[flang-rt] Remove hard-coded dependency on compiler-rt path on Windows (#150244)

This fixes an issue where if the build folder is no longer present flang cannot link anything on Windows because the path to compiler-rt in the binary is hard-coded. Flang already links compiler-rt on Windows so it isn't necessary for flang-rt to specify that it depends on compiler-rt at all, other than for the unit tests, so instead we can move that logic into the unit test compile lines.

Author: DavidTruby

flang-rt/cmake/modules/AddFlangRT.cmake

@@ -286,27 +286,6 @@ function (add_flangrt_library name)
  target_compile_options(${tgtname} PUBLIC -U_LIBCPP_ENABLE_ASSERTIONS)
  endif ()
 
- # Flang/Clang (including clang-cl) -compiled programs targeting the MSVC ABI
- # should only depend on msvcrt/ucrt. LLVM still emits libgcc/compiler-rt
- # functions in some cases like 128-bit integer math (__udivti3, __modti3,
- # __fixsfti, __floattidf, ...) that msvc does not support. We are injecting a
- # dependency to Compiler-RT's builtin library where these are implemented.
- if (MSVC AND CMAKE_CXX_COMPILER_ID MATCHES "Clang")
- if (FLANG_RT_BUILTINS_LIBRARY)
- target_compile_options(${tgtname} PRIVATE "$<$<COMPILE_LANGUAGE:CXX,C>:-Xclang>" "$<$<COMPILE_LANGUAGE:CXX,C>:--dependent-lib=${FLANG_RT_BUILTINS_LIBRARY}>")
- endif ()
- endif ()
- if (MSVC AND CMAKE_Fortran_COMPILER_ID STREQUAL "LLVMFlang")
- if (FLANG_RT_BUILTINS_LIBRARY)
- target_compile_options(${tgtname} PRIVATE "$<$<COMPILE_LANGUAGE:Fortran>:-Xflang>" "$<$<COMPILE_LANGUAGE:Fortran>:--dependent-lib=${FLANG_RT_BUILTINS_LIBRARY}>")
- else ()
- message(WARNING "Did not find libclang_rt.builtins.lib.
- LLVM may emit builtins that are not implemented in msvcrt/ucrt and
- instead falls back to builtins from Compiler-RT. Linking with ${tgtname}
- may result in a linker error.")
- endif ()
- endif ()
-
  # Non-GTest unittests depend on LLVMSupport
  if (ARG_LINK_TO_LLVM)
  if (LLVM_LINK_LLVM_DYLIB)

flang-rt/unittests/CMakeLists.txt

@@ -60,6 +60,27 @@ function(add_flangrt_unittest_offload_properties target)
  endif()
 endfunction()
 
+# flang-rt on Windows requires compiler-rt for some symbols. For binaries built
+# with flang this dependency is added by the flang driver, but since the unit
+# tests are built with clang we need to add the dependency manually.
+function(add_flangrt_dependent_libs target)
+ if (MSVC AND CMAKE_CXX_COMPILER_ID MATCHES "Clang")
+ if (FLANG_RT_BUILTINS_LIBRARY)
+ target_compile_options(${target} PRIVATE "$<$<COMPILE_LANGUAGE:CXX,C>:-Xclang>" "$<$<COMPILE_LANGUAGE:CXX,C>:--dependent-lib=${FLANG_RT_BUILTINS_LIBRARY}>")
+ endif ()
+ endif ()
+ if (MSVC AND CMAKE_Fortran_COMPILER_ID STREQUAL "LLVMFlang")
+ if (FLANG_RT_BUILTINS_LIBRARY)
+ target_compile_options(${target} PRIVATE "$<$<COMPILE_LANGUAGE:Fortran>:-Xflang>" "$<$<COMPILE_LANGUAGE:Fortran>:--dependent-lib=${FLANG_RT_BUILTINS_LIBRARY}>")
+ else ()
+ message(WARNING "Did not find libclang_rt.builtins.lib.
+ LLVM may emit builtins that are not implemented in msvcrt/ucrt and
+ instead falls back to builtins from Compiler-RT. Linking with ${tgtname}
+ may result in a linker error.")
+ endif ()
+ endif ()
+endfunction()
+
 
 function(add_flangrt_unittest test_dirname)
  cmake_parse_arguments(ARG
@@ -72,6 +93,7 @@ function(add_flangrt_unittest test_dirname)
 
  target_link_libraries(${test_dirname} PRIVATE ${ARG_LINK_LIBS})
  add_flangrt_unittest_offload_properties(${test_dirname})
+ add_flangrt_dependent_libs(${test_dirname})
 
  # Required because LLVMSupport is compiled with this option.
  # FIXME: According to CMake documentation, this is the default. Why is it
@@ -99,6 +121,7 @@ function(add_flangrt_nongtest_unittest test_name)
  set_target_properties(${test_name}${suffix} PROPERTIES FOLDER "Flang-RT/Tests/Unit")
 
  target_link_libraries(${test_name}${suffix} PRIVATE NonGTestTesting ${ARG_LINK_LIBS})
+ add_flangrt_dependent_libs(${test_name}${suffix})
 
  if(NOT ARG_SLOW_TEST)
  add_dependencies(FlangRTUnitTests ${test_name}${suffix})