diff --git a/clang/lib/Driver/ToolChains/AMDGPU.cpp b/clang/lib/Driver/ToolChains/AMDGPU.cpp
index 631eb0b98df7..55c94823376b 100644
--- a/clang/lib/Driver/ToolChains/AMDGPU.cpp
+++ b/clang/lib/Driver/ToolChains/AMDGPU.cpp
@@ -846,7 +846,7 @@ void AMDGPUToolChain::addClangTargetOptions(
   // TODO: remove the SPIR-V bypass once it can encode (hidden) visibility.
   if (!DriverArgs.hasArg(options::OPT_fvisibility_EQ,
                          options::OPT_fvisibility_ms_compat) &&
-      !getEffectiveTriple().isSPIRV()) {
+      !getEffectiveTriple().isSPIRV() && !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 9211803aa6a2..98be4861276f 100644
--- a/clang/lib/Driver/ToolChains/HIPAMD.cpp
+++ b/clang/lib/Driver/ToolChains/HIPAMD.cpp
@@ -261,7 +261,7 @@ void HIPAMDToolChain::addClangTargetOptions(
   // TODO: remove the SPIR-V bypass once it can encode (hidden) visibility.
   if (!DriverArgs.hasArg(options::OPT_fvisibility_EQ,
                          options::OPT_fvisibility_ms_compat) &&
-      !getEffectiveTriple().isSPIRV()) {
+      !getEffectiveTriple().isSPIRV() && !getDriver().IsFlangMode()) {
     CC1Args.append({"-fvisibility=hidden"});
     CC1Args.push_back("-fapply-global-visibility-to-externs");
   }
diff --git a/flang-rt/CMakeLists.txt b/flang-rt/CMakeLists.txt
index ab905cd46655..0d9696e32725 100644
--- a/flang-rt/CMakeLists.txt
+++ b/flang-rt/CMakeLists.txt
@@ -69,6 +69,7 @@ include(GetToolchainDirs)
 include(FlangCommon)
 include(HandleCompilerRT)
 include(ExtendPath)
+include(FlangRTIntrospection)
 
 
 ############################
@@ -112,6 +113,11 @@ else ()
   option(FLANG_RT_ENABLE_SHARED "Build Flang-RT as a shared library." OFF)
 endif ()
 
+# Enable building Fortran modules if Fortran is enabled
+option(FLANG_RT_FORTRAN_MODULES "Build Flang-RT modules" "${RUNTIMES_FORTRAN_MODULES}")
+if (NOT FLANG_RT_ENABLE_STATIC AND NOT FLANG_RT_ENABLE_SHARED AND NOT FLANG_RT_FORTRAN_MODULES)
+  message(WARNING "LLVM_ENABLE_RUNTIMES=flang-rt, but not building anything")
+endif ()
 
 # TODO: Support tests for the GPU target.
 set(FLANG_RT_INCLUDE_TESTS_default ${LLVM_INCLUDE_TESTS})
@@ -181,6 +187,10 @@ 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)
@@ -194,7 +204,7 @@ if (UNIX AND CMAKE_SYSTEM_NAME MATCHES "AIX")
 endif ()
 
 # Indicates REAL(16) support via an external library (e.g. libquadmath).
-add_compile_definitions(FLANG_RT_SUPPORTS_REAL16=$<BOOL:${FLANG_RUNTIME_F128_MATH_LIB}>)
+add_compile_definitions(FLANG_RT_SUPPORTS_REAL16=$<BOOL:${FORTRAN_SUPPORTS_REAL16}>)
 
 # Check whether the compiler can undefine a macro using the "-Wp,-U" flag.
 # Aternatively, we could use
diff --git a/flang-rt/cmake/modules/AddFlangRT.cmake b/flang-rt/cmake/modules/AddFlangRT.cmake
index 871524b47e0e..265725ddec3d 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
@@ -172,14 +176,18 @@ 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}")
@@ -194,6 +202,15 @@ function (add_flangrt_library name)
     endif ()
   endif ()
 
+  # An alias for the target that compiles the sources. When building a shared
+  # and static library at the same time, the sources are compiled in an object
+  # library, so there can be only one.
+  # Can be used to introspect and change the real target's properties, like:
+  #
+  # get_target_property(compile_target ${name}.compile ALIASED_TARGET)
+  # target_sources(${compile_target} more_sources.c)
+  add_library(${name}.compile ALIAS "${srctargets}")
+
   foreach (tgtname IN LISTS libtargets)
     if (NOT WIN32)
       # Use same stem name for .a and .so. Common in UNIX environments.
@@ -223,6 +240,16 @@ 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)
 
+    if (CMAKE_Fortran_COMPILER_ID MATCHES "LLVM")
+      target_compile_options(${tgtname} PRIVATE
+        # Always enable preprocessor regardless of file extension
+        "$<$<COMPILE_LANGUAGE:Fortran>:-cpp>"
+
+        # Missing type descriptors are expected for intrinsic modules
+        "$<$<COMPILE_LANGUAGE:Fortran>:SHELL:-mmlir;SHELL:-ignore-missing-type-desc>"
+      )
+    endif ()
+
     # When building the flang runtime if LTO is enabled the archive file
     # contains LLVM IR rather than object code. Currently flang is not
     # LTO aware so cannot link this file to compiled Fortran code.
@@ -230,6 +257,10 @@ function (add_flangrt_library name)
       target_compile_options(${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
diff --git a/flang-rt/cmake/modules/FlangRTIntrospection.cmake b/flang-rt/cmake/modules/FlangRTIntrospection.cmake
new file mode 100644
index 000000000000..6ffa41e08cd7
--- /dev/null
+++ b/flang-rt/cmake/modules/FlangRTIntrospection.cmake
@@ -0,0 +1,30 @@
+include(CMakePushCheckState)
+include(CheckFortranSourceCompiles)
+
+# 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.
+#
+#  * 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")
+  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/CMakeLists.txt b/flang-rt/lib/CMakeLists.txt
index 8738ae7b9c4b..58a7a24c19e0 100644
--- a/flang-rt/lib/CMakeLists.txt
+++ b/flang-rt/lib/CMakeLists.txt
@@ -12,7 +12,7 @@ if (FLANG_RT_ENABLE_STATIC OR FLANG_RT_ENABLE_SHARED)
   if (FLANG_RT_INCLUDE_CUF)
     add_subdirectory(cuda)
   endif()
-else ()
+elseif (FLANG_RT_FORTRAN_MODULES)
   # Generate modules files only, skip the libraries
   add_subdirectory(runtime)
 endif ()
diff --git a/flang-rt/lib/runtime/CMakeLists.txt b/flang-rt/lib/runtime/CMakeLists.txt
index f596bbed6f47..20aa3effeec9 100644
--- a/flang-rt/lib/runtime/CMakeLists.txt
+++ b/flang-rt/lib/runtime/CMakeLists.txt
@@ -12,6 +12,30 @@ 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
+)
+
+# Fortran sources for builtin .mod files
+set(module_sources
+  __fortran_ieee_exceptions.f90
+  __fortran_type_info.f90
+  flang_debug.f90
+  iso_fortran_env.f90
+  iso_fortran_env_impl.f90
+  ieee_arithmetic.f90
+  ieee_exceptions.f90
+  ieee_features.f90
+  iso_c_binding.f90
+
+  __cuda_device.f90
+  cooperative_groups.f90
+  cuda_runtime_api.f90
+  cudadevice.f90
+)
+
 # List of files that are buildable for all devices.
 set(supported_sources
   ${FLANG_SOURCE_DIR}/lib/Decimal/binary-to-decimal.cpp
@@ -190,6 +214,25 @@ file(GLOB_RECURSE private_headers
   "${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
+    cuda_runtime_api.f90
+    cudadevice.f90
+  APPEND PROPERTY
+    COMPILE_OPTIONS --offload-host-only -xcuda
+)
 
 # Import changes from flang_rt.quadmath
 set(f128_sources "")
@@ -220,6 +263,56 @@ if (TARGET FortranFloat128MathILib)
   endif ()
 endif ()
 
+
+# When a target depends on an object library, CMake seems to try to only build
+# the object files that the target actual needs. If we are only interested
+# in the module files, nothing get is built at all. To ensure that the module
+# files are built, insert a custom target that is opaque to CMake so it cannot
+# apply this optimization. Dependees on module files must depend on this
+# barrier instead. An actual COMMAND (that does nothing) seems to be necessary
+# on Windows to work.
+function (add_module_barrier barriername objlib)
+  add_custom_target(${barriername}
+    COMMAND ${CMAKE_COMMAND} -E true
+  )
+  add_dependencies(${barriername} ${objlib})
+endfunction ()
+
+
+# Build module files if requested.
+# The object files written by Flang for these are unused. In the future parts
+# of flang-rt may itself be implemented in Fortran in which case these Fortran
+# sources need to be added to ${sources} to be included in
+# libflang_rt.runtime{.a/.so}. If they also provide an importable .mod, add them
+# to flang_module_target(... PUBLIC).
+if (FLANG_RT_FORTRAN_MODULES)
+  # 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.mod.intrinsics OBJECT
+    ${intrinsics_sources}
+  )
+  flang_module_target(flang_rt.mod.intrinsics PUBLIC)
+  add_module_barrier(flang_rt.mod.intrinsics.barrier flang_rt.mod.intrinsics)
+
+  # The modules themselves
+  add_flangrt_library(flang_rt.mod OBJECT
+    ${module_sources}
+  )
+  add_dependencies(flang_rt.mod flang_rt.mod.intrinsics.barrier)
+  flang_module_target(flang_rt.mod PUBLIC)
+  add_module_barrier(flang-rt-mod flang_rt.mod)
+endif ()
+
+
+# Skip building libraries if not requested
+if (NOT FLANG_RT_ENABLE_STATIC AND NOT FLANG_RT_ENABLE_SHARED)
+  return ()
+endif ()
+
 if ("${LLVM_DEFAULT_TARGET_TRIPLE}" MATCHES "^amdgcn|^nvptx")
   set(sources ${gpu_sources})
 elseif(FLANG_RT_EXPERIMENTAL_OFFLOAD_SUPPORT STREQUAL "CUDA")
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 c63c0f03214f..4f9874a9bef2 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 98%
rename from flang/module/__fortran_ieee_exceptions.f90
rename to flang-rt/lib/runtime/__fortran_ieee_exceptions.f90
index 3ac9b993186a..ff5c6b44317f 100644
--- a/flang/module/__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/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 8bb4af3afa79..5ca0c3aa1f3a 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/cuda_runtime_api.f90 b/flang-rt/lib/runtime/cuda_runtime_api.f90
similarity index 100%
rename from flang/module/cuda_runtime_api.f90
rename to flang-rt/lib/runtime/cuda_runtime_api.f90
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/flang_debug.f90 b/flang-rt/lib/runtime/flang_debug.f90
similarity index 100%
rename from flang/module/flang_debug.f90
rename to flang-rt/lib/runtime/flang_debug.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 4e938a2daaa9..02cfae2dc6b1 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 98%
rename from flang/module/iso_fortran_env.f90
rename to flang-rt/lib/runtime/iso_fortran_env.f90
index 3729b95a339f..2dc38bd1acfe 100644
--- a/flang/module/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
 
diff --git a/flang-rt/lib/runtime/iso_fortran_env_impl.cpp b/flang-rt/lib/runtime/iso_fortran_env_impl.cpp
index 144662f1262a..70230d0f16c7 100644
--- a/flang-rt/lib/runtime/iso_fortran_env_impl.cpp
+++ b/flang-rt/lib/runtime/iso_fortran_env_impl.cpp
@@ -109,15 +109,15 @@ static constexpr std::int32_t selectedBfloat16{3};
 static constexpr std::int32_t selectedReal32{4};
 static constexpr std::int32_t selectedReal64{8};
 
-#if HAS_FLOAT80
-static constexpr std::int32_t selectedReal80{10};
-#elif HAS_LDBL128 || FLANG_RT_SUPPORTS_REAL16
+#if FLANG_RT_SUPPORTS_REAL16
 static constexpr std::int32_t selectedReal80{16};
+#elif HAS_FLOAT80
+static constexpr std::int32_t selectedReal80{10};
 #else
 static constexpr std::int32_t selectedReal80{-3};
 #endif
 
-#if HAS_LDBL128 || FLANG_RT_SUPPORTS_REAL16
+#if FLANG_RT_SUPPORTS_REAL16
 static constexpr std::int32_t selectedReal64x2{16};
 static constexpr std::int32_t selectedReal128{16};
 #elif HAS_FLOAT80
@@ -245,7 +245,7 @@ extern const std::int32_t FORTRAN_NAMED_CONST(__builtin_real_kinds)[]{
 #if HAS_FLOAT80
     10,
 #endif
-#if HAS_LDBL128 || FLANG_RT_SUPPORTS_REAL16
+#if FLANG_RT_SUPPORTS_REAL16
     16,
 #endif
 };
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/CMakeLists.txt b/flang-rt/test/CMakeLists.txt
index 054798d6ff53..1cf6269686bb 100644
--- a/flang-rt/test/CMakeLists.txt
+++ b/flang-rt/test/CMakeLists.txt
@@ -10,10 +10,12 @@
 # for use by Lit, and delegates to LLVM's lit test handlers.
 
 llvm_canonicalize_cmake_booleans(
+  FLANG_RT_FORTRAN_MODULES
   FLANG_STANDALONE_BUILD
   LLVM_BUILD_EXAMPLES
   LLVM_BYE_LINK_INTO_TOOLS
   LLVM_ENABLE_PLUGINS
+  LLVM_TREE_AVAILABLE
 )
 
 configure_lit_site_cfg(
diff --git a/flang-rt/test/Driver/compare_iso_fortran_env_symbols.f90 b/flang-rt/test/Driver/compare_iso_fortran_env_symbols.f90
index 8fbc1091f0e6..8e17fe4e8891 100644
--- a/flang-rt/test/Driver/compare_iso_fortran_env_symbols.f90
+++ b/flang-rt/test/Driver/compare_iso_fortran_env_symbols.f90
@@ -1,6 +1,7 @@
 ! UNSUPPORTED: offload-cuda, system-windows
+! REQUIRES: fortran-modules
 
-! RUN: %flang -c -funsigned %include/../module/iso_fortran_env_impl.f90 -o %t.f90.o
+! RUN: %flang -c -funsigned %S/../../lib/runtime/iso_fortran_env_impl.f90 -o %t.f90.o
 
 ! Extract defined symbol names and sizes from the Fortran object and the
 ! already-built runtime library (which was compiled with the correct CMake flags).
diff --git a/flang-rt/test/Driver/iso_fortran_env_impl.f90 b/flang-rt/test/Driver/iso_fortran_env_impl.f90
index f9dac6f0a20b..d856a9595ec4 100644
--- a/flang-rt/test/Driver/iso_fortran_env_impl.f90
+++ b/flang-rt/test/Driver/iso_fortran_env_impl.f90
@@ -2,6 +2,8 @@
 ! (iso_fortran_env_impl.cpp) match the Fortran module definitions.
 
 ! UNSUPPORTED: offload-cuda
+! REQUIRES: fortran-modules
+
 ! RUN: %flang %isysroot -L"%libdir" %s -o %t
 ! RUN: env LD_LIBRARY_PATH="$LD_LIBRARY_PATH:%libdir" %t | FileCheck %s
 
diff --git a/flang-rt/test/lit.cfg.py b/flang-rt/test/lit.cfg.py
index 067ca5e5f114..5769943285a5 100644
--- a/flang-rt/test/lit.cfg.py
+++ b/flang-rt/test/lit.cfg.py
@@ -78,10 +78,17 @@ if config.osx_sysroot:
     isysroot_flag = ["-isysroot", config.osx_sysroot]
 config.substitutions.append(("%isysroot", " ".join(isysroot_flag)))
 
+flang_args = []
+if not config.llvm_tree_available:
+    flang_args.append(
+        f"-fintrinsic-modules-path={config.flang_rt_output_resource_mod_dir}"
+    )
+
 tools = [
     ToolSubst(
         "%flang",
         command=config.flang,
+        extra_args=flang_args,
         unresolved="fatal",
     ),
     ToolSubst(
@@ -107,3 +114,6 @@ config.substitutions.append(("%libdir", config.flang_rt_output_resource_lib_dir)
 # For CUDA offloading, additional steps (device linking) and libraries (cudart) are needed.
 if config.flang_rt_experimental_offload_support == "CUDA":
     config.available_features.add("offload-cuda")
+
+if config.flang_rt_fortran_modules:
+    config.available_features.add("fortran-modules")
diff --git a/flang-rt/test/lit.site.cfg.py.in b/flang-rt/test/lit.site.cfg.py.in
index db7132b73192..8e3c902d4a3a 100644
--- a/flang-rt/test/lit.site.cfg.py.in
+++ b/flang-rt/test/lit.site.cfg.py.in
@@ -3,11 +3,14 @@
 import sys
 
 config.llvm_tools_dir = "@LLVM_TOOLS_DIR@"
+config.llvm_tree_available = @LLVM_TREE_AVAILABLE@
 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 = "@RUNTIMES_OUTPUT_RESOURCE_LIB_DIR@"
+config.flang_rt_output_resource_mod_dir = "@RUNTIMES_OUTPUT_RESOURCE_MOD_DIR@"
 config.flang_rt_experimental_offload_support = "@FLANG_RT_EXPERIMENTAL_OFFLOAD_SUPPORT@"
+config.flang_rt_fortran_modules = @FLANG_RT_FORTRAN_MODULES@
 config.cc = "@CMAKE_C_COMPILER@"
 config.flang = "@CMAKE_Fortran_COMPILER@"
 config.osx_sysroot = path(r"@CMAKE_OSX_SYSROOT@")
diff --git a/flang/CMakeLists.txt b/flang/CMakeLists.txt
index be0b1f3d9b27..a8bd5e266aef 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/lib/Semantics/semantics.cpp b/flang/lib/Semantics/semantics.cpp
index 8bca853f01a2..cde714c584d9 100644
--- a/flang/lib/Semantics/semantics.cpp
+++ b/flang/lib/Semantics/semantics.cpp
@@ -660,12 +660,15 @@ 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 e3845288a2ae..000000000000
--- 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 d3da00c755cf..f1b492ee6cdc 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_BYE_LINK_INTO_TOOLS
   LLVM_ENABLE_PLUGINS
   LLVM_INCLUDE_EXAMPLES
+  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_INCLUDE_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/resource_dir_with_per_target_subdir/finclude/flang/x86_64-unknown-linux-gnu/.keep b/flang/test/Driver/Inputs/resource_dir_with_per_target_subdir/finclude/flang/x86_64-unknown-linux-gnu/.keep
deleted file mode 100644
index e69de29bb2d1..000000000000
diff --git a/flang/test/Driver/intrinsic-module-path_per_target.f90 b/flang/test/Driver/intrinsic-module-path_per_target.f90
index c32ff0c3185c..b0a2ac9c7c6b 100644
--- a/flang/test/Driver/intrinsic-module-path_per_target.f90
+++ b/flang/test/Driver/intrinsic-module-path_per_target.f90
@@ -1,5 +1,4 @@
 ! Ensure argument -fintrinsic-modules-path works as expected.
-! REQUIRES: x86-registered-target
 
 !-----------------------------------------
 ! FLANG DRIVER
@@ -8,15 +7,15 @@
 !       or lower priority than -fintrinsic-modules-path added here. Using
 !       basictestmoduleone.mod from Inputs/module-dir/ will trigger an error.
 
-! RUN:     %flang -fsyntax-only --target=x86_64-unknown-linux-gnu -resource-dir %S/Inputs/resource_dir_with_per_target_subdir %s -### 2>&1 | FileCheck %s --check-prefix=DEFAULTPATH
+! RUN:     %flang -fsyntax-only %s -### 2>&1 | FileCheck %s --check-prefix=DEFAULTPATH
 
-! RUN:     %flang -fsyntax-only --target=x86_64-unknown-linux-gnu -resource-dir %S/Inputs/resource_dir_with_per_target_subdir %s -cpp -DINTRINSICS_DEFAULT
-! RUN: not %flang -fsyntax-only --target=x86_64-unknown-linux-gnu -resource-dir %S/Inputs/resource_dir_with_per_target_subdir %s -cpp -DINTRINSICS_INPUTONE 2>&1 | FileCheck %s --check-prefix=NOINPUTONE
-! RUN: not %flang -fsyntax-only --target=x86_64-unknown-linux-gnu -resource-dir %S/Inputs/resource_dir_with_per_target_subdir %s -cpp -DINTRINSICS_INPUTTWO 2>&1 | FileCheck %s --check-prefix=NOINPUTTWO
-! RUN:     %flang -fsyntax-only --target=x86_64-unknown-linux-gnu -resource-dir %S/Inputs/resource_dir_with_per_target_subdir %s -cpp -DINTRINSICS_DEFAULT -DINTRINSICS_INPUTTWO -fintrinsic-modules-path=%S/Inputs/module-dir/
-! RUN:     %flang -fsyntax-only --target=x86_64-unknown-linux-gnu -resource-dir %S/Inputs/resource_dir_with_per_target_subdir %s -cpp -DINTRINSICS_INPUTONE -fintrinsic-modules-path=%S/Inputs/module-dir-one/
-! RUN:     %flang -fsyntax-only --target=x86_64-unknown-linux-gnu -resource-dir %S/Inputs/resource_dir_with_per_target_subdir %s -cpp -DINTRINSICS_INPUTONE -DINTRINSICS_INPUTTWO -fintrinsic-modules-path=%S/Inputs/module-dir-one/ -fintrinsic-modules-path=%S/Inputs/module-dir/
-! RUN: not %flang -fsyntax-only --target=x86_64-unknown-linux-gnu -resource-dir %S/Inputs/resource_dir_with_per_target_subdir %s -cpp -DINTRINSICS_INPUTONE -DINTRINSICS_INPUTTWO -fintrinsic-modules-path=%S/Inputs/module-dir/ -fintrinsic-modules-path=%S/Inputs/module-dir-one/ 2>&1 | FileCheck %s --check-prefix=WRONGINPUTONE
+! RUN:     %flang -fsyntax-only %s -cpp -DINTRINSICS_DEFAULT
+! RUN: not %flang -fsyntax-only %s -cpp -DINTRINSICS_INPUTONE 2>&1 | FileCheck %s --check-prefix=NOINPUTONE
+! RUN: not %flang -fsyntax-only %s -cpp -DINTRINSICS_INPUTTWO 2>&1 | FileCheck %s --check-prefix=NOINPUTTWO
+! RUN:     %flang -fsyntax-only %s -cpp -DINTRINSICS_DEFAULT -DINTRINSICS_INPUTTWO -fintrinsic-modules-path=%S/Inputs/module-dir/
+! RUN:     %flang -fsyntax-only %s -cpp -DINTRINSICS_INPUTONE -fintrinsic-modules-path=%S/Inputs/module-dir-one/
+! RUN:     %flang -fsyntax-only %s -cpp -DINTRINSICS_INPUTONE -DINTRINSICS_INPUTTWO -fintrinsic-modules-path=%S/Inputs/module-dir-one/ -fintrinsic-modules-path=%S/Inputs/module-dir/
+! RUN: not %flang -fsyntax-only %s -cpp -DINTRINSICS_INPUTONE -DINTRINSICS_INPUTTWO -fintrinsic-modules-path=%S/Inputs/module-dir/ -fintrinsic-modules-path=%S/Inputs/module-dir-one/ 2>&1 | FileCheck %s --check-prefix=WRONGINPUTONE
 
 
 !-----------------------------------------
@@ -42,8 +41,8 @@
 
 !-----------------------------------------
 
-! DEFAULTPATH:      -fc1
-! DEFAULTPATH-SAME: -fintrinsic-modules-path" "{{.*(\\\\|/)}}resource_dir_with_per_target_subdir{{(\\\\|/)}}finclude{{(\\\\|/)}}flang{{(\\\\|/)}}x86_64-unknown-linux-gnu"
+! DEFAULTPATH:      "-fc1"
+! DEFAULTPATH-SAME: "-fintrinsic-modules-path" "{{.*(\\\\|/)}}finclude{{(\\\\|/)}}flang{{(\\\\|/)}}{{[^/\]+}}"
 
 ! NOINPUTONE: Source file 'basictestmoduleone.mod' was not found
 ! NOINPUTTWO: Source file 'basictestmoduletwo.mod' was not found
diff --git a/flang/test/Driver/pp-fixed-form.f90 b/flang/test/Driver/pp-fixed-form.f90
index bb869cd3341a..bdeb80497c31 100644
--- a/flang/test/Driver/pp-fixed-form.f90
+++ b/flang/test/Driver/pp-fixed-form.f90
@@ -8,12 +8,12 @@ FIXED-NEXT: "-fc1" {{.*}} "-ffixed-form" {{.*}} "-x" "f95-cpp-input" "fixed-form
 
 !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/OpenMP/simd_aarch64.f90 b/flang/test/Lower/OpenMP/simd_aarch64.f90
index 735237223bcb..20dd50d3ac91 100644
--- a/flang/test/Lower/OpenMP/simd_aarch64.f90
+++ b/flang/test/Lower/OpenMP/simd_aarch64.f90
@@ -1,6 +1,10 @@
-! 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
+! REQUIRES: aarch64-host
+
 ! 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 d3f287addc2e..1bd49333b306 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/Lower/where-loc.f90 b/flang/test/Lower/where-loc.f90
index 75d1452da9df..033a6fc74c86 100644
--- a/flang/test/Lower/where-loc.f90
+++ b/flang/test/Lower/where-loc.f90
@@ -1,5 +1,5 @@
 ! Test line location lowering of WHERE statements.
-! RUN: %flang -fc1 -emit-hlfir -mmlir -mlir-print-debuginfo -mmlir --mlir-print-local-scope -o - %s | FileCheck %s
+! RUN: %flang_fc1 -emit-hlfir -mmlir -mlir-print-debuginfo -mmlir --mlir-print-local-scope -o - %s | FileCheck %s
 
 ! CHECK-LABEL: func.func @_QPtest_where_construct
 subroutine test_where_construct(mask, m2, x, y)
diff --git a/flang/test/Parser/bug2280.f90 b/flang/test/Parser/bug2280.f90
index d24b26ddeb0d..2de644e159bd 100644
--- a/flang/test/Parser/bug2280.f90
+++ b/flang/test/Parser/bug2280.f90
@@ -1,4 +1,4 @@
-!RUN: %flang -fc1 -fdebug-unparse %s | FileCheck %s
+!RUN: %flang_fc1 -fdebug-unparse %s | FileCheck %s
 !CHECK: 1 FORMAT(1X)
 1 format(1x)
 !CHECK: 2 FORMAT(1X)
diff --git a/flang/test/Preprocessing/fixed-free.f b/flang/test/Preprocessing/fixed-free.f
index 95f63a4d71e4..7140bc6aec36 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 3e49df3deb25..ab08a4f838a9 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 5e020aeb4dc0..3c0a2b6b3222 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 c356c0739257..39af27e91424 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/Semantics/bug2021.f90 b/flang/test/Semantics/bug2021.f90
index f5214bce946a..4d914f34e9a5 100644
--- a/flang/test/Semantics/bug2021.f90
+++ b/flang/test/Semantics/bug2021.f90
@@ -1,4 +1,4 @@
-!RUN: %flang -fc1 -fsyntax-only -pedantic %s 2>&1 | FileCheck %s
+!RUN: %flang_fc1 -fsyntax-only -pedantic %s 2>&1 | FileCheck %s
 !CHECK-NOT: warning: Value of uninitialized local variable 'b' is used but never defined [-Wused-undefined-variable]
 real :: a, b
 pointer(p,a)
diff --git a/flang/test/lit.cfg.py b/flang/test/lit.cfg.py
index 3a87f9ea0680..92278a220cec 100644
--- a/flang/test/lit.cfg.py
+++ b/flang/test/lit.cfg.py
@@ -140,18 +140,92 @@ config.substitutions.append(("%isysroot", " ".join(isysroot_flag)))
 if config.default_sysroot:
     config.available_features.add("default_sysroot")
 
+host_triple = config.host_triple.split("-")
+config.available_features.add(f"{host_triple[0]}-host")
+
+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: In a bootstrapping build, openmp should write this file into a
+    #        shared 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",
     ),
 ]
@@ -194,16 +268,7 @@ result = lit_config.params.get("LIBPGMATH")
 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 2b66dd64b8c1..74c3e07e0a40 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_INCLUDE_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 1d2d2c608faf..1b297af74cae 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/f18/CMakeLists.txt b/flang/tools/f18/CMakeLists.txt
deleted file mode 100644
index 900b341e85c5..000000000000
--- a/flang/tools/f18/CMakeLists.txt
+++ /dev/null
@@ -1,160 +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"
-  "cuda_runtime_api"
-  "cudadevice"
-  "ieee_arithmetic"
-  "ieee_exceptions"
-  "ieee_features"
-  "iso_c_binding"
-  "iso_fortran_env"
-  "iso_fortran_env_impl"
-  "flang_debug"
-)
-
-# 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" OR
-           ${filename} STREQUAL "cuda_runtime_api")
-      set(opts -fc1 -xcuda)
-      if(${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 ("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_custom_target(flang-module-interfaces ALL DEPENDS module_files)
-  add_llvm_install_targets(install-flang-module-interfaces
-    COMPONENT flang-module-interfaces)
-  add_dependencies(install-flang-module-interfaces 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 ("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 f11b5aedf4c6..000000000000
--- 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 0905f09c8b79..686089efa963 100644
--- a/llvm/runtimes/CMakeLists.txt
+++ b/llvm/runtimes/CMakeLists.txt
@@ -287,6 +287,10 @@ function(runtime_default_target)
       endif ()
     endif ()
   endif ()
+  if ("flang-rt" IN_LIST LLVM_ENABLE_RUNTIMES)
+    # The target flang-rt-mod is a dependee of check-flang.
+    list(APPEND extra_targets "flang-rt-mod")
+  endif ()
 
   if(LLVM_INCLUDE_TESTS)
     set_property(GLOBAL APPEND PROPERTY LLVM_ALL_LIT_TESTSUITES "@${LLVM_BINARY_DIR}/runtimes/runtimes-bins/lit.tests")
@@ -581,22 +585,7 @@ if(build_runtimes)
       endif()
     endforeach()
   endif()
-  # Allow openmp to see the Fortran compiler
-  if ("openmp" IN_LIST LLVM_ENABLE_RUNTIMES AND "flang" IN_LIST LLVM_ENABLE_PROJECTS)
-    list(APPEND extra_args ENABLE_FORTRAN)
-  endif()
   if("openmp" IN_LIST LLVM_ENABLE_RUNTIMES OR "offload" IN_LIST LLVM_ENABLE_RUNTIMES)
-    if (${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")
-    endif()
     foreach(dep opt llvm-link llvm-extract clang llvm-offload-binary clang-nvlink-wrapper)
       if(TARGET ${dep})
         list(APPEND extra_deps ${dep})
@@ -621,12 +610,18 @@ if(build_runtimes)
   if(LLVM_LIBC_FULL_BUILD)
     list(APPEND extra_cmake_args "-DLLVM_LIBC_FULL_BUILD=ON")
   endif()
-  if("flang-rt" IN_LIST LLVM_ENABLE_RUNTIMES)
-    list(APPEND extra_args ENABLE_FORTRAN)
-    if (${LLVM_TOOL_FLANG_BUILD})
-      list(APPEND extra_deps "flang" "module_files")
+  if("flang" IN_LIST LLVM_ENABLE_PROJECTS)
+    # Allow runtimes that can use it to access the Flang compiler
+    if ("openmp" IN_LIST LLVM_ENABLE_RUNTIMES OR "flang-rt" IN_LIST LLVM_ENABLE_RUNTIMES)
+      list(APPEND extra_args ENABLE_FORTRAN)
     endif()
-  endif ()
+    # 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=1")
+    else()
+      list(APPEND extra_cmake_args "-DFORTRAN_SUPPORTS_REAL16=0")
+    endif()
+  endif()
 
   if(NOT LLVM_RUNTIME_TARGETS)
     runtime_default_target(
diff --git a/openmp/CMakeLists.txt b/openmp/CMakeLists.txt
index 512bd41f8a9e..08546dfaf249 100644
--- a/openmp/CMakeLists.txt
+++ b/openmp/CMakeLists.txt
@@ -106,7 +106,7 @@ math(EXPR LIBOMP_VERSION_BUILD_MONTH_DAY "${LIBOMP_VERSION_BUILD}%10000")
 set(LIBOMP_BUILD_DATE "No_Timestamp")
 
 
-set(LIBOMP_FORTRAN_MODULES FALSE CACHE BOOL
+set(LIBOMP_FORTRAN_MODULES "${RUNTIMES_FORTRAN_MODULES}" CACHE BOOL
   "Create Fortran module files? (requires fortran compiler)")
 
 option(LIBOMP_FORTRAN_MODULES_ONLY
@@ -122,6 +122,8 @@ 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 (e.g. additional module search paths via -fintrinsic-modules-path )")
 
 set(ENABLE_LIBOMPTARGET ON)
 # Currently libomptarget cannot be compiled on Windows or MacOS X.
@@ -158,13 +160,15 @@ add_custom_target(install-openmp-stripped
 add_dependencies(install-openmp openmp)
 add_dependencies(install-openmp-stripped openmp)
 
+if(LIBOMP_FORTRAN_MODULES)
+  add_subdirectory(module)
+endif()
+
 # Use the current compiler target to determine the appropriate runtime to build.
 if("${LLVM_DEFAULT_TARGET_TRIPLE}" MATCHES "^amdgcn|^nvptx|^spirv64" OR
    "${CMAKE_CXX_COMPILER_TARGET}" MATCHES "^amdgcn|^nvptx|^spirv64")
   add_subdirectory(device)
 else()
-  add_subdirectory(module)
-
   # Build host runtime library, after LIBOMPTARGET variables are set since they
   # are needed to enable time profiling support in the OpenMP runtime.
   if(NOT LIBOMP_FORTRAN_MODULES_ONLY)
diff --git a/openmp/cmake/modules/LibompCheckFortranFlag.cmake b/openmp/cmake/modules/LibompCheckFortranFlag.cmake
deleted file mode 100644
index 344389f98938..000000000000
--- 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/cmake/modules/LibompHandleFlags.cmake b/openmp/cmake/modules/LibompHandleFlags.cmake
index 980a62166dee..5d6558cc8ffc 100644
--- a/openmp/cmake/modules/LibompHandleFlags.cmake
+++ b/openmp/cmake/modules/LibompHandleFlags.cmake
@@ -161,17 +161,6 @@ 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/module/CMakeLists.txt b/openmp/module/CMakeLists.txt
index 9265e70dd78c..c0a873f9be55 100644
--- a/openmp/module/CMakeLists.txt
+++ b/openmp/module/CMakeLists.txt
@@ -6,87 +6,33 @@
 #//
 #//===----------------------------------------------------------------------===//
 
-include(LibompCheckFortranFlag)
+# Build the module files if a Fortran compiler is available.
 
-set(LIBOMP_FFLAGS "" CACHE STRING
-  "Appended user specified Fortran compiler flags.  These are only used if LIBOMP_FORTRAN_MODULES==TRUE.")
-
-# Enabling Fortran if it is needed
-if (LIBOMP_FORTRAN_MODULES)
-  enable_language(Fortran)
-
-  libomp_check_fortran_flag(-m32 LIBOMP_HAVE_M32_FORTRAN_FLAG)
-endif ()
-
-# Building the Fortran module files
-# One compilation step creates both omp_lib.mod and omp_lib_kinds.mod
-configure_file(omp_lib.F90.var omp_lib.F90 @ONLY)
+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)
 
-set(BUILD_FORTRAN_MODULES False)
-if (LIBOMP_FORTRAN_MODULES_COMPILER)
-  # 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 '${LIBOMP_FORTRAN_MODULES_COMPILER}'")
-  set(LIBOMP_FORTRAN_SOURCE_FILE omp_lib.F90)
-  # omp_lib_kinds uses iso_c_binding, which depends on these intrinsic modules.
-  # List them so omp_lib.mod is regenerated when intrinsic modules change; otherwise
-  # stale omp_lib.mod can reference an incompatible iso_c_binding.mod (see flang
-  # tests that load omp_lib.mod with -J).
-  set(_libomp_flang_intrinsic_mod_deps "")
-  if(LLVM_BINARY_DIR)
-    set(_flang_intrinsic_mod_dir "${LLVM_BINARY_DIR}/include/flang")
-    list(APPEND _libomp_flang_intrinsic_mod_deps
-      "${_flang_intrinsic_mod_dir}/__fortran_builtins.mod"
-      "${_flang_intrinsic_mod_dir}/__fortran_type_info.mod"
-      "${_flang_intrinsic_mod_dir}/iso_c_binding.mod"
-    )
-  endif()
-  add_custom_target(libomp-mod ALL DEPENDS "${CMAKE_CURRENT_BINARY_DIR}/../runtime/src/omp_lib.mod" "${CMAKE_CURRENT_BINARY_DIR}/../runtime/src/omp_lib_kinds.mod")
-  add_custom_command(
-    OUTPUT "${CMAKE_CURRENT_BINARY_DIR}/../runtime/src/omp_lib.mod" "${CMAKE_CURRENT_BINARY_DIR}/../runtime/src/omp_lib_kinds.mod"
-    COMMAND ${LIBOMP_FORTRAN_MODULES_COMPILER} -cpp -fsyntax-only ${LIBOMP_FORTRAN_SOURCE_FILE} "-J${CMAKE_CURRENT_BINARY_DIR}/../runtime/src"
-    DEPENDS "${CMAKE_CURRENT_BINARY_DIR}/${LIBOMP_FORTRAN_SOURCE_FILE}" ${_libomp_flang_intrinsic_mod_deps}
-  )
-  set(BUILD_FORTRAN_MODULES True)
-elseif (LIBOMP_FORTRAN_MODULES)
-  # The following requests explicit building of the Fortran module files
-  # Workaround for gfortran to build modules with the
-  # omp_sched_monotonic integer parameter
-  if (CMAKE_Fortran_COMPILER_ID STREQUAL "GNU")
-    set(ADDITIONAL_Fortran_FLAGS "-fno-range-check")
-  endif ()
-  add_custom_target(libomp-mod ALL DEPENDS "${CMAKE_CURRENT_BINARY_DIR}/../runtime/src/omp_lib.mod" "${CMAKE_CURRENT_BINARY_DIR}/../runtime/src/omp_lib_kinds.mod")
-  set_target_properties(libomp-mod PROPERTIES FOLDER "OpenMP/Misc")
-  libomp_get_fflags(LIBOMP_CONFIGURED_FFLAGS)
-  if (CMAKE_Fortran_COMPILER_SUPPORTS_F90)
-    set(LIBOMP_FORTRAN_SOURCE_FILE omp_lib.F90)
-  else ()
-    message(FATAL_ERROR "Fortran module build requires Fortran 90 compiler")
-  endif ()
-  add_custom_command(
-    OUTPUT "${CMAKE_CURRENT_BINARY_DIR}/../runtime/src/omp_lib.mod" "${CMAKE_CURRENT_BINARY_DIR}/../runtime/src/omp_lib_kinds.mod"
-    COMMAND ${CMAKE_Fortran_COMPILER} -c ${ADDITIONAL_Fortran_FLAGS}
-            ${LIBOMP_CONFIGURED_FFLAGS} ${LIBOMP_FORTRAN_SOURCE_FILE} "-J${CMAKE_CURRENT_BINARY_DIR}/../runtime/src"
-    DEPENDS "${CMAKE_CURRENT_BINARY_DIR}/${LIBOMP_FORTRAN_SOURCE_FILE}"
-  )
-  set_property(DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}/../runtime/src" PROPERTY ADDITIONAL_MAKE_CLEAN_FILES "omp_lib${CMAKE_C_OUTPUT_EXTENSION}")
-  set(BUILD_FORTRAN_MODULES True)
+# 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.
+# TODO: Adding it to libomp ($<TARGET_OBJECTS:libomp-mod>) would allow implementing Fortran API in Fortran
+add_library(libomp-mod OBJECT
+  "${CMAKE_CURRENT_BINARY_DIR}/omp_lib.F90"
+)
+set_target_properties(libomp-mod PROPERTIES FOLDER "OpenMP/Fortran Modules")
+
+# 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")
+  target_compile_options(libomp-mod PRIVATE -fno-range-check)
 endif ()
 
+flang_module_target(libomp-mod PUBLIC)
+add_dependencies(libomp-mod ${RUNTIMES_FORTRAN_BUILD_DEPS})
 
-if (BUILD_FORTRAN_MODULES)
-  set(destination "${LIBOMP_HEADERS_INSTALL_PATH}")
-  if (LIBOMP_MODULES_INSTALL_PATH)
-    set(destination "${LIBOMP_MODULES_INSTALL_PATH}")
-  endif ()
-  install(FILES
-    "${CMAKE_CURRENT_BINARY_DIR}/../runtime/src/omp_lib.mod"
-    "${CMAKE_CURRENT_BINARY_DIR}/../runtime/src/omp_lib_kinds.mod"
-    "${CMAKE_CURRENT_BINARY_DIR}/../runtime/src/omp_lib.h"
-    DESTINATION ${destination}
+install(FILES
+  "${CMAKE_CURRENT_BINARY_DIR}/../runtime/src/omp_lib.h"
+  DESTINATION ${LIBOMP_HEADERS_INSTALL_PATH}
     COMPONENT openmp
-  )
-endif ()
+)
 
 openmp_register_meta_dep(libomp-mod)
diff --git a/openmp/runtime/cmake/LibompExports.cmake b/openmp/runtime/cmake/LibompExports.cmake
index 7a0fe51d9698..805f128ebef2 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
@@ -69,8 +69,8 @@ if(LIBOMP_FORTRAN_MODULES)
   # to omp and ensure that libomp-mod is built before 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 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_dependencies(omp libomp-mod)
   add_custom_command(TARGET omp POST_BUILD
diff --git a/openmp/runtime/test/lit.cfg b/openmp/runtime/test/lit.cfg
index 4885f4e2cfbe..6a63fce1b169 100644
--- a/openmp/runtime/test/lit.cfg
+++ b/openmp/runtime/test/lit.cfg
@@ -3,6 +3,7 @@
 
 import os
 import re
+import shlex
 import subprocess
 import lit.formats
 from lit.llvm.subst import ToolSubst
@@ -51,6 +52,7 @@ if config.test_fortran_compiler:
         ToolSubst(
             "%flang",
             command=config.test_fortran_compiler,
+            extra_args=shlex.split(config.test_fortran_flags),
             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 a4d7c8d8b205..da8a12b23808 100644
--- a/openmp/runtime/test/lit.site.cfg.in
+++ b/openmp/runtime/test/lit.site.cfg.in
@@ -7,6 +7,7 @@ config.test_compiler_features = @OPENMP_TEST_COMPILER_FEATURES@
 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/cmake/config-Fortran.cmake b/runtimes/cmake/config-Fortran.cmake
index f5cea1fc67e2..74fd15021f0a 100644
--- a/runtimes/cmake/config-Fortran.cmake
+++ b/runtimes/cmake/config-Fortran.cmake
@@ -11,18 +11,18 @@
 # compiled. Contains the build targets for intrinsic modules, if necessary.
 # Otherweise, it is empty.
 #
-# RUNTIMES_ENABLE_FLANG_MODULES - Whether to build Flang modules and emit them
+# RUNTIMES_FORTRAN_MODULES - Whether to build Flang modules and emit them
 # into Flang's search path. This is a CMake CACHE option defined in
 # config-Fortran.cmake and default to ON iff the Fortran compiler is detected
 # for be a (compatible) version of Flang. In the OFF setting, modules are still
 # built, but not installed or emitted into a default path.
 #
 # RUNTIMES_OUTPUT_RESOURCE_MOD_DIR - Where to emit intrinsic module files in
-# the build directory. Most relevant when RUNTIMES_ENABLE_FLANG_MODULES is ON.
+# the build directory. Most relevant when RUNTIMES_FORTRAN_MODULES is ON.
 #
 # RUNTIMES_INSTALL_RESOURCE_MOD_PATH - Where to install intrinsic module files
 # in the install prefix. Relative to CMAKE_INSTALL_PREFIX. Only used when
-# RUNTIMES_ENABLE_FLANG_MODULES is ON.
+# RUNTIMES_FORTRAN_MODULES is ON.
 
 
 # Check whether the Fortran compiler already has access to builtin modules. Sets
@@ -180,17 +180,14 @@ endif ()
 
 
 # Check whether modules files are compatible with our version of Flang.
-set(RUNTIMES_ENABLE_FLANG_MODULES_default OFF)
-if (CMAKE_Fortran_COMPILER_ID STREQUAL "LLVMFlang")
-  set(RUNTIMES_ENABLE_FLANG_MODULES_default ON)
-else ()
-  set(RUNTIMES_ENABLE_FLANG_MODULES_default OFF)
+set(RUNTIMES_FORTRAN_MODULES_default OFF)
+if (RUNTIMES_ENABLE_FORTRAN AND CMAKE_Fortran_COMPILER_ID STREQUAL "LLVMFlang")
+  set(RUNTIMES_FORTRAN_MODULES_default ON)
 endif ()
-option(RUNTIMES_ENABLE_FLANG_MODULES "Make Fortran .mod files available to Flang; should only be enabled if compiling with a matching version of Flang" "${RUNTIMES_ENABLE_FLANG_MODULES_default}")
-
+option(RUNTIMES_FORTRAN_MODULES "Make Fortran .mod files available to Flang; should only be enabled if compiling with a matching version of Flang" "${RUNTIMES_FORTRAN_MODULES_default}")
 
 # Determine the paths for Fortran .mod files.
-if (RUNTIMES_ENABLE_FLANG_MODULES)
+if (RUNTIMES_FORTRAN_MODULES)
   # 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}")
@@ -261,7 +258,15 @@ function (flang_module_target tgtname)
         Fortran_MODULE_DIRECTORY "${RUNTIMES_OUTPUT_RESOURCE_MOD_DIR}"
     )
   else ()
-    # Keep non-public modules where CMake would put them normally;
-    # Modules of different target must not overwrite each other.
+    # Modules of different targets must not overwrite each other.
+    # Ideally, we would use $<TARGET_PROPERTY:${tgtname},BINARY_DIR> but
+    # Fortran_MODULE_DIRECTORY does not support generator expressions.
+    # Not defining Fortran_MODULE_DIRECTORY at all would but it into
+    # ${CMAKE_CURRENT_BINARY_DIR} where modules with the same name but compiled
+    # by different targets would clash.
+    set_target_properties(${tgtname}
+      PROPERTIES
+        Fortran_MODULE_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}/CMakeFiles/${tgtname}.dir/${CMAKE_CFG_INTDIR}"
+    )
   endif ()
 endfunction ()