https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92398
--- Comment #7 from Xiong Hu XS Luo <luoxhu at cn dot ibm.com> ---
Starting broken revision on Power8BE is r265398:
commit 171920e88fed13ed26336ca884123eff37176c36 (HEAD, refs/bisect/bad)
Author: segher <segher@138bc75d-0d04-0410-961f-82ee72b054a4>
Date: Mon Oct 22 20:23:39 2018 +0000
combine: Do not combine moves from hard registers
On most targets every function starts with moves from the parameter
passing (hard) registers into pseudos. Similarly, after every call
there is a move from the return register into a pseudo. These moves
usually combine with later instructions (leaving pretty much the same
instruction, just with a hard reg instead of a pseudo).
