Index: mlir/lib/Dialect/Affine/IR/AffineOps.cpp
===================================================================
--- mlir/lib/Dialect/Affine/IR/AffineOps.cpp
+++ mlir/lib/Dialect/Affine/IR/AffineOps.cpp
@@ -1550,6 +1550,12 @@
 }
 
 void AffineForOp::print(OpAsmPrinter &p) {
+  // Operation may be invalidated after applying a rewrite pattern.
+  if (region().empty()) {
+    p << " <NO REGION - INVALID>";
+    return;
+  }
+
   p << ' ';
   p.printOperand(getBody()->getArgument(0));
   p << " = ";