chore: optimize poseidon2 implementation (#4807)

# Description

## Problem\*

Resolves <!-- Link to GitHub Issue -->

## Summary\*

This PR removes the usage of a `BigUint` from the poseidon2 solver. I've
also wrapped all of the config in a `lazy_static` to avoid having to
re-instantiate it each time.

## Additional Context



## Documentation\*

Check one:
- [x] No documentation needed.
- [ ] Documentation included in this PR.
- [ ] **[For Experimental Features]** Documentation to be submitted in a
separate PR.

# PR Checklist\*

- [x] I have tested the changes locally.
- [x] I have formatted the changes with [Prettier](https://prettier.io/)
and/or `cargo fmt` on default settings.

acvm-repo/bn254_blackbox_solver/Cargo.toml

@@ -16,8 +16,9 @@ repository.workspace = true
 acir.workspace = true
 acvm_blackbox_solver.workspace = true
 thiserror.workspace = true
-num-traits.workspace = true
 cfg-if = "1.0.0"
+hex.workspace = true
+lazy_static = "1.4"
 
 # BN254 fixed base scalar multiplication solver
 grumpkin = { version = "0.1.0", package = "noir_grumpkin", features = ["std"] } 
@@ -38,6 +39,18 @@ js-sys.workspace = true
 getrandom.workspace = true
 wasmer = "4.2.6"
 
+[dev-dependencies]
+criterion = "0.5.0"
+pprof = { version = "0.12", features = [
+    "flamegraph",
+    "frame-pointer",
+    "criterion",
+] }
+
+[[bench]]
+name = "criterion"
+harness = false
+
 [features]
 default = ["bn254"]
 bn254 = ["acir/bn254"]

acvm-repo/bn254_blackbox_solver/benches/criterion.rs

@@ -0,0 +1,21 @@
+use criterion::{criterion_group, criterion_main, Criterion};
+use std::{hint::black_box, time::Duration};
+
+use acir::FieldElement;
+use bn254_blackbox_solver::poseidon2_permutation;
+
+use pprof::criterion::{Output, PProfProfiler};
+
+fn bench_poseidon2(c: &mut Criterion) {
+    let inputs = [FieldElement::zero(); 4];
+
+    c.bench_function("poseidon2", |b| b.iter(|| poseidon2_permutation(black_box(&inputs), 4)));
+}
+
+criterion_group!(
+    name = benches;
+    config = Criterion::default().sample_size(40).measurement_time(Duration::from_secs(20)).with_profiler(PProfProfiler::new(100, Output::Flamegraph(None)));
+    targets = bench_poseidon2
+);
+
+criterion_main!(benches);

acvm-repo/bn254_blackbox_solver/src/lib.rs

@@ -10,7 +10,7 @@ mod poseidon2;
 mod wasm;
 
 pub use fixed_base_scalar_mul::{embedded_curve_add, fixed_base_scalar_mul};
-use poseidon2::Poseidon2;
+pub use poseidon2::poseidon2_permutation;
 use wasm::Barretenberg;
 
 use self::wasm::{Pedersen, SchnorrSig};
@@ -112,7 +112,6 @@ impl BlackBoxFunctionSolver for Bn254BlackBoxSolver {
         inputs: &[FieldElement],
         len: u32,
     ) -> Result<Vec<FieldElement>, BlackBoxResolutionError> {
-        let poseidon = Poseidon2::new();
-        poseidon.permutation(inputs, len)
+        poseidon2_permutation(inputs, len)
     }
 }