[PATCH] D101194: [Driver] Push multiarch path setup to individual drivers

Tue Apr 27 19:30:10 PDT 2021

phosek added a comment.

In D101194#2721390 <https://reviews.llvm.org/D101194#2721390>, @MaskRay wrote:

> I thought this was NFC:(
>
> Yeah, personally I think the previous behavior (`lib/clang/13.0.0/lib/x86_64-unknown-linux-gnu/libclang_rt.asan.a`) is slightly better than the new `lib/clang/13.0.0/lib/x86_64-linux-gnu/libclang_rt.asan.a`.
> multiarch paths are suitable for GCC specific directories (`lib/$triple`, libstdc++ `aarch64-linux-gnu/include/c++/10`, etc) but llvm specific libraries don't necessarily use that.

I should have been clear, sorry about that. I think there are three separate issues:

1. Rather than trying various triple versions, we should use one canonical spelling when searching for Clang's standard and runtime libraries. That means less system calls and better error messages, this is what this change was primarily intended to do.
2. Following from the previous point, we need to decide which canonical spelling to use. Since we're trying to use the multiarch layout, I was following the Debian documentation <https://wiki.debian.org/Multiarch/Tuples> which is closest thing to a spec I'm aware of. The alternative would be to use the normalized target, the main disadvantage being that we would be diverging from existing quasi standard.
3. `-DLLVM_ENABLE_PER_TARGET_RUNTIME_DIR=ON` gives you a different result depending on how you spell the targets in `-DLLVM_BUILTIN_TARGETS=` and `-DLLVM_RUNTIME_TARGETS=`, this is what @bjope ran into and I'd consider that a bug since the directory layout is an implementation detail and we should be able to change it without users having to change their build.

I'm working on a solution for #3 and I should have a patch ready soon. I'm curious about your thoughts on #2.

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https://reviews.llvm.org/D101194