[libcxx-commits] [clang] [compiler-rt] [libcxx] Implement soft x87 `long double` for ARM64EC (PR #236406)

[LIU Hao via libcxx-commits]

lhmouse wrote:

@mstorsjo 
> I would go with the compiler changes first - changes to runtimes are secondary.
> 
> For the compiler-rt change, I'm unsure if that works for the current setup of llvm-mingw though. Since [mstorsjo/llvm-mingw at 9868478](https://github.com/mstorsjo/llvm-mingw/commit/986847858c5d598682bedef87987290c8754d7ad) we don't build compiler-rt twice for aarch64 and arm64ec, but just once for aarch64 with the `-marm64x` flag. So it runs the cmake configuration just once and builds the objects once. Internally, for each object file, clang then compiles it twice, for aarch64 and arm64ec. So for this case, the new file would need to be added for aarch64 too (but only for Windows targets), but the file can have internal ifdefs to make it an empty no-op for regular aarch64.
> 
> The changes to libcxx are even further down on the priority list; there's no instance that runs the libcxx tests in arm64ec mode at all right now, neither upstream nor downstream, as far as I know of.

OK I will file separate PRs as you request.


https://github.com/llvm/llvm-project/pull/236406