[clang] [llvm] [RISCV] Add support for Swift calling conventions and error handling (PR #205469)

[Jessica Clarke via llvm-commits]

================
@@ -399,6 +400,32 @@ static bool CC_RISCV_Impl(unsigned ValNo, MVT ValVT, MVT LocVT,
     }
   }
 
+  // Swift calling convention special registers. Use callee-saved s-registers
----------------
jrtc27 wrote:

Justification for ABI choices doesn't belong in the toolchain implementation, it belongs in the language ABI specification. Is there such a document?

https://github.com/llvm/llvm-project/pull/205469