10243: Fake verification routine for avm recursion in public base rollup

noir-projects/noir-protocol-circuits/crates/rollup-lib/src/base/public_base_rollup.nr

@@ -97,6 +97,11 @@ impl PublicBaseRollupInputs {
             // self.tube_data.vk_data.validate_in_vk_tree([TUBE_VK_INDEX]);
         }
 
+        // Warning: Fake verification! TODO(#8470)
+        if !dep::std::runtime::is_unconstrained() {
+            self.avm_proof_data.fake_verify();
+        }
+
         // TODO(#8470)
         // if !dep::std::runtime::is_unconstrained() {
         //     self.avm_proof_data.verify();

noir-projects/noir-protocol-circuits/crates/types/src/abis/avm_circuit_public_inputs.nr

@@ -16,11 +16,14 @@ use crate::{
         AVM_CIRCUIT_PUBLIC_INPUTS_LENGTH, AVM_VERIFICATION_KEY_LENGTH_IN_FIELDS,
         MAX_ENQUEUED_CALLS_PER_TX,
     },
+    hash::poseidon2_hash,
     proof::{avm_proof::AvmProof, traits::Verifiable, vk_data::VkData},
     traits::{Deserialize, Empty, Serialize},
     utils::reader::Reader,
 };
 
+use std::hash::{poseidon2, poseidon2_permutation};
+
 pub struct AvmCircuitPublicInputs {
     ///////////////////////////////////
     // Inputs.
@@ -180,6 +183,39 @@ pub struct AvmProofData {
     pub vk_data: VkData<AVM_VERIFICATION_KEY_LENGTH_IN_FIELDS>,
 }
 
+// The number of columns for the AVM recursive verifier we want to fake, i.e., the resulting
+// verify() routine below will create a similar number of gates as a real AVM recursive verifier
+// with the number of columns set by this constant.
+pub global DUMMY_AVM_VERIFIER_NUM_COLUMNS: u32 = 3000;
+
+// Current AVM recursive verifier has 7000 gates per column.
+// Note that the addition of a single column in AVM recursive verifier incurs 6600 gates.
+// (some additional costs due to lookups/perms, etc...).
+// 78 gates per Poseidon permutation
+// 7000/78 = 89.7
+pub global DUMMY_AVM_VERIFIER_NUM_ITERATIONS: u32 = DUMMY_AVM_VERIFIER_NUM_COLUMNS * 90;
+
+// Warning: This is a fake avm recursive verification whose sole goal is to reproduce a similar
+// computational effort (number of gates) as the real recursive verifier.
+// TODO(#8470): Replace with the real AVM recursive verifier
+impl AvmProofData {
+    pub fn fake_verify(self) {
+        let mut input_hash = poseidon2::Poseidon2::hash(
+            [self.public_inputs.transaction_fee, self.proof.fields[0], self.vk_data.vk.key[0]],
+            3,
+        );
+
+        //let mut result: [Field; 1] = [input_hash];
+        let mut result: [Field; 4] = [input_hash, 0, 0, 0];
+        for i in 0..DUMMY_AVM_VERIFIER_NUM_ITERATIONS {
+            result = poseidon2_permutation(result, 4);
+            //result = poseidon2_hash([result]);
+        }
+
+        assert(!result[0].lt(1));
+    }
+}
+
 impl Verifiable for AvmProofData {
     fn verify(self) {
         // TODO(#8470)