_ng -b linux_chromium_msan_rel_ng \
     -b linux_chromium_cfi_rel_ng &&
       git cl try -m tryserver.blink -b linux_trusty_blink_rel &&
       git cl try -m tryserver.chromium.chromiumos -b linux-chromeos-dbg
   

6. Commit roll CL from the first step

7. The bots will now pull the prebuilt binary, and goma will have a matching binary, too.