[ping] Small adjustments to Aarch64 and i386 back-ends

[Eric Botcazou via Gcc-patches]

For the Aarch64 back-end:
  https://gcc.gnu.org/pipermail/gcc-patches/2021-October/580952.html

For the i386 back-end:
  https://gcc.gnu.org/pipermail/gcc-patches/2021-October/580992.html

Thanks in advance.

-- 
Eric Botcazou