[PATCH] D86313: [runtimes] Allow LLVM_BUILTIN_TARGETS to include Darwin

[Petr Hosek via Phabricator via llvm-commits]

phosek added a comment.

In D86313#2229323 <https://reviews.llvm.org/D86313#2229323>, @smeenai wrote:

> In D86313#2229269 <https://reviews.llvm.org/D86313#2229269>, @phosek wrote:
>
>> I agree that the current situation is not optimal, I was never happy with the `default` case which is confusing for a lot of people I talked to. I would like to come up with a better solution, but I'm not sure if special casing the `x86_64-apple-darwin` is sufficient though. With Apple Silicon, I assume we're going to be building runtimes as universal binaries that target multiple architectures.
>>
>> We could consider completely decoupling runtimes from targets. Originally, each runtime build was identified only by its target, so you'd use `RUNTIMES_${target}_${variable}` to set target-specific variables. That became insufficient when we introduced the support for multilib, so now you also have a name and you can use `RUNTIMES_${target}+${name}_${variable}`. We could switch to `RUNTIMES_${name}_${variable}` and it'd be the responsibility of the user to set the target explicitly if they want it (FWIW it's something we already have to do in our build <https://github.com/llvm/llvm-project/blob/master/clang/cmake/caches/Fuchsia-stage2.cmake#L101> anyway because of Windows where the CMake behavior when you set `CMAKE_${LANG}_COMPILER_TARGET` breaks the build). If not, they get the default behavior, matching the `default` case today. What do you think?
>
> To clarify, what would be setting `${name}` in this scenario?

It'd be set by user. Today we have `BUILTIN_TARGETS` and `RUNTIME_TARGETS`, we could either repurpose those and create new variables. You'd use it as follows:

  list(APPEND BUILTIN_TARGETS "darwin")
  set(BUILTINS_darwin_CMAKE_SYSTEM_NAME Darwin CACHE STRING "")
  ...
  list(APPEND BUILTIN_TARGETS "linux")
  set(BUILTINS_linux_CMAKE_SYSTEM_NAME Linux CACHE STRING "")
  set(BUILTINS_linux_CMAKE_C_COMPILER_TARGET x86_64-linux-gnu CACHE STRING "")
  ...

Here `darwin` and `linux` are arbitrary names.


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https://reviews.llvm.org/D86313