[clang] [clang] Allow __attribute__((swiftcall)) on all targets (PR #71986)

[Sergei Barannikov via cfe-commits]

s-barannikov wrote:

I think the choice whether or not to support Swift calling convention should be made by individual targets without providing "safe" default. As pointed out in the linked PR, supporting Swift CC is not only about enabling the attribute support -- backend also needs modifications so that the calling convention is effective. This can only be done based on the ABI, which is target-dependent.


https://github.com/llvm/llvm-project/pull/71986