[clang] [CIR] Upstream initial support for fixed size VectorType (PR #136488)

[Henrich Lauko via cfe-commits]

================
@@ -307,6 +307,26 @@ def CIR_ArrayType : CIR_Type<"Array", "array",
   }];
 }
 
+//===----------------------------------------------------------------------===//
+// VectorType (fixed size)
+//===----------------------------------------------------------------------===//
+
+def CIR_VectorType : CIR_Type<"Vector", "vector",
+    [DeclareTypeInterfaceMethods<DataLayoutTypeInterface>]> {
+
+  let summary = "CIR vector type";
+  let description = [{
+    `cir.vector' represents fixed-size vector types.  The parameters are the
+    element type and the number of elements.
----------------
xlauko wrote:

```suggestion
    `!cir.vector' represents fixed-size vector types, parameterized 
    by the element type and the number of elements.

    Example:
    ```mlir
    !cir.vector<!u64i x 2>
    !cir.vector<!cir.float x 4>
    ```
```

https://github.com/llvm/llvm-project/pull/136488