add definition draft of SliceAttr

Author: chencha3

mlir/include/mlir/Dialect/XeGPU/IR/XeGPUAttrs.td

@@ -330,4 +330,25 @@ def XeGPU_LayoutAttr : XeGPUAttr<"Layout", "layout"> {
   let genVerifyDecl = 1;
 }
 
+
+def XeGPU_SliceAttr : XeGPUAttr<"Slice", "slice"> {
+  let summary = [{Describes the data distribution and sharing among subgroups or work-items.}];
+
+  let description = [{
+    Like LayoutAttr, SliceAttr describes data distribution among subgroups or work-items.
+    However, whereas LayoutAttr requires the data to have the same rank as the attribute,
+    SliceAttr permits the data to have a lower rank. In this case, compute units in the
+    specified dimensions share the data, provided that the remaining ranks match the data
+    rank. SliceAttr is commonly used by operations such as vector.multi_reduction and
+    vector.broadcast.
+  }];
+
+  let parameters = (ins
+    "Attribute": $parent,
+    "DenseI64ArrayAttr": $dims
+  );
+
+  let assemblyFormat = "`<` $parent `,` `dim` `=` $dims `>`";
+}
+
 #endif // MLIR_DIALECT_XEGPU_IR_XEGPUATTRS_TD