[CUDA] remove src/treelearner/kernels (#6766)

* remove src/treelearner/kernels

* Update CMakeLists.txt

* clean up

CMakeLists.txt

@@ -252,54 +252,6 @@ if(USE_CUDA)
       set(CMAKE_CUDA_STANDARD 11)
       set(CMAKE_CUDA_STANDARD_REQUIRED ON)
     endif()
-
-    set(
-      BASE_DEFINES
-      -DPOWER_FEATURE_WORKGROUPS=12
-      -DUSE_CONSTANT_BUF=0
-    )
-    set(
-      ALLFEATS_DEFINES
-      ${BASE_DEFINES}
-      -DENABLE_ALL_FEATURES
-    )
-    set(
-      FULLDATA_DEFINES
-      ${ALLFEATS_DEFINES}
-      -DIGNORE_INDICES
-    )
-
-    message(STATUS "ALLFEATS_DEFINES: ${ALLFEATS_DEFINES}")
-    message(STATUS "FULLDATA_DEFINES: ${FULLDATA_DEFINES}")
-
-    function(add_histogram hsize hname hadd hconst hdir)
-      add_library(histo${hsize}${hname} OBJECT src/treelearner/kernels/histogram${hsize}.cu)
-      set_target_properties(
-        histo${hsize}${hname}
-        PROPERTIES
-          CUDA_SEPARABLE_COMPILATION ON
-          CUDA_ARCHITECTURES ${CUDA_ARCHS}
-      )
-      if(hadd)
-        list(APPEND histograms histo${hsize}${hname})
-        set(histograms ${histograms} PARENT_SCOPE)
-      endif()
-      target_compile_definitions(
-        histo${hsize}${hname}
-        PRIVATE
-        -DCONST_HESSIAN=${hconst}
-        ${hdir}
-      )
-    endfunction()
-
-    foreach(hsize _16_64_256)
-      add_histogram("${hsize}" "_sp_const" "True" "1" "${BASE_DEFINES}")
-      add_histogram("${hsize}" "_sp" "True" "0" "${BASE_DEFINES}")
-      add_histogram("${hsize}" "-allfeats_sp_const" "False" "1" "${ALLFEATS_DEFINES}")
-      add_histogram("${hsize}" "-allfeats_sp" "False" "0" "${ALLFEATS_DEFINES}")
-      add_histogram("${hsize}" "-fulldata_sp_const" "True" "1" "${FULLDATA_DEFINES}")
-      add_histogram("${hsize}" "-fulldata_sp" "True" "0" "${FULLDATA_DEFINES}")
-    endforeach()
 endif()
 
 include(CheckCXXSourceCompiles)
@@ -634,14 +586,6 @@ if(USE_CUDA)
         CUDA_RESOLVE_DEVICE_SYMBOLS ON
     )
   endif()
-
-  # histograms are list of object libraries. Linking object library to other
-  # object libraries only gets usage requirements, the linked objects won't be
-  # used. Thus we have to call target_link_libraries on final targets here.
-  if(BUILD_CLI)
-    target_link_libraries(lightgbm PRIVATE ${histograms})
-  endif()
-  target_link_libraries(_lightgbm PRIVATE ${histograms})
 endif()
 
 if(WIN32)