[Mlir-commits] [mlir] b4280d6 - [mlir][docs] Clarify operation parser generation context (NFC) (#229460)

[llvmlistbot at llvm.org]

Author: Mehdi Amini
Date: 2026-10-06T15:48:45Z
New Revision: b4280d6b668ad2e1392f8cd677e140ff7508be1c

URL: https://github.com/llvm/llvm-project/commit/b4280d6b668ad2e1392f8cd677e140ff7508be1c
DIFF: https://github.com/llvm/llvm-project/commit/b4280d6b668ad2e1392f8cd677e140ff7508be1c.diff

LOG: [mlir][docs] Clarify operation parser generation context (NFC) (#229460)

Explain how GenContext and ODS optionality control attribute parsing,
and why attributes are required once an optional group selects a branch.

Assisted-by: Codex

Added: 
    

Modified: 
    mlir/tools/mlir-tblgen/OpFormatGen.cpp

Removed: 
    


################################################################################
diff  --git a/mlir/tools/mlir-tblgen/OpFormatGen.cpp b/mlir/tools/mlir-tblgen/OpFormatGen.cpp
index a4798440cf28d..dd635aef1e3a2 100644
--- a/mlir/tools/mlir-tblgen/OpFormatGen.cpp
+++ b/mlir/tools/mlir-tblgen/OpFormatGen.cpp
@@ -354,11 +354,17 @@ struct OperationFormat {
     std::optional<StringRef> variableTransformer;
   };
 
-  /// The context in which an element is generated.
+  /// The context used to generate an element's parser. This controls whether
+  /// attribute variables are parsed optionally; it does not change the parsing
+  /// of other element kinds.
   enum class GenContext {
-    /// The element is generated at the top-level or with the same behaviour.
+    /// Use the default parsing behaviour: an ODS optional attribute may be
+    /// absent. Used at the top level and by callers using the default context.
     Normal,
-    /// The element is generated inside an optional group.
+    /// Generate an element in a selected branch of an optional group. Attribute
+    /// variables must be present, even if they are optional in ODS. The group
+    /// is optional, but its contents are required once the branch is selected.
+    /// The group's first element is parsed separately to select the branch.
     Optional
   };
 
@@ -384,6 +390,8 @@ struct OperationFormat {
   /// Generate the operation parser from this format.
   void genParser(Operator &op, OpClass &opClass);
   /// Generate the parser code for a specific format element.
+  /// `genCtx`, together with ODS optionality, determines whether attribute
+  /// variables may be absent at this position.
   void genElementParser(FormatElement *element, MethodBody &body,
                         FmtContext &attrTypeCtx,
                         GenContext genCtx = GenContext::Normal);
@@ -1904,8 +1912,9 @@ void OperationFormat::genElementParser(FormatElement *element, MethodBody &body,
         }
       }
 
-      // Generate the rest of the elements inside an optional group. Elements in
-      // an optional group after the guard are parsed as required.
+      // Generate the remaining then-elements or all else-elements after the
+      // guard has selected a branch. Optional attributes must be parsed as
+      // required here so that an incomplete group is rejected.
       for (FormatElement *childElement : elements)
         if (childElement != elidedAnchorElement)
           genElementParser(childElement, body, attrTypeCtx,