[CMake] If the compiler supports _Atomic include atomic.c in builtins libraries

This fixes a long-standing TODO by implementing a compiler check for supporting the _Atomic keyword. If the _Atomic keyword is supported by the compiler we should include it in the builtin library sources.

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@278454 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 36 insertions, 5 deletions

diff --git a/cmake/Modules/BuiltinTests.cmake b/cmake/Modules/BuiltinTests.cmake
index c6da03023..6bbf44951 100644
--- a/cmake/Modules/BuiltinTests.cmake
+++ b/cmake/Modules/BuiltinTests.cmake
@@ -3,11 +3,15 @@ include(CMakeCheckCompilerFlagCommonPatterns)
 # This function takes an OS and a list of architectures and identifies the
 # subset of the architectures list that the installed toolchain can target.
 function(try_compile_only output)
+  cmake_parse_arguments(ARG "" "" "SOURCE;FLAGS" ${ARGN})
+  if(NOT ARG_SOURCE)
+    set(ARG_SOURCE "int foo(int x, int y) { return x + y; }\n")
+  endif()
   set(SIMPLE_C ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/src.c)
-  file(WRITE ${SIMPLE_C} "int foo(int x, int y) { return x + y; }\n")
+  file(WRITE ${SIMPLE_C} "${ARG_SOURCE}\n")
   string(REGEX MATCHALL "<[A-Za-z0-9_]*>" substitutions
          ${CMAKE_C_COMPILE_OBJECT})
-  string(REPLACE ";" " " extra_flags "${ARGN}")
+  string(REPLACE ";" " " extra_flags "${ARG_FLAGS}")
 
   set(test_compile_command "${CMAKE_C_COMPILE_OBJECT}")
   foreach(substitution ${substitutions})
@@ -63,7 +67,20 @@ endfunction()
 function(builtin_check_c_compiler_flag flag output)
   if(NOT DEFINED ${output})
     message(STATUS "Performing Test ${output}")
-    try_compile_only(result ${flag})
+    try_compile_only(result FLAGS ${flag})
+    set(${output} ${result} CACHE INTERNAL "Compiler supports ${flag}")
+    if(${result})
+      message(STATUS "Performing Test ${output} - Success")
+    else()
+      message(STATUS "Performing Test ${output} - Failed")
+    endif()
+  endif()
+endfunction()
+
+function(builtin_check_c_compiler_source output source)
+  if(NOT DEFINED ${output})
+    message(STATUS "Performing Test ${output}")
+    try_compile_only(result SOURCE ${source})
     set(${output} ${result} CACHE INTERNAL "Compiler supports ${flag}")
     if(${result})
       message(STATUS "Performing Test ${output} - Success")
diff --git a/cmake/builtin-config-ix.cmake b/cmake/builtin-config-ix.cmake
index 432b1fadb..83466d81b 100644
--- a/cmake/builtin-config-ix.cmake
+++ b/cmake/builtin-config-ix.cmake
@@ -1,4 +1,5 @@
 include(BuiltinTests)
+include(CheckCSourceCompiles)
 
 # Make all the tests only check the compiler
 set(TEST_COMPILE_ONLY On)
@@ -14,6 +15,15 @@ builtin_check_c_compiler_flag(-mfloat-abi=soft      COMPILER_RT_HAS_FLOAT_ABI_SO
 builtin_check_c_compiler_flag(-mfloat-abi=hard      COMPILER_RT_HAS_FLOAT_ABI_HARD_FLAG)
 builtin_check_c_compiler_flag(-static               COMPILER_RT_HAS_STATIC_FLAG)
 
+builtin_check_c_compiler_source(COMPILER_RT_SUPPORTS_ATOMIC_KEYWORD
+"
+int foo(int x, int y) {
+ _Atomic int result = x * y;
+ return result;
+}
+")
+
+
 set(ARM64 aarch64)
 set(ARM32 arm armhf)
 set(X86 i386 i686)
diff --git a/lib/builtins/CMakeLists.txt b/lib/builtins/CMakeLists.txt
index beacb8676..fc973a78c 100644
--- a/lib/builtins/CMakeLists.txt
+++ b/lib/builtins/CMakeLists.txt
@@ -42,8 +42,6 @@ set(GENERIC_SOURCES
   ashlti3.c
   ashrdi3.c
   ashrti3.c
-  # FIXME: atomic.c may only be compiled if host compiler understands _Atomic
-  # atomic.c
   clear_cache.c
   clzdi2.c
   clzsi2.c
@@ -166,6 +164,12 @@ set(GENERIC_SOURCES
   umodsi3.c
   umodti3.c)
 
+if(COMPILER_RT_SUPPORTS_ATOMIC_KEYWORD)
+  set(GENERIC_SOURCES
+    ${GENERIC_SOURCES}
+    atomic.c)
+endif()
+
 set(MSVC_SOURCES
  divsc3.c
  divdc3.c