[Bug tree-optimization/66675] Could improve vector lane folding style operations.

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66675

--- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Note for this optimization to be useful there needs to be a heurstic to find
out if folding CONSTRUCTOR + VECTOR_CST is going to be only one or no other
add.  Or using one element of the whole vector.

AKA it might not be profit able to fold CONSTRUCTOR + VECTOR_CST to CONSTRUCTOR
with all scalar additions.