diff --git a/src/libsyntax_ext/asm.rs b/src/libsyntax_ext/asm.rs
index e1eabc5cb01455919db258bcefeaae0abe8cdd98..369c5b1ff60dbba182d5c272b6b551d98af2b3b7 100644
--- a/src/libsyntax_ext/asm.rs
+++ b/src/libsyntax_ext/asm.rs
@@ -179,9 +179,11 @@ pub fn expand_asm<'cx>(cx: &'cx mut ExtCtxt,
                     let (constraint, _str_style) = panictry!(p.parse_str());
 
                     if constraint.as_str().starts_with("=") {
-                        cx.span_err(p.prev_span, "input operand constraint contains '='");
+                        span_err_if_not_stage0!(cx, p.prev_span, E0662,
+                                                "input operand constraint contains '='");
                     } else if constraint.as_str().starts_with("+") {
-                        cx.span_err(p.prev_span, "input operand constraint contains '+'");
+                        span_err_if_not_stage0!(cx, p.prev_span, E0663,
+                                                "input operand constraint contains '+'");
                     }
 
                     panictry!(p.expect(&token::OpenDelim(token::Paren)));
@@ -203,7 +205,8 @@ pub fn expand_asm<'cx>(cx: &'cx mut ExtCtxt,
                     if OPTIONS.iter().any(|&opt| s == opt) {
                         cx.span_warn(p.prev_span, "expected a clobber, found an option");
                     } else if s.as_str().starts_with("{") || s.as_str().ends_with("}") {
-                        cx.span_err(p.prev_span, "clobber should not be surrounded by braces");
+                        span_err_if_not_stage0!(cx, p.prev_span, E0664,
+                                                "clobber should not be surrounded by braces");
                     }
 
                     clobs.push(s);
diff --git a/src/libsyntax_ext/diagnostics.rs b/src/libsyntax_ext/diagnostics.rs
index a840c0392e9fe7cc663fd1a9bc85814a4bb4f98d..33ae24c37e53f2791c9bfe51630c3071a1e43816 100644
--- a/src/libsyntax_ext/diagnostics.rs
+++ b/src/libsyntax_ext/diagnostics.rs
@@ -38,6 +38,58 @@
 asm!("nop" : "r"(a));
 ```
 
+Considering that this would be a long explanation, we instead recommend you to
+take a look at the unstable book:
+https://doc.rust-lang.org/unstable-book/language-features/asm.html
+"##,
+
+E0662: r##"
+An invalid input operand constraint was passed to the `asm` macro (third line).
+
+Erroneous code example:
+
+```compile_fail,E0662
+asm!("xor %eax, %eax"
+     :
+     : "=test"("a")
+    );
+```
+
+Considering that this would be a long explanation, we instead recommend you to
+take a look at the unstable book:
+https://doc.rust-lang.org/unstable-book/language-features/asm.html
+"##,
+
+E0663: r##"
+An invalid input operand constraint was passed to the `asm` macro (third line).
+
+Erroneous code example:
+
+```compile_fail,E0663
+asm!("xor %eax, %eax"
+     :
+     : "+test"("a")
+    );
+```
+
+Considering that this would be a long explanation, we instead recommend you to
+take a look at the unstable book:
+https://doc.rust-lang.org/unstable-book/language-features/asm.html
+"##,
+
+E0664: r##"
+A clobber was surrounded by braces in the `asm` macro.
+
+Erroneous code example:
+
+```compile_fail,E0663
+asm!("mov $$0x200, %eax"
+     :
+     :
+     : "{eax}"
+    );
+```
+
 Considering that this would be a long explanation, we instead recommend you to
 take a look at the unstable book:
 https://doc.rust-lang.org/unstable-book/language-features/asm.html
diff --git a/src/test/ui/E0662.rs b/src/test/ui/E0662.rs
new file mode 100644
index 0000000000000000000000000000000000000000..6adb11c56169c956be8eb69665dad27a0ba15c33
--- /dev/null
+++ b/src/test/ui/E0662.rs
@@ -0,0 +1,20 @@
+// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// ignore-stage1
+
+#![feature(asm)]
+
+fn main() {
+    asm!("xor %eax, %eax"
+         :
+         : "=test"("a") //~ ERROR E0662
+        );
+}
diff --git a/src/test/ui/E0662.stderr b/src/test/ui/E0662.stderr
new file mode 100644
index 0000000000000000000000000000000000000000..215e3a6d2f02357e7d1087ad3415cc756361ea11
--- /dev/null
+++ b/src/test/ui/E0662.stderr
@@ -0,0 +1,9 @@
+error[E0662]: input operand constraint contains '='
+  --> $DIR/E0662.rs:18:12
+   |
+LL |          : "=test"("a") //~ ERROR E0662
+   |            ^^^^^^^
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0662`.
diff --git a/src/test/ui/E0663.rs b/src/test/ui/E0663.rs
new file mode 100644
index 0000000000000000000000000000000000000000..9eb05ada4a82a0c79d65d29149d1ce6efe198329
--- /dev/null
+++ b/src/test/ui/E0663.rs
@@ -0,0 +1,20 @@
+// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// ignore-stage1
+
+#![feature(asm)]
+
+fn main() {
+    asm!("xor %eax, %eax"
+         :
+         : "+test"("a") //~ ERROR E0663
+        );
+}
diff --git a/src/test/ui/E0663.stderr b/src/test/ui/E0663.stderr
new file mode 100644
index 0000000000000000000000000000000000000000..123aa73eccc5e9e0e135c49e432f61bf7a3e9184
--- /dev/null
+++ b/src/test/ui/E0663.stderr
@@ -0,0 +1,9 @@
+error[E0663]: input operand constraint contains '+'
+  --> $DIR/E0663.rs:18:12
+   |
+LL |          : "+test"("a") //~ ERROR E0663
+   |            ^^^^^^^
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0663`.
diff --git a/src/test/ui/E0664.rs b/src/test/ui/E0664.rs
new file mode 100644
index 0000000000000000000000000000000000000000..738ffc18e38271bd353dfc3063090e331990516a
--- /dev/null
+++ b/src/test/ui/E0664.rs
@@ -0,0 +1,21 @@
+// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// ignore-stage1
+
+#![feature(asm)]
+
+fn main() {
+    asm!("mov $$0x200, %eax"
+         :
+         :
+         : "{eax}" //~ ERROR E0664
+        );
+}
diff --git a/src/test/ui/E0664.stderr b/src/test/ui/E0664.stderr
new file mode 100644
index 0000000000000000000000000000000000000000..570811729be85a26bdb1142979a10a7cb0bb7807
--- /dev/null
+++ b/src/test/ui/E0664.stderr
@@ -0,0 +1,9 @@
+error[E0664]: clobber should not be surrounded by braces
+  --> $DIR/E0664.rs:19:12
+   |
+LL |          : "{eax}" //~ ERROR E0664
+   |            ^^^^^^^
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0664`.