From d8b42792a62d00de3f5a4998efc5dd7175eb6cac Mon Sep 17 00:00:00 2001
From: Alexander Alekhin <alexander.alekhin@intel.com>
Date: Thu, 30 May 2019 18:24:01 +0300
Subject: [PATCH] cmake: update ENABLE_FAST_MATH option

---
 CMakeLists.txt                          |  2 +-
 cmake/OpenCVCompilerOptimizations.cmake |  4 ----
 cmake/OpenCVCompilerOptions.cmake       | 27 +++++++++++++++++--------
 3 files changed, 20 insertions(+), 13 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 0ed7e41be3..25e7160841 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -473,7 +473,7 @@ OCV_OPTION(ENABLE_COVERAGE            "Enable coverage collection with  GCov"
 OCV_OPTION(OPENCV_ENABLE_MEMORY_SANITIZER "Better support for memory/address sanitizers"         OFF)
 OCV_OPTION(ENABLE_OMIT_FRAME_POINTER  "Enable -fomit-frame-pointer for GCC"                      ON   IF CV_GCC )
 OCV_OPTION(ENABLE_POWERPC             "Enable PowerPC for GCC"                                   ON   IF (CV_GCC AND CMAKE_SYSTEM_PROCESSOR MATCHES powerpc.*) )
-OCV_OPTION(ENABLE_FAST_MATH           "Enable -ffast-math (not recommended for GCC 4.6.x)"       OFF  IF (CV_GCC AND (X86 OR X86_64)) )
+OCV_OPTION(ENABLE_FAST_MATH           "Enable compiler options for fast math optimizations on FP computations (not recommended)" OFF)
 if(NOT IOS)  # Use CPU_BASELINE instead
 OCV_OPTION(ENABLE_NEON                "Enable NEON instructions"                                 (NEON OR ANDROID_ARM_NEON OR AARCH64) IF (CV_GCC OR CV_CLANG) AND (ARM OR AARCH64 OR IOS) )
 OCV_OPTION(ENABLE_VFPV3               "Enable VFPv3-D32 instructions"                            OFF  IF (CV_GCC OR CV_CLANG) AND (ARM OR AARCH64 OR IOS) )
diff --git a/cmake/OpenCVCompilerOptimizations.cmake b/cmake/OpenCVCompilerOptimizations.cmake
index 8247a9a53c..fcf31135f0 100644
--- a/cmake/OpenCVCompilerOptimizations.cmake
+++ b/cmake/OpenCVCompilerOptimizations.cmake
@@ -635,10 +635,6 @@ macro(ocv_compiler_optimization_options_finalize)
   if(MSVC)
     # Generate Intrinsic Functions
     set(OPENCV_EXTRA_FLAGS "${OPENCV_EXTRA_FLAGS} /Oi")
-
-    if((X86 OR X86_64) AND CMAKE_SIZEOF_VOID_P EQUAL 4 AND ";${CPU_BASELINE_FINAL};" MATCHES ";SSE;")
-      set(OPENCV_EXTRA_FLAGS "${OPENCV_EXTRA_FLAGS} /fp:fast") # !! important - be on the same wave with x64 compilers
-    endif()
   endif(MSVC)
 endmacro()
 
diff --git a/cmake/OpenCVCompilerOptions.cmake b/cmake/OpenCVCompilerOptions.cmake
index fc29d279c4..23b08b2f36 100644
--- a/cmake/OpenCVCompilerOptions.cmake
+++ b/cmake/OpenCVCompilerOptions.cmake
@@ -75,11 +75,25 @@ if(NOT MSVC)
   add_extra_compiler_option(-fsigned-char)
 endif()
 
-if(CV_ICC AND NOT ENABLE_FAST_MATH)
-  if(MSVC)
-    add_extra_compiler_option("/fp:precise")
-  else()
-    add_extra_compiler_option("-fp-model precise")
+if(MSVC)
+  if(NOT " ${CMAKE_CXX_FLAGS} ${OPENCV_EXTRA_FLAGS} ${OPENCV_EXTRA_CXX_FLAGS}" MATCHES " /fp:")
+    if(ENABLE_FAST_MATH)
+      add_extra_compiler_option("/fp:fast")
+    else()
+      add_extra_compiler_option("/fp:precise")
+    endif()
+  endif()
+elseif(CV_ICC)
+  if(NOT " ${CMAKE_CXX_FLAGS} ${OPENCV_EXTRA_FLAGS} ${OPENCV_EXTRA_CXX_FLAGS}" MATCHES " /fp:"
+      AND NOT " ${CMAKE_CXX_FLAGS} ${OPENCV_EXTRA_FLAGS} ${OPENCV_EXTRA_CXX_FLAGS}" MATCHES " -fp-model"
+  )
+    if(NOT ENABLE_FAST_MATH)
+      add_extra_compiler_option("-fp-model precise")
+    endif()
+  endif()
+elseif(CV_GCC OR CV_CLANG)
+  if(ENABLE_FAST_MATH)
+    add_extra_compiler_option(-ffast-math)
   endif()
 endif()
 
@@ -165,9 +179,6 @@ if(CV_GCC OR CV_CLANG)
   elseif(DEFINED ENABLE_OMIT_FRAME_POINTER)
     add_extra_compiler_option(-fno-omit-frame-pointer)
   endif()
-  if(ENABLE_FAST_MATH)
-    add_extra_compiler_option(-ffast-math)
-  endif()
 
   # Profiling?
   if(ENABLE_PROFILING)