tflite: Add fp16 headers to cmake rule

This is needed to build GPU delegate without XNNPACK enabled.
It fixes the issue #46386.

PiperOrigin-RevId: 351901574
Change-Id: Ib0dff4c51627dfcd72fbb23d688ab2ae37505056

tensorflow/lite/CMakeLists.txt

@@ -206,6 +206,7 @@ endif()
 if(TFLITE_ENABLE_GPU)
   find_package(opencl_headers REQUIRED)
   find_package(vulkan_headers REQUIRED)
+  find_package(fp16_headers REQUIRED)
   # Android NDK already has OpenGL, EGL headers.
   if(NOT "${CMAKE_SYSTEM_NAME}" STREQUAL "Android")
     find_package(opengl_headers REQUIRED)

tensorflow/lite/tools/cmake/modules/Findfp16_headers.cmake

@@ -0,0 +1,16 @@
+#
+# Copyright 2021 The TensorFlow Authors. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+include(fp16_headers)

tensorflow/lite/tools/cmake/modules/fp16_headers.cmake

@@ -0,0 +1,41 @@
+#
+# Copyright 2021 The TensorFlow Authors. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# Skip installation when xnnpack is used since it also has fp16 headers.
+if(TARGET fp16_headers OR fp16_headers_POPULATED OR TFLITE_ENABLE_XNNPACK)
+  return()
+endif()
+
+include(FetchContent)
+
+OverridableFetchContent_Declare(
+  fp16_headers
+  GIT_REPOSITORY https://github.com/Maratyszcza/FP16
+  # GIT_TAG must keep in sync with https://github.com/google/XNNPACK/blob/master/cmake/DownloadFP16.cmake
+  GIT_TAG 3c54eacb74f6f5e39077300c5564156c424d77ba
+  GIT_PROGRESS TRUE
+  PREFIX "${CMAKE_BINARY_DIR}"
+  SOURCE_DIR "${CMAKE_BINARY_DIR}/fp16_headers"
+)
+
+OverridableFetchContent_GetProperties(fp16_headers)
+if(NOT fp16_headers)
+  OverridableFetchContent_Populate(fp16_headers)
+endif()
+
+include_directories(
+  AFTER
+   "${fp16_headers_SOURCE_DIR}/include"
+)