[Bug target/91481] POWER9 "DARN" RNG intrinsic produces repeated output

[noloader at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91481

--- Comment #3 from Jeffrey Walton <noloader at gmail dot com> ---
Lloyd's finding can be confirmed on GCC135. For example,

    gcc135:~$ /opt/at12.0/bin/gcc -O3 -mcpu=power9 -m64 darn.c -o darn
    gcc135:~$ ./darn
    9FBE0B8B6E861BD6
    9FBE0B8B6E861BD6
    9FBE0B8B6E861BD6
    9FBE0B8B6E861BD6
    ...

I can't find a header with a declaration, though:

    gcc135:~$ grep -IR builtin_darn /opt/at12.0/ 2>/dev/null
    gcc135:~$ grep -IR builtin_darn /lib 2>/dev/null
    gcc135:~$

Does someone know where the header is located?