Add MontFp macros replacement to generate field literals

ff-macros/Cargo.toml

@@ -23,3 +23,6 @@ num-traits.workspace = true
 
 [lib]
 proc-macro = true
+
+[features]
+zkllvm = []

ff-macros/src/lib.rs

@@ -8,7 +8,7 @@
 #![forbid(unsafe_code)]
 
 use num_bigint::BigUint;
-use proc_macro::TokenStream;
+use proc_macro::{Literal, TokenStream, TokenTree};
 use syn::{Expr, Item, ItemFn, Lit};
 
 mod montgomery;
@@ -27,6 +27,13 @@ pub fn to_sign_and_limbs(input: TokenStream) -> TokenStream {
     quote::quote!(#tuple).into()
 }
 
+#[cfg(feature = "zkllvm")]
+#[proc_macro]
+pub fn to_field_literal(input: TokenStream) -> TokenStream {
+    let num = utils::parse_string(input).expect("expected decimal string");
+    TokenTree::Literal(Literal::field(&num)).into()
+}
+
 /// Derive the `MontConfig` trait.
 ///
 /// The attributes available to this macro are

ff/Cargo.toml

@@ -48,6 +48,7 @@ default = []
 std = [ "ark-std/std", "ark-serialize/std", "itertools/use_std" ]
 parallel = [ "std", "rayon", "ark-std/parallel" ]
 asm = []
+zkllvm = [ "ark-ff-macros/zkllvm" ]
 
 
 [package.metadata.docs.rs]

ff/src/fields/models/fp/montgomery_backend.rs

@@ -588,13 +588,22 @@ pub const fn sqrt_precomputation<const N: usize, T: MontConfig<N>>(
 /// }
 /// ```
 #[macro_export]
+#[cfg(not(feature = "zkllvm"))]
 macro_rules! MontFp {
     ($c0:expr) => {{
         let (is_positive, limbs) = $crate::ark_ff_macros::to_sign_and_limbs!($c0);
         $crate::Fp::from_sign_and_limbs(is_positive, &limbs)
     }};
 }
 
+#[macro_export]
+#[cfg(feature = "zkllvm")]
+macro_rules! MontFp {
+    ($c0:expr) => {{
+        $crate::ark_ff_macros::to_field_literal!($c0)
+    }};
+}
+
 pub use ark_ff_macros::MontConfig;
 
 pub use MontFp;