Index: mlir/lib/Conversion/SCFToGPU/SCFToGPU.cpp
===================================================================
--- mlir/lib/Conversion/SCFToGPU/SCFToGPU.cpp
+++ mlir/lib/Conversion/SCFToGPU/SCFToGPU.cpp
@@ -517,6 +517,16 @@
     }
     cloningMap.map(iv, newIndex);
   }
+
+  // Propagate custom user defined optional attributes, that can be used at
+  // later stage, such as extension data for GPU kernel dispatch
+  for (const auto &namedAttr : parallelOp.getAttrs()) {
+    if (namedAttr.first == gpu::getMappingAttrName() ||
+        namedAttr.first == ParallelOp::getOperandSegmentSizeAttr())
+      continue;
+    launchOp.setAttr(namedAttr.first, namedAttr.second);
+  }
+
   Block *body = parallelOp.getBody();
   worklist.reserve(worklist.size() + body->getOperations().size());
   for (Operation &op : llvm::reverse(body->without_terminator()))
Index: mlir/test/Conversion/SCFToGPU/parallel_loop.mlir
===================================================================
--- mlir/test/Conversion/SCFToGPU/parallel_loop.mlir
+++ mlir/test/Conversion/SCFToGPU/parallel_loop.mlir
@@ -304,6 +304,19 @@
 
 // -----
 
+// Optional attribute lowering test
+
+func @parallel_loop_optional_attr() {
+  %c0 = constant 0 : index
+  %c1 = constant 1 : index
+  scf.parallel (%i0) = (%c0) to (%c1) step (%c1) {
+  } { mapping = [{processor = 0, map = affine_map<(d0) -> (d0)>, bound = affine_map<(d0) -> (d0)>}], optional_attr = 1 }
+  // CHECK: optional_attr = 1
+  return
+}
+
+// -----
+
 // Mapping to the same processor twice.
 
 func @parallel_double_map(%arg0 : index, %arg1 : index, %arg2 : index,