[clang] [CIR] Add CIR vtable attribute (PR #154415)

[Bruno Cardoso Lopes via cfe-commits]

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@@ -496,6 +496,72 @@ def CIR_GlobalViewAttr : CIR_Attr<"GlobalView", "global_view", [
   }];
 }
 
+//===----------------------------------------------------------------------===//
+// VTableAttr
+//===----------------------------------------------------------------------===//
+
+def CIR_VTableAttr : CIR_Attr<"VTable", "vtable", [TypedAttrInterface]> {
+  let summary = "Represents a C++ vtable";
+  let description = [{
+    Wraps a #cir.const_record containing one or more vtable arrays.
+
+    In most cases, the anonymous record type wrapped by this attribute will
+    contain a single array corresponding to the vtable for one class. However,
+    in the case of multiple inheritence, the anonymous structure may contain
+    multiple arrays, each of which is a vtable.
+
+    Example 1 (single vtable):
+    ```mlir
+    cir.global linkonce_odr @_ZTV6Mother =
+      #cir.vtable<{
+        #cir.const_array<[
+          #cir.ptr<null> : !cir.ptr<!u8i>,
+          #cir.global_view<@_ZTI6Mother> : !cir.ptr<!u8i>,
+          #cir.global_view<@_ZN6Mother9MotherFooEv> : !cir.ptr<!u8i>,
+          #cir.global_view<@_ZN6Mother10MotherFoo2Ev> : !cir.ptr<!u8i>
+        ]> : !cir.array<!cir.ptr<!u8i> x 4>
+      }> : !rec_anon_struct1
+    ```
+
+    Example 2 (multiple vtables):
+    ```mlir
+    cir.global linkonce_odr @_ZTV5Child =
+      #cir.vtable<{
+        #cir.const_array<[
+          #cir.ptr<null> : !cir.ptr<!u8i>,
+          #cir.global_view<@_ZTI5Child> : !cir.ptr<!u8i>,
+          #cir.global_view<@_ZN5Child9MotherFooEv> : !cir.ptr<!u8i>,
+          #cir.global_view<@_ZN6Mother10MotherFoo2Ev> : !cir.ptr<!u8i>
+        ]> : !cir.array<!cir.ptr<!u8i> x 4>,
+        #cir.const_array<[
+          #cir.ptr<-8 : i64> : !cir.ptr<!u8i>,
+          #cir.global_view<@_ZTI5Child> : !cir.ptr<!u8i>,
+          #cir.global_view<@_ZN6Father9FatherFooEv> : !cir.ptr<!u8i>
+        ]> : !cir.array<!cir.ptr<!u8i> x 3>
+      }> : !rec_anon_struct2
+    ```
+  }];
+
+  // `vtable_data` is a const record with one element, containing an array of
+  // vtable information.
+  let parameters = (ins
+    AttributeSelfTypeParameter<"">:$type,
+    "mlir::ArrayAttr":$vtable_data
----------------
bcardosolopes wrote:

Should we just call this one `data` instead of `vtable_data`? To use the param you need the casted attribute anyways, so repeating the name might not help much here.

https://github.com/llvm/llvm-project/pull/154415