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

Tue Apr 27 21:06:44 PDT 2021

phosek added a comment.

In D101194#2721643 <https://reviews.llvm.org/D101194#2721643>, @MaskRay wrote:

> multiarch is not consistent within GCC, either (also note that not all GCC installations are configured with multiarch. `--print-multiarch` prints an empty line).
> I have tried various GCC installations and made a summary https://maskray.me/blog/2021-03-28-compiler-driver-and-cross-compilation : even if the multiarch triple for x86_64 Linux is `x86_64-linux-gnu`, there are a few `x86_64-pc-linux-gnu` paths. (You can configure and get `x86_64-pc-linux-gnu-gcc` or `x86_64-unknown-linux-gnu-gcc`)
> For musl systems (`*-linux-musl`), multiarch doesn't make sense. If we use multiarch, we'll need to invent `*-linux-musl` for them.
>
> For some GCC related paths, we have no choice but to detect their paths. For entirely clang internal stuff (runtime library paths), I actually appreciate that we have a useful, un-normalized 'vendor' part.
> It gives users a choice if they want to have `x86_64-pc[12345]-linux-gnu`. This argument is weak, but the other arguments are probably stronger. My viewpoint is: if we can avoid multiarch, just avoid it.

SGTM, I'll partially revert this change and switch back to using normalized triples if that's fine with you.

> I haven't figured out how to do a proper runtime build...
>
> `-DLLVM_ENABLE_PER_TARGET_RUNTIME_DIR=on -DLLVM_RUNTIME_TARGETS=default -DLLVM_ENABLE_RUNTIMES='compiler-rt;libcxx;libunwind' ` gives me
>
>   CMake Error at /usr/share/cmake-3.18/Modules/ExternalProject.cmake:3152 (add_custom_target):                                                                                                                                                                                                
>     add_custom_target cannot create target "builtins" because another target                                                                                                                                                                                                                  
>     with the same name already exists.  The existing target is a custom target                                                                                                                                                                                                                
>     created in source directory                                                                                                                                                                                                                                                               
>     "/home/maskray/llvm/compiler-rt/lib/builtins".  See                                                                                                                                                                                                                      
>     documentation for policy CMP0002 for more details.                                                                                                                                                                                                                                        
>   Call Stack (most recent call first):                                                                                                                                                                                                                                                        
>     cmake/modules/LLVMExternalProjectUtils.cmake:283 (ExternalProject_Add)                                                                                                                                                                                                                    
>     runtimes/CMakeLists.txt:81 (llvm_ExternalProject_Add)                                                                                                                                                                                                                                     
>     runtimes/CMakeLists.txt:134 (builtin_default_target)

You also need `-DLLVM_BUILTIN_TARGETS=default`.

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D101194/new/

https://reviews.llvm.org/D101194