Philip Herron and Arthur Cohen have posted an
update on the status of gccrs — the GCC frontend for the Rust language
— and why it will not be a part of the upcoming GCC 13 release.

While all of this appears like a lot of work, we are confident in
our progress and hope to get closer and closer to getting the
core crate working in the next few months. There is also a
lot of important work remaining in order to produce a valid Rust
compiler, which is why we will spend the coming months focusing on
the core crate as well as a borrow-checker implementation,
and the development of the necessary tooling to allow us to try and
pass the Rust 1.49 testsuite.

We aim to distribute the Rust 1.49 version of the standard library
with our compiler in the next major GCC release, GCC 14, and hope
to backport enough changes to the GCC 13 branch to get the core
crate working in time for the GCC 13.2 release. This will enable
users to easily start experimenting with the compiler for
#![no_std] Rust programs and, hopefully, some embedded
targets.

Source: LWN.net – An update on the GCC frontend for Rust