[clang] [CIR] Upstream Re-Throw with no return (PR #154994)

[Andy Kaylor via cfe-commits]

================
@@ -3864,4 +3864,63 @@ def CIR_VAArgOp : CIR_Op<"va_arg"> {
   }];
 }
 
+//===----------------------------------------------------------------------===//
+// ThrowOp
+//===----------------------------------------------------------------------===//
+
+def CIR_ThrowOp : CIR_Op<"throw"> {
+  let summary = "(Re)Throws an exception";
+  let description = [{
+    It's equivalent __cxa_throw:
----------------
andykaylor wrote:

```suggestion
    This operation is equivalent to either __cxa_throw or __cxa_rethrow, depending on the arguments.
```

https://github.com/llvm/llvm-project/pull/154994