[orc][cmake] Check if 8 byte atomics require libatomic for unittest

[sdardis]

Summary

rL319838 introduced SymbolStringPool which uses 8 byte atomics for
reference counters. On systems which do not support such atomics
natively such as MIPS32, explicitly add libatomic as one of the
libraries for SymbolStringPool's unittest.

[sdardis]

Ping.

[beanz]

I'm going to nitpick here a little. The patch is fine, but one of two things should change. Either line 29 should use list(APPEND...) instead of set, or you should do something more like:

if(NOT HAVE_CXX_ATOMICS64_WITHOUT_LIB)
  set(ORC_TEST_ATOMIC_LIB atomic)
endif()

target_link_libraries(OrcJITTests PRIVATE ${LLVM_PTHREAD_LIB} ${ORC_TEST_ATOMIC_LIB})

[sdardis]

Address nit.

[beanz]

LGTM

[sdardis]

Thanks for the review @beanz .

llvm/trunk/unittests/ExecutionEngine/Orc/CMakeLists.txt

add_llvm_unittest(OrcJITTests
   OrcTestCommon.cpp
   QueueChannel.cpp
   RemoteObjectLayerTest.cpp
   RPCUtilsTest.cpp
   RTDyldObjectLinkingLayerTest.cpp
   SymbolStringPoolTest.cpp
   )
 
-target_link_libraries(OrcJITTests PRIVATE ${LLVM_PTHREAD_LIB})
+set(ORC_JIT_TEST_LIBS ${LLVM_PTHREAD_LIB})
+if(NOT HAVE_CXX_ATOMICS64_WITHOUT_LIB)
+  list(APPEND ORC_JIT_TEST_LIBS atomic)
+endif()
+
+target_link_libraries(OrcJITTests PRIVATE ${ORC_JIT_TEST_LIBS})