[Mlir-commits] [mlir] [MLIR][LLVM] add metadata attrs and `llvm.named_metadata` op (PR #186703)

[Markus Böck]

================
@@ -1686,4 +1686,75 @@ def UWTableKindAttr : LLVM_Attr<"UWTableKind", "uwtableKind"> {
   let assemblyFormat = "`<` $uwtableKind `>`";
 }
 
+//===----------------------------------------------------------------------===//
+// Metadata Attributes
+//===----------------------------------------------------------------------===//
+//
+// These attributes model LLVM IR metadata nodes (llvm::Metadata and its
+// subclasses). They can be nested to form arbitrary metadata trees and are
+// translated to their LLVM IR counterparts during MLIR-to-LLVM-IR conversion.
+
+def LLVM_MDStringAttr : LLVM_Attr<"MDString", "md_string"> {
+  let summary = "LLVM metadata string";
+  let description = [{
+    Wraps a string as an LLVM metadata node, corresponding to
+    `llvm::MDString` in LLVM IR.
+
+    Example:
+    ```mlir
+    #llvm.md_string<"foo.buffer">
+    ```
+  }];
+  let parameters = (ins "StringAttr":$value);
+  let assemblyFormat = "`<` $value `>`";
+}
+
+def LLVM_MDConstantAttr : LLVM_Attr<"MDConstant", "md_const"> {
+  let summary = "LLVM constant-as-metadata";
+  let description = [{
+    Wraps an attribute as an LLVM metadata node, corresponding to
+    `llvm::ConstantAsMetadata` wrapping a `llvm::Constant*` in LLVM IR.
+    Currently, only integers/IntegerAttrs supported.
+
+    Example:
+    ```mlir
+    #llvm.md_const<42 : i32>
+    ```
+  }];
+  let parameters = (ins "Attribute":$value);
+  let assemblyFormat = "`<` $value `>`";
+}
+
+def LLVM_MDFuncAttr : LLVM_Attr<"MDFunc", "md_func"> {
+  let summary = "LLVM function-as-metadata";
+  let description = [{
+    References a function (or global) symbol as LLVM metadata, corresponding
+    to `llvm::ValueAsMetadata::get(function)` in LLVM IR.
+
+    Example:
+    ```mlir
+    #llvm.md_func<@my_kernel>
+    ```
+  }];
+  let parameters = (ins "FlatSymbolRefAttr":$name);
+  let assemblyFormat = "`<` $name `>`";
+}
+
+def LLVM_MDNodeAttr : LLVM_Attr<"MDNode", "md_node"> {
+  let summary = "LLVM metadata node";
+  let description = [{
+    Represents an LLVM metadata node. The operands
+    can be any combination of metadata attributes: `#llvm.md_string`,
+    `#llvm.md_const`, `#llvm.md_func`, or nested `#llvm.md_node`.
+
+    Example:
+    ```mlir
+    #llvm.md_node<[#llvm.md_const<0 : i32>, #llvm.md_string<"foo.buffer">]>
+    #llvm.md_node<[]>
+    ```
+  }];
+  let parameters = (ins "ArrayAttr":$operands);
----------------
zero9178 wrote:

Would it make more sense for this to be an `ArrayRefParameter` instead? Saves on one indirection + uniquing of an `ArrayAttr`

https://github.com/llvm/llvm-project/pull/186703