ark_ff_macros/montgomery/
double.rs

1pub(super) fn double_in_place_impl(modulus_has_spare_bit: bool) -> proc_macro2::TokenStream {
2    if modulus_has_spare_bit {
3        quote::quote! {
4            // This cannot exceed the backing capacity.
5            a.0.mul2();
6            // However, it may need to be reduced.
7            __subtract_modulus(a);
8        }
9    } else {
10        quote::quote! {
11            // This cannot exceed the backing capacity.
12            let c = a.0.mul2();
13            // However, it may need to be reduced.
14            __subtract_modulus_with_carry(a, c);
15        }
16    }
17}