Index: test/lit.cfg.py
===================================================================
--- test/lit.cfg.py
+++ test/lit.cfg.py
@@ -168,6 +168,9 @@
     config.available_features.add(arch.lower() + '-registered-target')
 
 # Features
+known_arches = ["x86_64", "mips64", "ppc64", "aarch64"]
+if any(config.llvm_host_triple.startswith(x) for x in known_arches):
+  config.available_features.add("llvm-64-bits")
 
 # Others/can-execute.txt
 if sys.platform not in ['win32']:
Index: test/lit.site.cfg.py.in
===================================================================
--- test/lit.site.cfg.py.in
+++ test/lit.site.cfg.py.in
@@ -42,6 +42,7 @@
 config.build_shared_libs = @BUILD_SHARED_LIBS@
 config.link_llvm_dylib = @LLVM_LINK_LLVM_DYLIB@
 config.llvm_libxml2_enabled = "@LLVM_LIBXML2_ENABLED@"
+config.llvm_host_triple = '@LLVM_HOST_TRIPLE@'
 
 # Support substitution of the tools_dir with user parameters. This is
 # used when we can't determine the tool dir at configuration time.