patch: G1Projective ops, fp6 compile to default target

src/g1.rs

@@ -657,6 +657,7 @@ impl_binops_multiplicative_mixed!(Scalar, G1Affine, G1Projective);
 impl_binops_multiplicative_mixed!(Scalar, G1Projective, G1Projective);
 
 #[inline(always)]
+#[cfg(not(target_os = "zkvm"))]
 fn mul_by_3b(a: Fp) -> Fp {
     let a = a + a; // 2
     let a = a + a; // 4
@@ -837,6 +838,7 @@ impl G1Projective {
     }
 
     /// Multiply `self` by `crate::BLS_X`, using double and add.
+    #[cfg(not(target_os = "zkvm"))]
     fn mul_by_x(&self) -> G1Projective {
         let mut xself = G1Projective::identity();
         // NOTE: in BLS12-381 we can just skip the first bit.
@@ -857,6 +859,27 @@ impl G1Projective {
         xself
     }
 
+    #[cfg(target_os = "zkvm")]
+    fn mul_by_x(&self) -> G1Projective {
+        let mut xself = G1Affine::identity();
+
+        let mut x = crate::BLS_X >> 1;
+        let mut tmp = G1Affine::from(*self);
+        while x != 0 {
+            tmp = tmp.double();
+
+            if x % 2 == 1 {
+                xself = &xself + tmp;
+            }
+            x >>= 1;
+        }
+        // finally, flip the sign
+        if crate::BLS_X_IS_NEGATIVE {
+            xself = -xself;
+        }
+        xself.into()
+    }
+
     /// Multiplies by $(1 - z)$, where $z$ is the parameter of BLS12-381, which
     /// [suffices to clear](https://ia.cr/2019/403) the cofactor and map
     /// elliptic curve points to elements of $\mathbb{G}\_1$.