[PGO] Add check in cmake to detect if atomics operations are available for target

[davidxl]

Summary

The check is similar to the one in cmake/modules/CheckAtomic.cmake

[davidxl]

Ping ..

[beanz]

Please prefix variables COMPILER_RT_ instead of LLVM_.

Other than that LGTM, sorry for the delay.

-Chris

lib/profile/CMakeLists.txt

+
+CHECK_CXX_SOURCE_COMPILES("
+#ifdef _MSC_VER
+#include <Intrin.h> /* Workaround for PR19898. */
+#include <windows.h>
+#endif
+int main() {
+#ifdef _MSC_VER
+        volatile LONG val = 1;
+        MemoryBarrier();
+        InterlockedCompareExchange(&val, 0, 1);
+        InterlockedIncrement(&val);
+        InterlockedDecrement(&val);
+#else
+        volatile unsigned long val = 1;
+        __sync_synchronize();
+        __sync_val_compare_and_swap(&val, 1, 0);
+        __sync_add_and_fetch(&val, 1);
+        __sync_sub_and_fetch(&val, 1);
+#endif
+        return 0;
+      }
+" LLVM_TARGET_HAS_ATOMICS)
+
 add_custom_target(profile)
 
 set(PROFILE_SOURCES
   GCDAProfiling.c
   InstrProfiling.c
   InstrProfilingBuffer.c
   InstrProfilingFile.c
   InstrProfilingWriter.c
   InstrProfilingPlatformDarwin.c
   InstrProfilingPlatformLinux.c
   InstrProfilingPlatformOther.c
   InstrProfilingRuntime.cc
   InstrProfilingUtil.c)
 
 if(UNIX)
  set(EXTRA_FLAGS
      -fPIC
      -Wno-pedantic)
 else()
  set(EXTRA_FLAGS
      -fPIC)
 endif()
 
+if(LLVM_TARGET_HAS_ATOMICS)
+ set(EXTRA_FLAGS
+     ${EXTRA_FLAGS}
+     -DLLVM_HAS_ATOMICS=1)
+endif() 
+
 if(APPLE)
   add_compiler_rt_runtime(clang_rt.profile
     STATIC
     OS ${PROFILE_SUPPORTED_OS}
     ARCHS ${PROFILE_SUPPORTED_ARCH}
     SOURCES ${PROFILE_SOURCES}
     PARENT_TARGET profile)
 else()