Segfaults everywhere on stable/13 after recent upgrade

Hi all,

I have a G5 running stable/13. A couple of weeks ago, I did the regular
fetch, rebuild world, and reinstall... and almost all new userland binaries
started crashing.I thought the crashes would be due to a kernel/userland
incompatibility, but after rebooting with the new kernel, the problem
persisted.

It took me some effort to recover the machine into a usable state. I had to
revert the source tree to right before clang was updated to 12.0.1 on June
13th, as I think this is the problematic change, and rebuild + reinstall
from there.

I just updated the tree again to the most recent stable/13, done another
buildworld, and I have confirmed that most binaries are still broken in the
same way:

root@g5:/usr/obj/usr/src/powerpc.powerpc64 # ./bin/echo/echo
Segmentation fault (core dumped)
root@g5:/usr/obj/usr/src/powerpc.powerpc64 # gdb ./bin/echo/echo
...
Reading symbols from ./bin/echo/echo...
Reading symbols from
/usr/obj/usr/src/powerpc.powerpc64/bin/echo/echo.debug...
(gdb) run
Starting program: /usr/obj/usr/src/powerpc.powerpc64/bin/echo/echo

Program received signal SIGSEGV, Segmentation fault.
0x0000000010011058 in main (argc=1, argv=0xfffffbfffeab8) at
/usr/src/bin/echo/echo.c:77
77      {
(gdb)

The stacktraces I get out of the binaries are meaningless. You can see echo
crashing upon entering main. ls crashes on a local variable assignment. But
cp gets further along and is able to print its own usage message before
crashing.

Anybody knows what might be going on?

Thanks!

-- 
jmmv.dev