[llvm-branch-commits] [clang] [flang] [llvm] [openmp] [Flang] Move builtin .mod generation into runtimes (Reapply #137828) (PR #169638)

Michael Kruse via llvm-branch-commits llvm-branch-commits at lists.llvm.org
Fri Nov 28 13:52:07 PST 2025


https://github.com/Meinersbur updated https://github.com/llvm/llvm-project/pull/169638

>From dc02b15735ffad56dccc8d3b3a0cd13ad552756f Mon Sep 17 00:00:00 2001
From: Michael Kruse <llvm-project at meinersbur.de>
Date: Tue, 25 Nov 2025 23:20:43 +0100
Subject: [PATCH 01/15] Reapply "[Flang] Move builtin .mod generation into
 runtimes" (#169489)

This reverts commit 4bc654d6497430c1dd5e4e25aaa84b3dec3e1113.
---
 clang/include/clang/Driver/ToolChain.h        |   4 +
 clang/include/clang/Options/Options.td        |   2 +-
 clang/lib/Driver/Driver.cpp                   |  11 +
 clang/lib/Driver/ToolChain.cpp                |   6 +
 clang/lib/Driver/ToolChains/Flang.cpp         |   8 +
 .../Modules}/GetToolchainDirs.cmake           |  11 +
 flang-rt/CMakeLists.txt                       |  97 +-------
 flang-rt/cmake/modules/AddFlangRT.cmake       |  29 ++-
 .../cmake/modules/AddFlangRTOffload.cmake     |  14 +-
 .../cmake/modules/FlangRTIntrospection.cmake  |  37 +++
 flang-rt/lib/runtime/CMakeLists.txt           | 115 ++++++++-
 .../lib/runtime}/__cuda_builtins.f90          |   0
 .../lib/runtime}/__cuda_device.f90            |   0
 .../lib/runtime}/__fortran_builtins.f90       |   2 +-
 .../runtime}/__fortran_ieee_exceptions.f90    |   0
 .../lib/runtime}/__fortran_type_info.f90      |   0
 .../lib/runtime}/__ppc_intrinsics.f90         |   0
 .../lib/runtime}/__ppc_types.f90              |   0
 .../lib/runtime}/cooperative_groups.f90       |   1 +
 .../lib/runtime}/cudadevice.f90               |   0
 .../lib/runtime}/ieee_arithmetic.f90          |   2 +-
 .../lib/runtime}/ieee_exceptions.f90          |   0
 .../lib/runtime}/ieee_features.f90            |   0
 .../lib/runtime}/iso_c_binding.f90            |   0
 .../lib/runtime}/iso_fortran_env.f90          |   0
 .../lib/runtime}/iso_fortran_env_impl.f90     |   0
 .../module => flang-rt/lib/runtime}/mma.f90   |   0
 flang-rt/test/lit.site.cfg.py.in              |   2 +-
 flang-rt/unittests/CMakeLists.txt             |   5 +-
 flang/CMakeLists.txt                          |   1 -
 .../flang/Frontend/CompilerInvocation.h       |   7 +
 flang/lib/Frontend/CompilerInvocation.cpp     |  26 +-
 flang/lib/Semantics/semantics.cpp             |  13 +-
 flang/module/.clang-format                    |   1 -
 flang/test/CMakeLists.txt                     |  31 ++-
 flang/test/Driver/Inputs/ieee_arithmetic.mod  |   1 +
 flang/test/Driver/Inputs/iso_fortran_env.mod  |   1 +
 flang/test/Driver/intrinsic-module-path.F90   |  55 +++++
 flang/test/Driver/intrinsic-module-path.f90   |  23 --
 flang/test/Driver/lto-fatlto.f90              |   4 +-
 flang/test/Driver/pp-fixed-form.f90           |   4 +-
 .../Lower/HLFIR/type-bound-call-mismatch.f90  |   2 +-
 flang/test/Lower/OpenMP/simd_aarch64.f90      |   7 +-
 .../target-enter-data-default-openmp52.f90    |   4 +-
 flang/test/Preprocessing/fixed-free.f         |   2 +-
 flang/test/Preprocessing/no-pp-if.f90         |   2 +-
 flang/test/Semantics/bug163242.f90            |   2 +-
 flang/test/Semantics/bug164303.f90            |   2 +-
 flang/test/lit.cfg.py                         |  94 +++++++-
 flang/test/lit.site.cfg.py.in                 |   9 +-
 flang/tools/CMakeLists.txt                    |   1 -
 flang/tools/bbc/bbc.cpp                       |  13 +-
 flang/tools/f18/CMakeLists.txt                | 170 -------------
 flang/tools/f18/dump.cpp                      |  42 ----
 llvm/runtimes/CMakeLists.txt                  |  24 +-
 openmp/CMakeLists.txt                         |   6 +
 openmp/runtime/CMakeLists.txt                 |   8 +-
 .../cmake/LibompCheckFortranFlag.cmake        |  29 ---
 openmp/runtime/cmake/LibompHandleFlags.cmake  |  11 -
 openmp/runtime/cmake/config-ix.cmake          |   4 -
 openmp/runtime/src/CMakeLists.txt             |  63 ++---
 openmp/runtime/test/lit.cfg                   |   1 +
 openmp/runtime/test/lit.site.cfg.in           |   1 +
 runtimes/CMakeLists.txt                       | 223 +++++++++++++++++-
 64 files changed, 705 insertions(+), 528 deletions(-)
 rename {flang-rt/cmake/modules => cmake/Modules}/GetToolchainDirs.cmake (94%)
 create mode 100644 flang-rt/cmake/modules/FlangRTIntrospection.cmake
 rename {flang/module => flang-rt/lib/runtime}/__cuda_builtins.f90 (100%)
 rename {flang/module => flang-rt/lib/runtime}/__cuda_device.f90 (100%)
 rename {flang/module => flang-rt/lib/runtime}/__fortran_builtins.f90 (99%)
 rename {flang/module => flang-rt/lib/runtime}/__fortran_ieee_exceptions.f90 (100%)
 rename {flang/module => flang-rt/lib/runtime}/__fortran_type_info.f90 (100%)
 rename {flang/module => flang-rt/lib/runtime}/__ppc_intrinsics.f90 (100%)
 rename {flang/module => flang-rt/lib/runtime}/__ppc_types.f90 (100%)
 rename {flang/module => flang-rt/lib/runtime}/cooperative_groups.f90 (96%)
 rename {flang/module => flang-rt/lib/runtime}/cudadevice.f90 (100%)
 rename {flang/module => flang-rt/lib/runtime}/ieee_arithmetic.f90 (99%)
 rename {flang/module => flang-rt/lib/runtime}/ieee_exceptions.f90 (100%)
 rename {flang/module => flang-rt/lib/runtime}/ieee_features.f90 (100%)
 rename {flang/module => flang-rt/lib/runtime}/iso_c_binding.f90 (100%)
 rename {flang/module => flang-rt/lib/runtime}/iso_fortran_env.f90 (100%)
 rename {flang/module => flang-rt/lib/runtime}/iso_fortran_env_impl.f90 (100%)
 rename {flang/module => flang-rt/lib/runtime}/mma.f90 (100%)
 delete mode 100644 flang/module/.clang-format
 create mode 100644 flang/test/Driver/intrinsic-module-path.F90
 delete mode 100644 flang/test/Driver/intrinsic-module-path.f90
 delete mode 100644 flang/tools/f18/CMakeLists.txt
 delete mode 100644 flang/tools/f18/dump.cpp
 delete mode 100644 openmp/runtime/cmake/LibompCheckFortranFlag.cmake

diff --git a/clang/include/clang/Driver/ToolChain.h b/clang/include/clang/Driver/ToolChain.h
index 1425714d34110..26af88242eb3e 100644
--- a/clang/include/clang/Driver/ToolChain.h
+++ b/clang/include/clang/Driver/ToolChain.h
@@ -538,6 +538,10 @@ class ToolChain {
   // Returns Triple without the OSs version.
   llvm::Triple getTripleWithoutOSVersion() const;
 
+  /// Returns the target-specific path for Flang's intrinsic modules in the
+  /// resource directory if it exists.
+  std::optional<std::string> getDefaultIntrinsicModuleDir() const;
+
   // Returns the target specific runtime path if it exists.
   std::optional<std::string> getRuntimePath() const;
 
diff --git a/clang/include/clang/Options/Options.td b/clang/include/clang/Options/Options.td
index a8fc1c4326cc5..0e88656c5e1bc 100644
--- a/clang/include/clang/Options/Options.td
+++ b/clang/include/clang/Options/Options.td
@@ -6082,7 +6082,7 @@ def prebind : Flag<["-"], "prebind">;
 def preload : Flag<["-"], "preload">;
 def print_file_name_EQ : Joined<["-", "--"], "print-file-name=">,
   HelpText<"Print the full library path of <file>">, MetaVarName<"<file>">,
-  Visibility<[ClangOption, CLOption]>;
+  Visibility<[ClangOption, FlangOption, CLOption]>;
 def print_ivar_layout : Flag<["-"], "print-ivar-layout">,
   Visibility<[ClangOption, CC1Option]>,
   HelpText<"Enable Objective-C Ivar layout bitmap print trace">,
diff --git a/clang/lib/Driver/Driver.cpp b/clang/lib/Driver/Driver.cpp
index de8d4601210ae..781bc74466da1 100644
--- a/clang/lib/Driver/Driver.cpp
+++ b/clang/lib/Driver/Driver.cpp
@@ -6602,6 +6602,17 @@ std::string Driver::GetFilePath(StringRef Name, const ToolChain &TC) const {
   if (llvm::sys::fs::exists(Twine(P)))
     return std::string(P);
 
+  // With Flang, also look for instrinsic modules
+  if (IsFlangMode()) {
+    if (std::optional<std::string> IntrPath =
+            TC.getDefaultIntrinsicModuleDir()) {
+      SmallString<128> P(*IntrPath);
+      llvm::sys::path::append(P, Name);
+      if (llvm::sys::fs::exists(Twine(P)))
+        return std::string(P);
+    }
+  }
+
   SmallString<128> D(Dir);
   llvm::sys::path::append(D, "..", Name);
   if (llvm::sys::fs::exists(Twine(D)))
diff --git a/clang/lib/Driver/ToolChain.cpp b/clang/lib/Driver/ToolChain.cpp
index 77a2c73f0d446..f8520725b9b03 100644
--- a/clang/lib/Driver/ToolChain.cpp
+++ b/clang/lib/Driver/ToolChain.cpp
@@ -1020,6 +1020,12 @@ ToolChain::getTargetSubDirPath(StringRef BaseDir) const {
   return {};
 }
 
+std::optional<std::string> ToolChain::getDefaultIntrinsicModuleDir() const {
+  SmallString<128> P(D.ResourceDir);
+  llvm::sys::path::append(P, "finclude", "flang");
+  return getTargetSubDirPath(P);
+}
+
 std::optional<std::string> ToolChain::getRuntimePath() const {
   SmallString<128> P(D.ResourceDir);
   llvm::sys::path::append(P, "lib");
diff --git a/clang/lib/Driver/ToolChains/Flang.cpp b/clang/lib/Driver/ToolChains/Flang.cpp
index cc4755cd6a9b0..bac421bb86f49 100644
--- a/clang/lib/Driver/ToolChains/Flang.cpp
+++ b/clang/lib/Driver/ToolChains/Flang.cpp
@@ -1060,6 +1060,14 @@ void Flang::ConstructJob(Compilation &C, const JobAction &JA,
   CmdArgs.push_back("-resource-dir");
   CmdArgs.push_back(D.ResourceDir.c_str());
 
+  // Default intrinsic module dirs must be added after any user-provided
+  // -fintrinsic-modules-path to have lower precedence
+  if (std::optional<std::string> IntrModPath =
+          TC.getDefaultIntrinsicModuleDir()) {
+    CmdArgs.push_back("-fintrinsic-modules-path");
+    CmdArgs.push_back(Args.MakeArgString(*IntrModPath));
+  }
+
   // Offloading related options
   addOffloadOptions(C, Inputs, JA, Args, CmdArgs);
 
diff --git a/flang-rt/cmake/modules/GetToolchainDirs.cmake b/cmake/Modules/GetToolchainDirs.cmake
similarity index 94%
rename from flang-rt/cmake/modules/GetToolchainDirs.cmake
rename to cmake/Modules/GetToolchainDirs.cmake
index fba12502b5946..ce2f8c294b2bc 100644
--- a/flang-rt/cmake/modules/GetToolchainDirs.cmake
+++ b/cmake/Modules/GetToolchainDirs.cmake
@@ -47,6 +47,17 @@ function (get_toolchain_library_subdir outvar)
 endfunction ()
 
 
+# Corresponds to Flang's ToolChain::getDefaultIntrinsicModuleDir().
+function (get_toolchain_module_subdir outvar)
+  set(outval "finclude/flang")
+
+  get_toolchain_arch_dirname(arch_dirname)
+  set(outval "${outval}/${arch_dirname}")
+
+  set(${outvar} "${outval}" PARENT_SCOPE)
+endfunction ()
+
+
 # Corresponds to Clang's ToolChain::getOSLibName(). Adapted from Compiler-RT.
 function (get_toolchain_os_dirname outvar)
   if (ANDROID)
diff --git a/flang-rt/CMakeLists.txt b/flang-rt/CMakeLists.txt
index 50b8e834776fb..db0d87d91ea83 100644
--- a/flang-rt/CMakeLists.txt
+++ b/flang-rt/CMakeLists.txt
@@ -23,40 +23,6 @@ set(FLANG_RT_SOURCE_DIR "${CMAKE_CURRENT_SOURCE_DIR}")
 set(FLANG_RT_BINARY_DIR "${CMAKE_CURRENT_BINARY_DIR}")
 set(FLANG_SOURCE_DIR "${CMAKE_CURRENT_SOURCE_DIR}/../flang")
 
-# CMake 3.24 is the first version of CMake that directly recognizes Flang.
-# LLVM's requirement is only CMake 3.20, teach CMake 3.20-3.23 how to use Flang.
-if (CMAKE_VERSION VERSION_LESS "3.24")
-  cmake_path(GET CMAKE_Fortran_COMPILER STEM _Fortran_COMPILER_STEM)
-  if (_Fortran_COMPILER_STEM STREQUAL "flang-new" OR _Fortran_COMPILER_STEM STREQUAL "flang")
-    include(CMakeForceCompiler)
-    CMAKE_FORCE_Fortran_COMPILER("${CMAKE_Fortran_COMPILER}" "LLVMFlang")
-
-    set(CMAKE_Fortran_COMPILER_ID "LLVMFlang")
-    set(CMAKE_Fortran_COMPILER_VERSION "${LLVM_VERSION_MAJOR}.${LLVM_VERSION_MINOR}")
-
-    set(CMAKE_Fortran_SUBMODULE_SEP "-")
-    set(CMAKE_Fortran_SUBMODULE_EXT ".mod")
-
-    set(CMAKE_Fortran_PREPROCESS_SOURCE
-      "<CMAKE_Fortran_COMPILER> -cpp <DEFINES> <INCLUDES> <FLAGS> -E <SOURCE> > <PREPROCESSED_SOURCE>")
-
-    set(CMAKE_Fortran_FORMAT_FIXED_FLAG "-ffixed-form")
-    set(CMAKE_Fortran_FORMAT_FREE_FLAG "-ffree-form")
-
-    set(CMAKE_Fortran_MODDIR_FLAG "-module-dir")
-
-    set(CMAKE_Fortran_COMPILE_OPTIONS_PREPROCESS_ON "-cpp")
-    set(CMAKE_Fortran_COMPILE_OPTIONS_PREPROCESS_OFF "-nocpp")
-    set(CMAKE_Fortran_POSTPROCESS_FLAG "-ffixed-line-length-72")
-
-    set(CMAKE_Fortran_COMPILE_OPTIONS_TARGET "--target=")
-
-    set(CMAKE_Fortran_LINKER_WRAPPER_FLAG "-Wl,")
-    set(CMAKE_Fortran_LINKER_WRAPPER_FLAG_SEP ",")
-  endif ()
-endif ()
-enable_language(Fortran)
-
 
 list(APPEND CMAKE_MODULE_PATH
     "${FLANG_RT_SOURCE_DIR}/cmake/modules"
@@ -65,69 +31,24 @@ list(APPEND CMAKE_MODULE_PATH
 include(AddFlangRT)
 include(GetToolchainDirs)
 include(FlangCommon)
+include(FlangRTIntrospection)
 include(HandleCompilerRT)
 include(ExtendPath)
+include(CheckFortranSourceCompiles)
+include(CMakePushCheckState)
 
 
 ############################
 # Build Mode Introspection #
 ############################
 
-# Determine whether we are in the runtimes/runtimes-bins directory of a
-# bootstrap build.
-set(LLVM_TREE_AVAILABLE OFF)
-if (LLVM_LIBRARY_OUTPUT_INTDIR AND LLVM_RUNTIME_OUTPUT_INTDIR AND PACKAGE_VERSION)
-  set(LLVM_TREE_AVAILABLE ON)
-endif()
-
 # Path to LLVM development tools (FileCheck, llvm-lit, not, ...)
 set(LLVM_TOOLS_DIR "${LLVM_BINARY_DIR}/bin")
 
-# Determine build and install paths.
-# The build path is absolute, but the install dir is relative, CMake's install
-# command has to apply CMAKE_INSTALL_PREFIX itself.
-get_toolchain_library_subdir(toolchain_lib_subdir)
-if (LLVM_TREE_AVAILABLE)
-  # In a bootstrap build emit the libraries into a default search path in the
-  # build directory of the just-built compiler. This allows using the
-  # just-built compiler without specifying paths to runtime libraries.
-  #
-  # Despite Clang in the name, get_clang_resource_dir does not depend on Clang
-  # being added to the build. Flang uses the same resource dir as clang.
-  include(GetClangResourceDir)
-  get_clang_resource_dir(FLANG_RT_OUTPUT_RESOURCE_DIR PREFIX "${LLVM_LIBRARY_OUTPUT_INTDIR}/..")
-  get_clang_resource_dir(FLANG_RT_INSTALL_RESOURCE_PATH_DEFAULT)
-
-  extend_path(FLANG_RT_OUTPUT_RESOURCE_LIB_DIR "${FLANG_RT_OUTPUT_RESOURCE_DIR}" "${toolchain_lib_subdir}")
-else ()
-  # In a standalone runtimes build, do not write into LLVM_BINARY_DIR. It may be
-  # read-only and/or shared by multiple runtimes with different build
-  # configurations (e.g. Debug/Release). Use the runtime's own lib dir like any
-  # non-toolchain library.
-  # For the install prefix, still use the resource dir assuming that Flang will
-  # be installed there using the same prefix. This is to not have a difference
-  # between bootstrap and standalone runtimes builds.
-  set(FLANG_RT_OUTPUT_RESOURCE_DIR "${CMAKE_CURRENT_BINARY_DIR}")
-  set(FLANG_RT_INSTALL_RESOURCE_PATH_DEFAULT "lib${LLVM_LIBDIR_SUFFIX}/clang/${LLVM_VERSION_MAJOR}")
-
-  extend_path(FLANG_RT_OUTPUT_RESOURCE_LIB_DIR "${FLANG_RT_OUTPUT_RESOURCE_DIR}" "lib${LLVM_LIBDIR_SUFFIX}")
-endif ()
-set(FLANG_RT_INSTALL_RESOURCE_PATH "${FLANG_RT_INSTALL_RESOURCE_PATH_DEFAULT}"
-    CACHE PATH "Path to install runtime libraries to (default: clang resource dir)")
-extend_path(FLANG_RT_INSTALL_RESOURCE_LIB_PATH "${FLANG_RT_INSTALL_RESOURCE_PATH}" "${toolchain_lib_subdir}")
-cmake_path(NORMAL_PATH FLANG_RT_OUTPUT_RESOURCE_DIR)
-cmake_path(NORMAL_PATH FLANG_RT_INSTALL_RESOURCE_PATH)
-# FIXME: For the libflang_rt.so, the toolchain resource lib dir is not a good
-#        destination because it is not a ld.so default search path.
-#        The machine where the executable is eventually executed may not be the
-#        machine where the Flang compiler and its resource dir is installed, so
-#        setting RPath by the driver is not an solution. It should belong into
-#        /usr/lib/<triple>/libflang_rt.so, like e.g. libgcc_s.so.
-#        But the linker as invoked by the Flang driver also requires
-#        libflang_rt.so to be found when linking and the resource lib dir is
-#        the only reliable location.
-cmake_path(NORMAL_PATH FLANG_RT_OUTPUT_RESOURCE_LIB_DIR)
-cmake_path(NORMAL_PATH FLANG_RT_INSTALL_RESOURCE_LIB_PATH)
+# Fortran compiler not optional for building Flang-RT
+enable_language(Fortran)
+
+flang_module_fortran_enable()
 
 
 #################
@@ -234,6 +155,10 @@ check_cxx_source_compiles(
   "
   HAVE_DECL_STRERROR_S)
 
+# Look for support of REAL(16), if not already defined via command
+# line via -DFORTRAN_SUPPORTS_REAL16=YES/NO
+check_fortran_quadmath_support()
+
 # Search for clang_rt.builtins library. Need in addition to msvcrt.
 if (WIN32)
   find_compiler_rt_library(builtins FLANG_RT_BUILTINS_LIBRARY)
diff --git a/flang-rt/cmake/modules/AddFlangRT.cmake b/flang-rt/cmake/modules/AddFlangRT.cmake
index 923507764d691..b3f2cd07c0aed 100644
--- a/flang-rt/cmake/modules/AddFlangRT.cmake
+++ b/flang-rt/cmake/modules/AddFlangRT.cmake
@@ -190,6 +190,12 @@ function (add_flangrt_library name)
     endif ()
   endif ()
 
+  if (build_object)
+    add_library(${name}.compile ALIAS "${name_object}")
+  else ()
+    add_library(${name}.compile ALIAS "${default_target}")
+  endif ()
+
   foreach (tgtname IN LISTS libtargets)
     if (NOT WIN32)
       # Use same stem name for .a and .so. Common in UNIX environments.
@@ -219,6 +225,17 @@ function (add_flangrt_library name)
     # Minimum required C++ version for Flang-RT, even if CMAKE_CXX_STANDARD is defined to something else.
     target_compile_features(${tgtname} PRIVATE cxx_std_17)
 
+    target_compile_options(${tgtname} PRIVATE
+      # Always enable preprocessor regardless of file extention
+      "$<$<COMPILE_LANGUAGE:Fortran>:-cpp>"
+
+      # Missing type descriptors are expected for intrinsic modules 
+      "$<$<COMPILE_LANGUAGE:Fortran>:SHELL:-mmlir;SHELL:-ignore-missing-type-desc>"
+
+      # Flang bug workaround: Reformating of cooked token buffer causes identifier to be split between lines
+      "$<$<COMPILE_LANGUAGE:Fortran>:SHELL:-Xflang;SHELL:-fno-reformat>"
+    )
+
     # When building the flang runtime if LTO is enabled the archive file
     # contains LLVM IR rather than object code. Currently flang is not
     # LTO aware so cannot link this file to compiled Fortran code.
@@ -226,6 +243,10 @@ function (add_flangrt_library name)
       target_compile_options(${tgtname} PRIVATE -fno-lto)
     endif ()
 
+    if (FORTRAN_SUPPORTS_REAL16)
+      target_compile_definitions(${tgtname} PRIVATE FLANG_SUPPORT_R16=1)
+    endif ()
+
     # Use compiler-specific options to disable exceptions and RTTI.
     if (LLVM_COMPILER_IS_GCC_COMPATIBLE)
       target_compile_options(${tgtname} PRIVATE
@@ -344,13 +365,13 @@ function (add_flangrt_library name)
     if (ARG_INSTALL_WITH_TOOLCHAIN)
       set_target_properties(${tgtname}
         PROPERTIES
-          ARCHIVE_OUTPUT_DIRECTORY "${FLANG_RT_OUTPUT_RESOURCE_LIB_DIR}"
-          LIBRARY_OUTPUT_DIRECTORY "${FLANG_RT_OUTPUT_RESOURCE_LIB_DIR}"
+          ARCHIVE_OUTPUT_DIRECTORY "${RUNTIMES_OUTPUT_RESOURCE_LIB_DIR}"
+          LIBRARY_OUTPUT_DIRECTORY "${RUNTIMES_OUTPUT_RESOURCE_LIB_DIR}"
         )
 
       install(TARGETS ${tgtname}
-          ARCHIVE DESTINATION "${FLANG_RT_INSTALL_RESOURCE_LIB_PATH}"
-          LIBRARY DESTINATION "${FLANG_RT_INSTALL_RESOURCE_LIB_PATH}"
+          ARCHIVE DESTINATION "${RUNTIMES_INSTALL_RESOURCE_LIB_PATH}"
+          LIBRARY DESTINATION "${RUNTIMES_INSTALL_RESOURCE_LIB_PATH}"
         )
     endif ()
 
diff --git a/flang-rt/cmake/modules/AddFlangRTOffload.cmake b/flang-rt/cmake/modules/AddFlangRTOffload.cmake
index cbc69f3a9656a..4a6f047a86af2 100644
--- a/flang-rt/cmake/modules/AddFlangRTOffload.cmake
+++ b/flang-rt/cmake/modules/AddFlangRTOffload.cmake
@@ -88,16 +88,16 @@ macro(enable_omp_offload_compilation name files)
         "${FLANG_RT_DEVICE_ARCHITECTURES}"
         )
 
-      set(OMP_COMPILE_OPTIONS
+      set(OMP_COMPILE_OPTIONS $<$<COMPILE_LANGUAGE:C,CXX>:
         -fopenmp
         -fvisibility=hidden
         -fopenmp-cuda-mode
         --offload-arch=${compile_for_architectures}
         # Force LTO for the device part.
         -foffload-lto
-        )
-      set_source_files_properties(${files} PROPERTIES COMPILE_OPTIONS
-        "${OMP_COMPILE_OPTIONS}"
+        >)
+      set_property(SOURCE ${files} APPEND
+        PROPERTY COMPILE_DEFINITIONS ${OMP_COMPILE_OPTIONS}
         )
       target_link_options(${name}.static PUBLIC ${OMP_COMPILE_OPTIONS})
 
@@ -105,6 +105,12 @@ macro(enable_omp_offload_compilation name files)
       set_source_files_properties(${files}
         PROPERTIES COMPILE_DEFINITIONS OMP_OFFLOAD_BUILD
         )
+
+     # If building flang-rt together with libomp, ensure that libomp is built first and found because -fopenmp will try to link it.
+     if (TARGET omp)
+       add_dependencies(${name} omp)
+       target_link_options(${name}.static PUBLIC "-L$<TARGET_FILE_DIR:omp>")
+     endif ()
     else()
       message(FATAL_ERROR
         "Flang-rt build with OpenMP offload is not supported for these compilers:\n"
diff --git a/flang-rt/cmake/modules/FlangRTIntrospection.cmake b/flang-rt/cmake/modules/FlangRTIntrospection.cmake
new file mode 100644
index 0000000000000..ddec624e320e7
--- /dev/null
+++ b/flang-rt/cmake/modules/FlangRTIntrospection.cmake
@@ -0,0 +1,37 @@
+#===-- cmake/modules/FlangRTIntrospection.cmake ----------------------------===#
+#
+# Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+# See https://llvm.org/LICENSE.txt for license information.
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+#
+#===------------------------------------------------------------------------===#
+
+
+# Check whether the Fortran compiler supports real(16)/quadmath types
+#
+# Implementation notes:
+#  * FORTRAN_SUPPORTS_REAL16 can be set externally in a bootstrapping-runtimes
+#    build to ensure consistency of real(16) support between compiler and
+#    runtime.
+#
+#  * Does not work with Flang and CMake < 3.24
+#
+#  * This is intentionally wrapped in a function to get its own namespace for
+#    CMAKE_REQUIRED_FLAGS and CMAKE_TRY_COMPILE_TARGET_TYPE. In particular,
+#    cmake_pop_check_state() does not reset CMAKE_TRY_COMPILE_TARGET_TYPE,
+#    causing later try_compile invocations to fail. If you see
+#    enable_language(CUDA) failing because CMAKE_RANLIB is empty, this is the
+#    reason.
+function (check_fortran_quadmath_support)
+  cmake_push_check_state(RESET)
+  set(CMAKE_REQUIRED_FLAGS "-ffree-form")
+  set(CMAKE_TRY_COMPILE_TARGET_TYPE "STATIC_LIBRARY") # Skip link step
+  check_fortran_source_compiles([[
+      subroutine test_quadmath
+        real(16) :: var1
+      end
+    ]]
+    FORTRAN_SUPPORTS_REAL16
+  )
+  cmake_pop_check_state()
+endfunction ()
diff --git a/flang-rt/lib/runtime/CMakeLists.txt b/flang-rt/lib/runtime/CMakeLists.txt
index e8f70bd544e0b..a678055430233 100644
--- a/flang-rt/lib/runtime/CMakeLists.txt
+++ b/flang-rt/lib/runtime/CMakeLists.txt
@@ -12,6 +12,13 @@ find_package(Backtrace)
 set(HAVE_BACKTRACE ${Backtrace_FOUND})
 set(BACKTRACE_HEADER ${Backtrace_HEADER})
 
+# Module sources that are required by other modules
+set(intrinsics_sources
+  __fortran_builtins.f90
+  __cuda_builtins.f90
+)
+
+
 # List of files that are buildable for all devices.
 set(supported_sources
   ${FLANG_SOURCE_DIR}/lib/Decimal/binary-to-decimal.cpp
@@ -73,7 +80,16 @@ set(supported_sources
 
 # List of source not used for GPU offloading.
 set(host_sources
-  ${FLANG_SOURCE_DIR}/module/iso_fortran_env_impl.f90
+  __fortran_ieee_exceptions.f90
+  __fortran_type_info.f90
+  iso_fortran_env.f90
+  ieee_arithmetic.f90
+  ieee_exceptions.f90
+  ieee_features.f90
+  iso_c_binding.f90
+  iso_fortran_env_impl.f90
+  iso_fortran_env.f90
+
   command.cpp
   complex-powi.cpp
   complex-reduction.c
@@ -88,8 +104,32 @@ set(host_sources
   temporary-stack.cpp
   time-intrinsic.cpp
   unit-map.cpp
+
+  __cuda_device.f90
+  cooperative_groups.f90
+  cudadevice.f90
 )
 
+if (LLVM_TARGET_TRIPLE MATCHES "^ppc|^powerpc")
+  list(APPEND intrinsics_sources
+    __ppc_types.f90
+  )
+  list(APPEND host_sources
+    __ppc_intrinsics.f90
+    mma.f90
+  )
+endif ()
+
+# Compile as CUDA-Fortran, not directly supported by CMake
+set_property(SOURCE
+    __cuda_device.f90
+    cooperative_groups.f90
+    cudadevice.f90
+  APPEND PROPERTY
+    COMPILE_OPTIONS --offload-host-only -xcuda
+)
+
+
 # Sources that can be compiled directly for the GPU.
 set(gpu_sources
   ${FLANG_SOURCE_DIR}/lib/Decimal/binary-to-decimal.cpp
@@ -175,19 +215,42 @@ else ()
   set(f128_sources "")
 endif ()
 
-if ("${LLVM_RUNTIMES_TARGET}" MATCHES "^amdgcn|^nvptx")
+if (LLVM_RUNTIMES_TARGET MATCHES "^amdgcn|^nvptx")
   set(sources ${gpu_sources})
-elseif(FLANG_RT_EXPERIMENTAL_OFFLOAD_SUPPORT STREQUAL "CUDA")
-  set(sources ${supported_sources})
 else ()
   set(sources ${supported_sources} ${host_sources} ${f128_sources})
 endif ()
 
 
+# check-flang depends on this to build intrinsic modules
+if (NOT TARGET flang-rt-mod)
+  add_custom_target(flang-rt-mod)
+endif ()
+
 if (NOT WIN32)
+  # CMake ignores intrinsic USE dependencies
+  # CMake has an option Fortran_BUILDING_INSTRINSIC_MODULES/Fortran_BUILDING_INTRINSIC_MODULES
+  # to disable this behavior, unfortunately it does not work with Ninja
+  # (https://gitlab.kitware.com/cmake/cmake/-/issues/26803)
+  # As a workaround, we build those intrinsic modules first such that the main
+  # runtime can depend on it.
+  add_flangrt_library(flang_rt.intrinsics.obj OBJECT
+    ${intrinsics_sources}
+  )
+
+  # This barrier exists to force all of the intrinsic modules of
+  # flang_rt.intrinsics.obj to be built before anything that depends on it.
+  # Without it, CMake/Ninja seem to think that the modules of
+  # flang_rt.intrinsics.obj can be built concurrently to those in
+  # flang_rt.runtime.
+  add_custom_target(flang_rt.intrinsics
+    COMMENT "Intrinsic module dependency barrier"
+  )
+  add_dependencies(flang_rt.intrinsics flang_rt.intrinsics.obj)
+
   add_flangrt_library(flang_rt.runtime STATIC SHARED
-    ${sources}
-    LINK_LIBRARIES ${Backtrace_LIBRARY}
+    ${sources} $<TARGET_OBJECTS:flang_rt.intrinsics.obj>
+    LINK_LIBRARIES flang_rt.intrinsics.obj ${Backtrace_LIBRARY}
     INSTALL_WITH_TOOLCHAIN
     ADDITIONAL_HEADERS ${public_headers} ${private_headers}
   )
@@ -198,6 +261,13 @@ if (NOT WIN32)
   # Select a default runtime, which is used for unit and regression tests.
   get_target_property(default_target flang_rt.runtime.default ALIASED_TARGET)
   add_library(flang_rt.runtime.unittest ALIAS "${default_target}")
+
+  # Select a target that compiles the sources to build the public module files.
+  get_target_property(compile_target flang_rt.runtime.compile ALIASED_TARGET)
+  flang_module_target(flang_rt.intrinsics.obj PUBLIC)
+  flang_module_target(${compile_target} PUBLIC)
+  add_dependencies(${compile_target} flang_rt.intrinsics)
+  add_dependencies(flang-rt-mod flang_rt.intrinsics ${compile_target})
 else()
   # Target for building all versions of the runtime
   add_custom_target(flang_rt.runtime)
@@ -205,12 +275,23 @@ else()
 
   function (add_win_flangrt_runtime libtype suffix msvc_lib)
     set(name "flang_rt.runtime.${suffix}")
+
+    add_flangrt_library(${name}.intrinsics.obj OBJECT
+      ${intrinsics_sources}
+    )
+    add_custom_target(${name}.intrinsics
+      COMMAND echo "${name} Dependency barrier"
+      COMMENT "Intrinsic module dependency barrier"
+    )
+    add_dependencies(${name}.intrinsics ${name}.intrinsics.obj)
+
     add_flangrt_library(${name} ${libtype}
-        ${sources}
+        ${sources} $<TARGET_OBJECTS:${name}.intrinsics.obj>
         ${ARGN}
-        LINK_LIBRARIES ${Backtrace_LIBRARY}
+        LINK_LIBRARIES ${name}.intrinsics.obj ${Backtrace_LIBRARY}
         ADDITIONAL_HEADERS ${public_headers} ${private_headers}
       )
+    get_target_property(compile_target ${name}.compile ALIASED_TARGET)
 
     if (msvc_lib)
       set_target_properties(${name}
@@ -220,11 +301,19 @@ else()
     endif ()
 
     # Setting an unique Fortran_MODULE_DIRECTORY is required for each variant to
-    # write a different .mod file.
-    set_target_properties(${name}
-        PROPERTIES
-          Fortran_MODULE_DIRECTORY "module.${suffix}"
-      )
+    # write a different .mod file. One of them has to be selected to be the
+    # public module that is to be installed. We select the first.
+    if (_has_public_intrinsics)
+      set(is_public "")
+    else ()
+      set(is_public PUBLIC)
+      add_dependencies(flang-rt-mod ${name}.intrinsics ${compile_target})
+      set(_has_public_intrinsics "YES" PARENT_SCOPE)
+    endif ()
+
+    flang_module_target(${name}.intrinsics.obj ${is_public})
+    flang_module_target(${compile_target} ${is_public})
+    add_dependencies(${compile_target} ${name}.intrinsics)
 
     enable_cuda_compilation(${name} "${supported_sources}")
     enable_omp_offload_compilation(${name} "${supported_sources}")
diff --git a/flang/module/__cuda_builtins.f90 b/flang-rt/lib/runtime/__cuda_builtins.f90
similarity index 100%
rename from flang/module/__cuda_builtins.f90
rename to flang-rt/lib/runtime/__cuda_builtins.f90
diff --git a/flang/module/__cuda_device.f90 b/flang-rt/lib/runtime/__cuda_device.f90
similarity index 100%
rename from flang/module/__cuda_device.f90
rename to flang-rt/lib/runtime/__cuda_device.f90
diff --git a/flang/module/__fortran_builtins.f90 b/flang-rt/lib/runtime/__fortran_builtins.f90
similarity index 99%
rename from flang/module/__fortran_builtins.f90
rename to flang-rt/lib/runtime/__fortran_builtins.f90
index 4d134fa4b62b1..7bb078c0b428e 100644
--- a/flang/module/__fortran_builtins.f90
+++ b/flang-rt/lib/runtime/__fortran_builtins.f90
@@ -6,7 +6,7 @@
 !
 !===------------------------------------------------------------------------===!
 
-#include '../include/flang/Runtime/magic-numbers.h'
+#include '../../../flang/include/flang/Runtime/magic-numbers.h'
 
 ! These naming shenanigans prevent names from Fortran intrinsic modules
 ! from being usable on INTRINSIC statements, and force the program
diff --git a/flang/module/__fortran_ieee_exceptions.f90 b/flang-rt/lib/runtime/__fortran_ieee_exceptions.f90
similarity index 100%
rename from flang/module/__fortran_ieee_exceptions.f90
rename to flang-rt/lib/runtime/__fortran_ieee_exceptions.f90
diff --git a/flang/module/__fortran_type_info.f90 b/flang-rt/lib/runtime/__fortran_type_info.f90
similarity index 100%
rename from flang/module/__fortran_type_info.f90
rename to flang-rt/lib/runtime/__fortran_type_info.f90
diff --git a/flang/module/__ppc_intrinsics.f90 b/flang-rt/lib/runtime/__ppc_intrinsics.f90
similarity index 100%
rename from flang/module/__ppc_intrinsics.f90
rename to flang-rt/lib/runtime/__ppc_intrinsics.f90
diff --git a/flang/module/__ppc_types.f90 b/flang-rt/lib/runtime/__ppc_types.f90
similarity index 100%
rename from flang/module/__ppc_types.f90
rename to flang-rt/lib/runtime/__ppc_types.f90
diff --git a/flang/module/cooperative_groups.f90 b/flang-rt/lib/runtime/cooperative_groups.f90
similarity index 96%
rename from flang/module/cooperative_groups.f90
rename to flang-rt/lib/runtime/cooperative_groups.f90
index 8bb4af3afa791..5ca0c3aa1f3a5 100644
--- a/flang/module/cooperative_groups.f90
+++ b/flang-rt/lib/runtime/cooperative_groups.f90
@@ -11,6 +11,7 @@
 module cooperative_groups
 
 use, intrinsic :: __fortran_builtins, only: c_devptr => __builtin_c_devptr
+use :: cudadevice ! implicit dependency, made explicit for CMake
 
 implicit none
 
diff --git a/flang/module/cudadevice.f90 b/flang-rt/lib/runtime/cudadevice.f90
similarity index 100%
rename from flang/module/cudadevice.f90
rename to flang-rt/lib/runtime/cudadevice.f90
diff --git a/flang/module/ieee_arithmetic.f90 b/flang-rt/lib/runtime/ieee_arithmetic.f90
similarity index 99%
rename from flang/module/ieee_arithmetic.f90
rename to flang-rt/lib/runtime/ieee_arithmetic.f90
index 4e938a2daaa91..02cfae2dc6b18 100644
--- a/flang/module/ieee_arithmetic.f90
+++ b/flang-rt/lib/runtime/ieee_arithmetic.f90
@@ -8,7 +8,7 @@
 
 ! Fortran 2018 Clause 17
 
-#include '../include/flang/Runtime/magic-numbers.h'
+#include '../../../flang/include/flang/Runtime/magic-numbers.h'
 
 module ieee_arithmetic
   ! F18 Clause 17.1p1:
diff --git a/flang/module/ieee_exceptions.f90 b/flang-rt/lib/runtime/ieee_exceptions.f90
similarity index 100%
rename from flang/module/ieee_exceptions.f90
rename to flang-rt/lib/runtime/ieee_exceptions.f90
diff --git a/flang/module/ieee_features.f90 b/flang-rt/lib/runtime/ieee_features.f90
similarity index 100%
rename from flang/module/ieee_features.f90
rename to flang-rt/lib/runtime/ieee_features.f90
diff --git a/flang/module/iso_c_binding.f90 b/flang-rt/lib/runtime/iso_c_binding.f90
similarity index 100%
rename from flang/module/iso_c_binding.f90
rename to flang-rt/lib/runtime/iso_c_binding.f90
diff --git a/flang/module/iso_fortran_env.f90 b/flang-rt/lib/runtime/iso_fortran_env.f90
similarity index 100%
rename from flang/module/iso_fortran_env.f90
rename to flang-rt/lib/runtime/iso_fortran_env.f90
diff --git a/flang/module/iso_fortran_env_impl.f90 b/flang-rt/lib/runtime/iso_fortran_env_impl.f90
similarity index 100%
rename from flang/module/iso_fortran_env_impl.f90
rename to flang-rt/lib/runtime/iso_fortran_env_impl.f90
diff --git a/flang/module/mma.f90 b/flang-rt/lib/runtime/mma.f90
similarity index 100%
rename from flang/module/mma.f90
rename to flang-rt/lib/runtime/mma.f90
diff --git a/flang-rt/test/lit.site.cfg.py.in b/flang-rt/test/lit.site.cfg.py.in
index 662d076b1fe24..0e9dc08b59925 100644
--- a/flang-rt/test/lit.site.cfg.py.in
+++ b/flang-rt/test/lit.site.cfg.py.in
@@ -6,7 +6,7 @@ config.llvm_tools_dir = "@LLVM_TOOLS_DIR@"
 config.flang_source_dir = "@FLANG_SOURCE_DIR@"
 config.flang_rt_source_dir = "@FLANG_RT_SOURCE_DIR@"
 config.flang_rt_binary_test_dir = os.path.dirname(__file__)
-config.flang_rt_output_resource_lib_dir = "@FLANG_RT_OUTPUT_RESOURCE_LIB_DIR@"
+config.flang_rt_output_resource_lib_dir = "@RUNTIMES_OUTPUT_RESOURCE_LIB_DIR@"
 config.flang_rt_experimental_offload_support = "@FLANG_RT_EXPERIMENTAL_OFFLOAD_SUPPORT@"
 config.cc = "@CMAKE_C_COMPILER@"
 config.flang = "@CMAKE_Fortran_COMPILER@"
diff --git a/flang-rt/unittests/CMakeLists.txt b/flang-rt/unittests/CMakeLists.txt
index e1ab73d7d9301..75b76e93cb56d 100644
--- a/flang-rt/unittests/CMakeLists.txt
+++ b/flang-rt/unittests/CMakeLists.txt
@@ -49,9 +49,8 @@ function(add_flangrt_unittest_offload_properties target)
   # FIXME: replace 'native' in --offload-arch option with the list
   #        of targets that Fortran Runtime was built for.
   if (FLANG_RT_EXPERIMENTAL_OFFLOAD_SUPPORT STREQUAL "OpenMP")
-    set_target_properties(${target}
-      PROPERTIES LINK_OPTIONS
-      "-fopenmp;--offload-arch=native"
+    set_property(TARGET ${target} APPEND
+      PROPERTY LINK_OPTIONS -fopenmp --offload-arch=native
       )
   endif()
 endfunction()
diff --git a/flang/CMakeLists.txt b/flang/CMakeLists.txt
index c01eb56d5e496..df38846998b9e 100644
--- a/flang/CMakeLists.txt
+++ b/flang/CMakeLists.txt
@@ -273,7 +273,6 @@ set(FLANG_TOOLS_INSTALL_DIR "${CMAKE_INSTALL_BINDIR}" CACHE PATH
     "Path for binary subdirectory (defaults to '${CMAKE_INSTALL_BINDIR}')")
 mark_as_advanced(FLANG_TOOLS_INSTALL_DIR)
 
-set(FLANG_INTRINSIC_MODULES_DIR ${CMAKE_BINARY_DIR}/include/flang)
 set(FLANG_INCLUDE_DIR ${FLANG_BINARY_DIR}/include)
 
 # TODO: Remove when libclangDriver is lifted out of Clang
diff --git a/flang/include/flang/Frontend/CompilerInvocation.h b/flang/include/flang/Frontend/CompilerInvocation.h
index d294955af780e..feaee28a53349 100644
--- a/flang/include/flang/Frontend/CompilerInvocation.h
+++ b/flang/include/flang/Frontend/CompilerInvocation.h
@@ -92,6 +92,10 @@ class CompilerInvocation : public CompilerInvocationBase {
   // intrinsic of iso_fortran_env.
   std::string allCompilerInvocOpts;
 
+  /// Location of the resource directory containing files specific to this
+  /// instance/version of Flang.
+  std::string resourceDir;
+
   /// Semantic options
   // TODO: Merge with or translate to frontendOpts. We shouldn't need two sets
   // of options.
@@ -177,6 +181,9 @@ class CompilerInvocation : public CompilerInvocationBase {
   getSemanticsCtx(Fortran::parser::AllCookedSources &allCookedSources,
                   const llvm::TargetMachine &);
 
+  std::string &getResourceDir() { return resourceDir; }
+  const std::string &getResourceDir() const { return resourceDir; }
+
   std::string &getModuleDir() { return moduleDir; }
   const std::string &getModuleDir() const { return moduleDir; }
 
diff --git a/flang/lib/Frontend/CompilerInvocation.cpp b/flang/lib/Frontend/CompilerInvocation.cpp
index 0c32f3914e04b..aea46b9d69587 100644
--- a/flang/lib/Frontend/CompilerInvocation.cpp
+++ b/flang/lib/Frontend/CompilerInvocation.cpp
@@ -885,16 +885,6 @@ static bool parseFrontendArgs(FrontendOptions &opts, llvm::opt::ArgList &args,
   return diags.getNumErrors() == numErrorsBefore;
 }
 
-// Generate the path to look for intrinsic modules
-static std::string getIntrinsicDir(const char *argv) {
-  // TODO: Find a system independent API
-  llvm::SmallString<128> driverPath;
-  driverPath.assign(llvm::sys::fs::getMainExecutable(argv, nullptr));
-  llvm::sys::path::remove_filename(driverPath);
-  driverPath.append("/../include/flang/");
-  return std::string(driverPath);
-}
-
 // Generate the path to look for OpenMP headers
 static std::string getOpenMPHeadersDir(const char *argv) {
   llvm::SmallString<128> includePath;
@@ -1568,6 +1558,14 @@ bool CompilerInvocation::createFromArgs(
     success = false;
   }
 
+  // User-specified or default resource dir
+  if (const llvm::opt::Arg *a =
+          args.getLastArg(clang::options::OPT_resource_dir))
+    invoc.resourceDir = a->getValue();
+  else
+    invoc.resourceDir = clang::driver::Driver::GetResourcesPath(
+        llvm::sys::fs::getMainExecutable(argv0, nullptr));
+
   // -flang-experimental-hlfir
   if (args.hasArg(clang::options::OPT_flang_experimental_hlfir) ||
       args.hasArg(clang::options::OPT_emit_hlfir)) {
@@ -1834,9 +1832,11 @@ void CompilerInvocation::setFortranOpts() {
       preprocessorOptions.searchDirectoriesFromIntrModPath.begin(),
       preprocessorOptions.searchDirectoriesFromIntrModPath.end());
 
-  //  Add the default intrinsic module directory
-  fortranOptions.intrinsicModuleDirectories.emplace_back(
-      getIntrinsicDir(getArgv0()));
+  // Add the ordered list of -fintrinsic-modules-path
+  fortranOptions.intrinsicModuleDirectories.insert(
+      fortranOptions.intrinsicModuleDirectories.end(),
+      preprocessorOptions.searchDirectoriesFromIntrModPath.begin(),
+      preprocessorOptions.searchDirectoriesFromIntrModPath.end());
 
   // Add the directory supplied through -J/-module-dir to the list of search
   // directories
diff --git a/flang/lib/Semantics/semantics.cpp b/flang/lib/Semantics/semantics.cpp
index 2606d997b1cd7..f4b90bf01abe3 100644
--- a/flang/lib/Semantics/semantics.cpp
+++ b/flang/lib/Semantics/semantics.cpp
@@ -621,12 +621,15 @@ bool Semantics::Perform() {
     const auto *frontModule{std::get_if<common::Indirection<parser::Module>>(
         &program_.v.front().u)};
     if (frontModule &&
-        (std::get<parser::Statement<parser::ModuleStmt>>(frontModule->value().t)
-                    .statement.v.source == "__fortran_builtins" ||
-            std::get<parser::Statement<parser::ModuleStmt>>(
-                frontModule->value().t)
-                    .statement.v.source == "__ppc_types")) {
+        std::get<parser::Statement<parser::ModuleStmt>>(frontModule->value().t)
+                .statement.v.source == "__fortran_builtins") {
       // Don't try to read the builtins module when we're actually building it.
+    } else if (frontModule &&
+        std::get<parser::Statement<parser::ModuleStmt>>(frontModule->value().t)
+                .statement.v.source == "__ppc_types") {
+      // Don't try to read the UsePPCBuiltinTypesModule() we are currently
+      // building, but __fortran_builtins is needed to build it.
+      context_.UseFortranBuiltinsModule();
     } else if (frontModule &&
         (std::get<parser::Statement<parser::ModuleStmt>>(frontModule->value().t)
                     .statement.v.source == "__ppc_intrinsics" ||
diff --git a/flang/module/.clang-format b/flang/module/.clang-format
deleted file mode 100644
index e3845288a2aec..0000000000000
--- a/flang/module/.clang-format
+++ /dev/null
@@ -1 +0,0 @@
-DisableFormat: true
diff --git a/flang/test/CMakeLists.txt b/flang/test/CMakeLists.txt
index 8c8e92faa787a..a35f14428ef6f 100644
--- a/flang/test/CMakeLists.txt
+++ b/flang/test/CMakeLists.txt
@@ -2,11 +2,31 @@
 # for use by Lit, and delegates to LLVM's lit test handlers.
 add_subdirectory(lib)
 
+set(FLANG_TEST_Fortran_FLAGS "" CACHE STRING "Additional Fortran flags for running tests, such as -fintrinsic-modules-path=<path>")
+
+if ("flang-rt" IN_LIST LLVM_ENABLE_RUNTIMES)
+  set(FLANG_TEST_ENABLE_MODULES_default ON)
+else ()
+  set(FLANG_TEST_ENABLE_MODULES_default OFF)
+endif ()
+option(FLANG_TEST_ENABLE_MODULES "Force-enable tests that require intrinsic modules from Flang-RT" "${FLANG_TEST_ENABLE_MODULES_default}")
+
+
+if ("openmp" IN_LIST LLVM_ENABLE_RUNTIMES AND FLANG_TEST_ENABLE_MODULES AND NOT FLANG_STANDALONE_BUILD)
+  set(FLANG_TEST_ENABLE_OPENMP_default ON)
+else ()
+  set(FLANG_TEST_ENABLE_OPENMP_default OFF)
+endif ()
+option(FLANG_TEST_ENABLE_OPENMP "Force-enable tests that require modules from OpenMP" "${FLANG_TEST_ENABLE_OPENMP_default}")
+
+
 llvm_canonicalize_cmake_booleans(
   FLANG_STANDALONE_BUILD
   LLVM_BUILD_EXAMPLES
   LLVM_BYE_LINK_INTO_TOOLS
   LLVM_ENABLE_PLUGINS
+  FLANG_TEST_ENABLE_MODULES
+  FLANG_TEST_ENABLE_OPENMP
 )
 
 set(FLANG_TOOLS_DIR ${FLANG_BINARY_DIR}/bin)
@@ -59,7 +79,6 @@ set(FLANG_TEST_PARAMS
 
 set(FLANG_TEST_DEPENDS
   flang
-  module_files
   fir-opt
   tco
   bbc
@@ -101,8 +120,14 @@ if (LLVM_BUILD_EXAMPLES)
     )
 endif ()
 
-if ("openmp" IN_LIST LLVM_ENABLE_RUNTIMES AND NOT FLANG_STANDALONE_BUILD)
-  list(APPEND FLANG_TEST_DEPENDS "libomp-mod")
+if ("flang-rt" IN_LIST LLVM_ENABLE_RUNTIMES AND NOT FLANG_STANDALONE_BUILD)
+  # For intrinsic module files (in flang-rt/)
+  list(APPEND FLANG_TEST_DEPENDS "flang-rt-mod") 
+  
+  if ("openmp" IN_LIST LLVM_ENABLE_RUNTIMES)
+    # For omplib.mod and omplib_kinds.mod (in openmp/)
+    list(APPEND FLANG_TEST_DEPENDS "libomp-mod") 
+  endif ()
 endif ()
 
 add_custom_target(flang-test-depends DEPENDS ${FLANG_TEST_DEPENDS})
diff --git a/flang/test/Driver/Inputs/ieee_arithmetic.mod b/flang/test/Driver/Inputs/ieee_arithmetic.mod
index 30fd57801970b..264ff8d035628 100644
--- a/flang/test/Driver/Inputs/ieee_arithmetic.mod
+++ b/flang/test/Driver/Inputs/ieee_arithmetic.mod
@@ -1,5 +1,6 @@
 ! DUMMY module
 ! Added for testing purposes. The contents of this file are currently not relevant.
+! Using this file will cause an error because of missing checksum
 module ieee_arithmetic
 type::ieee_round_type
 integer(1),private::mode=0_1
diff --git a/flang/test/Driver/Inputs/iso_fortran_env.mod b/flang/test/Driver/Inputs/iso_fortran_env.mod
index 689297d52027b..c53375d78dec5 100644
--- a/flang/test/Driver/Inputs/iso_fortran_env.mod
+++ b/flang/test/Driver/Inputs/iso_fortran_env.mod
@@ -1,5 +1,6 @@
 ! DUMMY module
 ! Added for testing purposes. The contents of this file are currently not relevant.
+! Using this file will cause an error because of missing checksum
 module iso_fortran_env
 use __fortran_builtins,only:event_type=>__builtin_event_type
 use __fortran_builtins,only:lock_type=>__builtin_lock_type
diff --git a/flang/test/Driver/intrinsic-module-path.F90 b/flang/test/Driver/intrinsic-module-path.F90
new file mode 100644
index 0000000000000..3317eb776f0a1
--- /dev/null
+++ b/flang/test/Driver/intrinsic-module-path.F90
@@ -0,0 +1,55 @@
+! Ensure argument -fintrinsic-modules-path works as expected.
+
+!-----------------------------------------
+! FLANG DRIVER
+!-----------------------------------------
+! NOTE: Depending on how Flang is built, the default intrinsics may have higher
+!       or lower priority than -fintrinsic-modules-path added here. Using
+!       basictestmoduleone.mod from Inputs/module-dir/ will trigger an error.
+
+! RUN:     %flang -fsyntax-only -### %s 2>&1 | FileCheck %s --check-prefix=DEFAULTPATH
+
+! RUN:     %flang -fsyntax-only -DINTRINSICS_DEFAULT %s
+! RUN: not %flang -fsyntax-only -DINTRINSICS_INPUTONE %s 2>&1 | FileCheck %s --check-prefix=NOINPUTONE
+! RUN: not %flang -fsyntax-only -DINTRINSICS_INPUTTWO %s 2>&1 | FileCheck %s --check-prefix=NOINPUTTWO
+! RUN:     %flang -fsyntax-only -DINTRINSICS_DEFAULT -DINTRINSICS_INPUTTWO -fintrinsic-modules-path=%S/Inputs/module-dir/ %s
+! RUN:     %flang -fsyntax-only -DINTRINSICS_INPUTONE -fintrinsic-modules-path=%S/Inputs/ %s
+! RUN:     %flang -fsyntax-only -DINTRINSICS_INPUTONE -DINTRINSICS_INPUTTWO -fintrinsic-modules-path=%S/Inputs/ -fintrinsic-modules-path=%S/Inputs/module-dir/ %s
+! RUN: not %flang -fsyntax-only -DINTRINSICS_INPUTONE -DINTRINSICS_INPUTTWO -fintrinsic-modules-path=%S/Inputs/module-dir/ -fintrinsic-modules-path=%S/Inputs/ %s 2>&1 | FileCheck %s --check-prefix=WRONGINPUTONE
+
+
+!-----------------------------------------
+! FLANG FRONTEND (flang -fc1)
+!-----------------------------------------
+! NOTE: %flang_cc1 the default intrinsics path always has higher priority than
+!       -fintrinsic-modules-path added here. Accidentally using
+!       ieee_arithmetic/iso_fortran_env from the Inputs/ directory will trigger
+!       an error (e.g. when the default intrinsics dir is empty).
+
+! RUN:     %flang_fc1 -fsyntax-only -DINTRINSICS_DEFAULT %s
+! RUN: not %flang_fc1 -fsyntax-only -DINTRINSICS_DEFAULT -DINTRINSICS_INPUTONE %s 2>&1 | FileCheck %s --check-prefix=NOINPUTONE
+! RUN: not %flang_fc1 -fsyntax-only -DINTRINSICS_DEFAULT -DINTRINSICS_INPUTTWO %s 2>&1 | FileCheck %s --check-prefix=NOINPUTTWO
+! RUN:     %flang_fc1 -fsyntax-only -DINTRINSICS_DEFAULT -DINTRINSICS_INPUTTWO -fintrinsic-modules-path=%S/Inputs/module-dir %s
+! RUN:     %flang_fc1 -fsyntax-only -DINTRINSICS_DEFAULT -DINTRINSICS_INPUTONE -fintrinsic-modules-path=%S/Inputs/ %s
+! RUN:     %flang_fc1 -fsyntax-only -DINTRINSICS_DEFAULT -DINTRINSICS_INPUTONE -DINTRINSICS_INPUTTWO -fintrinsic-modules-path=%S/Inputs/ -fintrinsic-modules-path=%S/Inputs/module-dir/ %s
+! RUN: not %flang_fc1 -fsyntax-only -DINTRINSICS_DEFAULT -DINTRINSICS_INPUTONE -DINTRINSICS_INPUTTWO -fintrinsic-modules-path=%S/Inputs/module-dir -fintrinsic-modules-path=%S/Inputs/ %s 2>&1 | FileCheck %s --check-prefix=WRONGINPUTONE
+
+
+! DEFAULTPATH: flang{{.*}}-fc1{{.*}}-fintrinsic-modules-path
+
+! NOINPUTONE: Source file 'basictestmoduleone.mod' was not found
+! NOINPUTTWO: Source file 'basictestmoduletwo.mod' was not found
+! WRONGINPUTONE: 't1' not found in module 'basictestmoduleone'
+
+program test_intrinsic_module_path
+#ifdef INTRINSICS_DEFAULT
+   use ieee_arithmetic, only: ieee_round_type
+   use iso_fortran_env, only: team_type, event_type, lock_type
+#endif
+#ifdef INTRINSICS_INPUTONE
+   use basictestmoduleone, only: t1
+#endif
+#ifdef INTRINSICS_INPUTTWO
+   use basictestmoduletwo, only: t2
+#endif
+end program
diff --git a/flang/test/Driver/intrinsic-module-path.f90 b/flang/test/Driver/intrinsic-module-path.f90
deleted file mode 100644
index 615d8f9a1730a..0000000000000
--- a/flang/test/Driver/intrinsic-module-path.f90
+++ /dev/null
@@ -1,23 +0,0 @@
-! Ensure argument -fintrinsic-modules-path works as expected.
-! WITHOUT the option, the default location for the module is checked and no error generated.
-! With the option GIVEN, the module with the same name is PREPENDED, and considered over the
-! default one, causing a CHECKSUM error.
-
-!-----------------------------------------
-! FRONTEND FLANG DRIVER (flang -fc1)
-!-----------------------------------------
-! RUN: %flang_fc1 -fsyntax-only %s  2>&1 | FileCheck %s --allow-empty --check-prefix=WITHOUT
-! RUN: not %flang_fc1 -fsyntax-only -fintrinsic-modules-path %S/Inputs/ %s  2>&1 | FileCheck %s --check-prefix=GIVEN
-! RUN: not %flang_fc1 -fsyntax-only -fintrinsic-modules-path=%S/Inputs/ %s  2>&1 | FileCheck %s --check-prefix=GIVEN
-
-! WITHOUT-NOT: 'ieee_arithmetic.mod' was not found
-! WITHOUT-NOT: 'iso_fortran_env.mod' was not found
-
-! GIVEN: error: Cannot use module file for module 'ieee_arithmetic': File has invalid checksum
-! GIVEN: error: Cannot use module file for module 'iso_fortran_env': File has invalid checksum
-
-
-program test_intrinsic_module_path
-   use ieee_arithmetic, only: ieee_round_type
-   use iso_fortran_env, only: team_type, event_type, lock_type
-end program
diff --git a/flang/test/Driver/lto-fatlto.f90 b/flang/test/Driver/lto-fatlto.f90
index 2ea251eafacbf..9adf264f114dc 100644
--- a/flang/test/Driver/lto-fatlto.f90
+++ b/flang/test/Driver/lto-fatlto.f90
@@ -1,7 +1,7 @@
 ! REQUIRES: x86-registered-target
 ! checks fatlto objects: that valid bitcode is included in the object file generated.
 
-! RUN: %flang -fc1 -triple x86_64-unknown-linux-gnu -flto -ffat-lto-objects -emit-obj %s -o %t.o
+! RUN: %flang_fc1 -triple x86_64-unknown-linux-gnu -flto -ffat-lto-objects -emit-obj %s -o %t.o
 ! RUN: llvm-readelf -S %t.o | FileCheck %s --check-prefixes=ELF
 ! RUN: llvm-objcopy --dump-section=.llvm.lto=%t.bc %t.o
 ! RUN: llvm-dis %t.bc -o - | FileCheck %s --check-prefixes=DIS
@@ -11,7 +11,7 @@
 ! DIS-NEXT:  ret void
 ! DIS-NEXT: }
 
-! RUN: %flang -fc1 -triple x86_64-unknown-linux-gnu -flto -ffat-lto-objects -S %s -o - | FileCheck %s --check-prefixes=ASM
+! RUN: %flang_fc1 -triple x86_64-unknown-linux-gnu -flto -ffat-lto-objects -S %s -o - | FileCheck %s --check-prefixes=ASM
 
 !      ASM: .section        .llvm.lto,"e", at llvm_lto
 ! ASM-NEXT: .Lllvm.embedded.object:
diff --git a/flang/test/Driver/pp-fixed-form.f90 b/flang/test/Driver/pp-fixed-form.f90
index bb869cd3341a7..fb9e1dd0d1e6b 100644
--- a/flang/test/Driver/pp-fixed-form.f90
+++ b/flang/test/Driver/pp-fixed-form.f90
@@ -8,12 +8,12 @@
 
 !RUN: %flang -save-temps -### -ffree-form %S/Inputs/free-form-test.f90  2>&1 | FileCheck %s --check-prefix=FREE-FLAG
 FREE-FLAG:           "-fc1" {{.*}} "-o" "free-form-test.i" {{.*}} "-x" "f95" "{{.*}}/free-form-test.f90"
-FREE-FLAG-NEXT:      "-fc1" {{.*}} "-emit-llvm-bc" "-ffree-form"
+FREE-FLAG-NEXT:      "-fc1" {{.*}} "-emit-llvm-bc" {{.*}}"-ffree-form"
 FREE-FLAG-NOT:       "-ffixed-form"
 FREE-FLAG-SAME:      "-x" "f95-cpp-input" "free-form-test.i"
 
 !RUN: %flang -save-temps -### -ffixed-form %S/Inputs/fixed-form-test.f  2>&1 | FileCheck %s --check-prefix=FIXED-FLAG
 FIXED-FLAG:          "-fc1" {{.*}} "-o" "fixed-form-test.i" {{.*}} "-x" "f95" "{{.*}}/fixed-form-test.f"
-FIXED-FLAG-NEXT:     "-fc1" {{.*}} "-emit-llvm-bc" "-ffixed-form"
+FIXED-FLAG-NEXT:     "-fc1" {{.*}} "-emit-llvm-bc" {{.*}}"-ffixed-form"
 FIXED-FLAG-NOT:      "-ffixed-form"
 FIXED-FLAG-SAME:     "-x" "f95-cpp-input" "fixed-form-test.i"
diff --git a/flang/test/Lower/HLFIR/type-bound-call-mismatch.f90 b/flang/test/Lower/HLFIR/type-bound-call-mismatch.f90
index 2e0c72ccfe048..29a9784b984b6 100644
--- a/flang/test/Lower/HLFIR/type-bound-call-mismatch.f90
+++ b/flang/test/Lower/HLFIR/type-bound-call-mismatch.f90
@@ -1,6 +1,6 @@
 ! Test interface that lowering handles small interface mismatch with
 ! type bound procedures.
-! RUN: bbc -emit-hlfir %s -o - -I nw | FileCheck %s
+! RUN: %bbc_bare -emit-hlfir %s -o - -I nw | FileCheck %s
 
 module dispatch_mismatch
 type t
diff --git a/flang/test/Lower/OpenMP/simd_aarch64.f90 b/flang/test/Lower/OpenMP/simd_aarch64.f90
index 735237223bcb5..2e4136273c75b 100644
--- a/flang/test/Lower/OpenMP/simd_aarch64.f90
+++ b/flang/test/Lower/OpenMP/simd_aarch64.f90
@@ -1,6 +1,11 @@
-! Tests for 2.9.3.1 Simd and target dependent defult alignment for AArch64
+! Tests for 2.9.3.1 Simd and target dependent default alignment for AArch64
 ! The default alignment for AARCH64 is 0 so we do not emit aligned clause
 ! REQUIRES: aarch64-registered-target
+
+! Requires aarch64 iso_c_binding.mod which currently is only available if your host is also aarch64
+! FIXME: Make flang a cross-compiler
+! UNSUPPORTED: true
+
 ! RUN: %flang_fc1 -triple aarch64-unknown-linux-gnu -emit-hlfir -fopenmp %s -o - | FileCheck  %s
 subroutine simdloop_aligned_cptr(A)
     use iso_c_binding
diff --git a/flang/test/Lower/OpenMP/target-enter-data-default-openmp52.f90 b/flang/test/Lower/OpenMP/target-enter-data-default-openmp52.f90
index 5f7c31bb931f6..d7785ae68bb16 100644
--- a/flang/test/Lower/OpenMP/target-enter-data-default-openmp52.f90
+++ b/flang/test/Lower/OpenMP/target-enter-data-default-openmp52.f90
@@ -1,7 +1,7 @@
 ! This test checks the lowering and application of default map types for the target enter/exit data constructs and map clauses
 
-!RUN: %flang -fc1 -emit-fir -fopenmp -fopenmp-version=52 -o - %s | FileCheck %s --check-prefix=CHECK-52
-!RUN: not %flang -fc1 -emit-fir -fopenmp -fopenmp-version=51 -o - %s 2>&1| FileCheck %s --check-prefix=CHECK-51
+!RUN: %flang_fc1 -emit-fir -fopenmp -fopenmp-version=52 -o - %s | FileCheck %s --check-prefix=CHECK-52
+!RUN: not %flang_fc1 -emit-fir -fopenmp -fopenmp-version=51 -o - %s 2>&1| FileCheck %s --check-prefix=CHECK-51
 
 module test
   real, allocatable :: A
diff --git a/flang/test/Preprocessing/fixed-free.f b/flang/test/Preprocessing/fixed-free.f
index 95f63a4d71e4c..7140bc6aec360 100644
--- a/flang/test/Preprocessing/fixed-free.f
+++ b/flang/test/Preprocessing/fixed-free.f
@@ -1,5 +1,5 @@
 !RUN: %flang -E %s 2>&1 | FileCheck %s
-!RUN: %flang -fc1 -fsyntax-only %s 2>&1 | FileCheck --allow-empty %s
+!RUN: %flang_fc1 -fsyntax-only %s 2>&1 | FileCheck --allow-empty %s
 !CHECK-NOT: dir$
 !CHECK-NOT: error:
 !dir$ fixed
diff --git a/flang/test/Preprocessing/no-pp-if.f90 b/flang/test/Preprocessing/no-pp-if.f90
index 3e49df3deb251..ab08a4f838a90 100644
--- a/flang/test/Preprocessing/no-pp-if.f90
+++ b/flang/test/Preprocessing/no-pp-if.f90
@@ -1,4 +1,4 @@
-!RUN: %flang -fc1 -fdebug-unparse %s 2>&1 | FileCheck %s
+!RUN: %flang_fc1 -fdebug-unparse %s 2>&1 | FileCheck %s
 !CHECK-NOT: ERROR STOP
 !CHECK: CONTINUE
 #if defined UNDEFINED
diff --git a/flang/test/Semantics/bug163242.f90 b/flang/test/Semantics/bug163242.f90
index 5e020aeb4dc0d..3c0a2b6b32229 100644
--- a/flang/test/Semantics/bug163242.f90
+++ b/flang/test/Semantics/bug163242.f90
@@ -1,4 +1,4 @@
-!RUN: %flang -fc1 -fsyntax-only %s | FileCheck --allow-empty %s
+!RUN: %flang_fc1 -fsyntax-only %s | FileCheck --allow-empty %s
 !CHECK-NOT: error:
 character(0), allocatable :: ch
 allocate(character(-1) :: ch)
diff --git a/flang/test/Semantics/bug164303.f90 b/flang/test/Semantics/bug164303.f90
index c356c07392577..39af27e914248 100644
--- a/flang/test/Semantics/bug164303.f90
+++ b/flang/test/Semantics/bug164303.f90
@@ -1,4 +1,4 @@
-!RUN: %flang -fc1 -fsyntax-only %s 2>&1 | FileCheck --allow-empty %s
+!RUN: %flang_fc1 -fsyntax-only %s 2>&1 | FileCheck --allow-empty %s
 module foo_mod
   use, intrinsic :: iso_fortran_env
   use, intrinsic :: iso_c_binding
diff --git a/flang/test/lit.cfg.py b/flang/test/lit.cfg.py
index 4221354df34a2..c3050dc876ec7 100644
--- a/flang/test/lit.cfg.py
+++ b/flang/test/lit.cfg.py
@@ -139,18 +139,95 @@
 if config.default_sysroot:
     config.available_features.add("default_sysroot")
 
+
+flang_exe = lit.util.which("flang", config.flang_llvm_tools_dir)
+if not flang_exe:
+    lit_config.fatal(f"Could not identify flang executable")
+
+# Intrinsic paths that are added implicitly by the `flang` driver, but have to be added manually when invoking the frontend `flang -fc1`.
+flang_driver_search_args = []
+
+# Intrinsic paths that are added to `flang` as well as `flang -fc1`.
+flang_extra_search_args = list(config.flang_test_fortran_flags)
+
+
+def get_resource_module_intrinsic_dir(modfile):
+    # Determine the intrinsic module search path that is added by the driver. If
+    # skipping the driver using -fc1, we need to append the path manually.
+    flang_intrinsics_dir = subprocess.check_output(
+        [flang_exe, *config.flang_test_fortran_flags, f"-print-file-name={modfile}"],
+        text=True,
+    ).strip()
+    flang_intrinsics_dir = os.path.dirname(flang_intrinsics_dir)
+    return flang_intrinsics_dir or None
+
+
+intrinsics_mod_path = get_resource_module_intrinsic_dir("__fortran_builtins.mod")
+if intrinsics_mod_path:
+    flang_driver_search_args += [f"-fintrinsic-modules-path={intrinsics_mod_path}"]
+
+openmp_mod_path = get_resource_module_intrinsic_dir("omp_lib.mod")
+if openmp_mod_path and openmp_mod_path != intrinsics_mod_path:
+    flang_driver_search_args += [f"-fintrinsic-modules-path={openmp_mod_path}"]
+
+
+# If intrinsic modules are not available, disable tests unless they are marked as 'module-independent'.
+config.available_features.add("module-independent")
+if config.flang_test_enable_modules or intrinsics_mod_path:
+    config.available_features.add("flangrt-modules")
+else:
+    lit_config.warning(
+        f"Intrinsic modules not in driver default paths: disabling most tests; Use FLANG_TEST_ENABLE_MODULES=ON to force-enable"
+    )
+    config.limit_to_features.add("module-independent")
+
+# Determine if OpenMP runtime was built (enable OpenMP tests via REQUIRES in test file)
+if config.flang_test_enable_openmp or openmp_mod_path:
+    config.available_features.add("openmp_runtime")
+
+    # Search path for omp_lib.h with LLVM_ENABLE_RUNTIMES=openmp
+    # FIXME: openmp should write this file into the resource directory
+    flang_extra_search_args += [
+        "-I",
+        f"{config.flang_obj_root}/../../runtimes/runtimes-bins/openmp/runtime/src",
+    ]
+else:
+    lit_config.warning(
+        f"OpenMP modules found not in driver default paths: OpenMP tests disabled; Use FLANG_TEST_ENABLE_OPENMP=ON to force-enable"
+    )
+
+
+lit_config.note(f"using flang: {flang_exe}")
+lit_config.note(
+    f"using flang implicit search paths: {' '.join(flang_driver_search_args)}"
+)
+lit_config.note(f"using flang extra search paths: {' '.join(flang_extra_search_args)}")
+
 # For each occurrence of a flang tool name, replace it with the full path to
 # the build directory holding that tool.
 tools = [
+    ToolSubst(
+        "bbc",
+        command=FindTool("bbc"),
+        extra_args=flang_driver_search_args + flang_extra_search_args,
+        unresolved="fatal",
+    ),
     ToolSubst(
         "%flang",
-        command=FindTool("flang"),
+        command=flang_exe,
+        extra_args=flang_extra_search_args,
         unresolved="fatal",
     ),
     ToolSubst(
         "%flang_fc1",
-        command=FindTool("flang"),
-        extra_args=["-fc1"],
+        command=flang_exe,
+        extra_args=["-fc1"] + flang_driver_search_args + flang_extra_search_args,
+        unresolved="fatal",
+    ),
+    # Variant that does not implicitly add intrinsic search paths
+    ToolSubst(
+        "%bbc_bare",
+        command=FindTool("bbc"),
         unresolved="fatal",
     ),
 ]
@@ -193,16 +270,7 @@
 if result:
     config.environment["LIBPGMATH"] = True
 
-# Determine if OpenMP runtime was built (enable OpenMP tests via REQUIRES in test file)
-openmp_flags_substitution = "-fopenmp"
-if config.have_openmp_rtl:
-    config.available_features.add("openmp_runtime")
-    # For the enabled OpenMP tests, add a substitution that is needed in the tests to find
-    # the omp_lib.{h,mod} files, depending on whether the OpenMP runtime was built as a
-    # project or runtime.
-    if config.openmp_module_dir:
-        openmp_flags_substitution += f" -J {config.openmp_module_dir}"
-config.substitutions.append(("%openmp_flags", openmp_flags_substitution))
+config.substitutions.append(("%openmp_flags", "-fopenmp"))
 
 # Add features and substitutions to test F128 math support.
 # %f128-lib substitution may be used to generate check prefixes
diff --git a/flang/test/lit.site.cfg.py.in b/flang/test/lit.site.cfg.py.in
index cc1f4fa6cc9c5..25f2a88d068d7 100644
--- a/flang/test/lit.site.cfg.py.in
+++ b/flang/test/lit.site.cfg.py.in
@@ -13,10 +13,12 @@ config.lit_tools_dir = "@LLVM_LIT_TOOLS_DIR@"
 config.errc_messages = "@LLVM_LIT_ERRC_MESSAGES@"
 config.flang_obj_root = "@FLANG_BINARY_DIR@"
 config.flang_tools_dir = lit_config.substitute("@FLANG_TOOLS_DIR@")
-config.flang_intrinsic_modules_dir = "@FLANG_INTRINSIC_MODULES_DIR@"
 config.flang_headers_dir = "@HEADER_BINARY_DIR@"
 config.flang_llvm_tools_dir = "@CMAKE_BINARY_DIR@/bin"
 config.flang_test_triple = "@FLANG_TEST_TARGET_TRIPLE@"
+config.flang_test_fortran_flags = "@FLANG_TEST_Fortran_FLAGS@".split()
+config.flang_test_enable_modules = @FLANG_TEST_ENABLE_MODULES@
+config.flang_test_enable_openmp = @FLANG_TEST_ENABLE_OPENMP@
 config.flang_examples = @LLVM_BUILD_EXAMPLES@
 config.python_executable = "@PYTHON_EXECUTABLE@"
 config.flang_standalone_build = @FLANG_STANDALONE_BUILD@
@@ -25,11 +27,6 @@ config.linked_bye_extension = @LLVM_BYE_LINK_INTO_TOOLS@
 config.osx_sysroot = path(r"@CMAKE_OSX_SYSROOT@")
 config.targets_to_build = "@TARGETS_TO_BUILD@"
 config.default_sysroot = "@DEFAULT_SYSROOT@"
-config.have_openmp_rtl = ("@LLVM_TOOL_OPENMP_BUILD@" == "TRUE") or ("openmp" in "@LLVM_ENABLE_RUNTIMES@".lower().split(";"))
-if "openmp" in "@LLVM_ENABLE_RUNTIMES@".lower().split(";"):
-    config.openmp_module_dir = "@CMAKE_BINARY_DIR@/runtimes/runtimes-bins/openmp/runtime/src"
-else:
-    config.openmp_module_dir = None
 config.flang_runtime_f128_math_lib = "@FLANG_RUNTIME_F128_MATH_LIB@"
 config.have_ldbl_mant_dig_113 = "@HAVE_LDBL_MANT_DIG_113@"
 
diff --git a/flang/tools/CMakeLists.txt b/flang/tools/CMakeLists.txt
index 1d2d2c608faf9..1b297af74cae7 100644
--- a/flang/tools/CMakeLists.txt
+++ b/flang/tools/CMakeLists.txt
@@ -7,7 +7,6 @@
 #===------------------------------------------------------------------------===#
 
 add_subdirectory(bbc)
-add_subdirectory(f18)
 add_subdirectory(flang-driver)
 add_subdirectory(tco)
 add_subdirectory(f18-parse-demo)
diff --git a/flang/tools/bbc/bbc.cpp b/flang/tools/bbc/bbc.cpp
index 8b12da3a7b50a..ab35fb3af6c2a 100644
--- a/flang/tools/bbc/bbc.cpp
+++ b/flang/tools/bbc/bbc.cpp
@@ -98,6 +98,11 @@ static llvm::cl::alias
                           llvm::cl::desc("intrinsic module directory"),
                           llvm::cl::aliasopt(intrinsicIncludeDirs));
 
+static llvm::cl::alias
+    intrinsicModulePath("fintrinsic-modules-path",
+                        llvm::cl::desc("intrinsic module search paths"),
+                        llvm::cl::aliasopt(intrinsicIncludeDirs));
+
 static llvm::cl::opt<std::string>
     moduleDir("module", llvm::cl::desc("module output directory (default .)"),
               llvm::cl::init("."));
@@ -574,14 +579,6 @@ int main(int argc, char **argv) {
 
   if (includeDirs.size() == 0) {
     includeDirs.push_back(".");
-    // Default Fortran modules should be installed in include/flang (a sibling
-    // to the bin) directory.
-    intrinsicIncludeDirs.push_back(
-        llvm::sys::path::parent_path(
-            llvm::sys::path::parent_path(
-                llvm::sys::fs::getMainExecutable(argv[0], nullptr)))
-            .str() +
-        "/include/flang");
   }
 
   Fortran::parser::Options options;
diff --git a/flang/tools/f18/CMakeLists.txt b/flang/tools/f18/CMakeLists.txt
deleted file mode 100644
index 715992c756c4b..0000000000000
--- a/flang/tools/f18/CMakeLists.txt
+++ /dev/null
@@ -1,170 +0,0 @@
-set(LLVM_LINK_COMPONENTS
-  FrontendOpenACC
-  FrontendOpenMP
-  Support
-  )
-
-# Define the list of Fortran module files for which it is
-# sufficient to generate the module file via -fsyntax-only.
-set(MODULES
-  "__fortran_builtins"
-  "__fortran_ieee_exceptions"
-  "__fortran_type_info"
-  "__ppc_types"
-  "__ppc_intrinsics"
-  "mma"
-  "__cuda_builtins"
-  "__cuda_device"
-  "cooperative_groups"
-  "cudadevice"
-  "ieee_arithmetic"
-  "ieee_exceptions"
-  "ieee_features"
-  "iso_c_binding"
-  "iso_fortran_env"
-  "iso_fortran_env_impl"
-)
-
-# Check if 128-bit float computations can be done via long double.
-check_cxx_source_compiles(
-  "#include <cfloat>
-   #if LDBL_MANT_DIG != 113
-   #error LDBL_MANT_DIG != 113
-   #endif
-   int main() { return 0; }
-  "
-  HAVE_LDBL_MANT_DIG_113)
-
-# Figure out whether we can support REAL(KIND=16)
-if (FLANG_RUNTIME_F128_MATH_LIB)
-  set(FLANG_SUPPORT_R16 "1")
-elseif (HAVE_LDBL_MANT_DIG_113)
-  set(FLANG_SUPPORT_R16 "1")
-else()
-  set(FLANG_SUPPORT_R16 "0")
-endif()
-
-# Init variable to hold extra object files coming from the Fortran modules;
-# these module files will be contributed from the CMakeLists in flang/tools/f18.
-set(module_objects "")
-
-# Create module files directly from the top-level module source directory.
-# If CMAKE_CROSSCOMPILING, then the newly built flang executable was
-# cross compiled, and thus can't be executed on the build system and thus
-# can't be used for generating module files.
-if (NOT CMAKE_CROSSCOMPILING)
-  foreach(filename ${MODULES})
-    set(depends "")
-    set(opts "")
-    if(${filename} STREQUAL "__fortran_builtins" OR
-       ${filename} STREQUAL "__ppc_types")
-    elseif(${filename} STREQUAL "__ppc_intrinsics" OR
-           ${filename} STREQUAL "mma")
-      set(depends ${FLANG_INTRINSIC_MODULES_DIR}/__ppc_types.mod)
-    elseif(${filename} STREQUAL "__cuda_device" OR
-           ${filename} STREQUAL "cudadevice" OR
-           ${filename} STREQUAL "cooperative_groups")
-      set(opts -fc1 -xcuda)
-      if(${filename} STREQUAL "__cuda_device")
-        set(depends ${FLANG_INTRINSIC_MODULES_DIR}/__cuda_builtins.mod)
-      elseif(${filename} STREQUAL "cudadevice")
-        set(depends ${FLANG_INTRINSIC_MODULES_DIR}/__cuda_device.mod)
-      elseif(${filename} STREQUAL "cooperative_groups")
-        set(depends ${FLANG_INTRINSIC_MODULES_DIR}/cudadevice.mod)
-      endif()
-    else()
-      set(depends ${FLANG_INTRINSIC_MODULES_DIR}/__fortran_builtins.mod)
-      if(${filename} STREQUAL "iso_fortran_env")
-        set(depends ${depends} ${FLANG_INTRINSIC_MODULES_DIR}/iso_fortran_env_impl.mod)
-      endif()
-      if(${filename} STREQUAL "ieee_arithmetic" OR
-         ${filename} STREQUAL "ieee_exceptions")
-        set(depends ${depends} ${FLANG_INTRINSIC_MODULES_DIR}/__fortran_ieee_exceptions.mod)
-      endif()
-    endif()
-    if(NOT ${filename} STREQUAL "__fortran_type_info" AND NOT ${filename} STREQUAL "__fortran_builtins")
-      set(depends ${depends} ${FLANG_INTRINSIC_MODULES_DIR}/__fortran_type_info.mod)
-    endif()
-
-    # The module contains PPC vector types that needs the PPC target.
-    if(${filename} STREQUAL "__ppc_intrinsics" OR
-       ${filename} STREQUAL "mma")
-      if (PowerPC IN_LIST LLVM_TARGETS_TO_BUILD)
-        set(opts "--target=ppc64le")
-      else()
-        # Do not compile PPC module if the target is not available.
-        continue()
-      endif()
-    endif()
-
-    set(decls "")
-    if (FLANG_SUPPORT_R16)
-      set(decls "-DFLANG_SUPPORT_R16")
-    endif()
-
-    # Some modules have an implementation part that needs to be added to the
-    # flang_rt.runtime library.
-    set(compile_with "-fsyntax-only")
-    set(object_output "")
-    set(include_in_link FALSE)
-
-    set(base ${FLANG_INTRINSIC_MODULES_DIR}/${filename})
-    # TODO: We may need to flag this with conditional, in case Flang is built w/o OpenMP support
-    add_custom_command(OUTPUT ${base}.mod ${object_output}
-      COMMAND ${CMAKE_COMMAND} -E make_directory ${FLANG_INTRINSIC_MODULES_DIR}
-      COMMAND flang ${opts} ${decls} -cpp ${compile_with} -module-dir ${FLANG_INTRINSIC_MODULES_DIR}
-        ${FLANG_SOURCE_DIR}/module/${filename}.f90
-      DEPENDS flang ${FLANG_SOURCE_DIR}/module/${filename}.f90 ${FLANG_SOURCE_DIR}/module/__fortran_builtins.f90 ${depends}
-    )
-    list(APPEND MODULE_FILES ${base}.mod)
-    install(FILES ${base}.mod DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}/flang" COMPONENT flang-module-interfaces)
-
-    # If a module has been compiled into an object file, add the file to
-    # the link line for the flang_rt.runtime library.
-    if(include_in_link)
-      list(APPEND module_objects ${object_output})
-    endif()
-  endforeach()
-
-  # Set a CACHE variable that is visible to the CMakeLists.txt in runtime/, so that
-  # the compiled Fortran modules can be added to the link line of the flang_rt.runtime
-  # library.
-  set(FORTRAN_MODULE_OBJECTS ${module_objects} CACHE INTERNAL "" FORCE)
-
-  # Special case for omp_lib.mod, because its source comes from openmp/runtime/src/include.
-  # It also produces two module files: omp_lib.mod and omp_lib_kinds.mod.  Compile these
-  # files only if OpenMP support has been configured.
-  if (LLVM_TOOL_OPENMP_BUILD)
-    message(STATUS "OpenMP runtime support enabled via LLVM_ENABLE_PROJECTS, building omp_lib.mod")
-    set(base ${FLANG_INTRINSIC_MODULES_DIR}/omp_lib)
-    add_custom_command(OUTPUT ${base}.mod ${base}_kinds.mod
-      COMMAND ${CMAKE_COMMAND} -E make_directory ${FLANG_INTRINSIC_MODULES_DIR}
-      COMMAND flang -cpp -fsyntax-only ${opts} -module-dir ${FLANG_INTRINSIC_MODULES_DIR}
-        ${CMAKE_BINARY_DIR}/projects/openmp/runtime/src/omp_lib.F90
-      DEPENDS flang ${FLANG_INTRINSIC_MODULES_DIR}/iso_c_binding.mod ${CMAKE_BINARY_DIR}/projects/openmp/runtime/src/omp_lib.F90 ${depends}
-    )
-    list(APPEND MODULE_FILES ${base}.mod ${base}_kinds.mod)
-    install(FILES ${base}.mod ${base}_kinds.mod DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}/flang" COMPONENT flang-module-interfaces)
-  elseif ("openmp" IN_LIST LLVM_ENABLE_RUNTIMES)
-    message(STATUS "OpenMP runtime support enabled via LLVM_ENABLE_RUNTIMES, assuming omp_lib.mod is built there")
-  else()
-    message(WARNING "Not building omp_lib.mod, no OpenMP runtime in either LLVM_ENABLE_PROJECTS or LLVM_ENABLE_RUNTIMES")
-  endif()
-  add_llvm_install_targets(install-flang-module-interfaces
-    COMPONENT flang-module-interfaces)
-endif()
-
-add_custom_target(module_files ALL DEPENDS ${MODULE_FILES})
-set_target_properties(module_files PROPERTIES FOLDER "Flang/Resources")
-
-# TODO Move this to a more suitable location
-# Copy the generated omp_lib.h header file, if OpenMP support has been configured.
-if (LLVM_TOOL_OPENMP_BUILD)
-  message(STATUS "OpenMP runtime support enabled via LLVM_ENABLE_PROJECTS, building omp_lib.h")
-  file(COPY ${CMAKE_BINARY_DIR}/projects/openmp/runtime/src/omp_lib.h DESTINATION "${CMAKE_BINARY_DIR}/include/flang/OpenMP/" FILE_PERMISSIONS OWNER_READ OWNER_WRITE)
-  install(FILES ${CMAKE_BINARY_DIR}/include/flang/OpenMP/omp_lib.h DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}/flang/OpenMP")
-elseif ("openmp" IN_LIST LLVM_ENABLE_RUNTIMES)
-  message(STATUS "OpenMP runtime support enabled via LLVM_ENABLE_RUNTIMES, assuming omp_lib.h is built there")
-else()
-  message(STATUS "Not copying omp_lib.h, no OpenMP runtime in either LLVM_ENABLE_PROJECTS or LLVM_ENABLE_RUNTIMES")
-endif()
diff --git a/flang/tools/f18/dump.cpp b/flang/tools/f18/dump.cpp
deleted file mode 100644
index f11b5aedf4c6a..0000000000000
--- a/flang/tools/f18/dump.cpp
+++ /dev/null
@@ -1,42 +0,0 @@
-//===-- tools/f18/dump.cpp ------------------------------------------------===//
-//
-// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
-// See https://llvm.org/LICENSE.txt for license information.
-// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-//
-//===----------------------------------------------------------------------===//
-
-// This file defines Dump routines available for calling from the debugger.
-// Each is based on operator<< for that type. There are overloadings for
-// reference and pointer, and for dumping to a provided raw_ostream or errs().
-
-#ifdef DEBUGF18
-
-#include "llvm/Support/raw_ostream.h"
-
-#define DEFINE_DUMP(ns, name) \
-  namespace ns { \
-  class name; \
-  llvm::raw_ostream &operator<<(llvm::raw_ostream &, const name &); \
-  } \
-  void Dump(llvm::raw_ostream &os, const ns::name &x) { os << x << '\n'; } \
-  void Dump(llvm::raw_ostream &os, const ns::name *x) { \
-    if (x == nullptr) \
-      os << "null\n"; \
-    else \
-      Dump(os, *x); \
-  } \
-  void Dump(const ns::name &x) { Dump(llvm::errs(), x); } \
-  void Dump(const ns::name *x) { Dump(llvm::errs(), *x); }
-
-namespace Fortran {
-DEFINE_DUMP(parser, Name)
-DEFINE_DUMP(parser, CharBlock)
-DEFINE_DUMP(semantics, Symbol)
-DEFINE_DUMP(semantics, Scope)
-DEFINE_DUMP(semantics, IntrinsicTypeSpec)
-DEFINE_DUMP(semantics, DerivedTypeSpec)
-DEFINE_DUMP(semantics, DeclTypeSpec)
-} // namespace Fortran
-
-#endif
diff --git a/llvm/runtimes/CMakeLists.txt b/llvm/runtimes/CMakeLists.txt
index d877f0b883cc4..d229a0a3aa09a 100644
--- a/llvm/runtimes/CMakeLists.txt
+++ b/llvm/runtimes/CMakeLists.txt
@@ -252,6 +252,11 @@ function(runtime_default_target)
     # OpenMP tests
     list(APPEND extra_targets "libomp-mod")
   endif ()
+  if ("flang-rt" IN_LIST LLVM_ENABLE_RUNTIMES)
+    # The target flang-rt-mod is a dependee of check-flang needed to run its
+    # tests.
+    list(APPEND extra_targets "flang-rt-mod")
+  endif ()
 
   if(LLVM_INCLUDE_TESTS)
     set_property(GLOBAL APPEND PROPERTY LLVM_ALL_LIT_TESTSUITES "@${LLVM_BINARY_DIR}/runtimes/runtimes-bins/lit.tests")
@@ -536,18 +541,15 @@ if(build_runtimes)
   if ("openmp" IN_LIST LLVM_ENABLE_RUNTIMES AND "flang" IN_LIST LLVM_ENABLE_PROJECTS)
     list(APPEND extra_args ENABLE_FORTRAN)
   endif()
-  if("openmp" IN_LIST LLVM_ENABLE_RUNTIMES OR "offload" IN_LIST LLVM_ENABLE_RUNTIMES)
-    if (${LLVM_TOOL_FLANG_BUILD})
-      message(STATUS "Configuring build of omp_lib.mod and omp_lib_kinds.mod via flang")
-      set(LIBOMP_FORTRAN_MODULES_COMPILER "${CMAKE_BINARY_DIR}/bin/flang")
-      set(LIBOMP_MODULES_INSTALL_PATH "${CMAKE_INSTALL_INCLUDEDIR}/flang")
-      # TODO: This is a workaround until flang becomes a first-class project
-      # in llvm/CMakeList.txt.  Until then, this line ensures that flang is
-      # built before "openmp" is built as a runtime project.  Besides "flang"
-      # to build the compiler, we also need to add "module_files" to make sure
-      # that all .mod files are also properly build.
-      list(APPEND extra_deps "flang" "module_files")
+  if("flang" IN_LIST LLVM_ENABLE_PROJECTS)
+    # Ensure REAL(16) support in runtimes to be consistent with compiler
+    if(FLANG_RUNTIME_F128_MATH_LIB OR HAVE_LDBL_MANT_DIG_113)
+      list(APPEND extra_cmake_args "-DFORTRAN_SUPPORTS_REAL16=TRUE")
+    else()
+      list(APPEND extra_cmake_args "-DFORTRAN_SUPPORTS_REAL16=FALSE")
     endif()
+  endif()
+  if("openmp" IN_LIST LLVM_ENABLE_RUNTIMES OR "offload" IN_LIST LLVM_ENABLE_RUNTIMES)
     foreach(dep opt llvm-link llvm-extract clang llvm-offload-binary clang-nvlink-wrapper)
       if(TARGET ${dep})
         list(APPEND extra_deps ${dep})
diff --git a/openmp/CMakeLists.txt b/openmp/CMakeLists.txt
index 44cef3fb3f413..ad1916a96ca1c 100644
--- a/openmp/CMakeLists.txt
+++ b/openmp/CMakeLists.txt
@@ -111,6 +111,12 @@ set(OPENMP_TEST_FLAGS "" CACHE STRING
   "Extra compiler flags to send to the test compiler.")
 set(OPENMP_TEST_OPENMP_FLAGS ${OPENMP_TEST_COMPILER_OPENMP_FLAGS} CACHE STRING
   "OpenMP compiler flag to use for testing OpenMP runtime libraries.")
+set(OPENMP_TEST_Fortran_FLAGS "${CMAKE_Fortran_FLAGS}" CACHE STRING
+  "Additional compiler flags to use for testing Fortran programs.")
+
+if (LLVM_RUNTIMES_BUILD)
+  flang_module_fortran_enable()
+endif ()
 
 set(ENABLE_LIBOMPTARGET ON)
 # Currently libomptarget cannot be compiled on Windows or MacOS X.
diff --git a/openmp/runtime/CMakeLists.txt b/openmp/runtime/CMakeLists.txt
index 93eb14f10a50a..6ed1b19c4e054 100644
--- a/openmp/runtime/CMakeLists.txt
+++ b/openmp/runtime/CMakeLists.txt
@@ -109,7 +109,7 @@ set(LIBOMP_MIC_ARCH knc CACHE STRING
 if("${LIBOMP_ARCH}" STREQUAL "mic")
   libomp_check_variable(LIBOMP_MIC_ARCH knf knc)
 endif()
-set(LIBOMP_FORTRAN_MODULES FALSE CACHE BOOL
+set(LIBOMP_FORTRAN_MODULES "${RUNTIMES_FLANG_MODULES_ENABLED}" CACHE BOOL
   "Create Fortran module files? (requires fortran compiler)")
 
 # - Support for universal fat binary builds on Mac
@@ -147,8 +147,6 @@ else()
   set(LIBOMP_LIBFLAGS "" CACHE STRING
     "Appended user specified linked libs flags. (e.g., -lm)")
 endif()
-set(LIBOMP_FFLAGS "" CACHE STRING
-  "Appended user specified Fortran compiler flags.  These are only used if LIBOMP_FORTRAN_MODULES==TRUE.")
 
 # Should the libomp library and generated headers be copied into the original source exports/ directory
 # Turning this to FALSE aids parallel builds to not interfere with each other.
@@ -272,10 +270,6 @@ set(LIBOMP_TOOLS_DIR ${LIBOMP_BASE_DIR}/tools)
 set(LIBOMP_INC_DIR ${LIBOMP_SRC_DIR}/include)
 set(LIBOMP_BINARY_DIR ${CMAKE_CURRENT_BINARY_DIR})
 
-# Enabling Fortran if it is needed
-if(${LIBOMP_FORTRAN_MODULES})
-  enable_language(Fortran)
-endif()
 # Enable MASM Compiler if it is needed (Windows only)
 if(WIN32)
   enable_language(ASM_MASM)
diff --git a/openmp/runtime/cmake/LibompCheckFortranFlag.cmake b/openmp/runtime/cmake/LibompCheckFortranFlag.cmake
deleted file mode 100644
index 344389f989388..0000000000000
--- a/openmp/runtime/cmake/LibompCheckFortranFlag.cmake
+++ /dev/null
@@ -1,29 +0,0 @@
-#
-#//===----------------------------------------------------------------------===//
-#//
-#// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
-#// See https://llvm.org/LICENSE.txt for license information.
-#// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-#//
-#//===----------------------------------------------------------------------===//
-#
-
-# Checking a fortran compiler flag
-# There is no real trivial way to do this in CMake, so we implement it here
-# this will have ${boolean} = TRUE if the flag succeeds, otherwise false.
-function(libomp_check_fortran_flag flag boolean)
-  if(NOT DEFINED "${boolean}")
-    set(retval TRUE)
-    set(fortran_source
-"      program hello
-           print *, \"Hello World!\"
-      end program hello")
-
-    # Compiling as a part of runtimes introduces ARCH-unknown-linux-gnu as a
-    # part of a working directory.  So adding a guard for unknown.
-    set(failed_regexes "[Ee]rror;[Uu]nknown[^-];[Ss]kipping")
-    include(CheckFortranSourceCompiles)
-    check_fortran_source_compiles("${fortran_source}" ${boolean} FAIL_REGEX "${failed_regexes}")
-    set(${boolean} ${${boolean}} PARENT_SCOPE)
-  endif()
-endfunction()
diff --git a/openmp/runtime/cmake/LibompHandleFlags.cmake b/openmp/runtime/cmake/LibompHandleFlags.cmake
index c36a88fb862ae..a27c8cc407e11 100644
--- a/openmp/runtime/cmake/LibompHandleFlags.cmake
+++ b/openmp/runtime/cmake/LibompHandleFlags.cmake
@@ -156,17 +156,6 @@ function(libomp_get_libflags libflags)
   set(${libflags} ${libflags_local_list} PARENT_SCOPE)
 endfunction()
 
-# Fortran flags
-function(libomp_get_fflags fflags)
-  set(fflags_local)
-  if(CMAKE_SIZEOF_VOID_P EQUAL 4)
-    libomp_append(fflags_local -m32 LIBOMP_HAVE_M32_FORTRAN_FLAG)
-  endif()
-  set(fflags_local ${fflags_local} ${LIBOMP_FFLAGS})
-  libomp_setup_flags(fflags_local)
-  set(${fflags} ${fflags_local} PARENT_SCOPE)
-endfunction()
-
 # Python generate-defs.py flags (For Windows only)
 function(libomp_get_gdflags gdflags)
   set(gdflags_local)
diff --git a/openmp/runtime/cmake/config-ix.cmake b/openmp/runtime/cmake/config-ix.cmake
index 30b69d46a8bd1..150a0c3c7217b 100644
--- a/openmp/runtime/cmake/config-ix.cmake
+++ b/openmp/runtime/cmake/config-ix.cmake
@@ -16,7 +16,6 @@ include(CheckIncludeFile)
 include(CheckLibraryExists)
 include(CheckIncludeFiles)
 include(CheckSymbolExists)
-include(LibompCheckFortranFlag)
 include(LLVMCheckCompilerLinkerFlag)
 
 # Check for versioned symbols
@@ -97,9 +96,6 @@ if(WIN32)
     endforeach()
   endforeach()
 endif()
-if(${LIBOMP_FORTRAN_MODULES})
-  libomp_check_fortran_flag(-m32 LIBOMP_HAVE_M32_FORTRAN_FLAG)
-endif()
 
 # Check non-posix pthread API here before CMAKE_REQUIRED_DEFINITIONS gets messed up
 check_symbol_exists(pthread_setname_np "pthread.h" LIBOMP_HAVE_PTHREAD_SETNAME_NP)
diff --git a/openmp/runtime/src/CMakeLists.txt b/openmp/runtime/src/CMakeLists.txt
index 3202bdcd13524..0b0154e8bf3a4 100644
--- a/openmp/runtime/src/CMakeLists.txt
+++ b/openmp/runtime/src/CMakeLists.txt
@@ -382,46 +382,6 @@ endif()
 configure_file(${LIBOMP_INC_DIR}/omp_lib.h.var omp_lib.h @ONLY)
 configure_file(${LIBOMP_INC_DIR}/omp_lib.F90.var omp_lib.F90 @ONLY)
 
-set(BUILD_FORTRAN_MODULES False)
-if (NOT ${LIBOMP_FORTRAN_MODULES_COMPILER} STREQUAL "")
-  # If libomp is built as an LLVM runtime and the flang compiler is available,
-  # compile the Fortran module files.
-  message(STATUS "configuring openmp to build Fortran module files using ${LIBOMP_FORTRAN_MODULES_COMPILER}")
-  set(LIBOMP_FORTRAN_SOURCE_FILE omp_lib.F90)
-  add_custom_target(libomp-mod ALL DEPENDS omp_lib.mod omp_lib_kinds.mod)
-  add_custom_command(
-    OUTPUT omp_lib.mod omp_lib_kinds.mod
-    COMMAND ${LIBOMP_FORTRAN_MODULES_COMPILER} -cpp -fsyntax-only ${LIBOMP_FORTRAN_SOURCE_FILE}
-    DEPENDS ${CMAKE_CURRENT_BINARY_DIR}/${LIBOMP_FORTRAN_SOURCE_FILE}
-      ${CMAKE_CURRENT_BINARY_DIR}/omp_lib.h
-  )
-  set(BUILD_FORTRAN_MODULES True)
-elseif(${LIBOMP_FORTRAN_MODULES})
-  # The following requests explicit building of the Fortran module files
-  # Workaround for gfortran to build modules with the
-  # omp_sched_monotonic integer parameter
-  if (CMAKE_Fortran_COMPILER_ID STREQUAL "GNU")
-    set(ADDITIONAL_Fortran_FLAGS "-fno-range-check")
-  endif()
-  add_custom_target(libomp-mod ALL DEPENDS omp_lib.mod omp_lib_kinds.mod)
-  set_target_properties(libomp-mod PROPERTIES FOLDER "OpenMP/Misc")
-  libomp_get_fflags(LIBOMP_CONFIGURED_FFLAGS)
-  if(CMAKE_Fortran_COMPILER_SUPPORTS_F90)
-    set(LIBOMP_FORTRAN_SOURCE_FILE omp_lib.F90)
-  else()
-    message(FATAL_ERROR "Fortran module build requires Fortran 90 compiler")
-  endif()
-  add_custom_command(
-    OUTPUT omp_lib.mod omp_lib_kinds.mod
-    COMMAND ${CMAKE_Fortran_COMPILER} -c ${ADDITIONAL_Fortran_FLAGS}
-            ${LIBOMP_CONFIGURED_FFLAGS} ${LIBOMP_FORTRAN_SOURCE_FILE}
-    DEPENDS ${CMAKE_CURRENT_BINARY_DIR}/${LIBOMP_FORTRAN_SOURCE_FILE}
-      ${CMAKE_CURRENT_BINARY_DIR}/omp_lib.h
-  )
-  set_directory_properties(PROPERTIES ADDITIONAL_MAKE_CLEAN_FILES omp_lib${CMAKE_C_OUTPUT_EXTENSION})
-  set(BUILD_FORTRAN_MODULES True)
-endif()
-
 # Move files to exports/ directory if requested
 if(${LIBOMP_COPY_EXPORTS})
   include(LibompExports)
@@ -502,15 +462,32 @@ if(${LIBOMP_OMPT_SUPPORT})
   install(FILES ${LIBOMP_HEADERS_INTDIR}/omp-tools.h DESTINATION ${LIBOMP_HEADERS_INSTALL_PATH} RENAME ompt.h)
   set(LIBOMP_OMP_TOOLS_INCLUDE_DIR ${CMAKE_CURRENT_BINARY_DIR} PARENT_SCOPE)
 endif()
-if(${BUILD_FORTRAN_MODULES})
+
+
+# Build the modules files if a Fortran compiler is available.
+# Only LLVM_ENABLE_RUNTIMES=openmp is supported, LLVM_ENABLE_PROJECTS=openmp
+# has been deprecated.
+if(LIBOMP_FORTRAN_MODULES)
+  add_library(libomp-mod OBJECT
+    omp_lib.F90
+  )
+  set_target_properties(libomp-mod PROPERTIES FOLDER "OpenMP/Fortran Modules")
+
+  if (CMAKE_Fortran_COMPILER_ID STREQUAL "GNU")
+   target_compile_options(libomp-mod PRIVATE -fno-range-check)
+  endif()
+
+  flang_module_target(libomp-mod PUBLIC)
+  if (FORTRAN_MODULE_DEPS)
+    add_dependencies(libomp-mod ${FORTRAN_MODULE_DEPS})
+  endif ()
+
   set (destination ${LIBOMP_HEADERS_INSTALL_PATH})
   if (NOT ${LIBOMP_MODULES_INSTALL_PATH} STREQUAL "")
     set (destination ${LIBOMP_MODULES_INSTALL_PATH})
   endif()
   install(FILES
     ${CMAKE_CURRENT_BINARY_DIR}/omp_lib.h
-    ${CMAKE_CURRENT_BINARY_DIR}/omp_lib.mod
-    ${CMAKE_CURRENT_BINARY_DIR}/omp_lib_kinds.mod
     DESTINATION ${destination}
   )
 endif()
diff --git a/openmp/runtime/test/lit.cfg b/openmp/runtime/test/lit.cfg
index 72da1ba1411f8..a4e3aa505638a 100644
--- a/openmp/runtime/test/lit.cfg
+++ b/openmp/runtime/test/lit.cfg
@@ -48,6 +48,7 @@ if config.test_fortran_compiler:
         ToolSubst(
             "%flang",
             command=config.test_fortran_compiler,
+            extra_args=config.test_fortran_flags.split(),
             unresolved="fatal",
         ),
     ], [config.llvm_tools_dir])
diff --git a/openmp/runtime/test/lit.site.cfg.in b/openmp/runtime/test/lit.site.cfg.in
index cc8b3b252d7d1..fd0ad30228026 100644
--- a/openmp/runtime/test/lit.site.cfg.in
+++ b/openmp/runtime/test/lit.site.cfg.in
@@ -8,6 +8,7 @@ config.test_compiler_has_omp_h = @OPENMP_TEST_COMPILER_HAS_OMP_H@
 config.test_filecheck = "@OPENMP_FILECHECK_EXECUTABLE@"
 config.test_not = "@OPENMP_NOT_EXECUTABLE@"
 config.test_openmp_flags = "@OPENMP_TEST_OPENMP_FLAGS@"
+config.test_fortran_flags = "@OPENMP_TEST_Fortran_FLAGS@"
 config.test_extra_flags = "@OPENMP_TEST_FLAGS@"
 config.libomp_obj_root = "@CMAKE_CURRENT_BINARY_DIR@"
 config.library_dir = "@LIBOMP_LIBRARY_DIR@"
diff --git a/runtimes/CMakeLists.txt b/runtimes/CMakeLists.txt
index 5220b9353fed7..2714126f3e5f1 100644
--- a/runtimes/CMakeLists.txt
+++ b/runtimes/CMakeLists.txt
@@ -85,6 +85,42 @@ include(CheckLibraryExists)
 include(LLVMCheckCompilerLinkerFlag)
 include(CheckCCompilerFlag)
 include(CheckCXXCompilerFlag)
+include(ExtendPath)
+
+
+# CMake 3.24 is the first version of CMake that directly recognizes Flang.
+# LLVM's requirement is only CMake 3.20, teach CMake 3.20-3.23 how to use Flang, if used.
+if (CMAKE_VERSION VERSION_LESS "3.24" AND CMAKE_Fortran_COMPILER)
+  cmake_path(GET CMAKE_Fortran_COMPILER STEM _Fortran_COMPILER_STEM)
+  if (_Fortran_COMPILER_STEM STREQUAL "flang-new" OR
+      _Fortran_COMPILER_STEM STREQUAL "flang")
+    include(CMakeForceCompiler)
+    CMAKE_FORCE_Fortran_COMPILER("${CMAKE_Fortran_COMPILER}" "LLVMFlang")
+
+    set(CMAKE_Fortran_COMPILER_ID "LLVMFlang")
+    set(CMAKE_Fortran_COMPILER_VERSION "${LLVM_VERSION_MAJOR}.${LLVM_VERSION_MINOR}")
+
+    set(CMAKE_Fortran_SUBMODULE_SEP "-")
+    set(CMAKE_Fortran_SUBMODULE_EXT ".mod")
+
+    set(CMAKE_Fortran_PREPROCESS_SOURCE
+      "<CMAKE_Fortran_COMPILER> -cpp <DEFINES> <INCLUDES> <FLAGS> -E <SOURCE> > <PREPROCESSED_SOURCE>")
+
+    set(CMAKE_Fortran_FORMAT_FIXED_FLAG "-ffixed-form")
+    set(CMAKE_Fortran_FORMAT_FREE_FLAG "-ffree-form")
+
+    set(CMAKE_Fortran_MODDIR_FLAG "-module-dir")
+
+    set(CMAKE_Fortran_COMPILE_OPTIONS_PREPROCESS_ON "-cpp")
+    set(CMAKE_Fortran_COMPILE_OPTIONS_PREPROCESS_OFF "-nocpp")
+    set(CMAKE_Fortran_POSTPROCESS_FLAG "-ffixed-line-length-72")
+
+    set(CMAKE_Fortran_COMPILE_OPTIONS_TARGET "--target=")
+
+    set(CMAKE_Fortran_LINKER_WRAPPER_FLAG "-Wl,")
+    set(CMAKE_Fortran_LINKER_WRAPPER_FLAG_SEP ",")
+  endif ()
+endif ()
 
 
 # Determine whether we are in the runtimes/runtimes-bins directory of a
@@ -94,17 +130,6 @@ if (LLVM_LIBRARY_DIR AND LLVM_TOOLS_BINARY_DIR AND PACKAGE_VERSION)
   set(LLVM_TREE_AVAILABLE ON)
 endif()
 
-if(LLVM_TREE_AVAILABLE)
-  # Setting these variables will allow the sub-build to put their outputs into
-  # the library and bin directories of the top-level build.
-  set(LLVM_LIBRARY_OUTPUT_INTDIR ${LLVM_LIBRARY_DIR})
-  set(LLVM_RUNTIME_OUTPUT_INTDIR ${LLVM_TOOLS_BINARY_DIR})
-else()
-  # Use own build directory for artifact output.
-  set(LLVM_LIBRARY_OUTPUT_INTDIR "${CMAKE_BINARY_DIR}/${CMAKE_CFG_INTDIR}/lib${LLVM_LIBDIR_SUFFIX}")
-  set(LLVM_RUNTIME_OUTPUT_INTDIR "${CMAKE_BINARY_DIR}/${CMAKE_CFG_INTDIR}/bin")
-endif()
-
 # CMake omits default compiler include paths, but in runtimes build, we use
 # -nostdinc and -nostdinc++ and control include paths manually so this behavior
 # is undesirable. Filtering CMAKE_{LANG}_IMPLICIT_INCLUDE_DIRECTORIES to remove
@@ -217,6 +242,61 @@ message(STATUS "LLVM default target triple: ${LLVM_DEFAULT_TARGET_TRIPLE}")
 
 set(LLVM_TARGET_TRIPLE "${LLVM_DEFAULT_TARGET_TRIPLE}")
 
+
+if(LLVM_TREE_AVAILABLE)
+  # In a bootstrap build emit the libraries into a default search path in the
+  # build directory of the just-built compiler. This allows using the
+  # just-built compiler without specifying paths to runtime libraries.
+  # LLVM_LIBRARY_OUTPUT_INTDIR/LLVM_RUNTIME_OUTPUT_INTDIR is used by
+  # AddLLVM.cmake as artifact output locations.
+  set(LLVM_LIBRARY_OUTPUT_INTDIR ${LLVM_LIBRARY_DIR})
+  set(LLVM_RUNTIME_OUTPUT_INTDIR ${LLVM_TOOLS_BINARY_DIR})
+
+  # Despite Clang in the name, get_clang_resource_dir does not depend on Clang
+  # being added to the build. Flang uses the same resource dir as Clang.
+  include(GetClangResourceDir)
+  get_clang_resource_dir(RUNTIMES_OUTPUT_RESOURCE_DIR PREFIX "${LLVM_LIBRARY_OUTPUT_INTDIR}/..")
+  get_clang_resource_dir(RUNTIMES_INSTALL_RESOURCE_PATH_DEFAULT)
+else()
+  # In a standalone runtimes build, do not write into LLVM_BINARY_DIR. It may be
+  # read-only and/or shared by multiple runtimes with different build
+  # configurations (e.g. Debug/Release). Use the runtime's own lib dir like any
+  # non-toolchain library. Use own build directory for artifact output.
+  set(LLVM_LIBRARY_OUTPUT_INTDIR "${CMAKE_BINARY_DIR}/${CMAKE_CFG_INTDIR}/lib${LLVM_LIBDIR_SUFFIX}")
+  set(LLVM_RUNTIME_OUTPUT_INTDIR "${CMAKE_BINARY_DIR}/${CMAKE_CFG_INTDIR}/bin")
+
+  # For the install prefix, still use the resource dir assuming that Flang will
+  # be installed there using the same prefix. This is to not have a difference
+  # between bootstrap and standalone runtimes builds.
+  set(RUNTIMES_OUTPUT_RESOURCE_DIR "${CMAKE_BINARY_DIR}/lib${LLVM_LIBDIR_SUFFIX}/clang/${LLVM_VERSION_MAJOR}")
+  set(RUNTIMES_INSTALL_RESOURCE_PATH_DEFAULT "lib${LLVM_LIBDIR_SUFFIX}/clang/${LLVM_VERSION_MAJOR}")
+endif()
+
+# Determine build and install paths.
+# The build path is absolute, but the install dir is relative, CMake's install
+# command has to apply CMAKE_INSTALL_PREFIX itself.
+# FIXME: For shared libraries, the toolchain resource lib dir is not a good
+#        destination because it is not a ld.so default search path.
+#        The machine where the executable is eventually executed may not be the
+#        machine where the Flang compiler and its resource dir is installed, so
+#        setting RPath by the driver is not an solution. It should belong into
+#        /usr/lib/<triple>/lib<name>.so, like e.g. libgcc_s.so.
+#        But the linker as invoked by the Flang driver also requires
+#        libflang_rt.so to be found when linking and the resource lib dir is
+#        the only reliable location.
+include(GetToolchainDirs)
+get_toolchain_library_subdir(toolchain_lib_subdir)
+extend_path(RUNTIMES_OUTPUT_RESOURCE_LIB_DIR "${RUNTIMES_OUTPUT_RESOURCE_DIR}" "${toolchain_lib_subdir}")
+
+set(RUNTIMES_INSTALL_RESOURCE_PATH "${RUNTIMES_INSTALL_RESOURCE_PATH_DEFAULT}" CACHE PATH "Path to install headers, runtime libraries, and Fortran modules to (default: Clang resource dir)")
+extend_path(RUNTIMES_INSTALL_RESOURCE_LIB_PATH "${RUNTIMES_INSTALL_RESOURCE_PATH}" "${toolchain_lib_subdir}")
+
+cmake_path(NORMAL_PATH RUNTIMES_OUTPUT_RESOURCE_DIR)
+cmake_path(NORMAL_PATH RUNTIMES_INSTALL_RESOURCE_PATH)
+cmake_path(NORMAL_PATH RUNTIMES_OUTPUT_RESOURCE_LIB_DIR)
+cmake_path(NORMAL_PATH RUNTIMES_INSTALL_RESOURCE_LIB_PATH)
+
+
 if(CMAKE_C_COMPILER_ID MATCHES "Clang")
   set(option_prefix "")
   if (CMAKE_C_SIMULATE_ID MATCHES "MSVC")
@@ -328,6 +408,127 @@ if(LLVM_INCLUDE_TESTS)
   umbrella_lit_testsuite_begin(check-runtimes)
 endif()
 
+
+include(CheckFortranSourceCompiles)
+
+# Enable building Fortran modules
+#  * Set up the Fortran compiler
+#  * Determine files location in the Clang/Flang resource dir
+#  * Install module files
+macro (flang_module_fortran_enable)
+  # Assume flang modules are enabled until all tests pass
+  set(FORTRAN_MODULE_DEPS "")
+  set(RUNTIMES_FLANG_MODULES_ENABLED_default OFF)
+
+  include(CheckLanguage)
+  check_language(Fortran)
+
+  if (CMAKE_Fortran_COMPILER)
+    enable_language(Fortran)
+
+    if (CMAKE_Fortran_COMPILER_ID STREQUAL "LLVMFlang" AND "flang-rt" IN_LIST LLVM_ENABLE_RUNTIMES)
+      # In a bootstrapping build, the intrinsic modules are not built yet.
+      # Targets can depend on flang-rt-mod to ensure they are built before.
+      set(FORTRAN_MODULE_DEPS flang-rt-mod)
+      set(RUNTIMES_FLANG_MODULES_ENABLED_default ON)
+      message(STATUS "${LLVM_SUBPROJECT_TITLE}: Building Fortran modules for Flang bootstrapping itself")
+    else ()
+      # Check whether building modules works, avoid causing the entire build to fail because of Fortran.
+      # The primary situation we want to support here is Flang or its intrinsic modules were built separately in a non-bootstrapping build.
+      cmake_push_check_state(RESET)
+      set(CMAKE_TRY_COMPILE_TARGET_TYPE "STATIC_LIBRARY")
+      check_fortran_source_compiles("
+        subroutine testroutine
+          use iso_c_binding
+          end subroutine
+        " HAVE_FORTRAN_INTRINSIC_MODS SRC_EXT F90)
+      cmake_pop_check_state()
+      if (HAVE_FORTRAN_INTRINSIC_MODS)
+        set(RUNTIMES_FLANG_MODULES_ENABLED_default ON)
+        message(STATUS "${LLVM_SUBPROJECT_TITLE}: Non-bootstrapping Fortran modules build (${CMAKE_Fortran_COMPILER_ID} located at ${CMAKE_Fortran_COMPILER})")
+      else ()
+        message(STATUS "Not compiling Flang modules: Not passing smoke check")
+      endif ()
+    endif ()
+  else ()
+    message(STATUS "Not compiling Flang modules: Fortran not enabled")
+  endif ()
+
+  option(RUNTIMES_FLANG_MODULES_ENABLED "Build Fortran modules" "${RUNTIMES_FLANG_MODULES_ENABLED_default}")
+
+  if (RUNTIMES_FLANG_MODULES_ENABLED)
+    if (CMAKE_Fortran_COMPILER_ID STREQUAL "LLVMFlang")
+      get_toolchain_module_subdir(toolchain_mod_subdir)
+      extend_path(RUNTIMES_OUTPUT_RESOURCE_MOD_DIR "${RUNTIMES_OUTPUT_RESOURCE_DIR}" "${toolchain_mod_subdir}")
+      extend_path(RUNTIMES_INSTALL_RESOURCE_MOD_PATH "${RUNTIMES_INSTALL_RESOURCE_PATH}" "${toolchain_mod_subdir}")
+    else ()
+      # For non-Flang compilers, avoid the risk of Flang accidentally picking them up.
+      extend_path(RUNTIMES_OUTPUT_RESOURCE_MOD_DIR "${RUNTIMES_OUTPUT_RESOURCE_DIR}" "finclude-${CMAKE_Fortran_COMPILER_ID}")
+      extend_path(RUNTIMES_INSTALL_RESOURCE_MOD_PATH "${RUNTIMES_INSTALL_RESOURCE_PATH}" "finclude-${CMAKE_Fortran_COMPILER_ID}")
+    endif ()
+    cmake_path(NORMAL_PATH RUNTIMES_OUTPUT_RESOURCE_MOD_DIR)
+    cmake_path(NORMAL_PATH RUNTIMES_INSTALL_RESOURCE_MOD_PATH)
+
+    # Avoid module files to be installed multiple times if this macro is called multiple times
+    get_property(is_installed GLOBAL PROPERTY RUNTIMES_MODS_INSTALLED)
+    if (NOT is_installed)
+      # No way to find out which mod files built by target individually, so install the entire output directory
+      # https://stackoverflow.com/questions/52712416/cmake-fortran-module-directory-to-be-used-with-add-library
+      set(destination "${RUNTIMES_INSTALL_RESOURCE_MOD_PATH}/..")
+      cmake_path(NORMAL_PATH destination)
+      install(DIRECTORY "${RUNTIMES_OUTPUT_RESOURCE_MOD_DIR}"
+        DESTINATION "${destination}"
+      )
+      set_property(GLOBAL PROPERTY RUNTIMES_MODS_INSTALLED TRUE)
+    endif ()
+  endif ()
+endmacro ()
+
+
+# Set options to compile Fortran module files.
+#
+# Usage:
+#
+# flang_module_target(name
+#   PUBLIC
+#     Modules files are to be used by other Fortran sources. If a library is
+#     compiled multiple times (e.g. static/shared, or msvcrt variants), only
+#     one of those can be public module files; non-public modules are still
+#     generated but to be forgotten deep inside the build directory to not
+#     conflict with each other.
+#     Also, installs the module with the toolchain.
+# )
+function (flang_module_target tgtname)
+  set(options PUBLIC)
+  cmake_parse_arguments(ARG
+    "${options}"
+    ""
+    ""
+    ${ARGN})
+
+  if (NOT RUNTIMES_FLANG_MODULES_ENABLED)
+    return ()
+  endif ()
+
+  # Let it find the other public module files
+  target_compile_options(${tgtname} PRIVATE
+      "$<$<COMPILE_LANGUAGE:Fortran>:-fintrinsic-modules-path=${RUNTIMES_OUTPUT_RESOURCE_MOD_DIR}>"
+    )
+
+  if (ARG_PUBLIC)
+    set_target_properties(${tgtname}
+      PROPERTIES
+        Fortran_MODULE_DIRECTORY "${RUNTIMES_OUTPUT_RESOURCE_MOD_DIR}"
+      )
+  else ()
+    set_target_properties(${tgtname}
+      PROPERTIES
+        Fortran_MODULE_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}/${tgtname}.mod"
+      )
+  endif ()
+endfunction ()
+
+
 # We do this in two loops so that HAVE_* is set for each runtime before the
 # other runtimes are added.
 foreach(entry ${runtimes})

>From 645a31995ee5205f20bdcc30b54d16de67fb15af Mon Sep 17 00:00:00 2001
From: Michael Kruse <llvm-project at meinersbur.de>
Date: Tue, 25 Nov 2025 23:36:56 +0100
Subject: [PATCH 02/15] Clarify try_compile isolation

---
 flang-rt/cmake/modules/FlangRTIntrospection.cmake | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/flang-rt/cmake/modules/FlangRTIntrospection.cmake b/flang-rt/cmake/modules/FlangRTIntrospection.cmake
index ddec624e320e7..c78c8a9b8a81a 100644
--- a/flang-rt/cmake/modules/FlangRTIntrospection.cmake
+++ b/flang-rt/cmake/modules/FlangRTIntrospection.cmake
@@ -6,22 +6,23 @@
 #
 #===------------------------------------------------------------------------===#
 
+include(CMakePushCheckState)
 
 # Check whether the Fortran compiler supports real(16)/quadmath types
 #
 # Implementation notes:
+#
 #  * FORTRAN_SUPPORTS_REAL16 can be set externally in a bootstrapping-runtimes
 #    build to ensure consistency of real(16) support between compiler and
 #    runtime.
 #
-#  * Does not work with Flang and CMake < 3.24
+#  * Does not work with Flang and CMake < 3.24; rely on an externally set
+#    FORTRAN_SUPPORTS_REAL16 instead.
 #
-#  * This is intentionally wrapped in a function to get its own namespace for
-#    CMAKE_REQUIRED_FLAGS and CMAKE_TRY_COMPILE_TARGET_TYPE. In particular,
-#    cmake_pop_check_state() does not reset CMAKE_TRY_COMPILE_TARGET_TYPE,
-#    causing later try_compile invocations to fail. If you see
-#    enable_language(CUDA) failing because CMAKE_RANLIB is empty, this is the
-#    reason.
+#  * cmake_push_check_state/cmake_pop_check_state is insufficient to isolate
+#    a compiler introspection environment, see
+#    https://gitlab.kitware.com/cmake/cmake/-/issues/27419
+#    Additionally wrap it in a function namespace.
 function (check_fortran_quadmath_support)
   cmake_push_check_state(RESET)
   set(CMAKE_REQUIRED_FLAGS "-ffree-form")

>From 3efb58a3c0ccbce0ab1047965b5bc53b2dbfdf80 Mon Sep 17 00:00:00 2001
From: Michael Kruse <llvm-project at meinersbur.de>
Date: Tue, 25 Nov 2025 23:38:23 +0100
Subject: [PATCH 03/15] Prefer -J over -module-dir

---
 runtimes/CMakeLists.txt | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/runtimes/CMakeLists.txt b/runtimes/CMakeLists.txt
index 2714126f3e5f1..253a6d693d8a6 100644
--- a/runtimes/CMakeLists.txt
+++ b/runtimes/CMakeLists.txt
@@ -109,7 +109,7 @@ if (CMAKE_VERSION VERSION_LESS "3.24" AND CMAKE_Fortran_COMPILER)
     set(CMAKE_Fortran_FORMAT_FIXED_FLAG "-ffixed-form")
     set(CMAKE_Fortran_FORMAT_FREE_FLAG "-ffree-form")
 
-    set(CMAKE_Fortran_MODDIR_FLAG "-module-dir")
+    set(CMAKE_Fortran_MODDIR_FLAG "-J")
 
     set(CMAKE_Fortran_COMPILE_OPTIONS_PREPROCESS_ON "-cpp")
     set(CMAKE_Fortran_COMPILE_OPTIONS_PREPROCESS_OFF "-nocpp")

>From 9041b784e3c054266a9109c2698030ea4f2aad44 Mon Sep 17 00:00:00 2001
From: Michael Kruse <llvm-project at meinersbur.de>
Date: Wed, 26 Nov 2025 11:49:06 +0100
Subject: [PATCH 04/15] Add modules-only mode

---
 clang/lib/Driver/ToolChains/AMDGPU.cpp  |  3 +-
 clang/lib/Driver/ToolChains/HIPAMD.cpp  |  3 +-
 clang/lib/Driver/ToolChains/HIPSPV.cpp  |  3 +-
 flang-rt/CMakeLists.txt                 | 35 ++++++----
 flang-rt/cmake/modules/AddFlangRT.cmake | 17 ++++-
 flang-rt/lib/runtime/CMakeLists.txt     | 85 +++++++++++++------------
 6 files changed, 90 insertions(+), 56 deletions(-)

diff --git a/clang/lib/Driver/ToolChains/AMDGPU.cpp b/clang/lib/Driver/ToolChains/AMDGPU.cpp
index 80e58d466b885..146effbb5bf98 100644
--- a/clang/lib/Driver/ToolChains/AMDGPU.cpp
+++ b/clang/lib/Driver/ToolChains/AMDGPU.cpp
@@ -851,7 +851,8 @@ void AMDGPUToolChain::addClangTargetOptions(
   // Default to "hidden" visibility, as object level linking will not be
   // supported for the foreseeable future.
   if (!DriverArgs.hasArg(options::OPT_fvisibility_EQ,
-                         options::OPT_fvisibility_ms_compat)) {
+                         options::OPT_fvisibility_ms_compat) &&
+      !getDriver().IsFlangMode()) {
     CC1Args.push_back("-fvisibility=hidden");
     CC1Args.push_back("-fapply-global-visibility-to-externs");
   }
diff --git a/clang/lib/Driver/ToolChains/HIPAMD.cpp b/clang/lib/Driver/ToolChains/HIPAMD.cpp
index 231a38c2d3717..beec8e07807cd 100644
--- a/clang/lib/Driver/ToolChains/HIPAMD.cpp
+++ b/clang/lib/Driver/ToolChains/HIPAMD.cpp
@@ -251,7 +251,8 @@ void HIPAMDToolChain::addClangTargetOptions(
   // Default to "hidden" visibility, as object level linking will not be
   // supported for the foreseeable future.
   if (!DriverArgs.hasArg(options::OPT_fvisibility_EQ,
-                         options::OPT_fvisibility_ms_compat)) {
+                         options::OPT_fvisibility_ms_compat) &&
+      !getDriver().IsFlangMode()) {
     CC1Args.append({"-fvisibility=hidden"});
     CC1Args.push_back("-fapply-global-visibility-to-externs");
   }
diff --git a/clang/lib/Driver/ToolChains/HIPSPV.cpp b/clang/lib/Driver/ToolChains/HIPSPV.cpp
index be0f49d8e1497..261adc2b1c440 100644
--- a/clang/lib/Driver/ToolChains/HIPSPV.cpp
+++ b/clang/lib/Driver/ToolChains/HIPSPV.cpp
@@ -143,7 +143,8 @@ void HIPSPVToolChain::addClangTargetOptions(
   // Default to "hidden" visibility, as object level linking will not be
   // supported for the foreseeable future.
   if (!DriverArgs.hasArg(options::OPT_fvisibility_EQ,
-                         options::OPT_fvisibility_ms_compat))
+                         options::OPT_fvisibility_ms_compat) &&
+      !getDriver().IsFlangMode())
     CC1Args.append(
         {"-fvisibility=hidden", "-fapply-global-visibility-to-externs"});
 
diff --git a/flang-rt/CMakeLists.txt b/flang-rt/CMakeLists.txt
index db0d87d91ea83..8fa934dbdbf29 100644
--- a/flang-rt/CMakeLists.txt
+++ b/flang-rt/CMakeLists.txt
@@ -58,8 +58,6 @@ flang_module_fortran_enable()
 # Important: flang-rt user options must be prefixed with "FLANG_RT_". Variables
 # with this prefix will be forwarded in bootstrap builds.
 
-option(FLANG_RT_INCLUDE_TESTS "Generate build targets for the flang-rt unit and regression-tests." "${LLVM_INCLUDE_TESTS}")
-
 # Provide an interface to link against the LLVM libc/libc++ projects directly.
 set(FLANG_RT_SUPPORTED_PROVIDERS system llvm)
 set(FLANG_RT_LIBC_PROVIDER "system" CACHE STRING "Specify C library to use. Supported values are ${FLANG_RT_SUPPORTED_PROVIDERS}.")
@@ -72,7 +70,15 @@ if (NOT "${FLANG_RT_LIBCXX_PROVIDER}" IN_LIST FLANG_RT_SUPPORTED_PROVIDERS)
   message(FATAL_ERROR "Unsupported library: '${FLANG_RT_LIBCXX_PROVIDER}'. Supported values are ${FLANG_RT_SUPPORTED_PROVIDERS}.")
 endif ()
 
-option(FLANG_RT_ENABLE_STATIC "Build Flang-RT as a static library." ON)
+if (LLVM_RUNTIMES_TARGET MATCHES "^amdgcn|^nvptx")
+  # Compiling libraries for offload targets is currently experimental;
+  # only build the buildtin modules by default.
+  set(FLANG_RT_ENABLE_STATIC_default OFF)
+else ()
+  set(FLANG_RT_ENABLE_STATIC_default ON)
+endif ()
+
+option(FLANG_RT_ENABLE_STATIC "Build Flang-RT as a static library." "${FLANG_RT_ENABLE_STATIC_default}")
 if (WIN32)
   # Windows DLL currently not implemented.
   set(FLANG_RT_ENABLE_SHARED OFF)
@@ -85,11 +91,14 @@ else ()
   #       breaking change unless the driver is changed.
   option(FLANG_RT_ENABLE_SHARED "Build Flang-RT as a shared library." OFF)
 endif ()
-if (NOT FLANG_RT_ENABLE_STATIC AND NOT FLANG_RT_ENABLE_SHARED)
-  message(FATAL_ERROR "
-      Must build at least one type of library
-      (FLANG_RT_ENABLE_STATIC=ON, FLANG_RT_ENABLE_SHARED=ON, or both)
-    ")
+
+
+if (FLANG_RT_ENABLE_STATIC OR FLANG_RT_ENABLE_SHARED)
+  option(FLANG_RT_INCLUDE_TESTS "Generate build targets for the flang-rt unit and regression-tests." "${LLVM_INCLUDE_TESTS}")
+else ()
+  # Tests require at least one libraries
+  message(STATUS "Testing disabled without either FLANG_RT_ENABLE_STATIC or FLANG_RT_ENABLE_SHARED")
+  set(FLANG_RT_INCLUDE_TESTS OFF)
 endif ()
 
 
@@ -107,8 +116,14 @@ elseif (FLANG_RT_EXPERIMENTAL_OFFLOAD_SUPPORT STREQUAL "CUDA")
   option(FLANG_RT_CUDA_RUNTIME_PTX_WITHOUT_GLOBAL_VARS "Do not compile global variables' definitions when producing PTX library" OFF)
 elseif (FLANG_RT_EXPERIMENTAL_OFFLOAD_SUPPORT STREQUAL "OpenMP")
   # Support for OpenMP offloading
+else ()
+  message(FATAL_ERROR "Invalid value '${FLANG_RT_EXPERIMENTAL_OFFLOAD_SUPPORT}' for FLANG_RT_EXPERIMENTAL_OFFLOAD_SUPPORT; must be empty, 'CUDA', or 'OpenMP'")
+endif ()
+
+
+if (FLANG_RT_EXPERIMENTAL_OFFLOAD_SUPPORT STREQUAL "OpenMP" OR LLVM_TARGET_TRIPLE MATCHES "^nvptx")
   set(FLANG_RT_DEVICE_ARCHITECTURES "all" CACHE STRING
-      "List of OpenMP device architectures to be used to compile the Fortran runtime (e.g. 'gfx1103;sm_90')"
+      "List of offload device architectures to be used to compile the Fortran runtime (e.g. 'gfx1103;sm_90')"
     )
 
   if (FLANG_RT_DEVICE_ARCHITECTURES STREQUAL "all")
@@ -127,8 +142,6 @@ elseif (FLANG_RT_EXPERIMENTAL_OFFLOAD_SUPPORT STREQUAL "OpenMP")
       set(FLANG_RT_DEVICE_ARCHITECTURES ${all_gpu_architectures})
   endif()
   list(REMOVE_DUPLICATES FLANG_RT_DEVICE_ARCHITECTURES)
-else ()
-  message(FATAL_ERROR "Invalid value '${FLANG_RT_EXPERIMENTAL_OFFLOAD_SUPPORT}' for FLANG_RT_EXPERIMENTAL_OFFLOAD_SUPPORT; must be empty, 'CUDA', or 'OpenMP'")
 endif ()
 
 
diff --git a/flang-rt/cmake/modules/AddFlangRT.cmake b/flang-rt/cmake/modules/AddFlangRT.cmake
index b3f2cd07c0aed..ea4f920e1d877 100644
--- a/flang-rt/cmake/modules/AddFlangRT.cmake
+++ b/flang-rt/cmake/modules/AddFlangRT.cmake
@@ -94,6 +94,10 @@ function (add_flangrt_library name)
     set(build_object ON)
   elseif (build_static AND build_shared)
     set(build_object ON)
+  elseif (NOT build_static AND NOT build_shared)
+    # If not building a library, still build the object files
+    # Needed to generate the .mod files as byproduct
+    set(build_object ON)
   endif ()
 
   # srctargets: targets that contain source files
@@ -168,14 +172,18 @@ function (add_flangrt_library name)
     if (BUILD_SHARED_LIBS)
       if (build_shared)
         set(default_target "${name_shared}")
-      else ()
+      elseif (build_static)
         set(default_target "${name_static}")
+      else ()
+        set(default_target "${name_object}")
       endif ()
     else ()
       if (build_static)
         set(default_target "${name_static}")
-      else ()
+      elseif (build_shared)
         set(default_target "${name_shared}")
+      else ()
+        set(default_target "${name_object}")
       endif ()
     endif ()
     add_library(${name}.default ALIAS "${default_target}")
@@ -292,6 +300,11 @@ function (add_flangrt_library name)
       target_compile_options(${tgtname} PRIVATE
           $<$<COMPILE_LANGUAGE:CXX>:-nogpulib -flto -fvisibility=hidden -Wno-unknown-cuda-version --cuda-feature=+ptx63>
         )
+      foreach (_arch IN LISTS FLANG_RT_DEVICE_ARCHITECTURES)
+        target_compile_options(${tgtname} PRIVATE
+         -march=${_arch}
+        )
+       endforeach()
     elseif (APPLE)
       # Clang on Darwin enables non-POSIX extensions by default.
       # This causes some macros to leak, such as HUGE from <math.h>, which
diff --git a/flang-rt/lib/runtime/CMakeLists.txt b/flang-rt/lib/runtime/CMakeLists.txt
index a678055430233..0c8db7e84d53c 100644
--- a/flang-rt/lib/runtime/CMakeLists.txt
+++ b/flang-rt/lib/runtime/CMakeLists.txt
@@ -18,6 +18,22 @@ set(intrinsics_sources
   __cuda_builtins.f90
 )
 
+# Fortran sources for builtin .mod files
+set(module_sources
+  __fortran_ieee_exceptions.f90
+  __fortran_type_info.f90
+  iso_fortran_env.f90
+  ieee_arithmetic.f90
+  ieee_exceptions.f90
+  ieee_features.f90
+  iso_c_binding.f90
+  iso_fortran_env.f90
+  iso_fortran_env_impl.f90
+
+  __cuda_device.f90
+  cooperative_groups.f90
+  cudadevice.f90
+)
 
 # List of files that are buildable for all devices.
 set(supported_sources
@@ -80,16 +96,6 @@ set(supported_sources
 
 # List of source not used for GPU offloading.
 set(host_sources
-  __fortran_ieee_exceptions.f90
-  __fortran_type_info.f90
-  iso_fortran_env.f90
-  ieee_arithmetic.f90
-  ieee_exceptions.f90
-  ieee_features.f90
-  iso_c_binding.f90
-  iso_fortran_env_impl.f90
-  iso_fortran_env.f90
-
   command.cpp
   complex-powi.cpp
   complex-reduction.c
@@ -104,32 +110,8 @@ set(host_sources
   temporary-stack.cpp
   time-intrinsic.cpp
   unit-map.cpp
-
-  __cuda_device.f90
-  cooperative_groups.f90
-  cudadevice.f90
 )
 
-if (LLVM_TARGET_TRIPLE MATCHES "^ppc|^powerpc")
-  list(APPEND intrinsics_sources
-    __ppc_types.f90
-  )
-  list(APPEND host_sources
-    __ppc_intrinsics.f90
-    mma.f90
-  )
-endif ()
-
-# Compile as CUDA-Fortran, not directly supported by CMake
-set_property(SOURCE
-    __cuda_device.f90
-    cooperative_groups.f90
-    cudadevice.f90
-  APPEND PROPERTY
-    COMPILE_OPTIONS --offload-host-only -xcuda
-)
-
-
 # Sources that can be compiled directly for the GPU.
 set(gpu_sources
   ${FLANG_SOURCE_DIR}/lib/Decimal/binary-to-decimal.cpp
@@ -189,6 +171,24 @@ file(GLOB_RECURSE private_headers
   "${FLANG_SOURCE_DIR}/lib/Common/*.h"
   )
 
+if (LLVM_TARGET_TRIPLE MATCHES "^ppc|^powerpc")
+  list(APPEND intrinsics_sources
+    __ppc_types.f90
+  )
+  list(APPEND module_sources
+    __ppc_intrinsics.f90
+    mma.f90
+  )
+endif ()
+
+# Compile as CUDA-Fortran, not directly supported by CMake
+set_property(SOURCE
+    __cuda_device.f90
+    cooperative_groups.f90
+    cudadevice.f90
+  APPEND PROPERTY
+    COMPILE_OPTIONS --offload-host-only -xcuda
+)
 
 # Import changes from flang_rt.quadmath
 get_target_property(f128_sources
@@ -215,14 +215,17 @@ else ()
   set(f128_sources "")
 endif ()
 
-if (LLVM_RUNTIMES_TARGET MATCHES "^amdgcn|^nvptx")
-  set(sources ${gpu_sources})
+if (NOT FLANG_RT_ENABLE_STATIC AND NOT FLANG_RT_ENABLE_STATIC)
+  # If not compiling the library, only build the modules.
+  set(sources ${module_sources})
+elseif (LLVM_RUNTIMES_TARGET MATCHES "^amdgcn|^nvptx")
+  set(sources ${gpu_sources} ${module_sources})
 else ()
-  set(sources ${supported_sources} ${host_sources} ${f128_sources})
+  set(sources ${supported_sources} ${host_sources} ${module_sources} ${f128_sources})
 endif ()
 
 
-# check-flang depends on this to build intrinsic modules
+# check-flang depends on flang-rt-mod to build intrinsic modules
 if (NOT TARGET flang-rt-mod)
   add_custom_target(flang-rt-mod)
 endif ()
@@ -259,8 +262,10 @@ if (NOT WIN32)
   enable_omp_offload_compilation(flang_rt.runtime "${supported_sources}")
 
   # Select a default runtime, which is used for unit and regression tests.
-  get_target_property(default_target flang_rt.runtime.default ALIASED_TARGET)
-  add_library(flang_rt.runtime.unittest ALIAS "${default_target}")
+  if (FLANG_RT_INCLUDE_TESTS)
+    get_target_property(default_target flang_rt.runtime.default ALIASED_TARGET)
+    add_library(flang_rt.runtime.unittest ALIAS "${default_target}")
+  endif ()
 
   # Select a target that compiles the sources to build the public module files.
   get_target_property(compile_target flang_rt.runtime.compile ALIASED_TARGET)

>From 0b6f11b0faee7f9ca540f139aecc3c1f044995c9 Mon Sep 17 00:00:00 2001
From: Michael Kruse <llvm-project at meinersbur.de>
Date: Wed, 26 Nov 2025 12:17:09 +0100
Subject: [PATCH 05/15] Fix remaining include paths

---
 flang-rt/lib/runtime/__fortran_ieee_exceptions.f90 | 2 +-
 flang-rt/lib/runtime/iso_fortran_env.f90           | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/flang-rt/lib/runtime/__fortran_ieee_exceptions.f90 b/flang-rt/lib/runtime/__fortran_ieee_exceptions.f90
index 3ac9b993186aa..ff5c6b44317f8 100644
--- a/flang-rt/lib/runtime/__fortran_ieee_exceptions.f90
+++ b/flang-rt/lib/runtime/__fortran_ieee_exceptions.f90
@@ -11,7 +11,7 @@
 ! here under another name so that IEEE_ARITHMETIC can USE it and export its
 ! declarations without clashing with a non-intrinsic module in a program.
 
-#include '../include/flang/Runtime/magic-numbers.h'
+#include '../../../flang/include/flang/Runtime/magic-numbers.h'
 
 module __fortran_ieee_exceptions
   use __fortran_builtins, only: &
diff --git a/flang-rt/lib/runtime/iso_fortran_env.f90 b/flang-rt/lib/runtime/iso_fortran_env.f90
index 3729b95a339f3..2dc38bd1acfe5 100644
--- a/flang-rt/lib/runtime/iso_fortran_env.f90
+++ b/flang-rt/lib/runtime/iso_fortran_env.f90
@@ -8,7 +8,7 @@
 
 ! See Fortran 2023, subclause 16.10.2
 
-#include '../include/flang/Runtime/magic-numbers.h'
+#include '../../../flang/include/flang/Runtime/magic-numbers.h'
 
 module iso_fortran_env
 

>From 81db5c802120a9f677073232459c5436d3a8aff7 Mon Sep 17 00:00:00 2001
From: Michael Kruse <llvm-project at meinersbur.de>
Date: Wed, 26 Nov 2025 14:33:26 +0100
Subject: [PATCH 06/15] Fix LIBOMP_COPY_EXPORTS

---
 openmp/runtime/cmake/LibompExports.cmake |  9 ++++----
 openmp/runtime/src/CMakeLists.txt        | 26 +++++++++++++-----------
 2 files changed, 19 insertions(+), 16 deletions(-)

diff --git a/openmp/runtime/cmake/LibompExports.cmake b/openmp/runtime/cmake/LibompExports.cmake
index 461e47d449157..662c207f8904f 100644
--- a/openmp/runtime/cmake/LibompExports.cmake
+++ b/openmp/runtime/cmake/LibompExports.cmake
@@ -56,8 +56,8 @@ set(LIBOMP_EXPORTS_LIB_DIR "${LIBOMP_EXPORTS_DIR}/${libomp_platform}${libomp_suf
 # Put headers in exports/ directory post build
 add_custom_command(TARGET omp POST_BUILD
   COMMAND ${CMAKE_COMMAND} -E make_directory ${LIBOMP_EXPORTS_CMN_DIR}
-  COMMAND ${CMAKE_COMMAND} -E copy omp.h ${LIBOMP_EXPORTS_CMN_DIR}
-  COMMAND ${CMAKE_COMMAND} -E copy ompx.h ${LIBOMP_EXPORTS_CMN_DIR}
+  COMMAND ${CMAKE_COMMAND} -E copy ${LIBOMP_HEADERS_INTDIR}/omp.h ${LIBOMP_EXPORTS_CMN_DIR}
+  COMMAND ${CMAKE_COMMAND} -E copy ${LIBOMP_HEADERS_INTDIR}/ompx.h ${LIBOMP_EXPORTS_CMN_DIR}
 )
 if(${LIBOMP_OMPT_SUPPORT})
   add_custom_command(TARGET omp POST_BUILD
@@ -67,9 +67,10 @@ endif()
 if(${LIBOMP_FORTRAN_MODULES})
   add_custom_command(TARGET libomp-mod POST_BUILD
     COMMAND ${CMAKE_COMMAND} -E make_directory ${LIBOMP_EXPORTS_MOD_DIR}
-    COMMAND ${CMAKE_COMMAND} -E copy omp_lib.mod ${LIBOMP_EXPORTS_MOD_DIR}
-    COMMAND ${CMAKE_COMMAND} -E copy omp_lib_kinds.mod ${LIBOMP_EXPORTS_MOD_DIR}
+    COMMAND ${CMAKE_COMMAND} -E copy ${RUNTIMES_OUTPUT_RESOURCE_MOD_DIR}/omp_lib.mod ${LIBOMP_EXPORTS_MOD_DIR}
+    COMMAND ${CMAKE_COMMAND} -E copy ${RUNTIMES_OUTPUT_RESOURCE_MOD_DIR}/omp_lib_kinds.mod ${LIBOMP_EXPORTS_MOD_DIR}
   )
+
   add_custom_command(TARGET omp POST_BUILD
     COMMAND ${CMAKE_COMMAND} -E copy omp_lib.h ${LIBOMP_EXPORTS_CMN_DIR}
   )
diff --git a/openmp/runtime/src/CMakeLists.txt b/openmp/runtime/src/CMakeLists.txt
index 0b0154e8bf3a4..23b178077ed3f 100644
--- a/openmp/runtime/src/CMakeLists.txt
+++ b/openmp/runtime/src/CMakeLists.txt
@@ -377,16 +377,6 @@ if(WIN32)
   endif()
 endif()
 
-# Building the Fortran module files
-# One compilation step creates both omp_lib.mod and omp_lib_kinds.mod
-configure_file(${LIBOMP_INC_DIR}/omp_lib.h.var omp_lib.h @ONLY)
-configure_file(${LIBOMP_INC_DIR}/omp_lib.F90.var omp_lib.F90 @ONLY)
-
-# Move files to exports/ directory if requested
-if(${LIBOMP_COPY_EXPORTS})
-  include(LibompExports)
-endif()
-
 # Micro test rules for after library has been built (cmake/LibompMicroTests.cmake)
 include(LibompMicroTests)
 add_custom_target(libomp-micro-tests)
@@ -464,11 +454,18 @@ if(${LIBOMP_OMPT_SUPPORT})
 endif()
 
 
-# Build the modules files if a Fortran compiler is available.
+# Build the module files if a Fortran compiler is available.
 # Only LLVM_ENABLE_RUNTIMES=openmp is supported, LLVM_ENABLE_PROJECTS=openmp
 # has been deprecated.
 if(LIBOMP_FORTRAN_MODULES)
-  add_library(libomp-mod OBJECT
+  configure_file(${LIBOMP_INC_DIR}/omp_lib.h.var omp_lib.h @ONLY)
+  configure_file(${LIBOMP_INC_DIR}/omp_lib.F90.var omp_lib.F90 @ONLY)
+
+  # One compilation step creates both omp_lib.mod and omp_lib_kinds.mod. Only
+  # these files are used, the library itself can be discarded. Cannot use an
+  # OBJECT library to avoid creating the library because LibompExports.cmake
+  # attaches a POST_BUILD command to libomp-mod.
+  add_library(libomp-mod STATIC
     omp_lib.F90
   )
   set_target_properties(libomp-mod PROPERTIES FOLDER "OpenMP/Fortran Modules")
@@ -491,3 +488,8 @@ if(LIBOMP_FORTRAN_MODULES)
     DESTINATION ${destination}
   )
 endif()
+
+# Move files to exports/ directory if requested
+if(LIBOMP_COPY_EXPORTS)
+  include(LibompExports)
+endif()

>From d2473de8c9e3048647db685ec1f322032197ebd7 Mon Sep 17 00:00:00 2001
From: Michael Kruse <llvm-project at meinersbur.de>
Date: Wed, 26 Nov 2025 17:34:14 +0100
Subject: [PATCH 07/15] Simplify by not using macro

---
 flang-rt/CMakeLists.txt                       |  11 +-
 .../cmake/modules/FlangRTIntrospection.cmake  |   4 +-
 openmp/CMakeLists.txt                         |   6 +-
 openmp/runtime/CMakeLists.txt                 |  10 +-
 runtimes/CMakeLists.txt                       | 268 +++++++-----------
 runtimes/cmake/Modules/HandleFortran.cmake    |  63 ++++
 6 files changed, 182 insertions(+), 180 deletions(-)
 create mode 100644 runtimes/cmake/Modules/HandleFortran.cmake

diff --git a/flang-rt/CMakeLists.txt b/flang-rt/CMakeLists.txt
index 8fa934dbdbf29..3708573005604 100644
--- a/flang-rt/CMakeLists.txt
+++ b/flang-rt/CMakeLists.txt
@@ -43,13 +43,11 @@ include(CMakePushCheckState)
 ############################
 
 # Path to LLVM development tools (FileCheck, llvm-lit, not, ...)
-set(LLVM_TOOLS_DIR "${LLVM_BINARY_DIR}/bin")
+set(LLVM_TOOLS_DIR "${LLVM_TOOLS_BINARY_DIR}")
 
 # Fortran compiler not optional for building Flang-RT
 enable_language(Fortran)
 
-flang_module_fortran_enable()
-
 
 #################
 # Build Options #
@@ -72,12 +70,11 @@ endif ()
 
 if (LLVM_RUNTIMES_TARGET MATCHES "^amdgcn|^nvptx")
   # Compiling libraries for offload targets is currently experimental;
-  # only build the buildtin modules by default.
+  # Only build the builtin modules by default.
   set(FLANG_RT_ENABLE_STATIC_default OFF)
 else ()
   set(FLANG_RT_ENABLE_STATIC_default ON)
 endif ()
-
 option(FLANG_RT_ENABLE_STATIC "Build Flang-RT as a static library." "${FLANG_RT_ENABLE_STATIC_default}")
 if (WIN32)
   # Windows DLL currently not implemented.
@@ -96,8 +93,8 @@ endif ()
 if (FLANG_RT_ENABLE_STATIC OR FLANG_RT_ENABLE_SHARED)
   option(FLANG_RT_INCLUDE_TESTS "Generate build targets for the flang-rt unit and regression-tests." "${LLVM_INCLUDE_TESTS}")
 else ()
-  # Tests require at least one libraries
-  message(STATUS "Testing disabled without either FLANG_RT_ENABLE_STATIC or FLANG_RT_ENABLE_SHARED")
+  # Tests require at least one of the libraries
+  message(STATUS "Testing disabled without either FLANG_RT_ENABLE_STATIC OR FLANG_RT_ENABLE_SHARED")
   set(FLANG_RT_INCLUDE_TESTS OFF)
 endif ()
 
diff --git a/flang-rt/cmake/modules/FlangRTIntrospection.cmake b/flang-rt/cmake/modules/FlangRTIntrospection.cmake
index c78c8a9b8a81a..10830ff1ac57e 100644
--- a/flang-rt/cmake/modules/FlangRTIntrospection.cmake
+++ b/flang-rt/cmake/modules/FlangRTIntrospection.cmake
@@ -16,9 +16,6 @@ include(CMakePushCheckState)
 #    build to ensure consistency of real(16) support between compiler and
 #    runtime.
 #
-#  * Does not work with Flang and CMake < 3.24; rely on an externally set
-#    FORTRAN_SUPPORTS_REAL16 instead.
-#
 #  * cmake_push_check_state/cmake_pop_check_state is insufficient to isolate
 #    a compiler introspection environment, see
 #    https://gitlab.kitware.com/cmake/cmake/-/issues/27419
@@ -36,3 +33,4 @@ function (check_fortran_quadmath_support)
   )
   cmake_pop_check_state()
 endfunction ()
+
diff --git a/openmp/CMakeLists.txt b/openmp/CMakeLists.txt
index ad1916a96ca1c..e9f6e82482aff 100644
--- a/openmp/CMakeLists.txt
+++ b/openmp/CMakeLists.txt
@@ -112,11 +112,7 @@ set(OPENMP_TEST_FLAGS "" CACHE STRING
 set(OPENMP_TEST_OPENMP_FLAGS ${OPENMP_TEST_COMPILER_OPENMP_FLAGS} CACHE STRING
   "OpenMP compiler flag to use for testing OpenMP runtime libraries.")
 set(OPENMP_TEST_Fortran_FLAGS "${CMAKE_Fortran_FLAGS}" CACHE STRING
-  "Additional compiler flags to use for testing Fortran programs.")
-
-if (LLVM_RUNTIMES_BUILD)
-  flang_module_fortran_enable()
-endif ()
+  "Additional compiler flags to use for testing Fortran programs (e.g. additional module search paths via -fintrinsic-modules-path )")
 
 set(ENABLE_LIBOMPTARGET ON)
 # Currently libomptarget cannot be compiled on Windows or MacOS X.
diff --git a/openmp/runtime/CMakeLists.txt b/openmp/runtime/CMakeLists.txt
index 6ed1b19c4e054..895388a834de2 100644
--- a/openmp/runtime/CMakeLists.txt
+++ b/openmp/runtime/CMakeLists.txt
@@ -109,8 +109,14 @@ set(LIBOMP_MIC_ARCH knc CACHE STRING
 if("${LIBOMP_ARCH}" STREQUAL "mic")
   libomp_check_variable(LIBOMP_MIC_ARCH knf knc)
 endif()
-set(LIBOMP_FORTRAN_MODULES "${RUNTIMES_FLANG_MODULES_ENABLED}" CACHE BOOL
-  "Create Fortran module files? (requires fortran compiler)")
+
+if (LLVM_RUNTIMES_BUILD)
+  set(LIBOMP_FORTRAN_MODULES "${RUNTIMES_FLANG_MODULES_ENABLED}" CACHE BOOL
+    "Create Fortran module files? (requires fortran compiler)")
+else ()
+  set(LIBOMP_FORTRAN_MODULES OFF)
+endif ()
+
 
 # - Support for universal fat binary builds on Mac
 # - Having this extra variable allows people to build this library as a universal library
diff --git a/runtimes/CMakeLists.txt b/runtimes/CMakeLists.txt
index 253a6d693d8a6..935946e8b523e 100644
--- a/runtimes/CMakeLists.txt
+++ b/runtimes/CMakeLists.txt
@@ -85,41 +85,81 @@ include(CheckLibraryExists)
 include(LLVMCheckCompilerLinkerFlag)
 include(CheckCCompilerFlag)
 include(CheckCXXCompilerFlag)
+include(GetToolchainDirs)
 include(ExtendPath)
 
 
-# CMake 3.24 is the first version of CMake that directly recognizes Flang.
-# LLVM's requirement is only CMake 3.20, teach CMake 3.20-3.23 how to use Flang, if used.
-if (CMAKE_VERSION VERSION_LESS "3.24" AND CMAKE_Fortran_COMPILER)
-  cmake_path(GET CMAKE_Fortran_COMPILER STEM _Fortran_COMPILER_STEM)
-  if (_Fortran_COMPILER_STEM STREQUAL "flang-new" OR
-      _Fortran_COMPILER_STEM STREQUAL "flang")
-    include(CMakeForceCompiler)
-    CMAKE_FORCE_Fortran_COMPILER("${CMAKE_Fortran_COMPILER}" "LLVMFlang")
+# Check whether the build environment supports building Fortran modules
+# flang-rt and openmp are the only runtimes that contain Fortran modules.
+set(FORTRAN_MODULE_DEPS "")
+if ("flang-rt" IN_LIST LLVM_ENABLE_RUNTIMES OR "openmp" IN_LIST LLVM_ENABLE_RUNTIMES)
+  # CMake 3.24 is the first version of CMake that directly recognizes Flang.
+  # LLVM's requirement is only CMake 3.20, teach CMake 3.20-3.23 how to use Flang, if used.
+  if (CMAKE_VERSION VERSION_LESS "3.24" AND CMAKE_Fortran_COMPILER)
+    cmake_path(GET CMAKE_Fortran_COMPILER STEM _Fortran_COMPILER_STEM)
+    if (_Fortran_COMPILER_STEM STREQUAL "flang-new" OR
+        _Fortran_COMPILER_STEM STREQUAL "flang")
+      include(CMakeForceCompiler)
+      CMAKE_FORCE_Fortran_COMPILER("${CMAKE_Fortran_COMPILER}" "LLVMFlang")
 
-    set(CMAKE_Fortran_COMPILER_ID "LLVMFlang")
-    set(CMAKE_Fortran_COMPILER_VERSION "${LLVM_VERSION_MAJOR}.${LLVM_VERSION_MINOR}")
+      set(CMAKE_Fortran_COMPILER_ID "LLVMFlang")
+      set(CMAKE_Fortran_COMPILER_VERSION "${LLVM_VERSION_MAJOR}.${LLVM_VERSION_MINOR}")
 
-    set(CMAKE_Fortran_SUBMODULE_SEP "-")
-    set(CMAKE_Fortran_SUBMODULE_EXT ".mod")
+      set(CMAKE_Fortran_SUBMODULE_SEP "-")
+      set(CMAKE_Fortran_SUBMODULE_EXT ".mod")
 
-    set(CMAKE_Fortran_PREPROCESS_SOURCE
-      "<CMAKE_Fortran_COMPILER> -cpp <DEFINES> <INCLUDES> <FLAGS> -E <SOURCE> > <PREPROCESSED_SOURCE>")
+      set(CMAKE_Fortran_PREPROCESS_SOURCE
+        "<CMAKE_Fortran_COMPILER> -cpp <DEFINES> <INCLUDES> <FLAGS> -E <SOURCE> > <PREPROCESSED_SOURCE>")
 
-    set(CMAKE_Fortran_FORMAT_FIXED_FLAG "-ffixed-form")
-    set(CMAKE_Fortran_FORMAT_FREE_FLAG "-ffree-form")
+      set(CMAKE_Fortran_FORMAT_FIXED_FLAG "-ffixed-form")
+      set(CMAKE_Fortran_FORMAT_FREE_FLAG "-ffree-form")
 
-    set(CMAKE_Fortran_MODDIR_FLAG "-J")
+      set(CMAKE_Fortran_MODDIR_FLAG "-J")
 
-    set(CMAKE_Fortran_COMPILE_OPTIONS_PREPROCESS_ON "-cpp")
-    set(CMAKE_Fortran_COMPILE_OPTIONS_PREPROCESS_OFF "-nocpp")
-    set(CMAKE_Fortran_POSTPROCESS_FLAG "-ffixed-line-length-72")
+      set(CMAKE_Fortran_COMPILE_OPTIONS_PREPROCESS_ON "-cpp")
+      set(CMAKE_Fortran_COMPILE_OPTIONS_PREPROCESS_OFF "-nocpp")
+      set(CMAKE_Fortran_POSTPROCESS_FLAG "-ffixed-line-length-72")
 
-    set(CMAKE_Fortran_COMPILE_OPTIONS_TARGET "--target=")
+      set(CMAKE_Fortran_COMPILE_OPTIONS_TARGET "--target=")
 
-    set(CMAKE_Fortran_LINKER_WRAPPER_FLAG "-Wl,")
-    set(CMAKE_Fortran_LINKER_WRAPPER_FLAG_SEP ",")
+      set(CMAKE_Fortran_LINKER_WRAPPER_FLAG "-Wl,")
+      set(CMAKE_Fortran_LINKER_WRAPPER_FLAG_SEP ",")
+    endif ()
   endif ()
+
+  include(HandleFortran)
+  include(CheckFortranSourceCompiles)
+  include(CheckLanguage)
+
+  set(RUNTIMES_FLANG_MODULES_ENABLED_default OFF)
+  check_language(Fortran)
+  if (CMAKE_Fortran_COMPILER)
+    enable_language(Fortran)
+
+    if (CMAKE_Fortran_COMPILER_ID STREQUAL "LLVMFlang" AND "flang-rt" IN_LIST LLVM_ENABLE_RUNTIMES)
+      # In a bootstrapping build (or any runtimes-build that includes flang-rt),
+      # the intrinsic modules are not built yet. Targets can depend on
+      # flang-rt-mod to ensure that flang-rt's modules are built first.
+      set(FORTRAN_MODULE_DEPS flang-rt-mod)
+      set(RUNTIMES_FLANG_MODULES_ENABLED_default ON)
+    else ()
+      # Check whether building modules works, avoid causing the entire build to
+      # fail because of Fortran. The primary situation we want to support here
+      # is Flang or its intrinsic modules were built separately in a
+      # non-bootstrapping build.
+      check_fortran_builtins_available()
+      if (HAVE_FORTRAN_INTRINSIC_MODS)
+        set(RUNTIMES_FLANG_MODULES_ENABLED_default ON)
+        message(STATUS "${LLVM_SUBPROJECT_TITLE}: Non-bootstrapping Fortran modules build (${CMAKE_Fortran_COMPILER_ID} located at ${CMAKE_Fortran_COMPILER})")
+      else ()
+        message(STATUS "Not compiling Flang modules: Not passing smoke check")
+      endif ()
+    endif ()
+  endif ()
+
+  option(RUNTIMES_FLANG_MODULES_ENABLED "Build Fortran modules" "${RUNTIMES_FLANG_MODULES_ENABLED_default}")
+else ()
+  set(RUNTIMES_FLANG_MODULES_ENABLED NO)
 endif ()
 
 
@@ -242,7 +282,26 @@ message(STATUS "LLVM default target triple: ${LLVM_DEFAULT_TARGET_TRIPLE}")
 
 set(LLVM_TARGET_TRIPLE "${LLVM_DEFAULT_TARGET_TRIPLE}")
 
+if(CMAKE_C_COMPILER_ID MATCHES "Clang")
+  set(option_prefix "")
+  if (CMAKE_C_SIMULATE_ID MATCHES "MSVC")
+    set(option_prefix "/clang:")
+  endif()
+  set(print_target_triple ${CMAKE_C_COMPILER} ${option_prefix}--target=${LLVM_DEFAULT_TARGET_TRIPLE} ${option_prefix}-print-target-triple)
+  execute_process(COMMAND ${print_target_triple}
+    RESULT_VARIABLE result
+    OUTPUT_VARIABLE output
+    OUTPUT_STRIP_TRAILING_WHITESPACE)
+  if(result EQUAL 0)
+    set(LLVM_DEFAULT_TARGET_TRIPLE ${output})
+  else()
+    string(REPLACE ";" " " print_target_triple "${print_target_triple}")
+    # TODO(#97876): Report an error.
+    message(WARNING "Failed to execute `${print_target_triple}` to normalize target triple.")
+  endif()
+endif()
 
+# Determine output and install paths based on LLVM_TARGET_TRIPLE
 if(LLVM_TREE_AVAILABLE)
   # In a bootstrap build emit the libraries into a default search path in the
   # build directory of the just-built compiler. This allows using the
@@ -284,7 +343,6 @@ endif()
 #        But the linker as invoked by the Flang driver also requires
 #        libflang_rt.so to be found when linking and the resource lib dir is
 #        the only reliable location.
-include(GetToolchainDirs)
 get_toolchain_library_subdir(toolchain_lib_subdir)
 extend_path(RUNTIMES_OUTPUT_RESOURCE_LIB_DIR "${RUNTIMES_OUTPUT_RESOURCE_DIR}" "${toolchain_lib_subdir}")
 
@@ -297,24 +355,29 @@ cmake_path(NORMAL_PATH RUNTIMES_OUTPUT_RESOURCE_LIB_DIR)
 cmake_path(NORMAL_PATH RUNTIMES_INSTALL_RESOURCE_LIB_PATH)
 
 
-if(CMAKE_C_COMPILER_ID MATCHES "Clang")
-  set(option_prefix "")
-  if (CMAKE_C_SIMULATE_ID MATCHES "MSVC")
-    set(option_prefix "/clang:")
-  endif()
-  set(print_target_triple ${CMAKE_C_COMPILER} ${option_prefix}--target=${LLVM_DEFAULT_TARGET_TRIPLE} ${option_prefix}-print-target-triple)
-  execute_process(COMMAND ${print_target_triple}
-    RESULT_VARIABLE result
-    OUTPUT_VARIABLE output
-    OUTPUT_STRIP_TRAILING_WHITESPACE)
-  if(result EQUAL 0)
-    set(LLVM_DEFAULT_TARGET_TRIPLE ${output})
-  else()
-    string(REPLACE ";" " " print_target_triple "${print_target_triple}")
-    # TODO(#97876): Report an error.
-    message(WARNING "Failed to execute `${print_target_triple}` to normalize target triple.")
-  endif()
-endif()
+if (RUNTIMES_FLANG_MODULES_ENABLED)
+  if (CMAKE_Fortran_COMPILER_ID STREQUAL "LLVMFlang")
+    # Flang expects its builtin modules in Clang's resource directory
+    get_toolchain_module_subdir(toolchain_mod_subdir)
+    extend_path(RUNTIMES_OUTPUT_RESOURCE_MOD_DIR "${RUNTIMES_OUTPUT_RESOURCE_DIR}" "${toolchain_mod_subdir}")
+    extend_path(RUNTIMES_INSTALL_RESOURCE_MOD_PATH "${RUNTIMES_INSTALL_RESOURCE_PATH}" "${toolchain_mod_subdir}")
+  else ()
+    # For non-Flang compilers, avoid the risk of Flang accidentally picking them up.
+    extend_path(RUNTIMES_OUTPUT_RESOURCE_MOD_DIR "${RUNTIMES_OUTPUT_RESOURCE_DIR}" "finclude-${CMAKE_Fortran_COMPILER_ID}")
+    extend_path(RUNTIMES_INSTALL_RESOURCE_MOD_PATH "${RUNTIMES_INSTALL_RESOURCE_PATH}" "finclude-${CMAKE_Fortran_COMPILER_ID}")
+  endif ()
+  cmake_path(NORMAL_PATH RUNTIMES_OUTPUT_RESOURCE_MOD_DIR)
+  cmake_path(NORMAL_PATH RUNTIMES_INSTALL_RESOURCE_MOD_PATH)
+
+  # No way to find out which mod files are built by a target, so install the
+  # entire output directory
+  # https://stackoverflow.com/questions/52712416/cmake-fortran-module-directory-to-be-used-with-add-library
+  set(destination "${RUNTIMES_INSTALL_RESOURCE_MOD_PATH}/..")
+  cmake_path(NORMAL_PATH destination)
+    install(DIRECTORY "${RUNTIMES_OUTPUT_RESOURCE_MOD_DIR}"
+      DESTINATION "${destination}"
+    )
+endif ()
 
 option(LLVM_INCLUDE_TESTS "Generate build targets for the runtimes unit tests." ON)
 option(LLVM_INCLUDE_DOCS "Generate build targets for the runtimes documentation." ON)
@@ -408,127 +471,6 @@ if(LLVM_INCLUDE_TESTS)
   umbrella_lit_testsuite_begin(check-runtimes)
 endif()
 
-
-include(CheckFortranSourceCompiles)
-
-# Enable building Fortran modules
-#  * Set up the Fortran compiler
-#  * Determine files location in the Clang/Flang resource dir
-#  * Install module files
-macro (flang_module_fortran_enable)
-  # Assume flang modules are enabled until all tests pass
-  set(FORTRAN_MODULE_DEPS "")
-  set(RUNTIMES_FLANG_MODULES_ENABLED_default OFF)
-
-  include(CheckLanguage)
-  check_language(Fortran)
-
-  if (CMAKE_Fortran_COMPILER)
-    enable_language(Fortran)
-
-    if (CMAKE_Fortran_COMPILER_ID STREQUAL "LLVMFlang" AND "flang-rt" IN_LIST LLVM_ENABLE_RUNTIMES)
-      # In a bootstrapping build, the intrinsic modules are not built yet.
-      # Targets can depend on flang-rt-mod to ensure they are built before.
-      set(FORTRAN_MODULE_DEPS flang-rt-mod)
-      set(RUNTIMES_FLANG_MODULES_ENABLED_default ON)
-      message(STATUS "${LLVM_SUBPROJECT_TITLE}: Building Fortran modules for Flang bootstrapping itself")
-    else ()
-      # Check whether building modules works, avoid causing the entire build to fail because of Fortran.
-      # The primary situation we want to support here is Flang or its intrinsic modules were built separately in a non-bootstrapping build.
-      cmake_push_check_state(RESET)
-      set(CMAKE_TRY_COMPILE_TARGET_TYPE "STATIC_LIBRARY")
-      check_fortran_source_compiles("
-        subroutine testroutine
-          use iso_c_binding
-          end subroutine
-        " HAVE_FORTRAN_INTRINSIC_MODS SRC_EXT F90)
-      cmake_pop_check_state()
-      if (HAVE_FORTRAN_INTRINSIC_MODS)
-        set(RUNTIMES_FLANG_MODULES_ENABLED_default ON)
-        message(STATUS "${LLVM_SUBPROJECT_TITLE}: Non-bootstrapping Fortran modules build (${CMAKE_Fortran_COMPILER_ID} located at ${CMAKE_Fortran_COMPILER})")
-      else ()
-        message(STATUS "Not compiling Flang modules: Not passing smoke check")
-      endif ()
-    endif ()
-  else ()
-    message(STATUS "Not compiling Flang modules: Fortran not enabled")
-  endif ()
-
-  option(RUNTIMES_FLANG_MODULES_ENABLED "Build Fortran modules" "${RUNTIMES_FLANG_MODULES_ENABLED_default}")
-
-  if (RUNTIMES_FLANG_MODULES_ENABLED)
-    if (CMAKE_Fortran_COMPILER_ID STREQUAL "LLVMFlang")
-      get_toolchain_module_subdir(toolchain_mod_subdir)
-      extend_path(RUNTIMES_OUTPUT_RESOURCE_MOD_DIR "${RUNTIMES_OUTPUT_RESOURCE_DIR}" "${toolchain_mod_subdir}")
-      extend_path(RUNTIMES_INSTALL_RESOURCE_MOD_PATH "${RUNTIMES_INSTALL_RESOURCE_PATH}" "${toolchain_mod_subdir}")
-    else ()
-      # For non-Flang compilers, avoid the risk of Flang accidentally picking them up.
-      extend_path(RUNTIMES_OUTPUT_RESOURCE_MOD_DIR "${RUNTIMES_OUTPUT_RESOURCE_DIR}" "finclude-${CMAKE_Fortran_COMPILER_ID}")
-      extend_path(RUNTIMES_INSTALL_RESOURCE_MOD_PATH "${RUNTIMES_INSTALL_RESOURCE_PATH}" "finclude-${CMAKE_Fortran_COMPILER_ID}")
-    endif ()
-    cmake_path(NORMAL_PATH RUNTIMES_OUTPUT_RESOURCE_MOD_DIR)
-    cmake_path(NORMAL_PATH RUNTIMES_INSTALL_RESOURCE_MOD_PATH)
-
-    # Avoid module files to be installed multiple times if this macro is called multiple times
-    get_property(is_installed GLOBAL PROPERTY RUNTIMES_MODS_INSTALLED)
-    if (NOT is_installed)
-      # No way to find out which mod files built by target individually, so install the entire output directory
-      # https://stackoverflow.com/questions/52712416/cmake-fortran-module-directory-to-be-used-with-add-library
-      set(destination "${RUNTIMES_INSTALL_RESOURCE_MOD_PATH}/..")
-      cmake_path(NORMAL_PATH destination)
-      install(DIRECTORY "${RUNTIMES_OUTPUT_RESOURCE_MOD_DIR}"
-        DESTINATION "${destination}"
-      )
-      set_property(GLOBAL PROPERTY RUNTIMES_MODS_INSTALLED TRUE)
-    endif ()
-  endif ()
-endmacro ()
-
-
-# Set options to compile Fortran module files.
-#
-# Usage:
-#
-# flang_module_target(name
-#   PUBLIC
-#     Modules files are to be used by other Fortran sources. If a library is
-#     compiled multiple times (e.g. static/shared, or msvcrt variants), only
-#     one of those can be public module files; non-public modules are still
-#     generated but to be forgotten deep inside the build directory to not
-#     conflict with each other.
-#     Also, installs the module with the toolchain.
-# )
-function (flang_module_target tgtname)
-  set(options PUBLIC)
-  cmake_parse_arguments(ARG
-    "${options}"
-    ""
-    ""
-    ${ARGN})
-
-  if (NOT RUNTIMES_FLANG_MODULES_ENABLED)
-    return ()
-  endif ()
-
-  # Let it find the other public module files
-  target_compile_options(${tgtname} PRIVATE
-      "$<$<COMPILE_LANGUAGE:Fortran>:-fintrinsic-modules-path=${RUNTIMES_OUTPUT_RESOURCE_MOD_DIR}>"
-    )
-
-  if (ARG_PUBLIC)
-    set_target_properties(${tgtname}
-      PROPERTIES
-        Fortran_MODULE_DIRECTORY "${RUNTIMES_OUTPUT_RESOURCE_MOD_DIR}"
-      )
-  else ()
-    set_target_properties(${tgtname}
-      PROPERTIES
-        Fortran_MODULE_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}/${tgtname}.mod"
-      )
-  endif ()
-endfunction ()
-
-
 # We do this in two loops so that HAVE_* is set for each runtime before the
 # other runtimes are added.
 foreach(entry ${runtimes})
diff --git a/runtimes/cmake/Modules/HandleFortran.cmake b/runtimes/cmake/Modules/HandleFortran.cmake
new file mode 100644
index 0000000000000..864852a09c849
--- /dev/null
+++ b/runtimes/cmake/Modules/HandleFortran.cmake
@@ -0,0 +1,63 @@
+
+
+# Check whether the Fortran compiler already access to builtin modules.
+#
+# This must be wrapped in a function because
+# cmake_push_check_state/cmake_pop_check_state is insufficient to isolate
+# a compiler introspection environment, see
+# https://gitlab.kitware.com/cmake/cmake/-/issues/27419
+function (check_fortran_builtins_available)
+  cmake_push_check_state(RESET)
+  set(CMAKE_TRY_COMPILE_TARGET_TYPE "STATIC_LIBRARY")
+  check_fortran_source_compiles("
+    subroutine testroutine
+      use iso_c_binding
+    end subroutine
+    " HAVE_FORTRAN_INTRINSIC_MODS SRC_EXT F90)
+  cmake_pop_check_state()
+endfunction ()
+
+
+# Set options to compile Fortran module files.
+#
+# Usage:
+#
+# flang_module_target(name
+#   PUBLIC
+#     Modules files are to be used by other Fortran sources. If a library is
+#     compiled multiple times (e.g. static/shared, or msvcrt variants), only
+#     one of those can be public module files; non-public modules are still
+#     generated but to be forgotten deep inside the build directory to not
+#     conflict with each other.
+#     Also, installs the module with the toolchain.
+# )
+function (flang_module_target tgtname)
+  set(options PUBLIC)
+  cmake_parse_arguments(ARG
+    "${options}"
+    ""
+    ""
+    ${ARGN})
+
+  if (NOT RUNTIMES_FLANG_MODULES_ENABLED)
+    message(WARNING "Cannot build module files for ${tgtname} when RUNTIMES_FLANG_MODULES_ENABLED is ${RUNTIMES_FLANG_MODULES_ENABLED}")
+    return ()
+  endif ()
+
+  # Let it find the other public module files
+  target_compile_options(${tgtname} PRIVATE
+      "$<$<COMPILE_LANGUAGE:Fortran>:-fintrinsic-modules-path=${RUNTIMES_OUTPUT_RESOURCE_MOD_DIR}>"
+    )
+
+  if (ARG_PUBLIC)
+    set_target_properties(${tgtname}
+      PROPERTIES
+        Fortran_MODULE_DIRECTORY "${RUNTIMES_OUTPUT_RESOURCE_MOD_DIR}"
+      )
+  else ()
+    set_target_properties(${tgtname}
+      PROPERTIES
+        Fortran_MODULE_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}/${tgtname}.mod"
+      )
+  endif ()
+endfunction ()
\ No newline at end of file

>From 5ed80b91d2b27c8d628ca76d3b1a2713951f414c Mon Sep 17 00:00:00 2001
From: Michael Kruse <llvm-project at meinersbur.de>
Date: Wed, 26 Nov 2025 20:04:23 +0100
Subject: [PATCH 08/15] Solve CMAKE_Fortran_PREPROCESS_SOURCE issue

---
 runtimes/CMakeLists.txt                    |   2 +-
 runtimes/cmake/Modules/HandleFortran.cmake | 149 ++++++++++++---------
 2 files changed, 88 insertions(+), 63 deletions(-)

diff --git a/runtimes/CMakeLists.txt b/runtimes/CMakeLists.txt
index 935946e8b523e..a836b489a0b53 100644
--- a/runtimes/CMakeLists.txt
+++ b/runtimes/CMakeLists.txt
@@ -145,7 +145,7 @@ if ("flang-rt" IN_LIST LLVM_ENABLE_RUNTIMES OR "openmp" IN_LIST LLVM_ENABLE_RUNT
     else ()
       # Check whether building modules works, avoid causing the entire build to
       # fail because of Fortran. The primary situation we want to support here
-      # is Flang or its intrinsic modules were built separately in a
+      # is Flang, or its intrinsic modules were built separately in a
       # non-bootstrapping build.
       check_fortran_builtins_available()
       if (HAVE_FORTRAN_INTRINSIC_MODS)
diff --git a/runtimes/cmake/Modules/HandleFortran.cmake b/runtimes/cmake/Modules/HandleFortran.cmake
index 864852a09c849..4bbcafa7fb794 100644
--- a/runtimes/cmake/Modules/HandleFortran.cmake
+++ b/runtimes/cmake/Modules/HandleFortran.cmake
@@ -1,63 +1,88 @@
-
-
-# Check whether the Fortran compiler already access to builtin modules.
-#
-# This must be wrapped in a function because
-# cmake_push_check_state/cmake_pop_check_state is insufficient to isolate
-# a compiler introspection environment, see
-# https://gitlab.kitware.com/cmake/cmake/-/issues/27419
-function (check_fortran_builtins_available)
-  cmake_push_check_state(RESET)
-  set(CMAKE_TRY_COMPILE_TARGET_TYPE "STATIC_LIBRARY")
-  check_fortran_source_compiles("
-    subroutine testroutine
-      use iso_c_binding
-    end subroutine
-    " HAVE_FORTRAN_INTRINSIC_MODS SRC_EXT F90)
-  cmake_pop_check_state()
-endfunction ()
-
-
-# Set options to compile Fortran module files.
-#
-# Usage:
-#
-# flang_module_target(name
-#   PUBLIC
-#     Modules files are to be used by other Fortran sources. If a library is
-#     compiled multiple times (e.g. static/shared, or msvcrt variants), only
-#     one of those can be public module files; non-public modules are still
-#     generated but to be forgotten deep inside the build directory to not
-#     conflict with each other.
-#     Also, installs the module with the toolchain.
-# )
-function (flang_module_target tgtname)
-  set(options PUBLIC)
-  cmake_parse_arguments(ARG
-    "${options}"
-    ""
-    ""
-    ${ARGN})
-
-  if (NOT RUNTIMES_FLANG_MODULES_ENABLED)
-    message(WARNING "Cannot build module files for ${tgtname} when RUNTIMES_FLANG_MODULES_ENABLED is ${RUNTIMES_FLANG_MODULES_ENABLED}")
-    return ()
-  endif ()
-
-  # Let it find the other public module files
-  target_compile_options(${tgtname} PRIVATE
-      "$<$<COMPILE_LANGUAGE:Fortran>:-fintrinsic-modules-path=${RUNTIMES_OUTPUT_RESOURCE_MOD_DIR}>"
-    )
-
-  if (ARG_PUBLIC)
-    set_target_properties(${tgtname}
-      PROPERTIES
-        Fortran_MODULE_DIRECTORY "${RUNTIMES_OUTPUT_RESOURCE_MOD_DIR}"
-      )
-  else ()
-    set_target_properties(${tgtname}
-      PROPERTIES
-        Fortran_MODULE_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}/${tgtname}.mod"
-      )
-  endif ()
+
+
+# Check whether the Fortran compiler already access to builtin modules. Sets
+# HAVE_FORTRAN_INTRINSIC_MODS when returning.
+#
+# This must be wrapped in a function because
+# cmake_push_check_state/cmake_pop_check_state is insufficient to isolate
+# a compiler introspection environment, see
+# https://gitlab.kitware.com/cmake/cmake/-/issues/27419
+function (check_fortran_builtins_available)
+  if (CMAKE_Fortran_COMPILER_FORCED AND CMAKE_Fortran_COMPILER_ID STREQUAL "LLVMFlang")
+    # CMake's try_compile does not take a user-defined
+    # CMAKE_Fortran_PREPROCESS_SOURCE into account. Instead of test-compiling,
+    # ask Flang directly for the builtin module files.
+    if (NOT DEFINED HAVE_FORTRAN_HAS_ISO_C_BINDING_MOD)
+      message(STATUS "Performing Test ISO_C_BINDING_PATH")
+      execute_process(
+        COMMAND ${CMAKE_Fortran_COMPILER} ${CMAKE_Fortran_FLAGS} "-print-file-name=iso_c_binding.mod"
+        OUTPUT_VARIABLE ISO_C_BINDING_PATH
+        OUTPUT_STRIP_TRAILING_WHITESPACE
+        ERROR_QUIET
+      )
+      set(HAVE_FORTRAN_HAS_ISO_C_BINDING_MOD "" )
+      if (EXISTS "${ISO_C_BINDING_PATH}")
+        message(STATUS "Performing Test ISO_C_BINDING_PATH -- Success")
+        set(HAVE_FORTRAN_HAS_ISO_C_BINDING_MOD TRUE CACHE INTERNAL "Existence result of ${CMAKE_Fortran_COMPILER} -print-file-name=iso_c_binding.mod")
+      else ()
+        message(STATUS "Performing Test ISO_C_BINDING_PATH -- Failed")
+        set(HAVE_FORTRAN_HAS_ISO_C_BINDING_MOD FALSE CACHE INTERNAL "Existence result of ${CMAKE_Fortran_COMPILER} -print-file-name=iso_c_binding.mod")
+      endif ()
+    endif ()
+  else ()
+    cmake_push_check_state(RESET)
+    set(CMAKE_TRY_COMPILE_TARGET_TYPE "STATIC_LIBRARY")
+    check_fortran_source_compiles("
+      subroutine testroutine
+        use iso_c_binding
+      end subroutine
+      " HAVE_FORTRAN_HAS_ISO_C_BINDING_MOD SRC_EXT F90)
+    cmake_pop_check_state()
+  endif ()
+  set(HAVE_FORTRAN_INTRINSIC_MODS "${HAVE_FORTRAN_HAS_ISO_C_BINDING_MOD}" PARENT_SCOPE)
+endfunction ()
+
+
+# Set options to compile Fortran module files.
+#
+# Usage:
+#
+# flang_module_target(name
+#   PUBLIC
+#     Modules files are to be used by other Fortran sources. If a library is
+#     compiled multiple times (e.g. static/shared, or msvcrt variants), only
+#     one of those can be public module files; non-public modules are still
+#     generated but to be forgotten deep inside the build directory to not
+#     conflict with each other.
+#     Also, installs the module with the toolchain.
+# )
+function (flang_module_target tgtname)
+  set(options PUBLIC)
+  cmake_parse_arguments(ARG
+    "${options}"
+    ""
+    ""
+    ${ARGN})
+
+  if (NOT RUNTIMES_FLANG_MODULES_ENABLED)
+    message(WARNING "Cannot build module files for ${tgtname} when RUNTIMES_FLANG_MODULES_ENABLED is ${RUNTIMES_FLANG_MODULES_ENABLED}")
+    return ()
+  endif ()
+
+  # Let it find the other public module files
+  target_compile_options(${tgtname} PRIVATE
+      "$<$<COMPILE_LANGUAGE:Fortran>:-fintrinsic-modules-path=${RUNTIMES_OUTPUT_RESOURCE_MOD_DIR}>"
+    )
+
+  if (ARG_PUBLIC)
+    set_target_properties(${tgtname}
+      PROPERTIES
+        Fortran_MODULE_DIRECTORY "${RUNTIMES_OUTPUT_RESOURCE_MOD_DIR}"
+      )
+  else ()
+    set_target_properties(${tgtname}
+      PROPERTIES
+        Fortran_MODULE_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}/${tgtname}.mod"
+      )
+  endif ()
 endfunction ()
\ No newline at end of file

>From 66f574059b06283f50960d70bbbd17ada2e2f39e Mon Sep 17 00:00:00 2001
From: Michael Kruse <llvm-project at meinersbur.de>
Date: Wed, 26 Nov 2025 20:17:55 +0100
Subject: [PATCH 09/15] Add TODO comment

---
 openmp/runtime/src/CMakeLists.txt | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/openmp/runtime/src/CMakeLists.txt b/openmp/runtime/src/CMakeLists.txt
index 23b178077ed3f..ff70fe167ad0e 100644
--- a/openmp/runtime/src/CMakeLists.txt
+++ b/openmp/runtime/src/CMakeLists.txt
@@ -457,6 +457,8 @@ endif()
 # Build the module files if a Fortran compiler is available.
 # Only LLVM_ENABLE_RUNTIMES=openmp is supported, LLVM_ENABLE_PROJECTS=openmp
 # has been deprecated.
+# TODO: openmp/runtimes/CMakeLists.txt is only included for host
+#       (non-amdgpu/nvptx) targets, but device side code needs a module as well.
 if(LIBOMP_FORTRAN_MODULES)
   configure_file(${LIBOMP_INC_DIR}/omp_lib.h.var omp_lib.h @ONLY)
   configure_file(${LIBOMP_INC_DIR}/omp_lib.F90.var omp_lib.F90 @ONLY)

>From 52cf5b3316b47b08c1c543a3cffe9532c371c7a2 Mon Sep 17 00:00:00 2001
From: Michael Kruse <llvm-project at meinersbur.de>
Date: Wed, 26 Nov 2025 20:40:00 +0100
Subject: [PATCH 10/15] Post-merge fixes

---
 flang/lib/Frontend/CompilerInvocation.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/flang/lib/Frontend/CompilerInvocation.cpp b/flang/lib/Frontend/CompilerInvocation.cpp
index 5d432ad1faea8..ace24e09d86ec 100644
--- a/flang/lib/Frontend/CompilerInvocation.cpp
+++ b/flang/lib/Frontend/CompilerInvocation.cpp
@@ -1562,7 +1562,7 @@ bool CompilerInvocation::createFromArgs(
           args.getLastArg(clang::options::OPT_resource_dir))
     invoc.resourceDir = a->getValue();
   else
-    invoc.resourceDir = clang::driver::Driver::GetResourcesPath(
+    invoc.resourceDir = clang::GetResourcesPath(
         llvm::sys::fs::getMainExecutable(argv0, nullptr));
 
   // -flang-experimental-hlfir

>From 109050c17e334f8156eb32de97bdc8a6041ca797 Mon Sep 17 00:00:00 2001
From: Michael Kruse <llvm-project at meinersbur.de>
Date: Wed, 26 Nov 2025 21:40:26 +0100
Subject: [PATCH 11/15] Integrate HandleFortran again

---
 runtimes/CMakeLists.txt                    | 90 +++++++++++++++++++++-
 runtimes/cmake/Modules/HandleFortran.cmake | 88 ---------------------
 2 files changed, 89 insertions(+), 89 deletions(-)
 delete mode 100644 runtimes/cmake/Modules/HandleFortran.cmake

diff --git a/runtimes/CMakeLists.txt b/runtimes/CMakeLists.txt
index a836b489a0b53..05a134d0917dd 100644
--- a/runtimes/CMakeLists.txt
+++ b/runtimes/CMakeLists.txt
@@ -89,6 +89,95 @@ include(GetToolchainDirs)
 include(ExtendPath)
 
 
+
+
+# Check whether the Fortran compiler already access to builtin modules. Sets
+# HAVE_FORTRAN_INTRINSIC_MODS when returning.
+#
+# This must be wrapped in a function because
+# cmake_push_check_state/cmake_pop_check_state is insufficient to isolate
+# a compiler introspection environment, see
+# https://gitlab.kitware.com/cmake/cmake/-/issues/27419
+function (check_fortran_builtins_available)
+  if (CMAKE_Fortran_COMPILER_FORCED AND CMAKE_Fortran_COMPILER_ID STREQUAL "LLVMFlang")
+    # CMake's try_compile does not take a user-defined
+    # CMAKE_Fortran_PREPROCESS_SOURCE into account. Instead of test-compiling,
+    # ask Flang directly for the builtin module files.
+    if (NOT DEFINED HAVE_FORTRAN_HAS_ISO_C_BINDING_MOD)
+      message(STATUS "Performing Test ISO_C_BINDING_PATH")
+      execute_process(
+        COMMAND ${CMAKE_Fortran_COMPILER} ${CMAKE_Fortran_FLAGS} "-print-file-name=iso_c_binding.mod"
+        OUTPUT_VARIABLE ISO_C_BINDING_PATH
+        OUTPUT_STRIP_TRAILING_WHITESPACE
+        ERROR_QUIET
+      )
+      set(HAVE_FORTRAN_HAS_ISO_C_BINDING_MOD "" )
+      if (EXISTS "${ISO_C_BINDING_PATH}")
+        message(STATUS "Performing Test ISO_C_BINDING_PATH -- Success")
+        set(HAVE_FORTRAN_HAS_ISO_C_BINDING_MOD TRUE CACHE INTERNAL "Existence result of ${CMAKE_Fortran_COMPILER} -print-file-name=iso_c_binding.mod")
+      else ()
+        message(STATUS "Performing Test ISO_C_BINDING_PATH -- Failed")
+        set(HAVE_FORTRAN_HAS_ISO_C_BINDING_MOD FALSE CACHE INTERNAL "Existence result of ${CMAKE_Fortran_COMPILER} -print-file-name=iso_c_binding.mod")
+      endif ()
+    endif ()
+  else ()
+    cmake_push_check_state(RESET)
+    set(CMAKE_TRY_COMPILE_TARGET_TYPE "STATIC_LIBRARY")
+    check_fortran_source_compiles("
+      subroutine testroutine
+        use iso_c_binding
+      end subroutine
+      " HAVE_FORTRAN_HAS_ISO_C_BINDING_MOD SRC_EXT F90)
+    cmake_pop_check_state()
+  endif ()
+  set(HAVE_FORTRAN_INTRINSIC_MODS "${HAVE_FORTRAN_HAS_ISO_C_BINDING_MOD}" PARENT_SCOPE)
+endfunction ()
+
+
+# Set options to compile Fortran module files.
+#
+# Usage:
+#
+# flang_module_target(name
+#   PUBLIC
+#     Modules files are to be used by other Fortran sources. If a library is
+#     compiled multiple times (e.g. static/shared, or msvcrt variants), only
+#     one of those can be public module files; non-public modules are still
+#     generated but to be forgotten deep inside the build directory to not
+#     conflict with each other.
+#     Also, installs the module with the toolchain.
+# )
+function (flang_module_target tgtname)
+  set(options PUBLIC)
+  cmake_parse_arguments(ARG
+    "${options}"
+    ""
+    ""
+    ${ARGN})
+
+  if (NOT RUNTIMES_FLANG_MODULES_ENABLED)
+    message(WARNING "Cannot build module files for ${tgtname} when RUNTIMES_FLANG_MODULES_ENABLED is ${RUNTIMES_FLANG_MODULES_ENABLED}")
+    return ()
+  endif ()
+
+  # Let it find the other public module files
+  target_compile_options(${tgtname} PRIVATE
+      "$<$<COMPILE_LANGUAGE:Fortran>:-fintrinsic-modules-path=${RUNTIMES_OUTPUT_RESOURCE_MOD_DIR}>"
+    )
+
+  if (ARG_PUBLIC)
+    set_target_properties(${tgtname}
+      PROPERTIES
+        Fortran_MODULE_DIRECTORY "${RUNTIMES_OUTPUT_RESOURCE_MOD_DIR}"
+      )
+  else ()
+    set_target_properties(${tgtname}
+      PROPERTIES
+        Fortran_MODULE_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}/${tgtname}.mod"
+      )
+  endif ()
+endfunction ()
+
 # Check whether the build environment supports building Fortran modules
 # flang-rt and openmp are the only runtimes that contain Fortran modules.
 set(FORTRAN_MODULE_DEPS "")
@@ -127,7 +216,6 @@ if ("flang-rt" IN_LIST LLVM_ENABLE_RUNTIMES OR "openmp" IN_LIST LLVM_ENABLE_RUNT
     endif ()
   endif ()
 
-  include(HandleFortran)
   include(CheckFortranSourceCompiles)
   include(CheckLanguage)
 
diff --git a/runtimes/cmake/Modules/HandleFortran.cmake b/runtimes/cmake/Modules/HandleFortran.cmake
deleted file mode 100644
index 4bbcafa7fb794..0000000000000
--- a/runtimes/cmake/Modules/HandleFortran.cmake
+++ /dev/null
@@ -1,88 +0,0 @@
-
-
-# Check whether the Fortran compiler already access to builtin modules. Sets
-# HAVE_FORTRAN_INTRINSIC_MODS when returning.
-#
-# This must be wrapped in a function because
-# cmake_push_check_state/cmake_pop_check_state is insufficient to isolate
-# a compiler introspection environment, see
-# https://gitlab.kitware.com/cmake/cmake/-/issues/27419
-function (check_fortran_builtins_available)
-  if (CMAKE_Fortran_COMPILER_FORCED AND CMAKE_Fortran_COMPILER_ID STREQUAL "LLVMFlang")
-    # CMake's try_compile does not take a user-defined
-    # CMAKE_Fortran_PREPROCESS_SOURCE into account. Instead of test-compiling,
-    # ask Flang directly for the builtin module files.
-    if (NOT DEFINED HAVE_FORTRAN_HAS_ISO_C_BINDING_MOD)
-      message(STATUS "Performing Test ISO_C_BINDING_PATH")
-      execute_process(
-        COMMAND ${CMAKE_Fortran_COMPILER} ${CMAKE_Fortran_FLAGS} "-print-file-name=iso_c_binding.mod"
-        OUTPUT_VARIABLE ISO_C_BINDING_PATH
-        OUTPUT_STRIP_TRAILING_WHITESPACE
-        ERROR_QUIET
-      )
-      set(HAVE_FORTRAN_HAS_ISO_C_BINDING_MOD "" )
-      if (EXISTS "${ISO_C_BINDING_PATH}")
-        message(STATUS "Performing Test ISO_C_BINDING_PATH -- Success")
-        set(HAVE_FORTRAN_HAS_ISO_C_BINDING_MOD TRUE CACHE INTERNAL "Existence result of ${CMAKE_Fortran_COMPILER} -print-file-name=iso_c_binding.mod")
-      else ()
-        message(STATUS "Performing Test ISO_C_BINDING_PATH -- Failed")
-        set(HAVE_FORTRAN_HAS_ISO_C_BINDING_MOD FALSE CACHE INTERNAL "Existence result of ${CMAKE_Fortran_COMPILER} -print-file-name=iso_c_binding.mod")
-      endif ()
-    endif ()
-  else ()
-    cmake_push_check_state(RESET)
-    set(CMAKE_TRY_COMPILE_TARGET_TYPE "STATIC_LIBRARY")
-    check_fortran_source_compiles("
-      subroutine testroutine
-        use iso_c_binding
-      end subroutine
-      " HAVE_FORTRAN_HAS_ISO_C_BINDING_MOD SRC_EXT F90)
-    cmake_pop_check_state()
-  endif ()
-  set(HAVE_FORTRAN_INTRINSIC_MODS "${HAVE_FORTRAN_HAS_ISO_C_BINDING_MOD}" PARENT_SCOPE)
-endfunction ()
-
-
-# Set options to compile Fortran module files.
-#
-# Usage:
-#
-# flang_module_target(name
-#   PUBLIC
-#     Modules files are to be used by other Fortran sources. If a library is
-#     compiled multiple times (e.g. static/shared, or msvcrt variants), only
-#     one of those can be public module files; non-public modules are still
-#     generated but to be forgotten deep inside the build directory to not
-#     conflict with each other.
-#     Also, installs the module with the toolchain.
-# )
-function (flang_module_target tgtname)
-  set(options PUBLIC)
-  cmake_parse_arguments(ARG
-    "${options}"
-    ""
-    ""
-    ${ARGN})
-
-  if (NOT RUNTIMES_FLANG_MODULES_ENABLED)
-    message(WARNING "Cannot build module files for ${tgtname} when RUNTIMES_FLANG_MODULES_ENABLED is ${RUNTIMES_FLANG_MODULES_ENABLED}")
-    return ()
-  endif ()
-
-  # Let it find the other public module files
-  target_compile_options(${tgtname} PRIVATE
-      "$<$<COMPILE_LANGUAGE:Fortran>:-fintrinsic-modules-path=${RUNTIMES_OUTPUT_RESOURCE_MOD_DIR}>"
-    )
-
-  if (ARG_PUBLIC)
-    set_target_properties(${tgtname}
-      PROPERTIES
-        Fortran_MODULE_DIRECTORY "${RUNTIMES_OUTPUT_RESOURCE_MOD_DIR}"
-      )
-  else ()
-    set_target_properties(${tgtname}
-      PROPERTIES
-        Fortran_MODULE_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}/${tgtname}.mod"
-      )
-  endif ()
-endfunction ()
\ No newline at end of file

>From 7732534216ede9d5cff2fcb1868479cb69a33618 Mon Sep 17 00:00:00 2001
From: Michael Kruse <llvm-project at meinersbur.de>
Date: Thu, 27 Nov 2025 00:10:00 +0100
Subject: [PATCH 12/15] Build omp_lib.mod on device

---
 flang-rt/CMakeLists.txt                       | 14 ++--
 flang-rt/cmake/modules/AddFlangRT.cmake       | 12 +--
 .../cmake/modules/AddFlangRTOffload.cmake     |  3 +-
 openmp/CMakeLists.txt                         | 29 +++++++
 openmp/{runtime => }/cmake/LibompUtils.cmake  |  0
 openmp/module/CMakeLists.txt                  | 30 ++++++++
 .../src/include => module}/omp_lib.F90.var    |  0
 openmp/runtime/CMakeLists.txt                 | 23 +-----
 openmp/runtime/cmake/LibompExports.cmake      |  6 +-
 openmp/runtime/src/CMakeLists.txt             | 40 ++--------
 runtimes/CMakeLists.txt                       | 76 +++++++++++++++----
 11 files changed, 144 insertions(+), 89 deletions(-)
 rename openmp/{runtime => }/cmake/LibompUtils.cmake (100%)
 create mode 100644 openmp/module/CMakeLists.txt
 rename openmp/{runtime/src/include => module}/omp_lib.F90.var (100%)

diff --git a/flang-rt/CMakeLists.txt b/flang-rt/CMakeLists.txt
index 3708573005604..bb49f3681b5d0 100644
--- a/flang-rt/CMakeLists.txt
+++ b/flang-rt/CMakeLists.txt
@@ -43,7 +43,7 @@ include(CMakePushCheckState)
 ############################
 
 # Path to LLVM development tools (FileCheck, llvm-lit, not, ...)
-set(LLVM_TOOLS_DIR "${LLVM_TOOLS_BINARY_DIR}")
+set(LLVM_TOOLS_DIR "${LLVM_BINARY_DIR}/bin")
 
 # Fortran compiler not optional for building Flang-RT
 enable_language(Fortran)
@@ -113,14 +113,8 @@ elseif (FLANG_RT_EXPERIMENTAL_OFFLOAD_SUPPORT STREQUAL "CUDA")
   option(FLANG_RT_CUDA_RUNTIME_PTX_WITHOUT_GLOBAL_VARS "Do not compile global variables' definitions when producing PTX library" OFF)
 elseif (FLANG_RT_EXPERIMENTAL_OFFLOAD_SUPPORT STREQUAL "OpenMP")
   # Support for OpenMP offloading
-else ()
-  message(FATAL_ERROR "Invalid value '${FLANG_RT_EXPERIMENTAL_OFFLOAD_SUPPORT}' for FLANG_RT_EXPERIMENTAL_OFFLOAD_SUPPORT; must be empty, 'CUDA', or 'OpenMP'")
-endif ()
-
-
-if (FLANG_RT_EXPERIMENTAL_OFFLOAD_SUPPORT STREQUAL "OpenMP" OR LLVM_TARGET_TRIPLE MATCHES "^nvptx")
-  set(FLANG_RT_DEVICE_ARCHITECTURES "all" CACHE STRING
-      "List of offload device architectures to be used to compile the Fortran runtime (e.g. 'gfx1103;sm_90')"
+  set(FLANG_RT_DEVICE_ARCHITECTURES "${RUNTIMES_DEVICE_ARCHITECTURES}" CACHE STRING
+      "List of OpenMP device architectures to be used to compile the Fortran runtime (e.g. 'gfx1103;sm_90')"
     )
 
   if (FLANG_RT_DEVICE_ARCHITECTURES STREQUAL "all")
@@ -139,6 +133,8 @@ if (FLANG_RT_EXPERIMENTAL_OFFLOAD_SUPPORT STREQUAL "OpenMP" OR LLVM_TARGET_TRIPL
       set(FLANG_RT_DEVICE_ARCHITECTURES ${all_gpu_architectures})
   endif()
   list(REMOVE_DUPLICATES FLANG_RT_DEVICE_ARCHITECTURES)
+else ()
+  message(FATAL_ERROR "Invalid value '${FLANG_RT_EXPERIMENTAL_OFFLOAD_SUPPORT}' for FLANG_RT_EXPERIMENTAL_OFFLOAD_SUPPORT; must be empty, 'CUDA', or 'OpenMP'")
 endif ()
 
 
diff --git a/flang-rt/cmake/modules/AddFlangRT.cmake b/flang-rt/cmake/modules/AddFlangRT.cmake
index ea4f920e1d877..0ba485a79beb8 100644
--- a/flang-rt/cmake/modules/AddFlangRT.cmake
+++ b/flang-rt/cmake/modules/AddFlangRT.cmake
@@ -234,14 +234,11 @@ function (add_flangrt_library name)
     target_compile_features(${tgtname} PRIVATE cxx_std_17)
 
     target_compile_options(${tgtname} PRIVATE
-      # Always enable preprocessor regardless of file extention
+      # Always enable preprocessor regardless of file extension
       "$<$<COMPILE_LANGUAGE:Fortran>:-cpp>"
 
-      # Missing type descriptors are expected for intrinsic modules 
+      # Missing type descriptors are expected for intrinsic modules
       "$<$<COMPILE_LANGUAGE:Fortran>:SHELL:-mmlir;SHELL:-ignore-missing-type-desc>"
-
-      # Flang bug workaround: Reformating of cooked token buffer causes identifier to be split between lines
-      "$<$<COMPILE_LANGUAGE:Fortran>:SHELL:-Xflang;SHELL:-fno-reformat>"
     )
 
     # When building the flang runtime if LTO is enabled the archive file
@@ -300,11 +297,6 @@ function (add_flangrt_library name)
       target_compile_options(${tgtname} PRIVATE
           $<$<COMPILE_LANGUAGE:CXX>:-nogpulib -flto -fvisibility=hidden -Wno-unknown-cuda-version --cuda-feature=+ptx63>
         )
-      foreach (_arch IN LISTS FLANG_RT_DEVICE_ARCHITECTURES)
-        target_compile_options(${tgtname} PRIVATE
-         -march=${_arch}
-        )
-       endforeach()
     elseif (APPLE)
       # Clang on Darwin enables non-POSIX extensions by default.
       # This causes some macros to leak, such as HUGE from <math.h>, which
diff --git a/flang-rt/cmake/modules/AddFlangRTOffload.cmake b/flang-rt/cmake/modules/AddFlangRTOffload.cmake
index 4a6f047a86af2..5b6464741c9c9 100644
--- a/flang-rt/cmake/modules/AddFlangRTOffload.cmake
+++ b/flang-rt/cmake/modules/AddFlangRTOffload.cmake
@@ -106,7 +106,8 @@ macro(enable_omp_offload_compilation name files)
         PROPERTIES COMPILE_DEFINITIONS OMP_OFFLOAD_BUILD
         )
 
-     # If building flang-rt together with libomp, ensure that libomp is built first and found because -fopenmp will try to link it.
+     # If building flang-rt together with libomp, ensure that libomp is built
+     # first and found because -fopenmp will try to link it.
      if (TARGET omp)
        add_dependencies(${name} omp)
        target_link_options(${name}.static PUBLIC "-L$<TARGET_FILE_DIR:omp>")
diff --git a/openmp/CMakeLists.txt b/openmp/CMakeLists.txt
index e9f6e82482aff..b93d8c5701210 100644
--- a/openmp/CMakeLists.txt
+++ b/openmp/CMakeLists.txt
@@ -95,6 +95,24 @@ endif()
 # Check and set up common compiler flags.
 include(config-ix)
 include(HandleOpenMPOptions)
+include(LibompUtils)
+
+
+# Set libomp version
+set(LIBOMP_VERSION_MAJOR 5)
+set(LIBOMP_VERSION_MINOR 0)
+
+# Set the OpenMP Year and Month associated with version
+set(LIBOMP_OMP_YEAR_MONTH 201611)
+
+# Get the build number from kmp_version.cpp
+libomp_get_build_number("${CMAKE_CURRENT_SOURCE_DIR}/runtime" LIBOMP_VERSION_BUILD)
+math(EXPR LIBOMP_VERSION_BUILD_YEAR "${LIBOMP_VERSION_BUILD}/10000")
+math(EXPR LIBOMP_VERSION_BUILD_MONTH_DAY "${LIBOMP_VERSION_BUILD}%10000")
+
+# Currently don't record any timestamps
+set(LIBOMP_BUILD_DATE "No_Timestamp")
+
 
 # Check for flang
 set(OPENMP_TEST_Fortran_COMPILER_default "")
@@ -104,6 +122,13 @@ endif ()
 set(OPENMP_TEST_Fortran_COMPILER "${OPENMP_TEST_Fortran_COMPILER_default}" CACHE STRING
   "Fortran compiler to use for testing OpenMP runtime libraries.")
 
+if (LLVM_RUNTIMES_BUILD)
+  set(LIBOMP_FORTRAN_MODULES "${RUNTIMES_FLANG_MODULES_ENABLED}" CACHE BOOL
+    "Create Fortran module files? (requires fortran compiler)")
+else ()
+  set(LIBOMP_FORTRAN_MODULES OFF)
+endif ()
+
 # Set up testing infrastructure.
 include(OpenMPTesting)
 
@@ -136,6 +161,10 @@ else()
   get_clang_resource_dir(LIBOMP_HEADERS_INSTALL_PATH SUBDIR include)
 endif()
 
+if(LIBOMP_FORTRAN_MODULES)
+  add_subdirectory(module)
+endif()
+
 # Use the current compiler target to determine the appropriate runtime to build.
 if("${LLVM_DEFAULT_TARGET_TRIPLE}" MATCHES "^amdgcn|^nvptx" OR
    "${CMAKE_CXX_COMPILER_TARGET}" MATCHES "^amdgcn|^nvptx")
diff --git a/openmp/runtime/cmake/LibompUtils.cmake b/openmp/cmake/LibompUtils.cmake
similarity index 100%
rename from openmp/runtime/cmake/LibompUtils.cmake
rename to openmp/cmake/LibompUtils.cmake
diff --git a/openmp/module/CMakeLists.txt b/openmp/module/CMakeLists.txt
new file mode 100644
index 0000000000000..29f7816aa5998
--- /dev/null
+++ b/openmp/module/CMakeLists.txt
@@ -0,0 +1,30 @@
+#//===----------------------------------------------------------------------===//
+#//
+#// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+#// See https://llvm.org/LICENSE.txt for license information.
+#// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+#//
+#//===----------------------------------------------------------------------===//
+
+# Build the module files if a Fortran compiler is available.
+# Only LLVM_ENABLE_RUNTIMES=openmp is supported, LLVM_ENABLE_PROJECTS=openmp
+# has been deprecated.
+
+configure_file(omp_lib.F90.var "{CMAKE_CURRENT_BINARY_DIR}/omp_lib.F90" @ONLY)
+
+# One compilation step creates both omp_lib.mod and omp_lib_kinds.mod. Only
+# these files are used, the object file itself can be discarded.
+# FIXME: Adding it to libomp.so would allow implementing Fortran API in Fortran
+add_library(libomp-mod OBJECT
+  "{CMAKE_CURRENT_BINARY_DIR}/omp_lib.F90"
+)
+set_target_properties(libomp-mod PROPERTIES FOLDER "OpenMP/Fortran Modules")
+
+if (CMAKE_Fortran_COMPILER_ID STREQUAL "GNU")
+ target_compile_options(libomp-mod PRIVATE -fno-range-check)
+endif()
+
+flang_module_target(libomp-mod PUBLIC)
+if (FORTRAN_MODULE_DEPS)
+  add_dependencies(libomp-mod ${FORTRAN_MODULE_DEPS})
+endif ()
diff --git a/openmp/runtime/src/include/omp_lib.F90.var b/openmp/module/omp_lib.F90.var
similarity index 100%
rename from openmp/runtime/src/include/omp_lib.F90.var
rename to openmp/module/omp_lib.F90.var
diff --git a/openmp/runtime/CMakeLists.txt b/openmp/runtime/CMakeLists.txt
index 895388a834de2..dc0e0e7a81e7c 100644
--- a/openmp/runtime/CMakeLists.txt
+++ b/openmp/runtime/CMakeLists.txt
@@ -15,10 +15,6 @@ endif()
 # Add cmake directory to search for custom cmake functions
 set(CMAKE_MODULE_PATH ${CMAKE_CURRENT_SOURCE_DIR}/cmake ${CMAKE_MODULE_PATH})
 
-# Set libomp version
-set(LIBOMP_VERSION_MAJOR 5)
-set(LIBOMP_VERSION_MINOR 0)
-
 # These include files are in the cmake/ subdirectory
 include(LibompUtils)
 include(LibompGetArchitecture)
@@ -102,21 +98,12 @@ libomp_check_variable(LIBOMP_ARCH 32e x86_64 32 i386 arm ppc ppc64 ppc64le aarch
 set(LIBOMP_LIB_TYPE normal CACHE STRING
   "Performance,Profiling,Stubs library (normal/profile/stubs)")
 libomp_check_variable(LIBOMP_LIB_TYPE normal profile stubs)
-# Set the OpenMP Year and Month associated with version
-set(LIBOMP_OMP_YEAR_MONTH 201611)
 set(LIBOMP_MIC_ARCH knc CACHE STRING
   "Intel(R) Many Integrated Core Architecture (Intel(R) MIC Architecture) (knf/knc).  Ignored if not Intel(R) MIC Architecture build.")
 if("${LIBOMP_ARCH}" STREQUAL "mic")
   libomp_check_variable(LIBOMP_MIC_ARCH knf knc)
 endif()
 
-if (LLVM_RUNTIMES_BUILD)
-  set(LIBOMP_FORTRAN_MODULES "${RUNTIMES_FLANG_MODULES_ENABLED}" CACHE BOOL
-    "Create Fortran module files? (requires fortran compiler)")
-else ()
-  set(LIBOMP_FORTRAN_MODULES OFF)
-endif ()
-
 
 # - Support for universal fat binary builds on Mac
 # - Having this extra variable allows people to build this library as a universal library
@@ -167,14 +154,6 @@ set(LIBOMP_USE_HWLOC FALSE CACHE BOOL
 set(LIBOMP_HWLOC_INSTALL_DIR /usr/local CACHE PATH
   "Install path for hwloc library")
 
-# Get the build number from kmp_version.cpp
-libomp_get_build_number("${CMAKE_CURRENT_SOURCE_DIR}" LIBOMP_VERSION_BUILD)
-math(EXPR LIBOMP_VERSION_BUILD_YEAR "${LIBOMP_VERSION_BUILD}/10000")
-math(EXPR LIBOMP_VERSION_BUILD_MONTH_DAY "${LIBOMP_VERSION_BUILD}%10000")
-
-# Currently don't record any timestamps
-set(LIBOMP_BUILD_DATE "No_Timestamp")
-
 # Architecture
 set(IA32 FALSE)
 set(INTEL64 FALSE)
@@ -477,3 +456,5 @@ set(LIBOMP_OMP_TOOLS_INCLUDE_DIR ${LIBOMP_OMP_TOOLS_INCLUDE_DIR} PARENT_SCOPE)
 # make these variables available for tools/libompd:
 set(LIBOMP_SRC_DIR ${LIBOMP_SRC_DIR} PARENT_SCOPE)
 set(LIBOMP_OMPD_SUPPORT ${LIBOMP_OMPD_SUPPORT} PARENT_SCOPE)
+
+
diff --git a/openmp/runtime/cmake/LibompExports.cmake b/openmp/runtime/cmake/LibompExports.cmake
index 662c207f8904f..5b50c570519fb 100644
--- a/openmp/runtime/cmake/LibompExports.cmake
+++ b/openmp/runtime/cmake/LibompExports.cmake
@@ -65,12 +65,14 @@ if(${LIBOMP_OMPT_SUPPORT})
   )
 endif()
 if(${LIBOMP_FORTRAN_MODULES})
-  add_custom_command(TARGET libomp-mod POST_BUILD
+  # We cannot attach a POST_BUILD command to libomp-mod, so instead attach it
+  # to omp and ensure that libomp-mod is built befoe by adding a dependency
+  add_custom_command(TARGET omp POST_BUILD
     COMMAND ${CMAKE_COMMAND} -E make_directory ${LIBOMP_EXPORTS_MOD_DIR}
     COMMAND ${CMAKE_COMMAND} -E copy ${RUNTIMES_OUTPUT_RESOURCE_MOD_DIR}/omp_lib.mod ${LIBOMP_EXPORTS_MOD_DIR}
     COMMAND ${CMAKE_COMMAND} -E copy ${RUNTIMES_OUTPUT_RESOURCE_MOD_DIR}/omp_lib_kinds.mod ${LIBOMP_EXPORTS_MOD_DIR}
   )
-
+  add_dependencies(omp libomp-mod)
   add_custom_command(TARGET omp POST_BUILD
     COMMAND ${CMAKE_COMMAND} -E copy omp_lib.h ${LIBOMP_EXPORTS_CMN_DIR}
   )
diff --git a/openmp/runtime/src/CMakeLists.txt b/openmp/runtime/src/CMakeLists.txt
index ff70fe167ad0e..40a94721bb7aa 100644
--- a/openmp/runtime/src/CMakeLists.txt
+++ b/openmp/runtime/src/CMakeLists.txt
@@ -377,6 +377,13 @@ if(WIN32)
   endif()
 endif()
 
+configure_file(${LIBOMP_INC_DIR}/omp_lib.h.var omp_lib.h @ONLY)
+
+# Move files to exports/ directory if requested
+if(${LIBOMP_COPY_EXPORTS})
+  include(LibompExports)
+endif()
+
 # Micro test rules for after library has been built (cmake/LibompMicroTests.cmake)
 include(LibompMicroTests)
 add_custom_target(libomp-micro-tests)
@@ -452,35 +459,7 @@ if(${LIBOMP_OMPT_SUPPORT})
   install(FILES ${LIBOMP_HEADERS_INTDIR}/omp-tools.h DESTINATION ${LIBOMP_HEADERS_INSTALL_PATH} RENAME ompt.h)
   set(LIBOMP_OMP_TOOLS_INCLUDE_DIR ${CMAKE_CURRENT_BINARY_DIR} PARENT_SCOPE)
 endif()
-
-
-# Build the module files if a Fortran compiler is available.
-# Only LLVM_ENABLE_RUNTIMES=openmp is supported, LLVM_ENABLE_PROJECTS=openmp
-# has been deprecated.
-# TODO: openmp/runtimes/CMakeLists.txt is only included for host
-#       (non-amdgpu/nvptx) targets, but device side code needs a module as well.
 if(LIBOMP_FORTRAN_MODULES)
-  configure_file(${LIBOMP_INC_DIR}/omp_lib.h.var omp_lib.h @ONLY)
-  configure_file(${LIBOMP_INC_DIR}/omp_lib.F90.var omp_lib.F90 @ONLY)
-
-  # One compilation step creates both omp_lib.mod and omp_lib_kinds.mod. Only
-  # these files are used, the library itself can be discarded. Cannot use an
-  # OBJECT library to avoid creating the library because LibompExports.cmake
-  # attaches a POST_BUILD command to libomp-mod.
-  add_library(libomp-mod STATIC
-    omp_lib.F90
-  )
-  set_target_properties(libomp-mod PROPERTIES FOLDER "OpenMP/Fortran Modules")
-
-  if (CMAKE_Fortran_COMPILER_ID STREQUAL "GNU")
-   target_compile_options(libomp-mod PRIVATE -fno-range-check)
-  endif()
-
-  flang_module_target(libomp-mod PUBLIC)
-  if (FORTRAN_MODULE_DEPS)
-    add_dependencies(libomp-mod ${FORTRAN_MODULE_DEPS})
-  endif ()
-
   set (destination ${LIBOMP_HEADERS_INSTALL_PATH})
   if (NOT ${LIBOMP_MODULES_INSTALL_PATH} STREQUAL "")
     set (destination ${LIBOMP_MODULES_INSTALL_PATH})
@@ -490,8 +469,3 @@ if(LIBOMP_FORTRAN_MODULES)
     DESTINATION ${destination}
   )
 endif()
-
-# Move files to exports/ directory if requested
-if(LIBOMP_COPY_EXPORTS)
-  include(LibompExports)
-endif()
diff --git a/runtimes/CMakeLists.txt b/runtimes/CMakeLists.txt
index 05a134d0917dd..885ddd837e73c 100644
--- a/runtimes/CMakeLists.txt
+++ b/runtimes/CMakeLists.txt
@@ -88,9 +88,6 @@ include(CheckCXXCompilerFlag)
 include(GetToolchainDirs)
 include(ExtendPath)
 
-
-
-
 # Check whether the Fortran compiler already access to builtin modules. Sets
 # HAVE_FORTRAN_INTRINSIC_MODS when returning.
 #
@@ -160,11 +157,22 @@ function (flang_module_target tgtname)
     return ()
   endif ()
 
-  # Let it find the other public module files
   target_compile_options(${tgtname} PRIVATE
+      # Let non-public modules find the public module files
       "$<$<COMPILE_LANGUAGE:Fortran>:-fintrinsic-modules-path=${RUNTIMES_OUTPUT_RESOURCE_MOD_DIR}>"
+
+      # Flang bug workaround: Reformating of cooked token buffer causes identifier to be split between lines
+      "$<$<COMPILE_LANGUAGE:Fortran>:SHELL:-Xflang;SHELL:-fno-reformat>"
     )
 
+  if (LLVM_RUNTIMES_TARGET MATCHES "^nvptx")
+    foreach (_arch IN LISTS RUNTIMES_DEVICE_ARCHITECTURES)
+      target_compile_options(${tgtname} PRIVATE
+       "$<$<COMPILE_LANGUAGE:Fortran>:-march=${_arch}>"
+      )
+    endforeach()
+  endif ()
+
   if (ARG_PUBLIC)
     set_target_properties(${tgtname}
       PROPERTIES
@@ -181,13 +189,13 @@ endfunction ()
 # Check whether the build environment supports building Fortran modules
 # flang-rt and openmp are the only runtimes that contain Fortran modules.
 set(FORTRAN_MODULE_DEPS "")
-if ("flang-rt" IN_LIST LLVM_ENABLE_RUNTIMES OR "openmp" IN_LIST LLVM_ENABLE_RUNTIMES)
-  # CMake 3.24 is the first version of CMake that directly recognizes Flang.
-  # LLVM's requirement is only CMake 3.20, teach CMake 3.20-3.23 how to use Flang, if used.
-  if (CMAKE_VERSION VERSION_LESS "3.24" AND CMAKE_Fortran_COMPILER)
-    cmake_path(GET CMAKE_Fortran_COMPILER STEM _Fortran_COMPILER_STEM)
-    if (_Fortran_COMPILER_STEM STREQUAL "flang-new" OR
-        _Fortran_COMPILER_STEM STREQUAL "flang")
+if (CMAKE_Fortran_COMPILER AND ("flang-rt" IN_LIST LLVM_ENABLE_RUNTIMES OR "openmp" IN_LIST LLVM_ENABLE_RUNTIMES))
+  cmake_path(GET CMAKE_Fortran_COMPILER STEM _Fortran_COMPILER_STEM)
+
+  if (_Fortran_COMPILER_STEM STREQUAL "flang-new" OR _Fortran_COMPILER_STEM STREQUAL "flang")
+    # CMake 3.24 is the first version of CMake that directly recognizes Flang.
+    # LLVM's requirement is only CMake 3.20, teach CMake 3.20-3.23 how to use Flang, if used.
+    if (CMAKE_VERSION VERSION_LESS "3.24")
       include(CMakeForceCompiler)
       CMAKE_FORCE_Fortran_COMPILER("${CMAKE_Fortran_COMPILER}" "LLVMFlang")
 
@@ -209,10 +217,27 @@ if ("flang-rt" IN_LIST LLVM_ENABLE_RUNTIMES OR "openmp" IN_LIST LLVM_ENABLE_RUNT
       set(CMAKE_Fortran_COMPILE_OPTIONS_PREPROCESS_OFF "-nocpp")
       set(CMAKE_Fortran_POSTPROCESS_FLAG "-ffixed-line-length-72")
 
-      set(CMAKE_Fortran_COMPILE_OPTIONS_TARGET "--target=")
-
       set(CMAKE_Fortran_LINKER_WRAPPER_FLAG "-Wl,")
       set(CMAKE_Fortran_LINKER_WRAPPER_FLAG_SEP ",")
+
+      set(CMAKE_Fortran_VERBOSE_FLAG "-v")
+
+      set(CMAKE_Fortran_LINK_MODE DRIVER)
+    endif ()
+
+    # Optimization flags are only passed after CMake 3.27
+    # https://gitlab.kitware.com/cmake/cmake/-/commit/1140087adea98bd8d8974e4c18979f4949b52c34
+    if (CMAKE_VERSION VERSION_LESS "3.27")
+      string(APPEND CMAKE_Fortran_FLAGS_DEBUG_INIT " -O0 -g")
+      string(APPEND CMAKE_Fortran_FLAGS_RELWITHDEBINFO_INIT " -O2 -g")
+      string(APPEND CMAKE_Fortran_FLAGS_RELEASE_INIT " -O3")
+    endif ()
+
+    # Only CMake 3.28+ pass --target= to Flang. But for cross-compiling, including
+    # to nvptx amd amdgpu targets, passing the target triple is essential.
+    # https://gitlab.kitware.com/cmake/cmake/-/commit/e9af7b968756e72553296ecdcde6f36606a0babf
+    if (CMAKE_VERSION VERSION_LESS "3.28")
+      set(CMAKE_Fortran_COMPILE_OPTIONS_TARGET "--target=")
     endif ()
   endif ()
 
@@ -467,6 +492,31 @@ if (RUNTIMES_FLANG_MODULES_ENABLED)
     )
 endif ()
 
+
+if (RUNTIMES_FLANG_MODULES_ENABLED)
+  set(RUNTIMES_DEVICE_ARCHITECTURES "all" CACHE STRING
+      "List of offload device architectures to be used to compile the Fortran offload code (e.g. 'gfx1103;sm_90')"
+    )
+
+  if (RUNTIMES_DEVICE_ARCHITECTURES STREQUAL "all")
+    # TODO: support auto detection on the build system.
+    set(all_amdgpu_architectures
+      "gfx700;gfx701;gfx801;gfx803;gfx900;gfx902;gfx906"
+      "gfx908;gfx90a;gfx90c;gfx940;gfx1010;gfx1030"
+      "gfx1031;gfx1032;gfx1033;gfx1034;gfx1035;gfx1036"
+      "gfx1100;gfx1101;gfx1102;gfx1103;gfx1150;gfx1151"
+      "gfx1152;gfx1153")
+    set(all_nvptx_architectures
+      "sm_35;sm_37;sm_50;sm_52;sm_53;sm_60;sm_61;sm_62"
+      "sm_70;sm_72;sm_75;sm_80;sm_86;sm_89;sm_90")
+    set(all_gpu_architectures
+      "${all_amdgpu_architectures};${all_nvptx_architectures}")
+      set(RUNTIMES_DEVICE_ARCHITECTURES ${all_gpu_architectures})
+  endif()
+  list(REMOVE_DUPLICATES RUNTIMES_DEVICE_ARCHITECTURES)
+endif ()
+
+
 option(LLVM_INCLUDE_TESTS "Generate build targets for the runtimes unit tests." ON)
 option(LLVM_INCLUDE_DOCS "Generate build targets for the runtimes documentation." ON)
 option(LLVM_ENABLE_SPHINX "Use Sphinx to generate the runtimes documentation." OFF)

>From 71290f9c1fe65248b82dc709dd91a970e20fbcbc Mon Sep 17 00:00:00 2001
From: Michael Kruse <llvm-project at meinersbur.de>
Date: Thu, 27 Nov 2025 16:45:28 +0100
Subject: [PATCH 13/15] Fix modules-only condition

---
 flang-rt/lib/runtime/CMakeLists.txt | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/flang-rt/lib/runtime/CMakeLists.txt b/flang-rt/lib/runtime/CMakeLists.txt
index 0c8db7e84d53c..548b063fd9ad4 100644
--- a/flang-rt/lib/runtime/CMakeLists.txt
+++ b/flang-rt/lib/runtime/CMakeLists.txt
@@ -215,7 +215,7 @@ else ()
   set(f128_sources "")
 endif ()
 
-if (NOT FLANG_RT_ENABLE_STATIC AND NOT FLANG_RT_ENABLE_STATIC)
+if (NOT FLANG_RT_ENABLE_STATIC AND NOT FLANG_RT_ENABLE_SHARED)
   # If not compiling the library, only build the modules.
   set(sources ${module_sources})
 elseif (LLVM_RUNTIMES_TARGET MATCHES "^amdgcn|^nvptx")

>From fcc7450ed47e88d3bfc933dc1fa8e65715035ae6 Mon Sep 17 00:00:00 2001
From: Michael Kruse <llvm-project at meinersbur.de>
Date: Fri, 28 Nov 2025 18:49:00 +0100
Subject: [PATCH 14/15] Post-merge fixes

---
 openmp/CMakeLists.txt                         |  2 +-
 .../modules/LibompCheckFortranFlag.cmake      | 29 -------------------
 openmp/module/CMakeLists.txt                  | 10 +++++++
 openmp/runtime/CMakeLists.txt                 |  2 --
 4 files changed, 11 insertions(+), 32 deletions(-)
 delete mode 100644 openmp/cmake/modules/LibompCheckFortranFlag.cmake

diff --git a/openmp/CMakeLists.txt b/openmp/CMakeLists.txt
index 3587c6b8d714e..189a85a6feaa2 100644
--- a/openmp/CMakeLists.txt
+++ b/openmp/CMakeLists.txt
@@ -128,7 +128,7 @@ if (LLVM_RUNTIMES_BUILD)
   set(LIBOMP_FORTRAN_MODULES "${RUNTIMES_FLANG_MODULES_ENABLED}" CACHE BOOL
     "Create Fortran module files? (requires fortran compiler)")
 else ()
-  set(LIBOMP_FORTRAN_MODULES OFF)
+  set(LIBOMP_FORTRAN_MODULES FALSE)
 endif ()
 
 # Set up testing infrastructure.
diff --git a/openmp/cmake/modules/LibompCheckFortranFlag.cmake b/openmp/cmake/modules/LibompCheckFortranFlag.cmake
deleted file mode 100644
index 344389f989388..0000000000000
--- a/openmp/cmake/modules/LibompCheckFortranFlag.cmake
+++ /dev/null
@@ -1,29 +0,0 @@
-#
-#//===----------------------------------------------------------------------===//
-#//
-#// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
-#// See https://llvm.org/LICENSE.txt for license information.
-#// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-#//
-#//===----------------------------------------------------------------------===//
-#
-
-# Checking a fortran compiler flag
-# There is no real trivial way to do this in CMake, so we implement it here
-# this will have ${boolean} = TRUE if the flag succeeds, otherwise false.
-function(libomp_check_fortran_flag flag boolean)
-  if(NOT DEFINED "${boolean}")
-    set(retval TRUE)
-    set(fortran_source
-"      program hello
-           print *, \"Hello World!\"
-      end program hello")
-
-    # Compiling as a part of runtimes introduces ARCH-unknown-linux-gnu as a
-    # part of a working directory.  So adding a guard for unknown.
-    set(failed_regexes "[Ee]rror;[Uu]nknown[^-];[Ss]kipping")
-    include(CheckFortranSourceCompiles)
-    check_fortran_source_compiles("${fortran_source}" ${boolean} FAIL_REGEX "${failed_regexes}")
-    set(${boolean} ${${boolean}} PARENT_SCOPE)
-  endif()
-endfunction()
diff --git a/openmp/module/CMakeLists.txt b/openmp/module/CMakeLists.txt
index b475251fcf3d6..2f54ccd18b4de 100644
--- a/openmp/module/CMakeLists.txt
+++ b/openmp/module/CMakeLists.txt
@@ -11,6 +11,7 @@
 # has been deprecated.
 
 configure_file(omp_lib.F90.var "{CMAKE_CURRENT_BINARY_DIR}/omp_lib.F90" @ONLY)
+configure_file(omp_lib.h.var "${CMAKE_CURRENT_BINARY_DIR}/../runtime/src/omp_lib.h" @ONLY)
 
 # One compilation step creates both omp_lib.mod and omp_lib_kinds.mod. Only
 # these files are used, the object file itself can be discarded.
@@ -28,3 +29,12 @@ flang_module_target(libomp-mod PUBLIC)
 if (FORTRAN_MODULE_DEPS)
   add_dependencies(libomp-mod ${FORTRAN_MODULE_DEPS})
 endif ()
+
+set(destination "${LIBOMP_HEADERS_INSTALL_PATH}")
+if (LIBOMP_MODULES_INSTALL_PATH)
+  set(destination "${LIBOMP_MODULES_INSTALL_PATH}")
+endif ()
+install(FILES
+  "${CMAKE_CURRENT_BINARY_DIR}/../runtime/src/omp_lib.h"
+  DESTINATION ${destination}
+)
diff --git a/openmp/runtime/CMakeLists.txt b/openmp/runtime/CMakeLists.txt
index 7773cbef9caed..93948b941f0dc 100644
--- a/openmp/runtime/CMakeLists.txt
+++ b/openmp/runtime/CMakeLists.txt
@@ -454,5 +454,3 @@ set(LIBOMP_OMP_TOOLS_INCLUDE_DIR ${LIBOMP_OMP_TOOLS_INCLUDE_DIR} PARENT_SCOPE)
 # make these variables available for tools/libompd:
 set(LIBOMP_SRC_DIR ${LIBOMP_SRC_DIR} PARENT_SCOPE)
 set(LIBOMP_OMPD_SUPPORT ${LIBOMP_OMPD_SUPPORT} PARENT_SCOPE)
-
-

>From 194898917152beb4220e6fec4894e63389b4ad6a Mon Sep 17 00:00:00 2001
From: Michael Kruse <llvm-project at meinersbur.de>
Date: Fri, 28 Nov 2025 20:06:25 +0100
Subject: [PATCH 15/15] Exact CMake version

---
 runtimes/CMakeLists.txt | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/runtimes/CMakeLists.txt b/runtimes/CMakeLists.txt
index 885ddd837e73c..a5bb2d975272e 100644
--- a/runtimes/CMakeLists.txt
+++ b/runtimes/CMakeLists.txt
@@ -225,9 +225,9 @@ if (CMAKE_Fortran_COMPILER AND ("flang-rt" IN_LIST LLVM_ENABLE_RUNTIMES OR "open
       set(CMAKE_Fortran_LINK_MODE DRIVER)
     endif ()
 
-    # Optimization flags are only passed after CMake 3.27
+    # Optimization flags are only passed after CMake 3.27.4
     # https://gitlab.kitware.com/cmake/cmake/-/commit/1140087adea98bd8d8974e4c18979f4949b52c34
-    if (CMAKE_VERSION VERSION_LESS "3.27")
+    if (CMAKE_VERSION VERSION_LESS "3.27.4")
       string(APPEND CMAKE_Fortran_FLAGS_DEBUG_INIT " -O0 -g")
       string(APPEND CMAKE_Fortran_FLAGS_RELWITHDEBINFO_INIT " -O2 -g")
       string(APPEND CMAKE_Fortran_FLAGS_RELEASE_INIT " -O3")



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