[Bug tree-optimization/110557] [13/14 Regression] Wrong code for x86_64-linux-gnu with -O3 -mavx2: vectorized loop mishandles signed bit-fields

[xry111 at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110557

--- Comment #3 from Xi Ruoyao <xry111 at gcc dot gnu.org> ---
It looks like if !UNSIGNED_TYPE (TREE_TYPE (bf_ref)), we need to generate
something like:

masked = (the signed variant of the wider type in {type_out, type_container})
container << (bitpos + bitsize);
result = (type_out) >> bitpos;