update CPU detection on ANDROID patch

3rdparty/cpufeatures/CMakeLists.txt

+if(NOT ANDROID)
+  message("cpufeatures is ANDROID project")
+endif()
 
-ocv_include_directories(${CMAKE_CURRENT_SOURCE_DIR})
-file(GLOB cpuf_s *.c)
-file(GLOB cpuf_h *.h)
-
-set(lib_srcs  ${cpuf_s})
-set(lib_hdrs  ${cpuf_h})
+set(CPUFEATURES_ROOT "${CMAKE_CURRENT_SOURCE_DIR}" CACHE PATH "Android cpufeatures project sources (for example, <android-ndk>/sources/android/cpufeatures)")
 
-set(CPUFEATURES_INCLUDE_DIR ${CMAKE_CURRENT_SOURCE_DIR} CACHE INTERNAL "")
+set(CPUFEATURES_INCLUDE_DIRS ${CPUFEATURES_ROOT} CACHE INTERNAL "")
 set(CPUFEATURES_LIBRARIES cpufeatures CACHE INTERNAL "")
 
-add_library(cpufeatures STATIC ${lib_srcs} ${lib_hdrs})
+if(NOT DEFINED CPUFEATURES_SOURCES)
+  set(CPUFEATURES_SOURCES ${CPUFEATURES_ROOT}/cpu-features.c ${CPUFEATURES_ROOT}/cpu-features.h)
+endif()
+
+include_directories(${CPUFEATURES_INCLUDE_DIRS})
+add_library(cpufeatures STATIC ${CPUFEATURES_SOURCES})
 
 set_target_properties(cpufeatures
   PROPERTIES OUTPUT_NAME cpufeatures
@@ -17,7 +20,7 @@ set_target_properties(cpufeatures
   COMPILE_PDB_NAME cpufeatures
   COMPILE_PDB_NAME_DEBUG "cpufeatures${OPENCV_DEBUG_POSTFIX}"
   ARCHIVE_OUTPUT_DIRECTORY ${3P_LIBRARY_OUTPUT_PATH}
-  )
+)
 
 if(ENABLE_SOLUTION_FOLDERS)
   set_target_properties(cpufeatures PROPERTIES FOLDER "3rdparty")
@@ -26,4 +29,3 @@ endif()
 if(NOT BUILD_SHARED_LIBS)
   ocv_install_target(cpufeatures EXPORT OpenCVModules ARCHIVE DESTINATION ${OPENCV_3P_LIB_INSTALL_PATH} COMPONENT dev)
 endif()
-

3rdparty/cpufeatures/LICENSE

+Copyright (C) 2016 The Android Open Source Project
+
+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
+
+     http://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.

3rdparty/cpufeatures/README.md

+The Android NDK provides a small library named cpufeatures that your app can use at runtime to detect the target device's CPU family and the optional features it supports.
+It is designed to work as-is on all official Android platform versions.
+
+https://developer.android.com/ndk/guides/cpu-features.html

3rdparty/libwebp/CMakeLists.txt

@@ -5,7 +5,7 @@
 project(${WEBP_LIBRARY})
 
 ocv_include_directories(${CMAKE_CURRENT_SOURCE_DIR})
-ocv_include_directories("${CPUFEATURES_INCLUDE_DIR}")
+ocv_include_directories(${CPUFEATURES_INCLUDE_DIRS})
 
 file(GLOB lib_srcs dec/*.c demux/*.c dsp/*.c enc/*.c mux/*.c utils/*.c webp/*.c)
 file(GLOB lib_hdrs dec/*.h demux/*.h dsp/*.h enc/*.h mux/*.h utils/*.h webp/*.h)

CMakeLists.txt

@@ -98,6 +98,10 @@ if(POLICY CMP0042)
   cmake_policy(SET CMP0042 NEW)
 endif()
 
+if(POLICY CMP0046)
+  cmake_policy(SET CMP0046 OLD)
+endif()
+
 if(POLICY CMP0051)
   cmake_policy(SET CMP0051 NEW)
 endif()

modules/core/CMakeLists.txt

@@ -32,7 +32,7 @@ source_group("Src" FILES "${OPENCV_MODULE_opencv_core_BINARY_DIR}/version_string
 ocv_glob_module_sources(SOURCES "${OPENCV_MODULE_opencv_core_BINARY_DIR}/version_string.inc"
                         HEADERS ${lib_cuda_hdrs} ${lib_cuda_hdrs_detail})
 
-ocv_module_include_directories(${the_module} ${ZLIB_INCLUDE_DIRS} ${OPENCL_INCLUDE_DIRS} ${CPUFEATURES_INCLUDE_DIR})
+ocv_module_include_directories(${the_module} ${ZLIB_INCLUDE_DIRS} ${OPENCL_INCLUDE_DIRS} ${CPUFEATURES_INCLUDE_DIRS})
 ocv_create_module(${extra_libs})
 
 ocv_target_link_libraries(${the_module} ${ZLIB_LIBRARIES} "${OPENCL_LIBRARIES}" "${VA_LIBRARIES}" "${LAPACK_LIBRARIES}" "${CPUFEATURES_LIBRARIES}")

modules/core/src/system.cpp

@@ -447,10 +447,16 @@ struct HWFeatures
         CV_UNUSED(cpuid_data_ex);
     #endif // OPENCV_HAVE_X86_CPUID
 
-    #if defined ANDROID || defined __linux__
+    #if defined __ANDROID__ || defined __linux__
     #ifdef __aarch64__
         have[CV_CPU_NEON] = true;
         have[CV_CPU_FP16] = true;
+    #elif defined __arm__ && defined __ANDROID__
+        __android_log_print(ANDROID_LOG_INFO, "OpenCV", "calling android_getCpuFeatures() ...");
+        uint64_t features = android_getCpuFeatures();
+        __android_log_print(ANDROID_LOG_INFO, "OpenCV", "calling android_getCpuFeatures() ... Done (%llx)", features);
+        have[CV_CPU_NEON] = (features & ANDROID_CPU_ARM_FEATURE_NEON) != 0;
+        have[CV_CPU_FP16] = (features & ANDROID_CPU_ARM_FEATURE_VFP_FP16) != 0;
     #elif defined __arm__
         int cpufile = open("/proc/self/auxv", O_RDONLY);
 
@@ -471,11 +477,6 @@ struct HWFeatures
 
             close(cpufile);
         }
-    #ifdef ANDROID
-        uint64_t features = android_getCpuFeatures();
-        have[CV_CPU_NEON] = (features & ANDROID_CPU_ARM_FEATURE_NEON) != 0;
-        have[CV_CPU_FP16] = (features & ANDROID_CPU_ARM_FEATURE_VFP_FP16) != 0;
-    #endif
     #endif
     #elif (defined __clang__ || defined __APPLE__)
     #if (defined __ARM_NEON__ || (defined __ARM_NEON && defined __aarch64__))