[clang] [CIR] Upstream TypeInfo attribute (PR #159426)

[Henrich Lauko via cfe-commits]

================
@@ -779,4 +779,54 @@ def CIR_AddressPointAttr : CIR_Attr<"AddressPoint", "address_point"> {
   }];
 }
 
+//===----------------------------------------------------------------------===//
+// TypeInfoAttr
+//===----------------------------------------------------------------------===//
+
+def CIR_TypeInfoAttr : CIR_Attr<"TypeInfo", "typeinfo", [TypedAttrInterface]> {
+  let summary = "Represents a typeinfo used for RTTI";
+  let description = [{
+    The typeinfo data for a given class is stored into an ArrayAttr. The
+    layout is determined by the C++ ABI used (clang only implements
+    itanium on CIRGen).
+
+    The verifier enforces that the output type is always a `!cir.record`,
+    and that the ArrayAttr element types match the equivalent member type
+    for the resulting record, i.e, a GlobalViewAttr for symbol reference or
+    an IntAttr for flags.
+
+    Example:
+
+    ```
+    cir.global "private" external @_ZTVN10__cxxabiv120__si_class_type_infoE
+      : !cir.ptr<i32>
+
+    !rec_anon_struct = !cir.record<struct  {!cir.ptr<!u8i>, !cir.ptr<!u8i>,
+      !cir.ptr<!u8i>}>
+
+    cir.global constant external @type_info = #cir.typeinfo<{
+      #cir.global_view<@_ZTVN10__cxxabiv120__si_class_type_infoE, [2 : i32]>
+      : !cir.ptr<!u8i>, #cir.global_view<@_ZTS1B> : !cir.ptr<!u8i>,
+      #cir.global_view<@_ZTI1A> : !cir.ptr<!u8i>}> : !rec_anon_struct
+    ```
+  }];
+
+  let parameters = (ins AttributeSelfTypeParameter<"">:$type,
+                        CIR_IntOrGlobalViewArrayAttr:$data);
----------------
xlauko wrote:

```suggestion
  let parameters = (ins 
    AttributeSelfTypeParameter<"">:$type,
    CIR_IntOrGlobalViewArrayAttr:$data
  );
```

https://github.com/llvm/llvm-project/pull/159426