also mention inline assembly const operands

Author: RalfJung

promotion.md

@@ -35,7 +35,7 @@ non-`Copy` types to be initialized idiomatically, for example
 
 [RFC 2203]: https://github.com/rust-lang/rfcs/blob/master/text/2203-const-repeat-expr.md
 
-### `#[rustc_args_required_const(...)]`
+### `#[rustc_args_required_const(...)]` and inline assembly `const` operands
 
 Additionally, some platform intrinsics require certain parameters to be
 immediates (known at compile-time). We use the `#[rustc_args_required_const]`
@@ -44,6 +44,9 @@ attribute, introduced in
 specify these parameters and (aggressively, see below) try to promote the
 corresponding arguments.
 
+Similarly, inline assembly has `const` operands, which are treated the same way
+as `rustc_args_required_const` arguments.
+
 ### Promotion inside `const` and `static`
 
 Lifetime extension is also responsible for making code like this work:
@@ -96,7 +99,7 @@ declaration. We can thus be less conservative. This is called *explicit*
 promotion.
 
 Currently, the following are considered explicit promotion contexts:
-* `#[rustc_args_required_const]` arguments
+* `#[rustc_args_required_const]` arguments and inline assembly `const` operands
 * lifetime extension in the bodies of `const` and `static` items and array lengths
 * the bodies of `const fn` -- but this is not justified by the above discussion; since `const fn` can be runtime-evaluated, the concerns about introducing hard errors where there would be none apply for `const fn` in exactly the same way as for `fn`, but this was overlooked when implementing the checks