[clang] [CIR] Upstream CIR Dialect TryOp with Catch Attrs (PR #162897)

[Andy Kaylor via cfe-commits]

================
@@ -4296,6 +4296,81 @@ def CIR_AllocExceptionOp : CIR_Op<"alloc.exception"> {
   }];
 }
 
+//===----------------------------------------------------------------------===//
+// TryOp
+//===----------------------------------------------------------------------===//
+
+def CIR_TryOp : CIR_Op<"try",[
+  DeclareOpInterfaceMethods<RegionBranchOpInterface>,
+  RecursivelySpeculatable, AutomaticAllocationScope, NoRegionArguments
+]> {
+  let summary = "C++ try block";
+  let description = [{
+    Holds the lexical scope of `try {}`. Note that resources used on catch
+    clauses are usually allocated in the same parent as `cir.try`.
+
+    `synthetic`: use `cir.try` to represent try/catches not originally
+    present in the source code (e.g. `g = new Class` under `-fexceptions`).
----------------
andykaylor wrote:

```suggestion
    present in the source code. For example, a synthetic `cir.try` region
    is created around the constructor call when `operator new` is used
    so that the memory allocated will be freed if the constructor throws
    an exception.
```

https://github.com/llvm/llvm-project/pull/162897