[Bug rtl-optimization/78437] [7 Regression] invalid sign-extend conversion in REE pass

[ubizjak at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78437

--- Comment #5 from Uroš Bizjak <ubizjak at gmail dot com> ---
(In reply to Uroš Bizjak from comment #4)

> I have started bootstrap+regtest with your patch on alpha native. Please
> expect results sometime tomorrow.

Bootstrap and regression tests pass OK, the patch fixes reported
gcc.dg/atomic/stdatomic-compare-exchange-[1,2].c failure.