[CMake] Support single target builtins build on Darwin

[phosek]

Summary

This change allows cross-compiling compiler-rt builtins for multiple targets as part of runtimes on Darwin. This functionality is already supported on other platforms.

[beanz]

cmake/modules/LLVMExternalProjectUtils.cmake

47 ↗

(On Diff #91784)

This part of the change can't be done without causing problems on Darwin. llvm-ar and llvm-ranlib don't correctly handle fat archives on Darwin, so if you have a Darwin target we really don't want this to be the case. That's why this isn't defaulted.

You really need to just override the TOOLCHAIN_TOOLS option at the call site. We also probably shouldn't have lld in the list, but it doesn't have any adverse side effects because we don't force its use.

runtimes/CMakeLists.txt

156 ↗

(On Diff #91784)

I believe this patch will misbehave if LLVM_BUILTIN_TARGETS is a Darwin target, so we probably need to put some sort of protection in to catch that.

[beanz]

One minor style comment, otherwise looks good to me.

runtimes/CMakeLists.txt

193 ↗

(On Diff #92417)

This shouldn't need to be semi-colon separated. Space separated should work because TOOLCHAIN_TOOLS is a list parameter.

[beanz]

LGTM!

[phosek]

Thanks, could you also please take at D30958?

llvm/trunk/runtimes/CMakeLists.txt

if(${CMAKE_SOURCE_DIR} STREQUAL ${CMAKE_CURRENT_SOURCE_DIR})
   # 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})
 
   # This variable makes sure that e.g. llvm-lit is found.
   set(LLVM_MAIN_SRC_DIR ${LLVM_BUILD_MAIN_SRC_DIR})
 
+  if(APPLE)
+   set(LLVM_ENABLE_LIBCXX ON CACHE BOOL "")
+  endif()
+
   # Handle common options used by all runtimes.
   include(AddLLVM)
   include(HandleLLVMOptions)
 
   foreach(entry ${runtimes})
     get_filename_component(projName ${entry} NAME)
 
     # TODO: Clean this up as part of an interface standardization
else() # if this is included from LLVM's CMake
   if(NOT LLVM_BUILD_RUNTIMES)
     set(EXTRA_ARGS EXCLUDE_FROM_ALL)
   endif()
 
   # If compiler-rt is present we need to build the builtin libraries first. This
   # is required because the other runtimes need the builtin libraries present
   # before the just-built compiler can pass the configuration tests.
   if(EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/compiler-rt)
-    if(APPLE OR NOT LLVM_BUILTIN_TARGETS)
+    if(NOT LLVM_BUILTIN_TARGETS)
       llvm_ExternalProject_Add(builtins
                                ${CMAKE_CURRENT_SOURCE_DIR}/compiler-rt/lib/builtins
                                CMAKE_ARGS -DLLVM_LIBRARY_OUTPUT_INTDIR=${LLVM_LIBRARY_DIR}
                                           -DLLVM_RUNTIME_OUTPUT_INTDIR=${LLVM_TOOLS_BINARY_DIR}
                                           -DCMAKE_C_COMPILER_TARGET=${TARGET_TRIPLE}
                                           -DCMAKE_ASM_COMPILER_TARGET=${TARGET_TRIPLE}
                                PASSTHROUGH_PREFIXES COMPILER_RT
                                USE_TOOLCHAIN
                                ${EXTRA_ARGS})
     else()
       get_cmake_property(variableNames VARIABLES)
       add_custom_target(builtins)
       foreach(target ${LLVM_BUILTIN_TARGETS})
+        string(REPLACE "-" ";" builtin_target_list ${target})
+        foreach(item ${builtin_target_list})
+          string(TOLOWER "${item}" item_lower)
+          if(item_lower MATCHES "darwin")
+            message(FATAL_ERROR "LLVM_BUILTIN_TARGETS isn't implemented for Darwin platform!")
+          endif()
+        endforeach()
+
         foreach(variableName ${variableNames})
           if(variableName MATCHES "^BUILTINS_${target}")
             string(REPLACE "BUILTINS_${target}_" "" new_name ${variableName})
             list(APPEND ${target}_extra_args "-D${new_name}=${${variableName}}")
           endif()
         endforeach()
         llvm_ExternalProject_Add(builtins-${target}
                                ${CMAKE_CURRENT_SOURCE_DIR}/compiler-rt/lib/builtins
                                CMAKE_ARGS -DLLVM_LIBRARY_OUTPUT_INTDIR=${LLVM_LIBRARY_DIR}
                                           -DLLVM_RUNTIME_OUTPUT_INTDIR=${LLVM_TOOLS_BINARY_DIR}
                                           -DCMAKE_C_COMPILER_TARGET=${target}
                                           -DCMAKE_ASM_COMPILER_TARGET=${target}
                                           -DCMAKE_C_COMPILER_WORKS=On
                                           -DCMAKE_ASM_COMPILER_WORKS=On
                                           -DCOMPILER_RT_DEFAULT_TARGET_ONLY=On
                                           ${${target}_extra_args}
+                               TOOLCHAIN_TOOLS clang lld llvm-ar llvm-ranlib
                                PASSTHROUGH_PREFIXES COMPILER_RT
                                USE_TOOLCHAIN
                                ${EXTRA_ARGS})
         add_dependencies(builtins builtins-${target})
       endforeach()
     endif()
     set(deps builtins)
     # We don't need to depend on the builtins if we're building instrumented