root-project · guitargeek · Oct 9, 2025 · Oct 9, 2025 · Oct 9, 2025
@@ -18,7 +18,6 @@ builtin_openssl=ON
 builtin_pcre=ON
 builtin_tbb=ON
 builtin_unuran=ON
-builtin_vc=ON
 builtin_vdt=ON
 builtin_veccore=ON
 builtin_xrootd=ON

@@ -47,6 +47,7 @@ The following people have contributed to this new version:
   Relative RPATHs to the main ROOT libraries are unconditionally appended to all ROOT executables and libraries if the operating system supports it.
   If you want a ROOT build without RPATHs, use the canonical CMake variable `CMAKE_SKIP_INSTALL_RPATH=TRUE`.
 * The `TH1K` class is deprecated and will be removed in 6.40. It did not implement the `TH1` interface consistently, and limited the usability of the k-neighbors method it implemented by closely coupling the algorithm with the histogram class. Please use the new `TMath::KNNDensity` function that implements the same mathematical logic.
+* The `vc` and `builtin_vc` build options are deprecated and will be removed in ROOT 6.40. They were not working anymore on newer platforms, and the vectorized math functions that they added to ROOT were not adopted by its users.
 
 ## Core Libraries
 * Behavior change: when selecting a template instantiation for a dictionary, all the template arguments have to be fully defined - the forward declarations are not enough any more. The error prompted by the dictionary generator will be `Warning: Unused class rule: MyTemplate<MyFwdDeclaredClass>`.

@@ -107,7 +107,7 @@ ROOT_BUILD_OPTION(builtin_pcre OFF "Build bundled copy of PCRE")
 ROOT_BUILD_OPTION(builtin_png OFF "Build bundled copy of libpng")
 ROOT_BUILD_OPTION(builtin_tbb OFF "Build TBB internally (requires network)")
 ROOT_BUILD_OPTION(builtin_unuran OFF "Build bundled copy of unuran")
-ROOT_BUILD_OPTION(builtin_vc OFF "Build Vc internally (requires network)")
+ROOT_BUILD_OPTION(builtin_vc OFF "Build Vc internally (requires network) [deprecated]")
 ROOT_BUILD_OPTION(builtin_vdt OFF "Build VDT internally (requires network)")
 ROOT_BUILD_OPTION(builtin_veccore OFF "Build VecCore internally (requires network)")
 ROOT_BUILD_OPTION(builtin_xrootd OFF "Build XRootD internally (requires network)")
@@ -180,7 +180,7 @@ ROOT_BUILD_OPTION(unfold OFF "Enable the unfold package [GPL]")
 ROOT_BUILD_OPTION(unuran OFF "Enable support for UNURAN (package for generating non-uniform random numbers) [GPL]")
 ROOT_BUILD_OPTION(uring OFF "Enable support for io_uring (requires liburing and Linux kernel >= 5.1)")
 ROOT_BUILD_OPTION(use_gsl_cblas ON "Use the CBLAS library from GSL instead of finding a more optimized BLAS library automatically with FindBLAS (the GSL CBLAS is less performant but more portable)")
-ROOT_BUILD_OPTION(vc OFF "Enable support for Vc (SIMD Vector Classes for C++)")
+ROOT_BUILD_OPTION(vc OFF "Enable support for Vc (SIMD Vector Classes for C++) [deprecated]")
 ROOT_BUILD_OPTION(vdt ON "Enable support for VDT (fast and vectorisable mathematical functions)")
 ROOT_BUILD_OPTION(veccore OFF "Enable support for VecCore SIMD abstraction library")
 ROOT_BUILD_OPTION(vecgeom OFF "Enable support for VecGeom vectorized geometry library")
@@ -402,7 +402,7 @@ foreach(opt afdsmgrd afs alien bonjour builtin_afterimage castor chirp cxx11 cxx
 endforeach()
 
 #---Deprecated options------------------------------------------------------------------------
-foreach(opt )
+foreach(opt builtin_vc vc)
   if(${opt})
     message(DEPRECATION ">>> Option '${opt}' is deprecated and will be removed in the next release of ROOT. Please contact root-dev@cern.ch should you still need it.")
   endif()

@@ -1365,106 +1365,12 @@ if(builtin_tbb)
   set(TBB_TARGET TBB)
 endif()
 
-#---Check for Vc---------------------------------------------------------------------
-if(builtin_vc)
-  unset(Vc_FOUND)
-  unset(Vc_FOUND CACHE)
-  set(vc ON CACHE BOOL "Enabled because builtin_vc requested (${vc_description})" FORCE)
-elseif(vc)
-  if(fail-on-missing)
-    find_package(Vc 1.4.4 CONFIG QUIET REQUIRED)
-  else()
-    find_package(Vc 1.4.4 CONFIG QUIET)
-    if(NOT Vc_FOUND)
-      message(STATUS "Vc library not found, support for it disabled.")
-      message(STATUS "Please enable the option 'builtin_vc' to build Vc internally.")
-      set(vc OFF CACHE BOOL "Disabled because Vc not found (${vc_description})" FORCE)
-    endif()
-  endif()
-  if(Vc_FOUND)
-    set_property(DIRECTORY APPEND PROPERTY INCLUDE_DIRECTORIES ${Vc_INCLUDE_DIR})
-    BUILD_ROOT_INCLUDE_PATH("${Vc_INCLUDE_DIR}")
-  endif()
-endif()
-
-if(vc AND NOT Vc_FOUND)
-  ROOT_CHECK_CONNECTION_AND_DISABLE_OPTION("vc")
-endif()
-
-if(vc AND NOT Vc_FOUND)
-  set(Vc_VERSION "1.4.4")
-  set(Vc_PROJECT "Vc-${Vc_VERSION}")
-  set(Vc_SRC_URI "${lcgpackages}/${Vc_PROJECT}.tar.gz")
-  set(Vc_DESTDIR "${CMAKE_BINARY_DIR}/externals")
-  set(Vc_ROOTDIR "${Vc_DESTDIR}/${CMAKE_INSTALL_PREFIX}")
-  set(Vc_LIBNAME "${CMAKE_STATIC_LIBRARY_PREFIX}Vc${CMAKE_STATIC_LIBRARY_SUFFIX}")
-  set(Vc_LIBRARY "${Vc_ROOTDIR}/lib/${Vc_LIBNAME}")
-
-  ExternalProject_Add(VC
-    URL     ${Vc_SRC_URI}
-    URL_HASH SHA256=5933108196be44c41613884cd56305df320263981fe6a49e648aebb3354d57f3
-    BUILD_IN_SOURCE 0
-    BUILD_BYPRODUCTS ${Vc_LIBRARY}
-    LOG_DOWNLOAD 1 LOG_CONFIGURE 1 LOG_BUILD 1 LOG_INSTALL 1 LOG_OUTPUT_ON_FAILURE 1
-    CMAKE_ARGS -G ${CMAKE_GENERATOR}
-               -DCMAKE_POLICY_VERSION_MINIMUM=3.5
-               -DCMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE}
-               -DCMAKE_C_COMPILER=${CMAKE_C_COMPILER}
-               -DCMAKE_C_FLAGS=${CMAKE_C_FLAGS}
-               -DCMAKE_CXX_COMPILER=${CMAKE_CXX_COMPILER}
-               -DCMAKE_CXX_FLAGS=${ROOT_EXTERNAL_CXX_FLAGS}
-               -DCMAKE_INSTALL_PREFIX=${CMAKE_INSTALL_PREFIX}
-    INSTALL_COMMAND env DESTDIR=${Vc_DESTDIR} ${CMAKE_COMMAND} --build . --target install
-    TIMEOUT 600
-  )
-
-  set(VC_TARGET Vc)
-  set(Vc_LIBRARIES Vc)
-  set(Vc_INCLUDE_DIR ${Vc_ROOTDIR}/include)
-  set(Vc_CMAKE_MODULES_DIR ${Vc_ROOTDIR}/lib/cmake/Vc)
-
-  add_library(VcExt STATIC IMPORTED)
-  set_property(TARGET VcExt PROPERTY IMPORTED_LOCATION ${Vc_LIBRARY})
-  add_dependencies(VcExt VC)
-
-  add_library(Vc INTERFACE)
-  target_include_directories(Vc SYSTEM BEFORE INTERFACE $<BUILD_INTERFACE:${Vc_INCLUDE_DIR}>)
-  target_link_libraries(Vc INTERFACE VcExt)
-
-  find_package_handle_standard_args(Vc
-    FOUND_VAR Vc_FOUND
-    REQUIRED_VARS Vc_INCLUDE_DIR Vc_LIBRARIES Vc_CMAKE_MODULES_DIR
-    VERSION_VAR Vc_VERSION)
-
-  # FIXME: This is a workaround to let ROOT find the headers at runtime if
-  # they are in the build directory. This is necessary until we decide how to
-  # treat externals with headers used by ROOT
-  if(NOT EXISTS ${CMAKE_BINARY_DIR}/include/Vc)
-    if (NOT EXISTS ${CMAKE_BINARY_DIR}/include)
-      execute_process(COMMAND ${CMAKE_COMMAND} -E make_directory ${CMAKE_BINARY_DIR}/include)
-    endif()
-    execute_process(COMMAND ${CMAKE_COMMAND} -E create_symlink
-      ${Vc_INCLUDE_DIR}/Vc ${CMAKE_BINARY_DIR}/include/Vc)
-  endif()
-  # end of workaround
-
-  install(DIRECTORY ${Vc_ROOTDIR}/ DESTINATION ".")
-endif()
-
-if(Vc_FOUND)
-  # Missing from VcConfig.cmake
-  set(Vc_INCLUDE_DIRS ${Vc_INCLUDE_DIR})
-endif()
-
 #---Check for VecCore--------------------------------------------------------------------
 if(builtin_veccore)
   unset(VecCore_FOUND)
   unset(VecCore_FOUND CACHE)
   set(veccore ON CACHE BOOL "Enabled because builtin_veccore requested (${veccore_description})" FORCE)
 elseif(veccore)
-  if(vc)
-    set(VecCore_COMPONENTS Vc)
-  endif()
   if(fail-on-missing)
     find_package(VecCore 0.4.2 CONFIG QUIET REQUIRED COMPONENTS ${VecCore_COMPONENTS})
   else()
@@ -1521,18 +1427,6 @@ if(builtin_veccore)
   target_include_directories(VecCore SYSTEM INTERFACE $<BUILD_INTERFACE:${VecCore_ROOTDIR}/include>)
   add_dependencies(VecCore VECCORE)
 
-  if (Vc_FOUND)
-    set(VecCore_Vc_FOUND True)
-    set(VecCore_Vc_DEFINITIONS -DVECCORE_ENABLE_VC)
-    set(VecCore_Vc_INCLUDE_DIR ${Vc_INCLUDE_DIR})
-    set(VecCore_Vc_LIBRARIES ${Vc_LIBRARIES})
-
-    set(VecCore_DEFINITIONS ${VecCore_Vc_DEFINITIONS})
-    list(APPEND VecCore_INCLUDE_DIRS ${VecCore_Vc_INCLUDE_DIR})
-    set(VecCore_LIBRARIES ${VecCore_LIBRARIES} ${Vc_LIBRARIES})
-    target_link_libraries(VecCore INTERFACE ${Vc_LIBRARIES})
-  endif()
-
   find_package_handle_standard_args(VecCore
     FOUND_VAR VecCore_FOUND
     REQUIRED_VARS VecCore_INCLUDE_DIRS VecCore_LIBRARIES

@@ -36,7 +36,6 @@
 #@haspthread@ R__HAS_PTHREAD    /**/
 #@hasxft@ R__HAS_XFT    /**/
 #@hascocoa@ R__HAS_COCOA    /**/
-#@hasvc@ R__HAS_VC    /**/
 #@hasvdt@ R__HAS_VDT    /**/
 #@hasveccore@ R__HAS_VECCORE    /**/
 #@usecxxmodules@ R__USE_CXXMODULES   /**/
@@ -54,12 +53,6 @@
 #@hastbb@ R__HAS_TBB /**/
 #define R__HARDWARE_INTERFERENCE_SIZE @hardwareinterferencesize@ /*Determined at CMake configure to be stable across all TUs*/
 
-#if defined(R__HAS_VECCORE) && defined(R__HAS_VC)
-#ifndef VECCORE_ENABLE_VC
-#define VECCORE_ENABLE_VC
-#endif
-#endif
-
 #@uselz4@ R__HAS_DEFAULT_LZ4  /**/
 #@usezlib@ R__HAS_DEFAULT_ZLIB  /**/
 #@uselzma@ R__HAS_DEFAULT_LZMA  /**/

@@ -117,9 +117,6 @@ set(clinginclude ${CMAKE_SOURCE_DIR}/interpreter/cling/include)
 set(custom_modulemaps)
 if (runtime_cxxmodules)
   set(custom_modulemaps boost.modulemap tinyxml2.modulemap cuda.modulemap module.modulemap.build)
-  if(vc)
-    set(custom_modulemaps ${custom_modulemaps} vc.modulemap)
-  endif()
 
   # We need to override the default modulemap because instead of producing a
   # single std.pcm, produces hundreds of pcms. This changed with MacOSX14.4.sdk

@@ -95,7 +95,6 @@ set(HEADERS
   TRandom3.h
   TRandomGen.h
   TStatistic.h
-  VectorizedTMath.h
 )
 
 if(runtime_cxxmodules)
@@ -104,14 +103,6 @@ if(runtime_cxxmodules)
   # 'abs' shadow declaration (from stl math.h) is broken.
   # FIXME: Revise after a llvm upgrade or reproduce it outside rootcling.
   list(REMOVE_ITEM HEADERS "Math/Math.h")
-
-  if(vc)
-    # We do not link against libVc.a thus it makes no sense to check for
-    # version compatibility between libraries and header files. This fixes
-    # ROOT-11002 where upon building the modules.idx we run the static ctor
-    # runLibraryAbiCheck which fails to find the corresponding symbol.
-    set(dictoptions "-m" "Vc" "-mByproduct" "Vc" "-D" "Vc_NO_VERSION_CHECK")
-  endif(vc)
 endif()
 
 ROOT_ADD_C_FLAG(_flags -Wno-strict-overflow)  # Avoid what it seems a compiler false positive warning
@@ -189,7 +180,6 @@ ROOT_STANDARD_LIBRARY_PACKAGE(MathCore
     src/TStatistic.cxx
     src/UnBinData.cxx
     src/Util.cxx
-    src/VectorizedTMath.cxx
   LIBRARIES
     ${MATHCORE_LIBRARIES}
   DICTIONARY_OPTIONS

@@ -5,36 +5,13 @@
 
 #ifdef R__HAS_VECCORE
 
-#if defined(R__HAS_VC)
-
-#pragma GCC diagnostic push
-#pragma GCC diagnostic ignored "-Wall"
-#pragma GCC diagnostic ignored "-Wunused-parameter"
-#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
-#if (__cplusplus >= 202002L) // only for C++20
-#pragma GCC diagnostic ignored "-Wdeprecated-enum-enum-conversion"
-#endif
-
-#ifdef __clang__
-#pragma clang diagnostic ignored "-Wconditional-uninitialized"
-#pragma clang diagnostic ignored "-Wdeprecated-copy"
-#endif
-
-#include <Vc/Vc>
-#pragma GCC diagnostic pop
-#endif
-
 #include <VecCore/VecCore>
 
 namespace ROOT {
 
 namespace Internal {
    using ScalarBackend = vecCore::backend::Scalar;
-#ifdef VECCORE_ENABLE_VC
-   using VectorBackend = vecCore::backend::VcVector;
-#else
    using VectorBackend = vecCore::backend::Scalar;
-#endif
 }
    using Float_v  = typename Internal::VectorBackend::Float_v;
    using Double_v = typename Internal::VectorBackend::Double_v;