[compiler-rt] Compile assembly files as ASM not C

[tambre]

Summary

It isn't very wise to pass an assembly file to the compiler and tell it to compile as a C file and hope that the compiler recognizes it as assembly instead.
Instead enable the ASM language and mark the files as being ASM.

[525/634] Building C object lib/tsan/CMakeFiles/clang_rt.tsan-aarch64.dir/rtl/tsan_rtl_aarch64.S.o
FAILED: lib/tsan/CMakeFiles/clang_rt.tsan-aarch64.dir/rtl/tsan_rtl_aarch64.S.o
/opt/tooling/drive/host/bin/clang --target=aarch64-linux-gnu -I/opt/tooling/drive/llvm/compiler-rt/lib/tsan/.. -isystem /opt/tooling/drive/toolchain/opt/drive/toolchain/include -x c -Wall -Wno-unused-parameter -fno-lto -fPIC -fno-builtin -fno-exceptions -fomit-frame-pointer -funwind-tables -fno-stack-protector -fno-sanitize=safe-stack -fvisibility=hidden -fno-lto -O3 -gline-tables-only -Wno-gnu -Wno-variadic-macros -Wno-c99-extensions -Wno-non-virtual-dtor -fPIE -fno-rtti -Wframe-larger-than=530 -Wglobal-constructors --sysroot=. -MD -MT lib/tsan/CMakeFiles/clang_rt.tsan-aarch64.dir/rtl/tsan_rtl_aarch64.S.o -MF lib/tsan/CMakeFiles/clang_rt.tsan-aarch64.dir/rtl/tsan_rtl_aarch64.S.o.d -o lib/tsan/CMakeFiles/clang_rt.tsan-aarch64.dir/rtl/tsan_rtl_aarch64.S.o -c /opt/tooling/drive/llvm/compiler-rt/lib/tsan/rtl/tsan_rtl_aarch64.S
/opt/tooling/drive/llvm/compiler-rt/lib/tsan/rtl/tsan_rtl_aarch64.S:29:1: error: expected identifier or '('
.section .text
^
1 error generated.

Fixed Clang not being passed as the assembly compiler for compiler-rt runtime build.

[phosek]

One concern I have with this change is that we may not always consistently update CMAKE_ASM_FLAGS or set CMAKE_ASM_COMPILER. This wouldn't make a difference before, but it'll with this change. Can you check if these variables are being updated as needed?

[tambre]

Pass CMAKE_ASM_COMPILER to compiler-rt in runtime build

[tambre]

In D85706#2214009, @phosek wrote:

One concern I have with this change is that we may not always consistently update CMAKE_ASM_FLAGS or set CMAKE_ASM_COMPILER. This wouldn't make a difference before, but it'll with this change. Can you check if these variables are being updated as needed?

I searched and was able to find only one instance. I've fixed it in this change.
I lack commit privileges, so whoever commits this should be ready to revert it, as there's a chance for breakage.

[tambre]

ping

[teemperor]

This broke Green Dragon's compiler-rt builds and also my local compiler-rt build. See for example here: http://green.lab.llvm.org/green/view/LLDB/job/lldb-cmake/23424/console

[teemperor]

I reverted in adf0b8cc70325f027d202139e3ff984c41896b57 to get the bots green again . Feel free to ping if you need someone to test the patch on macOS.

clang/runtime/CMakeLists.txt

ExternalProject_Add(compiler-rt
     DEPENDS llvm-config clang ${compiler_rt_configure_deps}
     PREFIX ${COMPILER_RT_PREFIX}
     SOURCE_DIR ${COMPILER_RT_SRC_ROOT}
     STAMP_DIR ${STAMP_DIR}
     BINARY_DIR ${BINARY_DIR}
     CMAKE_ARGS ${CLANG_COMPILER_RT_CMAKE_ARGS}
                -DCMAKE_C_COMPILER=${LLVM_RUNTIME_OUTPUT_INTDIR}/clang
                -DCMAKE_CXX_COMPILER=${LLVM_RUNTIME_OUTPUT_INTDIR}/clang++
+               -DCMAKE_ASM_COMPILER=${LLVM_RUNTIME_OUTPUT_INTDIR}/clang
                -DCMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE}
                -DCMAKE_MAKE_PROGRAM=${CMAKE_MAKE_PROGRAM}
                -DLLVM_CONFIG_PATH=${LLVM_RUNTIME_OUTPUT_INTDIR}/llvm-config
                -DLLVM_LIT_ARGS=${LLVM_LIT_ARGS}
                -DCOMPILER_RT_OUTPUT_DIR=${LLVM_LIBRARY_OUTPUT_INTDIR}/clang/${CLANG_VERSION}
                -DCOMPILER_RT_EXEC_OUTPUT_DIR=${LLVM_RUNTIME_OUTPUT_INTDIR}
                -DCOMPILER_RT_INSTALL_PATH:STRING=lib${LLVM_LIBDIR_SUFFIX}/clang/${CLANG_VERSION}
                -DCOMPILER_RT_INCLUDE_TESTS=${LLVM_INCLUDE_TESTS}

compiler-rt/cmake/Modules/AddCompilerRT.cmake

function(add_compiler_rt_component name)
   if(COMMAND runtime_register_component)
     runtime_register_component(${name})
   endif()
   add_dependencies(compiler-rt ${name})
 endfunction()
 
 function(add_asm_sources output)
   set(${output} ${ARGN} PARENT_SCOPE)
-  # Xcode will try to compile asm files as C ('clang -x c'), and that will fail.
-  if (${CMAKE_GENERATOR} STREQUAL "Xcode")
-    enable_language(ASM)
-  else()
-    # Pass ASM file directly to the C++ compiler.
-    set_source_files_properties(${ARGN} PROPERTIES LANGUAGE C)
-  endif()
+  # Make sure ASM language is available.
+  # We explicitly mark the source files as ASM, so they don't get passed to the
+  # C/CXX compiler and hopes that it recognizes them as assembly.
+  set_source_files_properties(${ARGN} PROPERTIES LANGUAGE ASM)
 endfunction()
 
 macro(set_output_name output name arch)
   if(LLVM_ENABLE_PER_TARGET_RUNTIME_DIR)
     set(${output} ${name})
   else()
     if(ANDROID AND ${arch} STREQUAL "i386")
       set(${output} "${name}-i686${COMPILER_RT_OS_SUFFIX}")