Running Thunderbird with the OpenPower Baseline JIT

The issues with Ion and Wasm in OpenPower Firefox notwithstanding, the Baseline JIT works well in Firefox ESR128, and many of you use it (including yours truly). Of course, that makes Thunderbird look sluggish without it.

I wasn't able to get a full LTO-PGO build for Thunderbird to build properly so far with gcc (workin' on it), but with the JIT patches for ESR128 an LTO optimized build will complete and run, and that's good enough for now. The diff for the .mozconfig is more or less the following:

export CC=/usr/bin/gcc
export CXX=/usr/bin/g++

mk_add_options MOZ_MAKE_FLAGS="-j24"

#ac_add_options --enable-application=browser
#ac_add_options MOZ_PGO=1
#
ac_add_options --enable-project=comm/mail
mk_add_options MOZ_OBJDIR=@TOPSRCDIR@/tbobj

ac_add_options --enable-optimize="-O3 -mcpu=power9 -fpermissive"
ac_add_options --enable-release
ac_add_options --enable-linker=bfd
ac_add_options --enable-lto=full
ac_add_options --without-wasm-sandboxed-libraries
ac_add_options --with-libclang-path=/usr/lib64

export GN=/home/censored/bin/gn # if you haz
export RUSTC_OPT_LEVEL=2

You can use a unified .mozconfig like this to handle both the browser and the E-mail client; if you do, to build the browser the commented lines should be uncommented and the two lines below the previously commented section should be commented.

You'll need comm-central embedded in your ESR128 tree as per the build instructions, and you may want to create an .hg/hgignore file inside your ESR128 source directory as well to keep changes to the core and Tbird from clashing, something like

^tbobj/
^comm/

which will ignore those directories but isn't a change to .hgignore that you have to manually edit out. Once constructed, your built client will be in tbobj/. If you were using a prebuilt Thunderbird before, you may need to start it with tbobj/dist/bin/thunderbird -p default-release (substitute your profile name if it differs) to make sure you get your old mailbox back, though as always backup your profile first.