fix: ec_mul

crates/evm/src/precompiles/ec_mul.cairo

@@ -94,7 +94,11 @@ fn get_bits_little(s: u256) -> Array<felt252> {
         s_low = q;
     };
     let mut s_high = s.high;
-
+    if s_high != 0 {
+        while bits.len() != 128 {
+            bits.append(0);
+        }
+    }
     while s_high != 0 {
         let (q, r) = core::traits::DivRem::div_rem(s_high, 2);
         bits.append(r.into());
@@ -108,21 +112,32 @@ fn get_bits_little(s: u256) -> Array<felt252> {
 // Returns Option::None in case of point at infinity.
 // The size of bits array must be at minimum 2 and the point must be on the curve.
 fn ec_mul_inner(pt: (u384, u384), mut bits: Array<felt252>) -> Option<(u384, u384)> {
-    let (x_o, y_o) = pt;
-    let mut pt = Option::Some(pt);
+    let (mut temp_x, mut temp_y) = pt;
+    let mut result: Option<(u384, u384)> = Option::None;
     while let Option::Some(bit) = bits.pop_front() {
-        match pt {
-            Option::Some((xt, yt)) => pt = Option::Some(double_ec_point_unchecked(xt, yt)),
-            Option::None => pt = Option::None,
-        }
-
         if bit != 0 {
-            match pt {
-                Option::Some((xt, yt)) => pt = ec_safe_add(x_o, y_o, xt, yt),
-                Option::None => pt = Option::Some((x_o, y_o)),
+            match result {
+                Option::Some((xr, yr)) => result = ec_safe_add(temp_x, temp_y, xr, yr),
+                Option::None => result = Option::Some((temp_x, temp_y)),
             };
         };
+        let (_temp_x, _temp_y) = double_ec_point_unchecked(temp_x, temp_y);
+        temp_x = _temp_x;
+        temp_y = _temp_y;
     };
 
-    pt
+    return result;
+}
+
+#[cfg(test)]
+mod tests {
+    use super::ec_mul;
+
+    #[test]
+    fn test_ec_mul() {
+        let (x1,y1,s) = (1,2,2);
+        let (x, y) = ec_mul(x1, y1, s).expect('ec_mul failed');
+        assert_eq!(x, 0x030644e72e131a029b85045b68181585d97816a916871ca8d3c208c16d87cfd3);
+        assert_eq!(y, 0x15ed738c0e0a7c92e7845f96b2ae9c0a68a6a449e3538fc7ff3ebf7a5a18a2c4);
+    }
 }