Index: openmp/CMakeLists.txt
===================================================================
--- openmp/CMakeLists.txt
+++ openmp/CMakeLists.txt
@@ -39,8 +39,6 @@
     set(OPENMP_TEST_C_COMPILER ${LLVM_RUNTIME_OUTPUT_INTDIR}/clang.exe)
     set(OPENMP_TEST_CXX_COMPILER ${LLVM_RUNTIME_OUTPUT_INTDIR}/clang++.exe)
   endif()
-
-  list(APPEND LIBOMPTARGET_LLVM_INCLUDE_DIRS ${LLVM_MAIN_INCLUDE_DIR} ${LLVM_BINARY_DIR}/include)
 endif()
 
 # Check and set up common compiler flags.
@@ -63,20 +61,6 @@
   set(ENABLE_LIBOMPTARGET OFF)
 endif()
 
-# Attempt to locate LLVM source, required by libomptarget
-if (NOT LIBOMPTARGET_LLVM_INCLUDE_DIRS)
-  if (LLVM_MAIN_INCLUDE_DIR)
-    list(APPEND LIBOMPTARGET_LLVM_INCLUDE_DIRS ${LLVM_MAIN_INCLUDE_DIR})
-  elseif (EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/../llvm/include)
-    list(APPEND LIBOMPTARGET_LLVM_INCLUDE_DIRS ${CMAKE_CURRENT_SOURCE_DIR}/../llvm/include)
-  endif()
-endif()
-
-if (NOT LIBOMPTARGET_LLVM_INCLUDE_DIRS)
-  message(STATUS "Missing definition for LIBOMPTARGET_LLVM_INCLUDE_DIRS, disabling libomptarget")
-  set(ENABLE_LIBOMPTARGET OFF)
-endif()
-
 option(OPENMP_ENABLE_LIBOMPTARGET "Enable building libomptarget for offloading."
        ${ENABLE_LIBOMPTARGET})
 option(OPENMP_ENABLE_LIBOMPTARGET_PROFILING "Enable time profiling for libomptarget."
Index: openmp/README.rst
===================================================================
--- openmp/README.rst
+++ openmp/README.rst
@@ -243,6 +243,15 @@
 Options for ``libomptarget``
 ----------------------------
 
+An installed LLVM package is a prerequisite for building ``libomptarget``
+library. So ``libomptarget`` may only be built in two cases:
+
+- As a project of a regular LLVM build via **LLVM_ENABLE_PROJECTS** or
+  **LLVM_EXTERNAL_PROJECTS**, or
+- as a standalone project build that uses a pre-installed LLVM package.
+  In this mode one has to make sure that the default CMake
+  ``find_package(LLVM)`` call `succeeds <https://cmake.org/cmake/help/latest/command/find_package.html#search-procedure>`_.
+
 **LIBOMPTARGET_OPENMP_HEADER_FOLDER** = ``""``
   Path of the folder that contains ``omp.h``.  This is required for testing
   out-of-tree builds.
Index: openmp/libomptarget/cmake/Modules/LibomptargetGetDependencies.cmake
===================================================================
--- openmp/libomptarget/cmake/Modules/LibomptargetGetDependencies.cmake
+++ openmp/libomptarget/cmake/Modules/LibomptargetGetDependencies.cmake
@@ -19,6 +19,25 @@
 
 include (FindPackageHandleStandardArgs)
 
+################################################################################
+# Looking for LLVM...
+################################################################################
+
+if (OPENMP_STANDALONE_BUILD)
+  # Complete LLVM package is required for building libomptarget
+  # in an out-of-tree mode.
+  find_package(LLVM REQUIRED)
+  message(STATUS "Found LLVM ${LLVM_PACKAGE_VERSION}")
+  message(STATUS "Using LLVM in: ${LLVM_DIR}")
+  list(APPEND LIBOMPTARGET_LLVM_INCLUDE_DIRS ${LLVM_INCLUDE_DIRS})
+  list(APPEND CMAKE_MODULE_PATH ${LLVM_CMAKE_DIR})
+  include(AddLLVM)
+else()
+  list(APPEND LIBOMPTARGET_LLVM_INCLUDE_DIRS
+    ${LLVM_MAIN_INCLUDE_DIR} ${LLVM_BINARY_DIR}/include
+    )
+endif()
+
 ################################################################################
 # Looking for libelf...
 ################################################################################
@@ -250,27 +269,4 @@
   endif()
 endif()
 
-if (OPENMP_STANDALONE_BUILD)
-  # This duplicates code from llvm/cmake/config-ix.cmake
-  if( WIN32 AND NOT CYGWIN )
-    # We consider Cygwin as another Unix
-    set(PURE_WINDOWS 1)
-  endif()
-
-  # library checks
-  if( NOT PURE_WINDOWS )
-    check_library_exists(pthread pthread_create "" HAVE_LIBPTHREAD)
-  endif()
-
-  if(HAVE_LIBPTHREAD)
-    # We want to find pthreads library and at the moment we do want to
-    # have it reported as '-l<lib>' instead of '-pthread'.
-    # TODO: switch to -pthread once the rest of the build system can deal with it.
-    set(CMAKE_THREAD_PREFER_PTHREAD TRUE)
-    set(THREADS_HAVE_PTHREAD_ARG Off)
-    find_package(Threads REQUIRED)
-    set(OPENMP_PTHREAD_LIB ${CMAKE_THREAD_LIBS_INIT})
-  endif()
-else()
-  set(OPENMP_PTHREAD_LIB ${LLVM_PTHREAD_LIB})
-endif()
+set(OPENMP_PTHREAD_LIB ${LLVM_PTHREAD_LIB})
Index: openmp/libomptarget/deviceRTLs/amdgcn/CMakeLists.txt
===================================================================
--- openmp/libomptarget/deviceRTLs/amdgcn/CMakeLists.txt
+++ openmp/libomptarget/deviceRTLs/amdgcn/CMakeLists.txt
@@ -10,20 +10,8 @@
 #
 ##===----------------------------------------------------------------------===##
 
-find_package(LLVM QUIET CONFIG
-  PATHS
-  $ENV{AOMP}
-  $ENV{HOME}/rocm/aomp
-  /opt/rocm/aomp
-  /usr/lib/rocm/aomp
-  ${LIBOMPTARGET_NVPTX_CUDA_COMPILER_DIR}
-  ${LIBOMPTARGET_NVPTX_CUDA_LINKER_DIR}
-  ${CMAKE_CXX_COMPILER_DIR}
-  NO_DEFAULT_PATH)
-
-if (LLVM_DIR)
-  libomptarget_say("Found LLVM ${LLVM_PACKAGE_VERSION}. Configure: ${LLVM_DIR}/LLVMConfig.cmake")
-else()
+# An installed LLVM package should have been discovered before.
+if (NOT LLVM_DIR)
   libomptarget_say("Not building AMDGCN device RTL: AOMP not found")
   return()
 endif()
Index: openmp/libomptarget/src/CMakeLists.txt
===================================================================
--- openmp/libomptarget/src/CMakeLists.txt
+++ openmp/libomptarget/src/CMakeLists.txt
@@ -24,23 +24,19 @@
 
 include_directories(${LIBOMPTARGET_LLVM_INCLUDE_DIRS})
 
-# Build libomptarget library with libdl dependency. Add LLVMSupport
-# dependency if building in-tree with profiling enabled.
-if(OPENMP_STANDALONE_BUILD OR (NOT OPENMP_ENABLE_LIBOMPTARGET_PROFILING))
-  add_library(omptarget SHARED ${LIBOMPTARGET_SRC_FILES})
-  target_link_libraries(omptarget
-    ${CMAKE_DL_LIBS}
-    "-Wl,--version-script=${CMAKE_CURRENT_SOURCE_DIR}/exports")
-else()
-  set(LLVM_LINK_COMPONENTS
-    Support
-    )
-  add_llvm_library(omptarget SHARED ${LIBOMPTARGET_SRC_FILES}
-      LINK_LIBS ${CMAKE_DL_LIBS}
-      "-Wl,--version-script=${CMAKE_CURRENT_SOURCE_DIR}/exports"
-      )
+# Build libomptarget library with libdl dependency.
+add_library(omptarget SHARED ${LIBOMPTARGET_SRC_FILES})
+if (OPENMP_ENABLE_LIBOMPTARGET_PROFILING)
+  # Add LLVMSupport dependency if profiling is enabled.
+  # Linking with LLVM component libraries also requires
+  # aligning the compile flags.
+  llvm_update_compile_flags(omptarget)
   target_compile_definitions(omptarget PUBLIC OMPTARGET_PROFILE_ENABLED)
+  target_link_libraries(omptarget PRIVATE LLVMSupport)
 endif()
+target_link_libraries(omptarget PRIVATE
+  ${CMAKE_DL_LIBS}
+  "-Wl,--version-script=${CMAKE_CURRENT_SOURCE_DIR}/exports")
 
 # libomptarget needs to be set separately because add_llvm_library doesn't
 # conform with location configuration of its parent scope.