Function apply_deduced_attributes 

fn apply_deduced_attributes<'tcx>(
    cx: &LayoutCx<'tcx>,
    deduced: &[DeducedParamAttrs],
    idx: usize,
    arg: &mut ArgAbi<'tcx, Ty<'tcx>>,
)

Apply deduced optimization attributes to a parameter using an indirect pass mode.

deduced is a possibly truncated list of deduced attributes for a return place and arguments. idx the index of the parameter on the list (0 for a return place, and 1.. for arguments).