Introduce PhantomData for SignedExtendConfig

ceno_zkvm/src/gadgets/signed_ext.rs

@@ -7,31 +7,33 @@ use crate::{
     witness::LkMultiplicity,
 };
 use ff_ext::ExtensionField;
-use std::mem::MaybeUninit;
+use std::{marker::PhantomData, mem::MaybeUninit};
 
-pub struct SignedExtendConfig {
+pub struct SignedExtendConfig<E> {
     /// most significant bit
     msb: WitIn,
     /// number of bits contained in the value
     n_bits: usize,
+
+    _marker: PhantomData<E>,
 }
 
-impl SignedExtendConfig {
-    pub fn construct_limb<E: ExtensionField>(
+impl<E: ExtensionField> SignedExtendConfig<E> {
+    pub fn construct_limb(
         cb: &mut CircuitBuilder<E>,
         val: Expression<E>,
     ) -> Result<Self, ZKVMError> {
         Self::construct_circuit(cb, 16, val)
     }
 
-    pub fn construct_byte<E: ExtensionField>(
+    pub fn construct_byte(
         cb: &mut CircuitBuilder<E>,
         val: Expression<E>,
     ) -> Result<Self, ZKVMError> {
         Self::construct_circuit(cb, 8, val)
     }
 
-    fn construct_circuit<E: ExtensionField>(
+    fn construct_circuit(
         cb: &mut CircuitBuilder<E>,
         n_bits: usize,
         val: Expression<E>, // it's assumed that val is within [0, 2^N_BITS)
@@ -56,11 +58,15 @@ impl SignedExtendConfig {
             2 * val - (msb.expr() << n_bits),
         )?;
 
-        Ok(SignedExtendConfig { msb, n_bits })
+        Ok(SignedExtendConfig {
+            msb,
+            n_bits,
+            _marker: PhantomData,
+        })
     }
 
     /// Get the signed extended value
-    pub fn signed_extended_value<E: ExtensionField>(&self, val: Expression<E>) -> UInt<E> {
+    pub fn signed_extended_value(&self, val: Expression<E>) -> UInt<E> {
         assert_eq!(UInt::<E>::LIMB_BITS, 16);
 
         let limb0 = match self.n_bits {
@@ -71,7 +77,7 @@ impl SignedExtendConfig {
         UInt::from_exprs_unchecked(vec![limb0, self.msb.expr() * 0xffff])
     }
 
-    pub fn assign_instance<E: ExtensionField>(
+    pub fn assign_instance(
         &self,
         instance: &mut [MaybeUninit<E::BaseField>],
         lk_multiplicity: &mut LkMultiplicity,

ceno_zkvm/src/instructions/riscv/memory/load.rs

@@ -30,7 +30,7 @@ pub struct LoadConfig<E: ExtensionField> {
     memory_read: UInt<E>,
     target_limb: Option<WitIn>,
     target_limb_bytes: Option<Vec<WitIn>>,
-    signed_extend_config: Option<SignedExtendConfig>,
+    signed_extend_config: Option<SignedExtendConfig<E>>,
 }
 
 pub struct LoadInstruction<E, I>(PhantomData<(E, I)>);
@@ -249,7 +249,7 @@ impl<E: ExtensionField, I: RIVInstruction> Instruction<E> for LoadInstruction<E,
             _ => 0,
         };
         if let Some(signed_ext_config) = config.signed_extend_config.as_ref() {
-            signed_ext_config.assign_instance::<E>(instance, lk_multiplicity, val)?;
+            signed_ext_config.assign_instance(instance, lk_multiplicity, val)?;
         }
 
         Ok(())