Index: mlir/test/lib/Dialect/Test/TestOps.td
===================================================================
--- mlir/test/lib/Dialect/Test/TestOps.td
+++ mlir/test/lib/Dialect/Test/TestOps.td
@@ -602,6 +602,20 @@
 def OpK : TEST_Op<"op_k">, Arguments<(ins)>, Results<(outs I32)>;
 def : Pat<(OpJ), (OpK)>;
 
+// Test patterns for redundant computation of operands
+def OpM : TEST_Op<"op_m"> {
+  let arguments = (ins I32, OptionalAttr<I32Attr>:$optional_attr);
+  let results = (outs I32);
+}
+// Pattern add the argument plus a increasing static number hidden in
+// OpMTest function. That value is set into the optional argument.
+// That way, we will know if operations is called once or twice.
+def OpM_GetNullAttr : NativeCodeCall<"Attribute()">;
+def OpM_AttributeIsNull : Constraint<CPred<"! ($_self)">, "Attribute is null">;
+def OpM_Val : NativeCodeCall<"OpM_Test($_builder, $0)">;
+def : Pat<(OpM $attr, $optAttr), (OpM $attr, (OpM_Val $attr) ),
+    [(OpM_AttributeIsNull:$optAttr)]>;
+
 // Test `$_` for ignoring op argument match.
 def TestIgnoreArgMatchSrcOp : TEST_Op<"ignore_arg_match_src"> {
   let arguments = (ins
Index: mlir/test/lib/Dialect/Test/TestPatterns.cpp
===================================================================
--- mlir/test/lib/Dialect/Test/TestPatterns.cpp
+++ mlir/test/lib/Dialect/Test/TestPatterns.cpp
@@ -32,6 +32,16 @@
                                     op.operand());
 }
 
+// Native function for testing redundant calls to Native calls.
+// OpM_Test will return Pi, increased by 1 for each subsequent calls.
+// This let us check the number of times OpM_Test was called by inspecting
+// the returned value in the MLIR output.
+static int64_t OpM_IncrasingValue = 314159265;
+static Attribute OpM_Test(PatternRewriter &rewriter, Value val){
+  int64_t i = OpM_IncrasingValue++;
+  return rewriter.getIntegerAttr(rewriter.getIntegerType(32), i);
+}
+
 namespace {
 #include "TestPatterns.inc"
 } // end anonymous namespace
Index: mlir/test/mlir-tblgen/pattern.mlir
===================================================================
--- mlir/test/mlir-tblgen/pattern.mlir
+++ mlir/test/mlir-tblgen/pattern.mlir
@@ -359,3 +359,14 @@
   %0 = "test.one_i32_out"() : () -> (i32)
   return %0 : i32
 }
+
+//===----------------------------------------------------------------------===//
+// Test Rewrite rules calling native calls only once
+//===----------------------------------------------------------------------===//
+
+// CHECK-LABEL: redundantTest
+func @redundantTest(%arg0: i32) -> i32 {
+  %0 = "test.op_m"(%arg0) : (i32) -> i32
+  // CHECK: "test.op_m"(%arg0) {optional_attr = 314159265 : i32} : (i32) -> i32
+  return %0 : i32
+}
Index: mlir/tools/mlir-tblgen/RewriterGen.cpp
===================================================================
--- mlir/tools/mlir-tblgen/RewriterGen.cpp
+++ mlir/tools/mlir-tblgen/RewriterGen.cpp
@@ -1046,9 +1046,9 @@
 
   for (int argIndex = 0, e = resultOp.getNumArgs(); argIndex < e; ++argIndex) {
     if (resultOp.getArg(argIndex).is<NamedAttribute *>()) {
-      const char *addAttrCmd = "if ({1}) {{"
-                               "  tblgen_attrs.emplace_back(rewriter."
-                               "getIdentifier(\"{0}\"), {1}); }\n";
+      const char *addAttrCmd = "{ if (auto tmpAttr = {1}) "
+                               "tblgen_attrs.emplace_back(rewriter."
+                               "getIdentifier(\"{0}\"), tmpAttr); }\n";
       // The argument in the op definition.
       auto opArgName = resultOp.getArgName(argIndex);
       if (auto subTree = node.getArgAsNestedDag(argIndex)) {