fix: input size for exp_reverse_bits_len

extensions/native/compiler/src/ir/utils.rs

@@ -141,8 +141,7 @@ impl<C: Config> Builder<C> {
 
     /// Exponentiates a variable to a list of reversed bits with a given length.
     ///
-    /// Example: if power_bits = [1, 0, 1, 0] and bit_len = Const(4), then
-    ///          the result should be x^8 * x^2 = x^10.
+    /// Example: if power_bits = [1, 0, 1, 0], then the result should be x^8 * x^2 = x^10.
     ///
     /// Reference: [`openvm_stark_backend::p3_util::reverse_bits_len`]
     pub fn exp_reverse_bits_len<V>(&mut self, x: V, power_bits: &Array<C, Var<C::N>>) -> V

extensions/native/recursion/src/challenger/duplex.rs

@@ -139,7 +139,6 @@ impl<C: Config> DuplexChallengerVariable<C> {
         builder.range(nb_bits, bits.len()).for_each(|i, builder| {
             builder.set(&bits, i, C::N::ZERO);
         });
-
         bits
     }
 

extensions/native/recursion/src/fri/mod.rs

@@ -51,7 +51,8 @@ where
     let two_adic_gen_ext = two_adic_generator_f.to_operand().symbolic();
     let two_adic_generator_ef: Ext<_, _> = builder.eval(two_adic_gen_ext);
 
-    let x = builder.exp_reverse_bits_len(two_adic_generator_ef, index_bits);
+    let index_bits_truncated = index_bits.slice(builder, 0, log_max_height);
+    let x = builder.exp_reverse_bits_len(two_adic_generator_ef, &index_bits_truncated);
 
     builder
         .range(0, commit_phase_commits.len())

extensions/native/recursion/src/fri/two_adic_pcs.rs

@@ -197,13 +197,19 @@ pub fn verify_two_adic_pcs<C: Config>(
                             let cur_alpha_pow = builder.get(&alpha_pow, log_height);
 
                             let bits_reduced: Usize<_> = builder.eval(log_max_height - log_height);
-                            let index_bits_shifted = index_bits.shift(builder, bits_reduced);
+                            let index_bits_shifted =
+                                index_bits.shift(builder, bits_reduced.clone());
 
                             let two_adic_generator =
                                 config.get_two_adic_generator(builder, log_height);
                             builder.cycle_tracker_start("exp-reverse-bits-len");
-                            let two_adic_generator_exp = builder
-                                .exp_reverse_bits_len(two_adic_generator, &index_bits_shifted);
+
+                            let index_bits_shifted_truncated =
+                                index_bits_shifted.slice(builder, 0, log_height);
+                            let two_adic_generator_exp = builder.exp_reverse_bits_len(
+                                two_adic_generator,
+                                &index_bits_shifted_truncated,
+                            );
                             builder.cycle_tracker_end("exp-reverse-bits-len");
                             let x: Felt<C::F> = builder.eval(two_adic_generator_exp * g);