Description
Summary
Downloading and building LLVM on a somewhat recent 8c Laptop takes around 30 minutes and is a major annoyance for new contributors who like to help std::autodiff or related LLVM based modules.
It's also annoying that we have to rebuild it every two weeks when we get a new LLVM version (btw. thanks to nikita and all for the quick updates).
There isn't really a higher reason why std::autodiff forces rebuilding, except of cmake shenanigans of which I am not an expert. Most of the work here is likely not coding, but talking to bootstrap and/or LLVM people to figure out how we can build Enzyme against a pre-build and downloaded LLVM.
Previous discussions are here on github and here on zulip.
This gh comment seems to be especially relevant. To get started, just summarizing and verifying that these are still up to date would be good.
One thing that changed since we opened the issues last time, is that these days we only need (and build) libEnzyme-<Version>.so, we don't need to support LLVMEnzyme-X.so, ClangEnzyme-X.so and LLDEnzyme-X.so, since I added an Enzyme flag to skip building them. We therefore don't need LLVM to be build with it's plugin interface enabled anymore. That should make it easier to use the download-llvm.
EnzymeAD/Enzyme#2249
Current build instruction for autodiff can be found here: https://enzyme.mit.edu/rust/installation.html
Command used
./configure --enable-llvm-enzyme --release-channel=nightlyExpected behaviour
It should work!
Actual behaviour
It does not work :(
Bootstrap configuration (bootstrap.toml)
flexible.
Operating system
any (except MSVC which has another Enzyme bug)
HEAD
Additional context
Build Log
<log>