[Bug rtl-optimization/115877] [15 Regression] wrong code at -Os (missing zero extension)

[law at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115877

--- Comment #8 from Jeffrey A. Law <law at gcc dot gnu.org> ---
So testing my fix for this bug has exposed another secondary issue.  Assuming
there's not something else lurking, then plan is to address that secondary
issue, then come back to this one, then dive into the harfbuzz bug.