Index: test/CodeGen/SystemZ/Large/lit.local.cfg
===================================================================
--- test/CodeGen/SystemZ/Large/lit.local.cfg
+++ test/CodeGen/SystemZ/Large/lit.local.cfg
@@ -2,7 +2,7 @@
 
 # These tests take on the order of seconds to run, so skip them unless
 # running natively.
-if config.root.host_arch not in ['SystemZ']:
+if 'long_tests' not in config.available_features:
     config.unsupported = True
 
 if not 'SystemZ' in config.root.targets:
Index: test/lit.cfg
===================================================================
--- test/lit.cfg
+++ test/lit.cfg
@@ -312,6 +312,10 @@
 else:
     config.available_features.add("not_ubsan")
 
+# Check if we should run long running tests.
+if lit_config.params.get("run_long_tests", None) == "true":
+    config.available_features.add("long_tests")
+
 # Direct object generation
 # Suppress x86_64-mingw32 while investigating since r219108.
 if not 'hexagon' in config.target_triple and not re.match(r'^x86_64.*-(mingw32|windows-gnu|win32)', config.target_triple):