cherry pick 452a80c

Cargo.toml

@@ -31,6 +31,7 @@ ethers-core = { git = "https://github.com/scroll-tech/ethers-rs.git", branch = "
 [features]
 # printout the layout of circuits for demo and some unittests
 print_layout = ["halo2_proofs/dev-graph"]
+default = ["halo2_proofs/mock-batch-inv", "halo2_proofs/parallel_syn"]
 
 [dev-dependencies]
 mpt-zktrie = { git = "https://github.com/scroll-tech/zkevm-circuits.git", rev = "7d9bc181953cfc6e7baf82ff0ce651281fd70a8a" }

src/constraint_builder/column.rs

@@ -3,7 +3,7 @@ use crate::assignment_map::Column as ColumnEnum;
 use halo2_proofs::{
     arithmetic::FieldExt,
     circuit::{Region, Value},
-    plonk::{Advice, Column, Fixed},
+    plonk::{Advice, Assigned, Column, Fixed},
 };
 use std::fmt::Debug;
 
@@ -141,6 +141,22 @@ impl AdviceColumn {
             Value::known(value.try_into().unwrap()),
         )
     }
+
+    pub fn assign_inverse_or_zero<F: FieldExt>(
+        &self,
+        region: &mut Region<'_, F>,
+        offset: usize,
+        value: F,
+    ) {
+        region
+            .assign_advice(
+                || "advice",
+                self.0,
+                offset,
+                || Value::known(Assigned::<F>::from(value).invert()),
+            )
+            .expect("failed assign_inverse_or_zero");
+    }
 }
 
 #[derive(Clone, Copy, Hash, Eq, PartialEq, PartialOrd, Ord)]

src/gadgets/is_zero.rs

@@ -30,11 +30,8 @@ impl IsZeroGadget {
     ) where
         <T as TryInto<F>>::Error: Debug,
     {
-        self.inverse_or_zero.assign(
-            region,
-            offset,
-            value.try_into().unwrap().invert().unwrap_or(F::zero()),
-        );
+        self.inverse_or_zero
+            .assign_inverse_or_zero(region, offset, value.try_into().unwrap());
     }
 
     pub fn assignments<F: FieldExt, T: Copy + TryInto<F>>(
@@ -49,7 +46,7 @@ impl IsZeroGadget {
             self.value.assignment(offset, value),
             self.inverse_or_zero.assignment(
                 offset,
-                value.try_into().unwrap().invert().unwrap_or(F::zero()),
+                (value.try_into().unwrap()).invert().unwrap_or_else(F::zero),
             ),
         ]
     }