SERVER-12064 SERVER-12283 Use gcc atomic builtins if available

Switch to using gcc atomic builtins for atomic operations if using a new
enough gcc and clang and support is available. Otherwise, fall back to
the old behaviour of existing non-portable inline assembly to continue
to support builds on older versions of gcc.

Signed-off-by: Benety Goh <benety@mongodb.com>

1 files changed, 24 insertions, 0 deletions

diff --git a/SConstruct b/SConstruct
index 2d7e9a2b4a5..5c7c664bd5e 100644
--- a/SConstruct
+++ b/SConstruct
@@ -1431,6 +1431,30 @@ def doConfigure(myenv):
         if haveUUThread:
             myenv.Append(CPPDEFINES=['MONGO_HAVE___THREAD'])
 
+    if using_gcc() or using_clang():
+        def CheckGCCAtomicBuiltins(context):
+            test_body = """
+            int main(int argc, char **argv) {
+                int a = 0;
+                int b = 0;
+                int c = 0;
+
+                __atomic_compare_exchange(&a, &b, &c, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST);
+                return 0;
+            }
+            """
+            context.Message('Checking for gcc atomic builtins... ')
+            ret = context.TryLink(textwrap.dedent(test_body), '.cpp')
+            context.Result(ret)
+            return ret
+        conf = Configure(myenv, help=False, custom_tests = {
+            'CheckGCCAtomicBuiltins': CheckGCCAtomicBuiltins,
+        })
+        haveGCCAtomicBuiltins = conf.CheckGCCAtomicBuiltins()
+        conf.Finish()
+        if haveGCCAtomicBuiltins:
+            conf.env.Append(CPPDEFINES=["HAVE_GCC_ATOMIC_BUILTINS"])
+
     conf = Configure(myenv)
     libdeps.setup_conftests(conf)