[clang] [CIR] Upstream Exception ThrowOp with subexpr (PR #161818)

[Andy Kaylor via cfe-commits]

================
@@ -4166,6 +4166,40 @@ def CIR_ThrowOp : CIR_Op<"throw"> {
   let hasVerifier = 1;
 }
 
+//===----------------------------------------------------------------------===//
+// AllocExceptionOp
+//===----------------------------------------------------------------------===//
+
+def CIR_AllocExceptionOp : CIR_Op<"alloc.exception"> {
+  let summary = "Allocates an exception according to Itanium ABI";
+  let description = [{
+    Implements a slightly higher level __cxa_allocate_exception:
+
+    `void *__cxa_allocate_exception(size_t thrown_size);`
+
+    If operation fails, program terminates, not throw.
----------------
andykaylor wrote:

```suggestion
    If the operation fails, the program terminates rather than throw.
```

https://github.com/llvm/llvm-project/pull/161818