Fix linking error of Flex delegate for iOS

This cl fixes three different issues about Flex delegate on iOS:
1. Duplicated symbols of C API exported by TensorFlowLiteC and
   TensorFlowLiteSelectTfOps. This is fixed by using avoid_deps.
2. Undefined symbol of uprv::getICUData::conversion
3. TensorFlowLiteC do not export the weak symbol AcquireFlexDelegate.
   This cl replaces the use of weak symbol by LoadLibrary::GetSymbol.

PiperOrigin-RevId: 339798211
Change-Id: I2e15c008a48b9638568c1a16b3c3b7bcc61e448f

tensorflow/core/kernels/BUILD

@@ -6475,6 +6475,7 @@ cc_library(
         "//tensorflow/core/platform:strong_hash",
         "//third_party/eigen3",
         "//third_party/fft2d:fft2d_headers",
+        "//third_party/icu/data:conversion_data",
         "@com_google_absl//absl/base",
         "@com_google_protobuf//:protobuf",
         "@fft2d",

tensorflow/lite/delegates/flex/build_def.bzl

@@ -20,6 +20,7 @@ load(
     "tflite_jni_linkopts",
 )
 load("@build_bazel_rules_android//android:rules.bzl", "android_library")
+load("//tensorflow/lite:special_rules.bzl", "flex_portable_tensorflow_deps")
 
 def generate_flex_kernel_header(
         name,
@@ -130,13 +131,7 @@ def tflite_flex_cc_library(
                 clean_dep("//tensorflow/core/kernels:android_all_ops_textual_hdrs"),
             ],
             visibility = visibility,
-            deps = [
-                "@com_google_absl//absl/strings:str_format",
-                "//third_party/fft2d:fft2d_headers",
-                "//third_party/eigen3",
-                "@com_google_absl//absl/types:optional",
-                "@gemmlowp",
-                "@icu//:common",
+            deps = flex_portable_tensorflow_deps() + [
                 clean_dep("//tensorflow/core:protos_all_cc"),
                 clean_dep("//tensorflow/core:portable_tensorflow_lib_lite"),
                 clean_dep("//tensorflow/core/platform:strong_hash"),

tensorflow/lite/experimental/ios/BUILD.apple

@@ -71,6 +71,7 @@ tflite_ios_static_framework(
 # bazel build -c opt --config=ios --ios_multi_cpus=armv7,arm64,x86_64 //tensorflow/lite/experimental/ios:TensorFlowLiteSelectTfOps_framework
 ios_static_framework(
     name = "TensorFlowLiteSelectTfOps_framework",
+    avoid_deps = ["//tensorflow/lite/c:common"],
     bundle_name = "TensorFlowLiteSelectTfOps",
     minimum_os_version = TFL_MINIMUM_OS_VERSION,
     deps = [

tensorflow/lite/interpreter_builder.cc

@@ -44,6 +44,20 @@ limitations under the License.
 #endif
 #endif
 
+// TODO(b/139446230): Move to portable platform header.
+#if defined(__ANDROID__)
+#define TFLITE_IS_MOBILE_PLATFORM
+#endif  // defined(__ANDROID__)
+
+#if defined(__APPLE__)
+#include "TargetConditionals.h"
+#if TARGET_IPHONE_SIMULATOR
+#define TFLITE_IS_MOBILE_PLATFORM
+#elif TARGET_OS_IPHONE
+#define TFLITE_IS_MOBILE_PLATFORM
+#endif
+#endif  // defined(__APPLE__)
+
 namespace tflite {
 
 namespace {
@@ -112,9 +126,16 @@ const char* kEmptyTensorName = "";
 // For flex delegate, see also the strong override in
 // lite/delegates/flex/delegate.cc.
 TFLITE_ATTRIBUTE_WEAK Interpreter::TfLiteDelegatePtr AcquireFlexDelegate() {
-#if !defined(__ANDROID__)
-  // If _pywrap_tensorflow_internal.so is available, use
-  // TF_AcquireFlexDelegate() to initialize flex delegate.
+  auto acquire_flex_delegate_func =
+      reinterpret_cast<Interpreter::TfLiteDelegatePtr (*)()>(
+          SharedLibrary::GetSymbol("TF_AcquireFlexDelegate"));
+  if (acquire_flex_delegate_func) {
+    return acquire_flex_delegate_func();
+  }
+
+#if !defined(TFLITE_IS_MOBILE_PLATFORM)
+  // Load TF_AcquireFlexDelegate() from _pywrap_tensorflow_internal.so if it is
+  // available.
   const char* filename_pywrap_tensorflow_internal =
 #if defined(_WIN32)
       "_pywrap_tensorflow_internal.pyd";
@@ -126,15 +147,16 @@ TFLITE_ATTRIBUTE_WEAK Interpreter::TfLiteDelegatePtr AcquireFlexDelegate() {
   void* lib_tf_internal =
       SharedLibrary::LoadLibrary(filename_pywrap_tensorflow_internal);
   if (lib_tf_internal) {
-    auto TF_AcquireFlexDelegate =
+    acquire_flex_delegate_func =
         reinterpret_cast<Interpreter::TfLiteDelegatePtr (*)()>(
             SharedLibrary::GetLibrarySymbol(lib_tf_internal,
                                             "TF_AcquireFlexDelegate"));
-    if (TF_AcquireFlexDelegate) {
-      return TF_AcquireFlexDelegate();
+    if (acquire_flex_delegate_func) {
+      return acquire_flex_delegate_func();
     }
   }
-#endif
+#endif  // !defined(TFLITE_IS_MOBILE_PLATFORM)
+
   return Interpreter::TfLiteDelegatePtr(nullptr, [](TfLiteDelegate*) {});
 }
 

tensorflow/lite/special_rules.bzl

@@ -77,3 +77,16 @@ def tflite_schema_utils_friends():
     # Its usage should be rare, and is often abused by tools that are doing
     # Flatbuffer creation/manipulation in unofficially supported ways."
     return ["//..."]
+
+def flex_portable_tensorflow_deps():
+    """Returns dependencies for building portable tensorflow in Flex delegate."""
+
+    return [
+        "//third_party/fft2d:fft2d_headers",
+        "//third_party/eigen3",
+        "@com_google_absl//absl/types:optional",
+        "@com_google_absl//absl/strings:str_format",
+        "@gemmlowp",
+        "@icu//:common",
+        "//third_party/icu/data:conversion_data",
+    ]