[CMake] Passthrough OSX CMake options to builtins and runtimes

[phosek]

Summary

When using the default target, there's no other way to pass these
into the builtins and runtimes subbuilds.

[phosek]

Ping?

[smeenai]

LGTM

[smeenai]

Actually, could you give an example of the type of variables you want to pass in? I thought the CMAKE_OSX_* options were mostly for setting OS and architecture, which the Darwin compiler-rt build does itself anyway.

[phosek]

In D116976#3242390, @smeenai wrote:

Actually, could you give an example of the type of variables you want to pass in? I thought the CMAKE_OSX_* options were mostly for setting OS and architecture, which the Darwin compiler-rt build does itself anyway.

Yes, the concrete example we ran into recently is CMAKE_OSX_DEPLOYMENT_TARGET which is set here https://github.com/llvm/llvm-project/blob/58ec17cb4ea4f3b76f0c948cf4c894ea7ea43552/clang/cmake/caches/Fuchsia-stage2.cmake#L49. In the future I'd also like to take advantage of CMAKE_OSX_ARCHITECTURES to build libc++ as a universal library.

I'm not particular happy with this approach since the runtimes build might accidentally pick up a flag you didn't intend to, which is the motivation for D117263.

[smeenai]

In D116976#3242464, @phosek wrote:

In D116976#3242390, @smeenai wrote:

Actually, could you give an example of the type of variables you want to pass in? I thought the CMAKE_OSX_* options were mostly for setting OS and architecture, which the Darwin compiler-rt build does itself anyway.

Yes, the concrete example we ran into recently is CMAKE_OSX_DEPLOYMENT_TARGET which is set here https://github.com/llvm/llvm-project/blob/58ec17cb4ea4f3b76f0c948cf4c894ea7ea43552/clang/cmake/caches/Fuchsia-stage2.cmake#L49. In the future I'd also like to take advantage of CMAKE_OSX_ARCHITECTURES to build libc++ as a universal library.

I'm not particular happy with this approach since the runtimes build might accidentally pick up a flag you didn't intend to, which is the motivation for D117263.

Ah, right, I forgot that runtimes other than compiler-rt don't do any of its special OS/architecture handling. This makes sense then.

llvm/runtimes/CMakeLists.txt

llvm_ExternalProject_Add(builtins
                            CMAKE_ARGS -DLLVM_LIBRARY_OUTPUT_INTDIR=${LLVM_LIBRARY_DIR}
                                       -DLLVM_RUNTIME_OUTPUT_INTDIR=${LLVM_TOOLS_BINARY_DIR}
                                       -DLLVM_DEFAULT_TARGET_TRIPLE=${TARGET_TRIPLE}
                                       -DLLVM_ENABLE_PER_TARGET_RUNTIME_DIR=${LLVM_ENABLE_PER_TARGET_RUNTIME_DIR_default}
                                       -DCMAKE_C_COMPILER_WORKS=ON
                                       -DCMAKE_ASM_COMPILER_WORKS=ON
                                       ${COMMON_CMAKE_ARGS}
                                       ${BUILTINS_CMAKE_ARGS}
-                           PASSTHROUGH_PREFIXES COMPILER_RT
+                           PASSTHROUGH_PREFIXES CMAKE_OSX
+                                                COMPILER_RT
                            USE_TOOLCHAIN
                            TARGET_TRIPLE ${TARGET_TRIPLE}
                            ${EXTRA_ARGS})
 endfunction()
 
 function(builtin_register_target compiler_rt_path target)
   cmake_parse_arguments(ARG "" "" "DEPENDS" ${ARGN})
 
if(projName STREQUAL "libc")
     set(projName "llvmlibc")
   endif()
   string(REPLACE "-" "_" canon_name ${projName})
   string(TOUPPER ${canon_name} canon_name)
   list(APPEND prefixes ${canon_name})
   if (${canon_name} STREQUAL "OPENMP")
     list(APPEND prefixes "LIBOMP" "LIBOMPTARGET")
   endif()
-  # Many compiler-rt options start with SANITIZER_ rather than COMPILER_RT_,
-  # so when compiler-rt is enabled, consider both.
+  # Many compiler-rt options start with SANITIZER_ and DARWIN_ rather than
+  # COMPILER_RT_, so when compiler-rt is enabled, consider both.
   if(canon_name STREQUAL "COMPILER_RT")
-    list(APPEND prefixes SANITIZER)
+    list(APPEND prefixes SANITIZER DARWIN)
   endif()
 
   string(FIND ${projName} "lib" LIB_IDX)
   if(LIB_IDX EQUAL 0)
     string(SUBSTRING ${projName} 3 -1 projName)
   endif()
   list(APPEND runtime_names ${projName})
 endforeach()
llvm_ExternalProject_Add(runtimes
                                       -DLLVM_ENABLE_PROJECTS_USED=${LLVM_ENABLE_PROJECTS_USED}
                                       -DLLVM_ENABLE_PER_TARGET_RUNTIME_DIR=${LLVM_ENABLE_PER_TARGET_RUNTIME_DIR_default}
                                       -DLLVM_BUILD_TOOLS=${LLVM_BUILD_TOOLS}
                                       -DCMAKE_C_COMPILER_WORKS=ON
                                       -DCMAKE_CXX_COMPILER_WORKS=ON
                                       -DCMAKE_ASM_COMPILER_WORKS=ON
                                       ${COMMON_CMAKE_ARGS}
                                       ${RUNTIMES_CMAKE_ARGS}
-                           PASSTHROUGH_PREFIXES LLVM_ENABLE_RUNTIMES
+                           PASSTHROUGH_PREFIXES CMAKE_OSX
+                                                LLVM_ENABLE_RUNTIMES
                                                 LLVM_USE_LINKER
                                                 ${ARG_PREFIXES}
                            EXTRA_TARGETS ${extra_targets}
                                          ${test_targets}
                                          ${SUB_COMPONENTS}
                                          ${SUB_CHECK_TARGETS}
                                          ${SUB_INSTALL_TARGETS}
                            USE_TOOLCHAIN