[Bug rtl-optimization/111835] Suboptimal codegen: zero extended load instead of sign extended one

[lis8215 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111835

--- Comment #3 from Siarhei Volkau <lis8215 at gmail dot com> ---
I don't think that it is duplicate of the bug 104387 because there's only one
store.
And this bug is simply disappears if we change the source code a bit.
e.g.
 - change (int8_t)*src; to *(int8_t*)src;
or change argument uint8_t * dst to int8_t * dst

But if we have multiple stores, extension will remain in any condition.