update submodules
diff --git a/llvm b/llvm
index 17dce3b..4f840f1 160000
--- a/llvm
+++ b/llvm
@@ -1 +1 @@
-Subproject commit 17dce3bea3d23a5d20a00922725e6841e8423be5
+Subproject commit 4f840f1dc36c8940d4b6ee257cde54850cf2ac6e