Build with zlib on Unix

[am11]

llvm-dwarfdump requires zlib support in dotnet/runtime#85192 (comment). It doesn't hurt having it enabled in the other tools (distro, such as Ubuntu, have it enabled for llvm-*).

[am11]

cc @jkotas, @agocke, @MichalStrehovsky

[MichalStrehovsky]

This likely brings a dependency on zlib to objwriter as well (i.e. this is also a product change). The pre-existing -DLLVM_ENABLE_ZLIB=OFF on Windows is there because LLVM will bring in something that depends on zlib if left unchecked, at least on Windows.

I don't have big concerns around it since ilc already seems to depend on zlib on Linux anyway, but calling it out.

I assume mac is fine and ships with a zlib?

[agocke]

LGTM, thanks!

[am11]

From the docs: https://llvm.org/docs/HowToCrossCompileLLVM.html

2. The ARM libraries won’t be installed in your system. But the CMake prepare step, which checks for dependencies, will check the host libraries, not the target ones. Below there’s a list of some dependencies, but your project could have more, or this document could be outdated. You’ll see the errors while linking as an indication of that.

Debian based distros have a way to add multiarch, which adds a new architecture and allows you to install packages for those systems. See https://wiki.debian.org/Multiarch/HOWTO for more info.

But not all distros will have that, and possibly not an easy way to install them in any anyway, so you’ll have to build/download them separately.

which (after trying out different ways to satisfy cmake's "find_package() config-mode" on CBL-mariner without modifying the LLVM source files) translates to my second commit. Lets see how it goes. 🤞😅

[akoeplinger]

@am11

/__w/_temp/13f0d39e-dcfc-4f55-8b65-a14369a4d938.sh: line 1: ROOTFS_DIR: command not found
ln: failed to create symbolic link '/usr/lib/aarch64-alpine-linux-musl': Permission denied

should be $ROOTFS_DIR since it is an env var (or use $(rootfs)), and you'll need sudo

[am11]

Switching images with rootfs to use include(FindZLIB) makes all platform happy simultaneously. It is supported since cmake v3.1. This approach does not require symlinks.

[akoeplinger]

So in https://reviews.llvm.org/D70519 there was an attempt to use FindZLIB and it was noted it changes the value in llvm-config --system-libs, is that still the case?

[am11]

It will select $ZLIB_ROOT/libz.so which is enough for our purposes. As long as RPATH is correct (which I haven't checked as full cross-build was taking ages on my machine), it will load on any system with libz. On NativeAOT, libz is a system prerequisite on build machine, so ilc will be ok.

[am11]

Good to merge?

[MichalStrehovsky]

Good to merge?

@directhex @akoeplinger any concerns from Mono side? This is changing build configuration everywhere. It looks good from CoreCLR test tools/objwriter perspective.

[am11]

Don't use FindZLIB, just setting ZLIB_ROOT is enough

Cool 👍 (assuming it works 😅)

[akoeplinger]

Thank you!