[runtimes] adds llvm-libgcc to the list of runtimes to be sorted

[cjdb]

Summary

llvm-libgcc is not a part of LLVM_ALL_RUNTIMES because llvm-libgcc is
incompatible with an explicit libunwind and compiler-rt. This meant that
it was being filtered out and not built.

[phosek]

LGTM

[ldionne]

runtimes/CMakeLists.txt

18–26

I'd like to suggest this instead:

set(LLVM_DEFAULT_RUNTIMES "libc;libunwind;libcxxabi;libcxx;compiler-rt;openmp")
set(LLVM_ALL_RUNTIMES "${LLVM_DEFAULT_RUNTIMES};llvm-libgcc")
set(LLVM_ENABLE_RUNTIMES "" CACHE STRING
  "Semicolon-separated list of runtimes to build (which must be in ${LLVM_ALL_RUNTIMES}), or \"all\", in which case the following set of default runtimes will be used: ${LLVM_DEFAULT_RUNTIMES}.")
if(LLVM_ENABLE_RUNTIMES STREQUAL "all" )
  set(LLVM_ENABLE_RUNTIMES ${LLVM_DEFAULT_RUNTIMES})
endif()
include(SortSubset)
sort_subset("${LLVM_ALL_RUNTIMES}" "${LLVM_ENABLE_RUNTIMES}" LLVM_ENABLE_RUNTIMES)

This opens the door to adding other "alternative" runtimes that are not selected by default when one uses all. Note that all becomes a slight misnomer, but it seems like it already is anyway cause there exists some runtimes (such as llvm-libgcc) that are not selected by all.

[cjdb]

makes requested change

[cjdb]

runtimes/CMakeLists.txt

18–26

Thanks for the improvement, this should future-proof it.

I'm okay with duping users into thinking that all still means everything, because it does from a user's perspective. llvm-libgcc is incompatible with compiler-rt and libunwind because it builds them both with strict opinions (and then does extra stuff). As a user, even I'm not supposed to install llvm-libgcc and expect it to work. That's something only toolchain release managers who own pretty much everything (that would be cjdb@ only when concerned with the ChromeOS toolchain). That's a really small group of people to cater for, and llvm-libgcc actually makes them go quite out of their way to say "yes, I know what I'm doing!" before it'll build for them.

I think the same should be true for anything else that shouldn't be covered by default, so I've left the LLVM_ENABLE_RUNTIMES description unchanged (but this should otherwise be the same as your suggestion).

runtimes/CMakeLists.txt

list(INSERT CMAKE_MODULE_PATH 0
   "${LLVM_COMMON_CMAKE_UTILS}"
   "${LLVM_COMMON_CMAKE_UTILS}/Modules"
   "${CMAKE_CURRENT_SOURCE_DIR}/../llvm/cmake"
   "${CMAKE_CURRENT_SOURCE_DIR}/../llvm/cmake/modules"
 )
 
 # We order libraries to mirror roughly how they are layered, except that compiler-rt can depend
 # on libc++, so we put it after.
-set(LLVM_ALL_RUNTIMES "libc;libunwind;libcxxabi;libcxx;compiler-rt;openmp")
+set(LLVM_DEFAULT_RUNTIMES "libc;libunwind;libcxxabi;libcxx;compiler-rt;openmp")
+set(LLVM_ALL_RUNTIMES "${LLVM_DEFAULT_RUNTIMES};llvm-libgcc")
 set(LLVM_ENABLE_RUNTIMES "" CACHE STRING
   "Semicolon-separated list of runtimes to build (${LLVM_ALL_RUNTIMES}), or \"all\".")
 if(LLVM_ENABLE_RUNTIMES STREQUAL "all" )
-  set(LLVM_ENABLE_RUNTIMES ${LLVM_ALL_RUNTIMES})
+  set(LLVM_ENABLE_RUNTIMES ${LLVM_DEFAULT_RUNTIMES})
 endif()
 include(SortSubset)
 sort_subset("${LLVM_ALL_RUNTIMES}" "${LLVM_ENABLE_RUNTIMES}" LLVM_ENABLE_RUNTIMES)
 
 foreach(proj ${LLVM_ENABLE_RUNTIMES})
   set(proj_dir "${CMAKE_CURRENT_SOURCE_DIR}/../${proj}")
   if(IS_DIRECTORY ${proj_dir} AND EXISTS ${proj_dir}/CMakeLists.txt)
     list(APPEND runtimes ${proj_dir})
   else()
     message(FATAL_ERROR "LLVM_ENABLE_RUNTIMES requests ${proj} but directory not found: ${proj_dir}")
   endif()