[PATCH] D130255: [Clang][LoongArch] Add initial LoongArch target and driver support

Mon Jul 25 17:44:21 PDT 2022

MaskRay added inline comments.

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Comment at: clang/lib/Driver/ToolChains/Gnu.cpp:2226

+  static const char *const LoongArch64LibDirs[] = {"/lib64", "/lib"};
+  static const char *const LoongArch64Triples[] = {
----------------
xry111 wrote:
> SixWeining wrote:
> > xry111 wrote:
> > > SixWeining wrote:
> > > > MaskRay wrote:
> > > > > I don't know which of /lib64, /lib has been used. For purity, I'd hope that we just have /lib, no multilib style /lib64
> > > > I also don't know the actual usage of /lib64 but I just tried and it works fine if I remove /lib64.
> > > I don't like `lib64` too.  But for LoongArch LP64D, the path to ELF interpreter is hard coded `/lib64/ld-linux-loongarch-lp64d.so.1` and it seems too late to change it.  And LoongArch GCC installs libstdc++ etc. for LP64D into $PREFIX/lib64 by default (like x86_64).
> > > 
> > > As a distro (LFS) maintainer: we are already hacking GCC code to get rid of `/usr/lib64`.
> > Thanks for the quick reply. So I should keep the /lib64 here?
> I think you should keep it.  A multilib distro may have `/usr/lib64`, `/usr/lib32`, and `/usr/lib32sf` (`sf` for soft float or whatever) and make `/usr/lib` a symlink.  A "mostly 32-bit distro" may have symlink `/usr/lib` -> `/usr/lib32`, but still capable to build & run LA64 programs with libraries in `/usr/lib64`.  Removing `lib64` will break clang on such distros with `-mabi=64`.
> 
> Personally, I don't like `lib64`.  But we can't really predict what the distro maintainers will do (unless you say something explicitly like "a LP64D capable distro SHALL have LP64D libraries in `/usr/lib`" in a spec).
Dynamic loader selection is orthogonal to the LibDirs variable here. You can use /lib64/ld-linux-loongarch-lp64d.so.1 while the library paths are from /lib .

If anything, riscv multilib support is quite broken at this point so probably don't use it as a reference.
If there is ever a 32-bit distro which wants to do 64-bit compilation, you can leverage multiarch, which is less broken. https://maskray.me/blog/2021-03-28-compiler-driver-and-cross-compilation

Repository:
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CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D130255/new/

https://reviews.llvm.org/D130255