[llvm] [llvm] annotate interfaces in llvm/Target for DLL export (PR #143615)

[Saleem Abdulrasool via llvm-commits]

compnerd wrote:

I think that we should file a follow up issue to remove `LLVM_EXTERNAL_VISIBILITY`.

I suspect that MSVC does some proper homing for the symbol and thus re-uses the definition across the module. This would be hidden in the static linking due to the local resolution.

https://github.com/llvm/llvm-project/pull/143615