Restore with_select_tf_ops build flag.

This remains useful for testing and development. Restore the ability
to inject support for TF ops in TFLite using `--define=with_select_tf_ops=true`.

See also issue #34277.

PiperOrigin-RevId: 313873470
Change-Id: I6b68cd863efc17f5ae0667c0d2c9d68958d6e4ad

tensorflow/lite/BUILD

@@ -56,6 +56,15 @@ config_setting(
     visibility = ["//visibility:public"],
 )
 
+# Enables inclusion of select TensorFlow kernels via the TFLite Flex delegate
+# when building TFLite shared libraries.
+# WARNING: This build flag is experimental and subject to change.
+config_setting(
+    name = "with_select_tf_ops",
+    define_values = {"with_select_tf_ops": "true"},
+    visibility = ["//visibility:public"],
+)
+
 TFLITE_DEFAULT_COPTS = if_not_windows([
     "-Wall",
     "-Wno-comment",

tensorflow/lite/build_def.bzl

@@ -110,6 +110,26 @@ def tflite_jni_linkopts():
     """Defines linker flags to reduce size of TFLite binary with JNI."""
     return tflite_jni_linkopts_unstripped() + tflite_symbol_opts()
 
+def maybe_flex_deps(deps):
+    """Returns necessary flex deps when with_select_tf_ops build flag is used
+
+    Args:
+      deps: The source deps for the target (to avoid deps duplication).
+    Returns:
+       A list of additional flex deps required, based on the build flags used.
+       If with_select_tf_ops is not true, this will be an empty list.
+    """
+
+    # Filter redundant flex deps if already provided.
+    flex_dep = clean_dep("//tensorflow/lite/delegates/flex:delegate")
+    if type(deps) == type([]) and flex_dep in deps:
+        return []
+
+    return select({
+        clean_dep("//tensorflow/lite:with_select_tf_ops"): [flex_dep],
+        "//conditions:default": [],
+    })
+
 def tflite_jni_binary(
         name,
         copts = tflite_copts(),
@@ -139,7 +159,7 @@ def tflite_jni_binary(
         copts = copts,
         linkshared = linkshared,
         linkstatic = linkstatic,
-        deps = deps + [linkscript, exported_symbols],
+        deps = deps + [linkscript, exported_symbols] + maybe_flex_deps(deps),
         srcs = srcs,
         tags = tags,
         linkopts = linkopts,
@@ -149,6 +169,7 @@ def tflite_jni_binary(
 def tflite_cc_shared_object(
         name,
         copts = tflite_copts(),
+        deps = [],
         linkopts = [],
         linkstatic = 1,
         per_os_targets = False,
@@ -160,6 +181,7 @@ def tflite_cc_shared_object(
         linkstatic = linkstatic,
         linkopts = linkopts + tflite_jni_linkopts(),
         framework_so = [],
+        deps = deps + maybe_flex_deps(deps),
         per_os_targets = per_os_targets,
         **kwargs
     )

tensorflow/lite/g3doc/guide/ops_select.md

@@ -212,8 +212,11 @@ TensorFlow ops library can be included and enabled as follows:
 
 *   Enable monolithic builds if necessary by adding the `--config=monolithic`
     build flag.
-*   Add the TensorFlow ops delegate library dependency to the build
-    dependencies: `tensorflow/lite/delegates/flex:delegate`.
+*   Do one of the following:
+    *   Include the `--define=with_select_tf_ops=true` build flag in the `bazel
+        build` invocation when building the TensorFlow Lite binary.
+    *   Add the TensorFlow ops delegate library dependency to the build
+        dependencies: `tensorflow/lite/delegates/flex:delegate`.
 
 Note that the necessary `TfLiteDelegate` will be installed automatically when
 creating the interpreter at runtime as long as the delegate is linked into the