Merge ref '47cd7120d9b4' from rust-lang/rust

Pull recent changes from https://github.com/rust-lang/rust via Josh.

Upstream ref: 47cd7120d9b4e1b64eb27c87522a07888197fae8
Filtered ref: b5a5cb8
Upstream diff: rust-lang/rust@caccb4d...47cd712

This merge was created using https://github.com/rust-lang/josh-sync.

Author: The rustc-josh-sync Cronjob Bot

compiler-builtins/src/lib.rs

@@ -7,7 +7,6 @@
 #![feature(compiler_builtins)]
 #![feature(core_intrinsics)]
 #![feature(linkage)]
-#![feature(asm_cfg)]
 #![feature(naked_functions)]
 #![feature(repr_simd)]
 #![feature(macro_metavar_expr_concat)]