1.53.0 causes {rc,arc}::shared_from_iter_normal to hang on powerpc, powerpc64 (regression)

[infinity0]

The same tests passed fine on 1.52 on the same architectures. It is also fine on 1.53 on powerpc64le (little-endian).

• https://buildd.debian.org/status/fetch.php?pkg=rustc&arch=powerpc&ver=1.53.0%2Bdfsg1-1&stamp=1633487393&raw=0
• https://buildd.debian.org/status/fetch.php?pkg=rustc&arch=ppc64&ver=1.53.0%2Bdfsg1-1&stamp=1633486677&raw=0

[jieyouxu]

Triage: this is really old, but @infinity0 is this is a problem on latest stable?

[Fabian-Gruenbichler]

@jieyouxu @infinity0 is no longer active in maintaining rustc in Debian, I will take a look at this!