When using GNU binutils, clang passes the LLVMgold.so plugin to the
linker for certain operations that require special support in the linker
like doing link time optimization (LTO). When passing the plugin to the
linker's command line, clang assumes that llvm and itself are installed
in the same prefix and thus `/path/to/clang/bin/../lib/LLVMgold.so` is
the plugin.
Since we install clang and llvm to separate store paths, this assumption
does not hold. When clang-unwrapped only had a single output, we worked
around this issue by symlinking `$out/lib/LLVMgold.so` to
`${llvm}/lib/LLVMgold.so`. However since we split all llvm packages into
multiple outputs clang's `$out` no longer has a lib directory and clang
can't discover clangs lib output on its own. As a result LTO was broken.
Instead of introducing yet another hack and having a symlink to
LLVMgold.so in `$out/lib` (despite having `$lib/lib` as well), we patch
clang to use a hard coded path to `${libllvm.lib}/lib` for discovering
`LLVMgold.so`.
Resolves#123361.
The main thing was using `llvm_meta` in all versions.
Secondarily:
- libunwindx7: Forgot to split outputs
- libcxx{,abi} 12: Forgot to apply output-splitting patches.
- simplify `useLLVM` stdenv-switching logic.
- openmp always gets its own directory
Also begin to start work on cross compilation, though that will have to
be finished later.
The patches are based on the first version of
https://reviews.llvm.org/D99484. It's very annoying to do the
back-porting but the review has uncovered nothing super major so I'm
fine sticking with what I've got.
Beyond making the outputs work, I also strove to re-sync the packages,
as they have been drifting pointlessly apart for some time.
----
Other misc notes, highly incomplete
- lvm-config-native and llvm-config are put in `dev` because they are
tools just for build time.
- Clang no longer has an lld dep. That was introduced in
db29857eb3, but if clang needs help
finding lld when it is used we should just pass it flags / put in the
resource dir. Providing it at build time increases critical path
length for no good reason.
----
A note on `nativeCC`:
`stdenv` takes tools from the previous stage, so:
1. `pkgsBuildBuild`: `(?1, x, x)`
2. `pkgsBuildBuild.stdenv.cc`: `(?0, ?1, x)`
while:
1. `pkgsBuildBuild`: `(?1, x, x)`
2. `pkgsBuildBuild.targetPackages`: `(x, x, ?2)`
3. `pkgsBuildBuild.targetPackages.stdenv.cc`: `(?1, x, x)`
This flag was introduced for clang 9, but we use it in the `lldClang`
wrapper for `llvmPackages` 7, 8 and 9. For this purpose the patch was
backported for `llvmPackages_8.clang`, but not for `llvmPackages_7.clang`
which has been done in this commit.
`lldClang` is mostly used when cross compiling and
`stdenv.hostPlatform.useLLVM` is true. Most likely this problem wasn't
noticed since `useLLVM` with `llvmPackages_7` was broken for other
reasons as well and all cross targets (like `wasi32`) which have
`useLLVM` at the moment use `llvmPackages_8`.
With this change tests.cross.llvm.hello.{musl64, …} works again.
This reverts commit c778945806.
I believe this is exactly what brings the staging branch into
the right shape after the last merge from master (through staging-next);
otherwise part of staging changes would be lost
(due to being already reachable from master but reverted).
You can build (partially) with LLVM toolchain using the useLLVM flag.
This works like so:
nix-build -A hello --arg crossSystem '{ system =
"aarch64-unknown-linux-musl"; useLLVM = true }'
also don’t separate debug info in lldClang
It doesn’t work currently with that setup hook. Missing build-id?
* llvm: build w/polly in-tree, optionally
Don't enable by default yet, defer rebuilds.
* top-level: llvm-polly, clang-polly
* bit hacky re:overrides
* need to explicitly set cmake flags for clang to link in polly
