Add support for generic integer type conversions to Expression::Constant

ceno_zkvm/src/expression.rs

@@ -652,12 +652,43 @@ impl<F: SmallField, E: ExtensionField<BaseField = F>> ToExpr<E> for F {
     }
 }
 
-impl<F: SmallField, E: ExtensionField<BaseField = F>> From<usize> for Expression<E> {
-    fn from(value: usize) -> Self {
-        Expression::Constant(F::from(value as u64))
+// Implement From trait for unsigned types of at most 64 bits
+macro_rules! impl_from_unsigned {
+    ($($t:ty),*) => {
+        $(
+            impl<F: SmallField, E: ExtensionField<BaseField = F>> From<$t> for Expression<E> {
+                fn from(value: $t) -> Self {
+                    Expression::Constant(F::from(value as u64))
+                }
+            }
+        )*
+    };
+}
+impl_from_unsigned!(u8, u16, u32, u64, usize);
+
+// Implement From trait for u128 separately since it requires explicit reduction
+impl<F: SmallField, E: ExtensionField<BaseField = F>> From<u128> for Expression<E> {
+    fn from(value: u128) -> Self {
+        let reduced = value.rem_euclid(F::MODULUS_U64 as u128) as u64;
+        Expression::Constant(F::from(reduced))
     }
 }
 
+// Implement From trait for signed types
+macro_rules! impl_from_signed {
+    ($($t:ty),*) => {
+        $(
+            impl<F: SmallField, E: ExtensionField<BaseField = F>> From<$t> for Expression<E> {
+                fn from(value: $t) -> Self {
+                    let reduced = (value as i128).rem_euclid(F::MODULUS_U64 as i128) as u64;
+                    Expression::Constant(F::from(reduced))
+                }
+            }
+        )*
+    };
+}
+impl_from_signed!(i8, i16, i32, i64, i128, isize);
+
 impl<E: ExtensionField> Display for Expression<E> {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         let mut wtns = vec![];

ceno_zkvm/src/gadgets/is_lt.rs

@@ -81,7 +81,7 @@ impl IsLtConfig {
                     .reduce(|a, b| a + b)
                     .expect("reduce error");
 
-                let range = (1 << (max_num_u16_limbs * u16::BITS as usize)).into();
+                let range = (1u64 << (max_num_u16_limbs * u16::BITS as usize)).into();
 
                 cb.require_equal(|| name.clone(), lhs - rhs, diff_expr - is_lt_expr * range)?;
 

ceno_zkvm/src/instructions/riscv/b_insn.rs

@@ -62,9 +62,9 @@ impl<E: ExtensionField> BInstructionConfig<E> {
         // Fetch instruction
         circuit_builder.lk_fetch(&InsnRecord::new(
             vm_state.pc.expr(),
-            (insn_kind.codes().opcode as usize).into(),
+            insn_kind.codes().opcode.into(),
             0.into(),
-            (insn_kind.codes().func3 as usize).into(),
+            insn_kind.codes().func3.into(),
             rs1.id.expr(),
             rs2.id.expr(),
             imm.expr(),

ceno_zkvm/src/instructions/riscv/divu.rs

@@ -60,7 +60,7 @@ impl<E: ExtensionField, I: RIVInstruction> Instruction<E> for ArithInstruction<E
                 || "outcome_is_zero",
                 is_zero.expr(),
                 outcome_value.clone(),
-                ((1 << UInt::<E>::M) - 1).into(),
+                ((1u64 << UInt::<E>::M) - 1).into(),
                 outcome_value,
             )
             .unwrap();

ceno_zkvm/src/instructions/riscv/i_insn.rs

@@ -44,9 +44,9 @@ impl<E: ExtensionField> IInstructionConfig<E> {
         // Fetch the instruction.
         circuit_builder.lk_fetch(&InsnRecord::new(
             vm_state.pc.expr(),
-            (insn_kind.codes().opcode as usize).into(),
+            insn_kind.codes().opcode.into(),
             rd.id.expr(),
-            (insn_kind.codes().func3 as usize).into(),
+            insn_kind.codes().func3.into(),
             rs1.id.expr(),
             0.into(),
             imm.clone(),

ceno_zkvm/src/instructions/riscv/r_insn.rs

@@ -44,12 +44,12 @@ impl<E: ExtensionField> RInstructionConfig<E> {
         // Fetch instruction
         circuit_builder.lk_fetch(&InsnRecord::new(
             vm_state.pc.expr(),
-            (insn_kind.codes().opcode as usize).into(),
+            insn_kind.codes().opcode.into(),
             rd.id.expr(),
-            (insn_kind.codes().func3 as usize).into(),
+            insn_kind.codes().func3.into(),
             rs1.id.expr(),
             rs2.id.expr(),
-            (insn_kind.codes().func7 as usize).into(),
+            insn_kind.codes().func7.into(),
         ))?;
 
         Ok(RInstructionConfig {