[Bug tree-optimization/70509] wrong code with extract from a v64qi

[zsojka at seznam dot cz]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70509

--- Comment #2 from Zdenek Sojka <zsojka at seznam dot cz> ---
(In reply to Zdenek Sojka from comment #0)
> First broken dump seems to be .forwprop, where is:

.forwprop4 , that is. The problem might be that simplify_bitfield_ref() does:
tree-ssa-forwprop.c
...
1793:      index = build_int_cst (TREE_TYPE (TREE_TYPE (m)), idx * size);
...

which builds the index of type "unsigned char", which wraps around from 256 to
0.
Is there any reason to have index of type "TREE_TYPE (TREE_TYPE (m))" in that
statement? or am I reading the code incorrectly?