Fix CUDA detection problem

Author: Meinersbur

flang-rt/CMakeLists.txt

@@ -31,6 +31,7 @@ list(APPEND CMAKE_MODULE_PATH
 include(AddFlangRT)
 include(GetToolchainDirs)
 include(FlangCommon)
+include(FlangRTIntrospection)
 include(HandleCompilerRT)
 include(ExtendPath)
 include(CheckFortranSourceCompiles)
@@ -154,21 +155,9 @@ check_cxx_source_compiles(
   "
   HAVE_DECL_STRERROR_S)
 
-
-# Look for support of REAL(16), if not already defined via command line.
-# NOTE: Does not work with Flang and CMake < 3.24
-cmake_push_check_state(RESET)
-set(CMAKE_REQUIRED_FLAGS "-ffree-form")
-set(CMAKE_TRY_COMPILE_TARGET_TYPE "STATIC_LIBRARY")
-check_fortran_source_compiles([[
-    subroutine test_quadmath
-      real(16) :: var1
-    end
-  ]]
-  FORTRAN_SUPPORTS_REAL16
-)
-cmake_pop_check_state()
-
+# 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)

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 ()