diff --git a/crates/fayalite/src/expr/ops.rs b/crates/fayalite/src/expr/ops.rs
index 0c8c4fa..15c195e 100644
--- a/crates/fayalite/src/expr/ops.rs
+++ b/crates/fayalite/src/expr/ops.rs
@@ -265,7 +265,7 @@ impl Neg {
         };
         let result_ty = retval.ty();
         retval.literal_bits = arg.to_literal_bits().map(|bits| {
-            Intern::intern_owned(result_ty.bits_from_bigint_wrapping(-SInt::bits_to_bigint(&bits)))
+            Intern::intern_owned(result_ty.bits_from_bigint_wrapping(&-SInt::bits_to_bigint(&bits)))
         });
         retval
     }
@@ -372,7 +372,7 @@ fn binary_op_literal_bits<ResultTy: BoolOrIntType, Lhs: BoolOrIntType, Rhs: Bool
     let rhs = Rhs::bits_to_bigint(&rhs);
     let result = f(lhs, rhs)?;
     Ok(Intern::intern_owned(
-        result_ty.bits_from_bigint_wrapping(result),
+        result_ty.bits_from_bigint_wrapping(&result),
     ))
 }
 
@@ -1347,7 +1347,7 @@ macro_rules! binary_op_fixed_shift {
                     literal_bits: Err(NotALiteralExpr),
                 };
                 retval.literal_bits = lhs.to_literal_bits().map(|bits| {
-                    Intern::intern_owned(retval.ty().bits_from_bigint_wrapping($Trait::$method(
+                    Intern::intern_owned(retval.ty().bits_from_bigint_wrapping(&$Trait::$method(
                         $ty::bits_to_bigint(&bits),
                         rhs,
                     )))
@@ -1624,7 +1624,7 @@ macro_rules! impl_cast_int_op {
                     ty,
                     literal_bits: arg.to_literal_bits().map(|bits| {
                         Intern::intern_owned(
-                            ty.bits_from_bigint_wrapping($from::bits_to_bigint(&bits)),
+                            ty.bits_from_bigint_wrapping(&$from::bits_to_bigint(&bits)),
                         )
                     }),
                 }
diff --git a/crates/fayalite/src/int.rs b/crates/fayalite/src/int.rs
index b80c2b6..b49ca3f 100644
--- a/crates/fayalite/src/int.rs
+++ b/crates/fayalite/src/int.rs
@@ -202,17 +202,17 @@ macro_rules! impl_int {
                     bit_width: self.width(),
                 }
             }
-            pub fn bits_from_bigint_wrapping(self, v: BigInt) -> BitVec {
+            pub fn bits_from_bigint_wrapping(self, v: &BigInt) -> BitVec {
                 BoolOrIntType::bits_from_bigint_wrapping(self, v)
             }
-            pub fn from_bigint_wrapping(self, v: BigInt) -> $value<Width> {
+            pub fn from_bigint_wrapping(self, v: &BigInt) -> $value<Width> {
                 $value {
                     bits: Arc::new(self.bits_from_bigint_wrapping(v)),
                     _phantom: PhantomData,
                 }
             }
             pub fn from_int_wrapping(self, v: impl Into<BigInt>) -> $value<Width> {
-                self.from_bigint_wrapping(v.into())
+                self.from_bigint_wrapping(&v.into())
             }
             pub fn zero(self) -> $value<Width> {
                 self.from_int_wrapping(0u8)
@@ -234,7 +234,7 @@ macro_rules! impl_int {
             fn new(width: Width::SizeType) -> Self {
                 $name { width }
             }
-            fn value_from_bigint_wrapping(self, v: BigInt) -> Self::Value {
+            fn value_from_bigint_wrapping(self, v: &BigInt) -> Self::Value {
                 $value::<Width>::from_bigint_wrapping(self, v)
             }
             fn bits_to_value(bits: Cow<'_, BitSlice>) -> Self::Value {
@@ -378,7 +378,7 @@ macro_rules! impl_int {
                     self.bits.len()
                 }
             }
-            pub fn from_bigint_wrapping(ty: $name<Width>, v: BigInt) -> $value<Width> {
+            pub fn from_bigint_wrapping(ty: $name<Width>, v: &BigInt) -> $value<Width> {
                 ty.from_bigint_wrapping(v)
             }
             pub fn to_bigint(&self) -> BigInt {
@@ -603,20 +603,23 @@ pub trait BoolOrIntType: Type + sealed::BoolOrIntTypeSealed {
         UIntType::new(Self::Width::from_usize(self.width()))
     }
     fn value_from_int_wrapping(self, v: impl Into<BigInt>) -> Self::Value {
-        self.value_from_bigint_wrapping(v.into())
+        self.value_from_bigint_wrapping(&v.into())
     }
-    fn value_from_bigint_wrapping(self, v: BigInt) -> Self::Value;
-    fn bits_from_bigint_wrapping(self, v: BigInt) -> BitVec {
-        let width = self.width();
+    fn value_from_bigint_wrapping(self, v: &BigInt) -> Self::Value;
+    fn bits_from_bigint_wrapping(self, v: &BigInt) -> BitVec {
+        let mut bits = BitVec::repeat(false, self.width());
+        Self::copy_bits_from_bigint_wrapping(v, &mut bits);
+        bits
+    }
+    fn copy_bits_from_bigint_wrapping(v: &BigInt, bits: &mut BitSlice) {
+        let width = bits.len();
         let mut bytes = v.to_signed_bytes_le();
         bytes.resize(
             width.div_ceil(u8::BITS as usize),
             if v.is_negative() { 0xFF } else { 0 },
         );
         let bitslice = &BitSlice::<u8, Lsb0>::from_slice(&bytes)[..width];
-        let mut bits = BitVec::new();
-        bits.extend_from_bitslice(bitslice);
-        bits
+        bits.clone_from_bitslice(bitslice);
     }
     fn bits_to_bigint(bits: &BitSlice) -> BigInt {
         let sign_byte = if Self::Signed::VALUE && bits.last().as_deref().copied().unwrap_or(false) {
@@ -712,7 +715,7 @@ impl BoolOrIntType for Bool {
         Bool
     }
 
-    fn value_from_bigint_wrapping(self, v: BigInt) -> Self::Value {
+    fn value_from_bigint_wrapping(self, v: &BigInt) -> Self::Value {
         v.bit(0)
     }