added comments

Author: ayokunle321

mlir/lib/Dialect/Affine/IR/AffineOps.cpp

@@ -1902,13 +1902,14 @@ LogicalResult AffineForOp::verifyRegions() {
     if (failed(verifyDimAndSymbolIdentifiers(*this, getUpperBoundOperands(),
                                              getUpperBoundMap().getNumDims())))
       return failure();
-
+  // Verify that the bound maps produce at least one result.
+  /// Lower bound.
   if (getLowerBoundMap().getNumResults() < 1)
     return emitOpError("expected lower bound map to have at least one result");
-
+  /// Upper bound.
   if (getUpperBoundMap().getNumResults() < 1)
     return emitOpError("expected upper bound map to have at least one result");
-    
+
   unsigned opNumResults = getNumResults();
   if (opNumResults == 0)
     return success();