By default, both qemu and gcc5 produce code on ppc64el which will run on POWER7 platform. However, in debian gcc build instruction, gcc is explicitly built to produce code for POWER8 platform, which, obviously has additional instructions.
Right. In the past, we bootstrapped ppc64el on a POWER7 and it was able to run on that platform.
Now we changed it to be POWER8 only, so, we can assume that ppc64el requires POWER8 at minimum processor level. I just documented it explicitly at:
https://wiki.debian.org/ppc64el#Required_Hardware
