Add benchmarks for Scalar::from_canonical_bytes

Author: elichai

benches/dalek_benchmarks.rs

@@ -1,7 +1,7 @@
 #![allow(non_snake_case)]
 
 use rand::rngs::OsRng;
-use rand::thread_rng;
+use rand::{thread_rng, Rng};
 
 use criterion::measurement::Measurement;
 use criterion::BatchSize;
@@ -47,6 +47,25 @@ mod edwards_benches {
         });
     }
 
+    fn scalar_from_canonical_bytes(c: &mut Criterion) {
+        let bytes = [0xFF; 32];
+        c.bench_function("Max scalar from_canonical_bytes", move |b| {
+            b.iter(|| Scalar::from_canonical_bytes(bytes))
+        });
+        let bytes = [0u8; 32];
+        c.bench_function("Zero scalar from_canonical_bytes", move |b| {
+            b.iter(|| Scalar::from_canonical_bytes(bytes))
+        });
+        c.bench_function("Rand scalar from_canonical_bytes", |bench| {
+            let mut rng = thread_rng();
+            bench.iter_batched(
+                || rng.gen(),
+                |bytes| Scalar::from_canonical_bytes(bytes),
+                BatchSize::SmallInput,
+            );
+        });
+    }
+
     fn vartime_double_base_scalar_mul(c: &mut Criterion) {
         c.bench_function("Variable-time aA+bB, A variable, B fixed", |bench| {
             let mut rng = thread_rng();
@@ -68,6 +87,7 @@ mod edwards_benches {
         consttime_fixed_base_scalar_mul,
         consttime_variable_base_scalar_mul,
         vartime_double_base_scalar_mul,
+        scalar_from_canonical_bytes,
     }
 }