From 7fcfafff8bab4d24608d6897a5db137f380d7a4b Mon Sep 17 00:00:00 2001
From: Alexander Smorkalov <alexander.smorkalov@opencv.ai>
Date: Wed, 22 Apr 2026 13:05:39 +0300
Subject: [PATCH] Use fast math for dnn module.

---
 cmake/OpenCVUtils.cmake    | 11 +++++++++++
 modules/dnn/CMakeLists.txt |  7 +++++++
 2 files changed, 18 insertions(+)

diff --git a/cmake/OpenCVUtils.cmake b/cmake/OpenCVUtils.cmake
index 93e93c157c..880a72c9e1 100644
--- a/cmake/OpenCVUtils.cmake
+++ b/cmake/OpenCVUtils.cmake
@@ -1519,6 +1519,17 @@ function(ocv_target_compile_definitions target)
   endif()
 endfunction()
 
+function(ocv_target_compile_options target)
+  _ocv_fix_target(target)
+  if(NOT TARGET ${target})
+    if(NOT DEFINED OPENCV_MODULE_${target}_LOCATION)
+      message(FATAL_ERROR "ocv_target_compile_definitions: invalid target: '${target}'")
+    endif()
+    set(OPENCV_MODULE_${target}_COMPILE_OPTIONS ${OPENCV_MODULE_${target}_COMPILE_OPTIONS} ${ARGN} CACHE INTERNAL "" FORCE)
+  else()
+    target_compile_options(${target} ${ARGN})
+  endif()
+endfunction()
 
 function(_ocv_append_target_includes target)
   if(DEFINED OCV_TARGET_INCLUDE_DIRS_${target})
diff --git a/modules/dnn/CMakeLists.txt b/modules/dnn/CMakeLists.txt
index f1e8132daa..76f4515f9a 100644
--- a/modules/dnn/CMakeLists.txt
+++ b/modules/dnn/CMakeLists.txt
@@ -37,6 +37,13 @@ if(HAVE_CANN)
   ocv_target_compile_definitions(${the_module} PRIVATE "HAVE_CANN=1")
 endif()
 
+if(MSVC)
+  ocv_target_compile_options(${the_module} PRIVATE "/fp:fast")
+elseif(CV_GCC OR CV_CLANG)
+  ocv_target_compile_options(${the_module} PRIVATE -ffast-math)
+  ocv_target_compile_options(${the_module} PRIVATE -fno-finite-math-only)
+endif()
+
 ocv_option(OPENCV_DNN_CUDA "Build with CUDA support"
     HAVE_CUDA
     AND HAVE_CUBLAS