Pass modulus to prime_field_constants_and_sqrt by reference

ff/ff_derive/src/lib.rs

@@ -47,7 +47,7 @@ pub fn prime_field(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
     let mut gen = proc_macro2::TokenStream::new();
 
     let (constants_impl, sqrt_impl) =
-        prime_field_constants_and_sqrt(&ast.ident, &repr_ident, modulus, limbs, generator);
+        prime_field_constants_and_sqrt(&ast.ident, &repr_ident, &modulus, limbs, generator);
 
     gen.extend(constants_impl);
     gen.extend(prime_field_repr_impl(&repr_ident, limbs));
@@ -383,7 +383,7 @@ fn test_exp() {
 fn prime_field_constants_and_sqrt(
     name: &syn::Ident,
     repr: &syn::Ident,
-    modulus: BigUint,
+    modulus: &BigUint,
     limbs: usize,
     generator: BigUint,
 ) -> (proc_macro2::TokenStream, proc_macro2::TokenStream) {
@@ -396,28 +396,26 @@ fn prime_field_constants_and_sqrt(
     let repr_shave_bits = (64 * limbs as u32) - biguint_num_bits(modulus.clone());
 
     // Compute R = 2**(64 * limbs) mod m
-    let r = (BigUint::one() << (limbs * 64)) % &modulus;
+    let r = (BigUint::one() << (limbs * 64)) % modulus;
 
     // modulus - 1 = 2^s * t
     let mut s: u32 = 0;
-    let mut t = &modulus - BigUint::from_str("1").unwrap();
+    let mut t = modulus - BigUint::from_str("1").unwrap();
     while t.is_even() {
         t = t >> 1;
         s += 1;
     }
 
     // Compute 2^s root of unity given the generator
-    let root_of_unity = biguint_to_u64_vec(
-        (exp(generator.clone(), &t, &modulus) * &r) % &modulus,
-        limbs,
-    );
-    let generator = biguint_to_u64_vec((generator.clone() * &r) % &modulus, limbs);
+    let root_of_unity =
+        biguint_to_u64_vec((exp(generator.clone(), &t, &modulus) * &r) % modulus, limbs);
+    let generator = biguint_to_u64_vec((generator.clone() * &r) % modulus, limbs);
 
-    let sqrt_impl = if (&modulus % BigUint::from_str("4").unwrap())
+    let sqrt_impl = if (modulus % BigUint::from_str("4").unwrap())
         == BigUint::from_str("3").unwrap()
     {
         let mod_plus_1_over_4 =
-            biguint_to_u64_vec((&modulus + BigUint::from_str("1").unwrap()) >> 2, limbs);
+            biguint_to_u64_vec((modulus + BigUint::from_str("1").unwrap()) >> 2, limbs);
 
         quote! {
             impl ::ff::SqrtField for #name {
@@ -436,7 +434,7 @@ fn prime_field_constants_and_sqrt(
                 }
             }
         }
-    } else if (&modulus % BigUint::from_str("16").unwrap()) == BigUint::from_str("1").unwrap() {
+    } else if (modulus % BigUint::from_str("16").unwrap()) == BigUint::from_str("1").unwrap() {
         let t_minus_1_over_2 = biguint_to_u64_vec((&t - BigUint::one()) >> 1, limbs);
 
         quote! {
@@ -490,10 +488,10 @@ fn prime_field_constants_and_sqrt(
     };
 
     // Compute R^2 mod m
-    let r2 = biguint_to_u64_vec((&r * &r) % &modulus, limbs);
+    let r2 = biguint_to_u64_vec((&r * &r) % modulus, limbs);
 
     let r = biguint_to_u64_vec(r, limbs);
-    let modulus = biguint_to_real_u64_vec(modulus, limbs);
+    let modulus = biguint_to_real_u64_vec(modulus.clone(), limbs);
 
     // Compute -m^-1 mod 2**64 by exponentiating by totient(2**64) - 1
     let mut inv = 1u64;