Erase control dependencies from feeds.

Prior, when ops with ".input" are created for feeds, control dependencies can be placed on them. As ".input" are going away, these control dependencies should be removed, as they are not necessary.

PiperOrigin-RevId: 278395166
Change-Id: I9c730f2fff782d128d7fc0fc098000ca3202bd3b

tensorflow/compiler/mlir/tensorflow/tests/graphdef2mlir/feed-control-dep.pbtxt

@@ -0,0 +1,68 @@
+# RUN: tf-mlir-translate -graphdef-to-mlir %s -tf-input-arrays=input -tf-input-data-types=DT_FLOAT -tf-output-arrays=output_node -o - | FileCheck %s --dump-input=fail
+
+node {
+  name: "input"
+  op: "Placeholder"
+  attr {
+    key: "dtype"
+    value {
+      type: DT_FLOAT
+    }
+  }
+  attr {
+    key: "shape"
+    value {
+      shape {
+        dim {
+          size: 1
+        }
+      }
+    }
+  }
+}
+node {
+  name: "variable_node"
+  op: "Const"
+  input: "^input"
+  attr {
+    key: "dtype"
+    value {
+      type: DT_FLOAT
+    }
+  }
+  attr {
+    key: "value"
+    value {
+      tensor {
+        dtype: DT_FLOAT
+        tensor_shape {
+        }
+        float_val: 1
+      }
+    }
+  }
+}
+node {
+  name: "output_node"
+  op: "Identity"
+  input: "variable_node"
+  input: "^input"
+  attr {
+    key: "T"
+    value {
+      type: DT_FLOAT
+    }
+  }
+}
+library {
+}
+versions {
+}
+
+# CHECK:      func @main(%[[ARG_0:[a-z0-9]+]]: tensor<f32>) -> tensor<f32>
+# CHECK-NEXT: tf.entry_function = {inputs = "input", outputs = "output_node"}
+# CHECK:        %[[GRAPH:[0-9]+]] = tf_executor.graph
+# CHECK:          %[[CONST:[0-9]+]]:2 = tf_executor.island wraps "tf.Const"()
+# CHECK:          %[[OUTPUT:[0-9]+]]:2 = tf_executor.island wraps "tf.Identity"(%[[CONST]]#0)
+# CHECK:          tf_executor.fetch %[[OUTPUT]]#0
+# CHECK:        return %[[GRAPH]]

tensorflow/compiler/mlir/tensorflow/translate/import_model.cc

@@ -1064,6 +1064,11 @@ Status ImporterBase::ConvertFunctionArgAndRets(
       // Collect mapping of OutputTensor to associated block arg.
       arg_nodes_to_values.try_emplace({arg_node.node, arg_node.index}, arg_def);
       island->getResult(0)->replaceAllUsesWith(arg_def);
+      // Erase control outputs from feed.
+      auto control_uses = island->getResult(1)->getUses();
+      for (auto& control_use : llvm::make_early_inc_range(control_uses))
+        control_use.getOwner()->eraseOperand(control_use.getOperandNumber());
+
       island->dropAllReferences();
       island->erase();
       continue;