diff --git a/src/libcore/lib.rs b/src/libcore/lib.rs
index 5ea765d3585..19bf4ab15bf 100644
--- a/src/libcore/lib.rs
+++ b/src/libcore/lib.rs
@@ -110,6 +110,7 @@
 #![feature(aarch64_target_feature)]
 #![feature(wasm_target_feature)]
 #![feature(avx512_target_feature)]
+#![cfg_attr(not(stage0), feature(cmpxchg16b_target_feature))]
 #![feature(const_slice_len)]
 #![feature(const_str_as_bytes)]
 #![feature(const_str_len)]
diff --git a/src/stdsimd b/src/stdsimd
index 513e067908f..ddb30221d79 160000
--- a/src/stdsimd
+++ b/src/stdsimd
@@ -1 +1 @@
-Subproject commit 513e067908f3e2eb8b31ad1c12b2e0a62817e557
+Subproject commit ddb30221d7985e813b4214d14c2a560ed6ee0991