[Bug target/126454] [16/17 Regression] RISCV: cm.popretz pass deletes "li a0,0" and gives wrong return value

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D126454

--- Comment #9 from Luke Wren <wren6991 at gmail dot com> ---
Going through the history a bit:

* 7a345d0314 (Jul 9th 2024) fixed PR113715 by deleting cm.popretz recogniti=
on
  from epilogue expansion

* c738d4ef52 (Nov 5th 2025) introduced a new RTL pass to recognise cm.popre=
tz
  using backward BB scan (trying to fix the size regression from 7a345d0314)

There are no changes to the cm.popretz pass since c738d4ef52 so I think it =
has
been broken since that commit.

I think this is just an oversight in the new pass: it does a backward BB sc=
an
to find a related `li a0, 0` but misses that CALL instructions are consider=
ed
part of the BB, and can consume and/or clobber a0.=