check FP16 build condition correctly

* use __GNUC_MINOR__ in correct place to check the version of GCC
  * check processor support of FP16 at run time
  * check compiler support of FP16 and pass correct compiler option
  * rely on ENABLE_AVX on gcc since AVX is generated when mf16c is passed
  * guard correctly using ifdef in case of various configuration
  * use v_float16x4 correctly by including the right header file

cmake/OpenCVCompilerOptions.cmake

@@ -151,7 +151,7 @@ if(CMAKE_COMPILER_IS_GNUCXX)
     add_extra_compiler_option("-mfp16-format=ieee")
   endif(ARM)
   if(ENABLE_NEON)
-    add_extra_compiler_option("-mfpu=neon-fp16")
+    add_extra_compiler_option("-mfpu=neon")
   endif()
   if(ENABLE_VFPV3 AND NOT ENABLE_NEON)
     add_extra_compiler_option("-mfpu=vfpv3")
@@ -336,6 +336,34 @@ if(CMAKE_COMPILER_IS_GNUCXX AND CMAKE_OPENCV_GCC_VERSION_NUM GREATER 399)
   add_extra_compiler_option(-fvisibility-inlines-hidden)
 endif()
 
+if(NOT OPENCV_FP16_DISABLE)
+  if(ARM AND ENABLE_NEON)
+    set(FP16_OPTION "-mfpu=neon-fp16")
+  elseif((X86 OR X86_64) AND NOT MSVC AND ENABLE_AVX)
+    set(FP16_OPTION "-mf16c")
+  endif()
+  try_compile(__VALID_FP16
+    "${OpenCV_BINARY_DIR}"
+    "${OpenCV_SOURCE_DIR}/cmake/checks/fp16.cpp"
+    COMPILE_DEFINITIONS "-DCHECK_FP16" "${FP16_OPTION}"
+    OUTPUT_VARIABLE TRY_OUT
+    )
+  if(NOT __VALID_FP16)
+    if((X86 OR X86_64) AND NOT MSVC AND NOT ENABLE_AVX)
+      # GCC enables AVX when mf16c is passed
+      message(STATUS "FP16: Feature disabled")
+    else()
+      message(STATUS "FP16: Compiler support is not available")
+    endif()
+  else()
+    message(STATUS "FP16: Compiler support is available")
+    set(HAVE_FP16 1)
+    if(NOT ${FP16_OPTION} STREQUAL "")
+      add_extra_compiler_option(${FP16_OPTION})
+    endif()
+  endif()
+endif()
+
 #combine all "extra" options
 set(CMAKE_C_FLAGS           "${CMAKE_C_FLAGS} ${OPENCV_EXTRA_FLAGS} ${OPENCV_EXTRA_C_FLAGS}")
 set(CMAKE_CXX_FLAGS         "${CMAKE_CXX_FLAGS} ${OPENCV_EXTRA_FLAGS} ${OPENCV_EXTRA_CXX_FLAGS}")
@@ -376,21 +404,6 @@ if(MSVC)
   endif()
 endif()
 
-if(NOT OPENCV_FP16_DISABLE)
-  try_compile(__VALID_FP16
-    "${OpenCV_BINARY_DIR}"
-    "${OpenCV_SOURCE_DIR}/cmake/checks/fp16.cpp"
-    COMPILE_DEFINITIONS "-DCHECK_FP16"
-    OUTPUT_VARIABLE TRY_OUT
-    )
-  if(NOT __VALID_FP16)
-    message(STATUS "FP16: Compiler support is not available")
-  else()
-    message(STATUS "FP16: Compiler support is available")
-    set(HAVE_FP16 1)
-  endif()
-endif()
-
 if(APPLE AND NOT CMAKE_CROSSCOMPILING AND NOT DEFINED ENV{LDFLAGS} AND EXISTS "/usr/local/lib")
   link_directories("/usr/local/lib")
 endif()

modules/core/include/opencv2/core/cvdef.h

@@ -310,7 +310,7 @@ enum CpuFeatures {
 typedef union Cv16suf
 {
     short i;
-#if ( defined (__arm__) || defined (__aarch64__) ) && !defined (__CUDACC__) && ( defined (__GNUC__) && ( ( ( 4 <= __GNUC__ ) && ( 7 <= __GNUC__ ) ) || ( 5 <= __GNUC__ ) ) )
+#if ( defined (__arm__) || defined (__aarch64__) ) && !defined (__CUDACC__) && ( defined (__GNUC__) && ( ( ( 4 <= __GNUC__ ) && ( 7 <= __GNUC_MINOR__ ) ) || ( 5 <= __GNUC__ ) ) )
     __fp16 h;
 #endif
     struct _fp16Format

modules/core/src/convert.cpp

@@ -44,6 +44,7 @@
 #include "precomp.hpp"
 
 #include "opencl_kernels_core.hpp"
+#include "opencv2/core/hal/intrin.hpp"
 
 #ifdef __APPLE__
 #undef CV_NEON
@@ -4379,7 +4380,7 @@ struct Cvt_SIMD<float, int>
 
 #endif
 
-#if !( ( defined (__arm__) || defined (__aarch64__) ) && ( defined (__GNUC__) && ( ( ( 4 <= __GNUC__ ) && ( 7 <= __GNUC__ ) ) || ( 5 <= __GNUC__ ) ) ) )
+#if !( ( defined (__arm__) || defined (__aarch64__) ) && ( defined (__GNUC__) && ( ( ( 4 <= __GNUC__ ) && ( 7 <= __GNUC_MINOR__ ) ) || ( 5 <= __GNUC__ ) ) ) )
 // const numbers for floating points format
 const unsigned int kShiftSignificand    = 13;
 const unsigned int kMaskFp16Significand = 0x3ff;
@@ -4387,7 +4388,7 @@ const unsigned int kBiasFp16Exponent    = 15;
 const unsigned int kBiasFp32Exponent    = 127;
 #endif
 
-#if ( defined (__arm__) || defined (__aarch64__) ) && ( defined (__GNUC__) && ( ( ( 4 <= __GNUC__ ) && ( 7 <= __GNUC__ ) ) || ( 5 <= __GNUC__ ) ) )
+#if ( defined (__arm__) || defined (__aarch64__) ) && ( defined (__GNUC__) && ( ( ( 4 <= __GNUC__ ) && ( 7 <= __GNUC_MINOR__ ) ) || ( 5 <= __GNUC__ ) ) )
 static float convertFp16SW(short fp16)
 {
     // Fp16 -> Fp32
@@ -4449,7 +4450,7 @@ static float convertFp16SW(short fp16)
 }
 #endif
 
-#if ( defined (__arm__) || defined (__aarch64__) ) && ( defined (__GNUC__) && ( ( ( 4 <= __GNUC__ ) && ( 7 <= __GNUC__ ) ) || ( 5 <= __GNUC__ ) ) )
+#if ( defined (__arm__) || defined (__aarch64__) ) && ( defined (__GNUC__) && ( ( ( 4 <= __GNUC__ ) && ( 7 <= __GNUC_MINOR__ ) ) || ( 5 <= __GNUC__ ) ) )
 static short convertFp16SW(float fp32)
 {
     // Fp32 -> Fp16
@@ -4557,7 +4558,7 @@ cvtScaleHalf_<float, short>( const float* src, size_t sstep, short* dst, size_t
             if ( ( (intptr_t)dst & 0xf ) == 0 )
 #endif
             {
-#if CV_FP16
+#if CV_FP16 && CV_SIMD128
                 for ( ; x <= size.width - 4; x += 4)
                 {
                     v_float32x4 v_src = v_load(src + x);
@@ -4603,7 +4604,7 @@ cvtScaleHalf_<short, float>( const short* src, size_t sstep, float* dst, size_t
             if ( ( (intptr_t)src & 0xf ) == 0 )
 #endif
             {
-#if CV_FP16
+#if CV_FP16 && CV_SIMD128
                 for ( ; x <= size.width - 4; x += 4)
                 {
                     v_float16x4 v_src = v_load_f16(src + x);

modules/core/test/test_intrin.cpp

@@ -711,12 +711,14 @@ template<typename R> struct TheTest
         return *this;
     }
 
-#if CV_FP16
     TheTest & test_loadstore_fp16()
     {
+#if CV_FP16
         AlignedData<R> data;
         AlignedData<R> out;
 
+        if(checkHardwareSupport(CV_CPU_FP16))
+        {
             // check if addresses are aligned and unaligned respectively
             EXPECT_EQ((size_t)0, (size_t)&data.a.d % 16);
             EXPECT_NE((size_t)0, (size_t)&data.u.d % 16);
@@ -735,24 +737,30 @@ template<typename R> struct TheTest
             out.a.clear();
             v_store_f16(out.a.d, r1);
             EXPECT_EQ(data.a, out.a);
+        }
 
         return *this;
+#endif
     }
 
     TheTest & test_float_cvt_fp16()
     {
+#if CV_FP16
         AlignedData<v_float32x4> data;
 
+        if(checkHardwareSupport(CV_CPU_FP16))
+        {
             // check conversion
             v_float32x4 r1 = v_load(data.a.d);
             v_float16x4 r2 = v_cvt_f16(r1);
             v_float32x4 r3 = v_cvt_f32(r2);
             EXPECT_EQ(0x3c00, r2.get0());
             EXPECT_EQ(r3.get0(), r1.get0());
+        }
 
         return *this;
-    }
 #endif
+    }
 
 };