diff --git a/src/ast.rs b/src/ast.rs
index 0c987f9..ae47fc6 100644
--- a/src/ast.rs
+++ b/src/ast.rs
@@ -1,7 +1,5 @@
 use std::num::NonZero;
 
-use itertools::Itertools;
-
 use crate::string_table::{self, ImmOrIndex};
 
 pub type Node = NonZero<u32>;
@@ -229,6 +227,9 @@ impl IntegralType {
             bits: 32,
         }
     }
+    pub fn u64_bitmask(self) -> u64 {
+        (1u64 << self.bits) - 1
+    }
 }
 
 #[derive(Debug, Clone, Eq, Hash)]
diff --git a/src/comptime.rs b/src/comptime.rs
new file mode 100644
index 0000000..2eed83e
--- /dev/null
+++ b/src/comptime.rs
@@ -0,0 +1,995 @@
+pub mod bigint {
+
+    use crate::lexer::Radix;
+    /// A base-4_294_967_295 number.
+    #[derive(Clone)]
+    pub struct BigInt(Vec<u32>);
+
+    impl BigInt {
+        pub fn parse_digits<C: IntoIterator<Item = char>>(text: C, radix: Radix) -> BigInt {
+            parse_bigint(text.into_iter(), radix)
+        }
+
+        pub fn one() -> BigInt {
+            Self(vec![1])
+        }
+        pub fn zero() -> BigInt {
+            Self(vec![])
+        }
+
+        pub fn num_digits(&self) -> usize {
+            self.0.iter().rposition(|&d| d != 0).map_or(0, |i| i + 1)
+        }
+
+        pub fn bit_width(&self) -> usize {
+            count_bits(&self.0)
+        }
+
+        pub fn is_zero(&self) -> bool {
+            bigint_is_zero(&self.0)
+        }
+
+        pub fn is_one(&self) -> bool {
+            bigint_is_one(&self.0)
+        }
+
+        pub fn is_power_of_two(&self) -> bool {
+            is_power_of_two(&self.0)
+        }
+
+        pub fn trailing_zeros(&self) -> usize {
+            trailing_zeros(&self.0)
+        }
+
+        pub fn from_bytes_le(bytes: &[u8]) -> BigInt {
+            let data = bytes
+                .chunks(4)
+                .map(|chunk| {
+                    let mut int = [0u8; 4];
+                    int[..chunk.len()].copy_from_slice(chunk);
+                    u32::from_le_bytes(int)
+                })
+                .collect::<Vec<_>>();
+
+            BigInt(data)
+        }
+
+        pub fn into_bytes_le(&self) -> Vec<u8> {
+            let mut bytes = Vec::<u8>::new();
+
+            for d in &self.0[..] {
+                bytes.extend(&d.to_le_bytes());
+            }
+
+            let count = bytes.iter().rev().take_while(|&&b| b == 0).count();
+            bytes.truncate(bytes.len() - count);
+
+            bytes
+        }
+
+        pub fn normalise(&mut self) {
+            let len = self.0.iter().rposition(|&d| d != 0).map_or(0, |i| i + 1);
+            self.0.truncate(len);
+        }
+
+        pub fn normalised(mut self) -> BigInt {
+            self.normalise();
+            self
+        }
+
+        pub fn into_u64(&self) -> Option<u64> {
+            if self.0.len() <= 2 {
+                let mut bytes = [0u8; 8];
+                self.0
+                    .get(0)
+                    .map(|&dw| bytes[..4].copy_from_slice(&dw.to_le_bytes()));
+                self.0
+                    .get(1)
+                    .map(|&dw| bytes[4..].copy_from_slice(&dw.to_le_bytes()));
+                Some(u64::from_le_bytes(bytes))
+            } else {
+                None
+            }
+        }
+    }
+
+    impl core::cmp::PartialEq for BigInt {
+        fn eq(&self, other: &Self) -> bool {
+            cmp_bigint(&self.0, &other.0) == core::cmp::Ordering::Equal
+        }
+    }
+
+    impl core::cmp::Eq for BigInt {}
+
+    impl core::cmp::PartialOrd for BigInt {
+        fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
+            Some(cmp_bigint(&self.0, &other.0))
+        }
+    }
+    impl core::cmp::Ord for BigInt {
+        fn cmp(&self, other: &Self) -> std::cmp::Ordering {
+            cmp_bigint(&self.0, &other.0)
+        }
+    }
+
+    impl core::ops::Shl<usize> for BigInt {
+        type Output = Self;
+
+        fn shl(mut self, rhs: usize) -> Self::Output {
+            shl_bitint(&mut self.0, rhs);
+            self
+        }
+    }
+    impl core::ops::Shr<usize> for BigInt {
+        type Output = Self;
+
+        fn shr(mut self, rhs: usize) -> Self::Output {
+            shr_bitint(&mut self.0, rhs);
+            self
+        }
+    }
+
+    impl core::ops::Add for BigInt {
+        type Output = Self;
+
+        fn add(mut self, mut rhs: Self) -> Self::Output {
+            let (mut digits, carry) = if self.0.len() > rhs.0.len() {
+                let c = add_bigint(&mut self.0, &rhs.0);
+                (self.0, c)
+            } else {
+                let c = add_bigint(&mut rhs.0, &self.0);
+                (rhs.0, c)
+            };
+
+            if carry {
+                digits.push(u32::from(carry));
+            }
+
+            BigInt(digits)
+        }
+    }
+
+    impl core::ops::Sub for BigInt {
+        type Output = Self;
+
+        fn sub(mut self, rhs: Self) -> Self::Output {
+            if self.0.len() < rhs.0.len() {
+                println!("extending self by {} zeroes", rhs.0.len() - self.0.len());
+                self.0
+                    .extend(core::iter::repeat(0).take(rhs.0.len() - self.0.len()));
+                println!("self: {self:?}");
+            }
+            sub_bigint(&mut self.0, &rhs.0);
+
+            self
+        }
+    }
+
+    impl core::ops::Mul for BigInt {
+        type Output = Self;
+
+        fn mul(self, rhs: Self) -> Self::Output {
+            BigInt(mul_bigint(&self.0, &rhs.0))
+        }
+    }
+
+    impl core::ops::Div for BigInt {
+        type Output = Self;
+
+        fn div(self, rhs: Self) -> Self::Output {
+            div_rem_bigint(self, rhs).0
+        }
+    }
+
+    impl core::ops::Rem for BigInt {
+        type Output = Self;
+
+        fn rem(self, rhs: Self) -> Self::Output {
+            div_rem_bigint(self, rhs).1
+        }
+    }
+
+    impl core::ops::Not for BigInt {
+        type Output = Self;
+
+        fn not(mut self) -> Self::Output {
+            self.0.iter_mut().for_each(|c| *c = !*c);
+            self
+        }
+    }
+
+    impl core::fmt::Debug for BigInt {
+        fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+            let mut list = f.debug_list();
+            list.entries(self.0.iter().rev()).finish()
+        }
+    }
+
+    /// counts used bits in a u32 slice, discards leading zeros in MSB.
+    /// `[0xff,0xff,0x00,0x00]` -> 16
+    /// `[0xff,0xff,0x00]` -> 16
+    /// `[0xff,0xff,0x0f]` -> 20
+    pub fn count_bits(bytes: &[u32]) -> usize {
+        let mut bits = bytes.len() * u32::BITS as usize;
+
+        for &d in bytes.iter().rev() {
+            if d == 0 {
+                bits -= u32::BITS as usize;
+            } else {
+                bits -= d.leading_zeros() as usize;
+                break;
+            }
+        }
+
+        bits
+    }
+
+    #[test]
+    fn test_count_bits() {
+        assert_eq!(count_bits(&[0xffffffff, 0x00, 0x00]), 32);
+        assert_eq!(count_bits(&[0x00, 0x00, 0x00]), 0);
+        assert_eq!(count_bits(&[]), 0);
+        assert_eq!(count_bits(&[0xffffffff, 0xff, 0x00]), 40);
+        assert_eq!(count_bits(&[0xffffffff, 0xff]), 40);
+        assert_eq!(count_bits(&[0xffffffff, 0xff, 0xffff]), 64 + 16);
+    }
+    #[test]
+    fn test_count_trailing_zeros() {
+        assert_eq!(trailing_zeros(&[0xffffffff, 0x00, 0x00]), 0);
+        assert_eq!(trailing_zeros(&[0x00, 0x00, 0x00]), 0);
+        assert_eq!(trailing_zeros(&[]), 0);
+        assert_eq!(trailing_zeros(&[0x00, 0xffffffff, 0xff]), 32);
+        assert_eq!(trailing_zeros(&[0x00, 0xffffff00, 0xff]), 40);
+    }
+
+    #[allow(unused)]
+    /// lhs <=> rhs
+    fn cmp_bigint(lhs: &[u32], rhs: &[u32]) -> core::cmp::Ordering {
+        use core::cmp::Ordering;
+        let lhs_bits = count_bits(lhs);
+        let rhs_bits = count_bits(rhs);
+
+        match lhs_bits.cmp(&rhs_bits) {
+            Ordering::Less => Ordering::Less,
+            Ordering::Greater => Ordering::Greater,
+            Ordering::Equal => {
+                for (a, b) in lhs[..(lhs_bits / u32::BITS as usize)]
+                    .iter()
+                    .zip(rhs[..(lhs_bits / u32::BITS as usize)].iter())
+                    .rev()
+                {
+                    let ord = a.cmp(b);
+                    if ord != Ordering::Equal {
+                        return ord;
+                    }
+                }
+                return Ordering::Equal;
+            }
+        }
+    }
+
+    fn bigint_is_zero(lhs: &[u32]) -> bool {
+        if lhs.len() == 0 {
+            true
+        } else {
+            lhs.iter().all(|c| c == &0)
+        }
+    }
+
+    #[allow(dead_code)]
+    fn bigint_is_one(lhs: &[u32]) -> bool {
+        lhs.len() > 0 && lhs[0] == 1 && lhs[1..].iter().all(|c| c == &0)
+    }
+
+    #[allow(dead_code)]
+    fn bitnot_bigint(lhs: &mut [u32]) {
+        for d in lhs.iter_mut() {
+            *d = !*d;
+        }
+    }
+
+    #[allow(dead_code)]
+    fn u32_mul_bigint(lhs: &mut Vec<u32>, scalar: u32) {
+        match scalar {
+            0 => {
+                lhs.clear();
+                lhs.push(0)
+            }
+            1 => {}
+            _ => {
+                if scalar.is_power_of_two() {
+                    lhs.push(0);
+                    shl_bitint(lhs.as_mut_slice(), scalar.trailing_zeros() as usize);
+                } else {
+                    let mut carry = 0;
+                    for a in lhs.iter_mut() {
+                        (*a, carry) = (*a).carrying_mul(scalar, carry);
+                    }
+                    if carry != 0 {
+                        lhs.push(carry);
+                    }
+                }
+            }
+        }
+    }
+
+    #[allow(dead_code)]
+    fn u64_mul_bigint(lhs: &mut Vec<u32>, scalar: u64) {
+        let lo = scalar as u32;
+        let hi = (scalar >> 32) as u32;
+        u32_mul_bigint(lhs, lo);
+        shl_bitint(lhs, 32);
+        u32_mul_bigint(lhs, hi);
+    }
+
+    #[allow(dead_code)]
+    fn mul_bigint(lhs: &[u32], rhs: &[u32]) -> Vec<u32> {
+        if bigint_is_zero(lhs) || bigint_is_zero(rhs) {
+            return vec![];
+        }
+
+        let len = lhs.len() + rhs.len() + 1;
+        let mut product = vec![0u32; len];
+
+        for (bth, &b) in rhs.iter().enumerate() {
+            let mut carry = 0u32;
+
+            for (ath, &a) in lhs.iter().enumerate() {
+                let prod;
+                (prod, carry) = a.carrying_mul(b, carry);
+                let (digit, c) = product[ath + bth].carrying_add(prod, false);
+                carry += c as u32;
+                product[ath + bth] = digit;
+            }
+
+            if carry != 0 {
+                product[bth + lhs.len()] += carry;
+            }
+        }
+
+        product
+    }
+
+    #[allow(dead_code)]
+    fn sum_digits(digits: &[u32]) -> u64 {
+        let mut sum = 0u64;
+
+        let mut carry = false;
+        for &d in digits {
+            (sum, carry) = sum.carrying_add(d as u64, carry);
+        }
+
+        sum + carry as u64
+    }
+
+    #[allow(dead_code)]
+    fn count_ones(lhs: &[u32]) -> usize {
+        lhs.iter()
+            .fold(0usize, |acc, c| acc + c.count_ones() as usize)
+    }
+
+    #[allow(dead_code)]
+    fn trailing_zeros(lhs: &[u32]) -> usize {
+        lhs.iter()
+            .enumerate()
+            .find(|(_, &c)| c != 0)
+            .map(|(i, &c)| i * u32::BITS as usize + c.trailing_zeros() as usize)
+            .unwrap_or(0)
+    }
+
+    #[allow(dead_code)]
+    fn is_power_of_two(lhs: &[u32]) -> bool {
+        count_ones(lhs) == 1
+    }
+
+    #[allow(dead_code)]
+    /// divident must be at least as wide as divisor
+    /// returns (quotient, remainder)
+    fn div_rem_bigint(divident: BigInt, divisor: BigInt) -> (BigInt, BigInt) {
+        let divident = divident.normalised();
+        let mut divisor = divisor.normalised();
+
+        if bigint_is_zero(&divisor.0) {
+            panic!("divide by zero!");
+        }
+        if bigint_is_zero(&divident.0) {
+            return (BigInt::zero(), BigInt::zero());
+        }
+        use core::cmp::Ordering;
+        match cmp_bigint(&divident.0, &divisor.0) {
+            Ordering::Less => return (BigInt::zero(), divident),
+            Ordering::Equal => {
+                return (BigInt::one(), BigInt::zero());
+            }
+            Ordering::Greater => {}
+        }
+
+        if divisor.is_power_of_two() {
+            let exp = divisor.trailing_zeros();
+            let (div, rem) = divident.0.split_at(exp.div_floor(u32::BITS as usize));
+            let (mut div, mut rem) = (div.to_vec(), rem.to_vec());
+
+            shr_bitint(&mut div, exp % u32::BITS as usize);
+            let mask = (1u32 << exp as u32 % u32::BITS) - 1;
+            if let Some(last) = rem.last_mut() {
+                *last &= mask;
+            }
+
+            return (BigInt(div), BigInt(rem));
+        }
+
+        if divisor.num_digits() == 1 {
+            if divisor.0[0] == 1 {
+                return (divident, BigInt::zero());
+            }
+
+            let (div, rem) = div_digit_bigint(divident, divisor.0[0]);
+            divisor.0.clear();
+            divisor.0.push(rem);
+            return (div, divisor);
+        }
+
+        let shift = divisor.0.last().unwrap().leading_zeros() as usize;
+        if shift == 0 {
+            div_rem_core(divident, &divisor.0)
+        } else {
+            let (q, r) = div_rem_core(divident << shift, &(divisor << shift).0);
+
+            (q, r >> shift)
+        }
+    }
+
+    fn scalar_div_wide(hi: u32, lo: u32, divisor: u32) -> (u32, u32) {
+        let (div, rem);
+
+        unsafe {
+            core::arch::asm! {
+                "div {0:e}",
+                in(reg) divisor,
+                inout("dx") hi => rem,
+                inout("ax") lo => div,
+            }
+        }
+
+        (div, rem)
+    }
+
+    #[allow(dead_code)]
+    fn div_digit_bigint(mut divident: BigInt, divisor: u32) -> (BigInt, u32) {
+        assert!(divisor != 0);
+        let mut rem = 0;
+
+        for d in divident.0.iter_mut().rev() {
+            (*d, rem) = scalar_div_wide(rem, *d, divisor);
+        }
+
+        (divident.normalised(), rem)
+    }
+
+    fn from_lo_hi(lo: u32, hi: u32) -> u64 {
+        lo as u64 | (hi as u64) << 32
+    }
+    fn into_lo_hi(qword: u64) -> (u32, u32) {
+        (qword as u32, (qword >> 32) as u32)
+    }
+
+    // from rust num_bigint
+    /// Subtract a multiple.
+    /// a -= b * c
+    /// Returns a borrow (if a < b then borrow > 0).
+    fn sub_mul_digit_same_len(a: &mut [u32], b: &[u32], c: u32) -> u32 {
+        assert!(a.len() == b.len());
+
+        // carry is between -big_digit::MAX and 0, so to avoid overflow we store
+        // offset_carry = carry + big_digit::MAX
+        let mut offset_carry = u32::MAX;
+
+        for (x, y) in a.iter_mut().zip(b) {
+            // We want to calculate sum = x - y * c + carry.
+            // sum >= -(big_digit::MAX * big_digit::MAX) - big_digit::MAX
+            // sum <= big_digit::MAX
+            // Offsetting sum by (big_digit::MAX << big_digit::BITS) puts it in DoubleBigDigit range.
+            let offset_sum = from_lo_hi(u32::MAX, *x) - u32::MAX as u64 + offset_carry as u64
+                - *y as u64 * c as u64;
+
+            let (new_x, new_offset_carry) = into_lo_hi(offset_sum);
+            offset_carry = new_offset_carry;
+            *x = new_x;
+        }
+
+        // Return the borrow.
+        u32::MAX - offset_carry
+    }
+
+    // from rust num_bigint
+    fn div_rem_core(mut a: BigInt, b: &[u32]) -> (BigInt, BigInt) {
+        // sanity check on fast paths
+        assert!(a.0.len() >= b.len() && b.len() > 1);
+
+        // a0 stores an additional extra most significant digit of the dividend, not stored in a.
+        let mut a0 = 0;
+
+        // [b1, b0] are the two most significant digits of the divisor. They never change.
+        let b0 = b[b.len() - 1];
+        let b1 = b[b.len() - 2];
+
+        let q_len = a.0.len() - b.len() + 1;
+        let mut q = BigInt(vec![0; q_len]);
+
+        for j in (0..q_len).rev() {
+            assert!(a.0.len() == b.len() + j);
+
+            let a1 = *a.0.last().unwrap();
+            let a2 = a.0[a.0.len() - 2];
+
+            // The first q0 estimate is [a1,a0] / b0. It will never be too small, it may be too large
+            // by at most 2.
+            let (mut q0, mut r) = if a0 < b0 {
+                let (q0, r) = scalar_div_wide(a0, a1, b0);
+                (q0, r as u64)
+            } else {
+                assert!(a0 == b0);
+                // Avoid overflowing q0, we know the quotient fits in BigDigit.
+                // [a1,a0] = b0 * (1<<BITS - 1) + (a0 + a1)
+                (u32::MAX, a0 as u64 + a1 as u64)
+            };
+
+            // r = [a1,a0] - q0 * b0
+            //
+            // Now we want to compute a more precise estimate [a2,a1,a0] / [b1,b0] which can only be
+            // less or equal to the current q0.
+            //
+            // q0 is too large if:
+            // [a2,a1,a0] < q0 * [b1,b0]
+            // (r << BITS) + a2 < q0 * b1
+            while r <= u32::MAX as u64 && from_lo_hi(r as u32, a2) < q0 as u64 * b1 as u64 {
+                q0 -= 1;
+                r += b0 as u64;
+            }
+
+            // q0 is now either the correct quotient digit, or in rare cases 1 too large.
+            // Subtract (q0 << j) from a. This may overflow, in which case we will have to correct.
+
+            let mut borrow = sub_mul_digit_same_len(&mut a.0[j..], b, q0);
+            if borrow > a0 {
+                // q0 is too large. We need to add back one multiple of b.
+                q0 -= 1;
+                borrow -= add_bigint(&mut a.0[j..], b) as u32;
+            }
+            // The top digit of a, stored in a0, has now been zeroed.
+            assert!(borrow == a0);
+
+            q.0[j] = q0;
+
+            // Pop off the next top digit of a.
+            a0 = a.0.pop().unwrap();
+        }
+
+        a.0.push(a0);
+        a.normalise();
+
+        assert_eq!(cmp_bigint(&a.0, b), core::cmp::Ordering::Less);
+
+        (q.normalised(), a)
+    }
+
+    #[allow(unused)]
+    fn shr_bitint(lhs: &mut [u32], shift: usize) {
+        if bigint_is_zero(lhs) || shift == 0 {
+            return;
+        }
+
+        let len = lhs.len();
+        let digit_offset = shift / 32;
+        let bit_shift = shift % 32;
+
+        if digit_offset != 0 {
+            lhs.copy_within(digit_offset..len, 0);
+            lhs[(len - digit_offset)..].fill(0);
+        }
+        if bit_shift != 0 {
+            let lo_mask = (1u32 << (u32::BITS as usize - bit_shift)) - 1;
+            let hi_mask = !lo_mask;
+
+            eprintln!("lhs >> {shift}");
+            eprintln!("\tdigit_offset: {digit_offset}");
+            eprintln!("\tbit_shift: {bit_shift}");
+            eprintln!("\tlo_mask: 0b{lo_mask:0>32b}");
+            eprintln!("\thi_mask: 0b{hi_mask:0>32b}");
+
+            let mut carry = 0u32;
+            for i in 0..lhs.len() {
+                let digit = ((lhs[i] as u64) << 32) >> bit_shift;
+                let lo = digit as u32;
+                let hi = (digit >> 32) as u32;
+
+                lhs[i] &= hi_mask;
+                lhs[i] |= hi;
+
+                if i > 0 {
+                    lhs[i - 1] &= lo_mask;
+                    lhs[i - 1] |= lo;
+                }
+            }
+        }
+    }
+
+    #[allow(unused)]
+    /// lhs must have shift / 32 + 1 digits past the last bit if shifted-past bits are desired.
+    fn shl_bitint(lhs: &mut [u32], shift: usize) {
+        if bigint_is_zero(lhs) || shift == 0 {
+            return;
+        }
+
+        let len = lhs.len();
+        let digit_offset = shift / 32;
+        let bit_shift = shift % 32;
+
+        if digit_offset != 0 {
+            lhs.copy_within(0..(len - digit_offset), digit_offset);
+            lhs[..digit_offset].fill(0);
+        }
+        if bit_shift != 0 {
+            let hi_mask = (1u32 << bit_shift) - 1;
+            let lo_mask = !hi_mask;
+
+            eprintln!("lhs << {shift}");
+            eprintln!("\tdigit_offset: {digit_offset}");
+            eprintln!("\tbit_shift: {bit_shift}");
+            eprintln!("\tlo_mask: 0b{lo_mask:0>32b}");
+            eprintln!("\thi_mask: 0b{hi_mask:0>32b}");
+
+            // example with u8 digits, shift = 3;
+            // hi_mask = 0b00000111
+            // lo_mask = 0b11111000
+            //
+            // lhs[i] as u16 = 0b00000000_01111000
+            // digit         = 0b00000011_11000000
+            // hi            = 0b00000011
+            // lo            = 0b11000000
+
+            let mut carry = 0u32;
+            for i in (digit_offset..len).rev() {
+                let digit = (lhs[i] as u64) << bit_shift;
+                let lo = digit as u32;
+                let hi = (digit >> 32) as u32;
+
+                lhs[i] &= lo_mask;
+                lhs[i] |= lo;
+
+                if i + 1 < len {
+                    lhs[i + 1] &= hi_mask;
+                    lhs[i + 1] |= hi;
+                }
+            }
+        }
+    }
+
+    #[allow(unused)]
+    /// lhs must be bigger than rhs
+    fn sub_bigint(lhs: &mut [u32], rhs: &[u32]) {
+        if bigint_is_zero(rhs) {
+            return;
+        }
+
+        let len = lhs.len().min(rhs.len());
+        let (l_lo, l_hi) = lhs.split_at_mut(len);
+        let (r_lo, r_hi) = rhs.split_at(len);
+
+        println!("lhs: {{ lo: {l_lo:?}, hi: {l_hi:?} }}");
+        println!("rhs: {{ lo: {r_lo:?}, hi: {r_hi:?} }}");
+
+        let mut borrow = false;
+        for (lhs, rhs) in l_lo.iter_mut().zip(r_lo) {
+            (*lhs, borrow) = lhs.borrowing_sub(*rhs, borrow);
+        }
+
+        if borrow {
+            for lhs in l_hi {
+                (*lhs, borrow) = lhs.borrowing_sub(0, borrow);
+            }
+        }
+
+        if borrow || !r_hi.iter().all(|&v| v == 0) {
+            panic!("sub failed: borrow: {borrow}");
+        }
+    }
+
+    /// lhs must be bigger than rhs
+    /// returns carry
+    fn add_bigint(lhs: &mut [u32], rhs: &[u32]) -> bool {
+        if bigint_is_zero(rhs) {
+            return false;
+        }
+
+        let (l_lo, l_hi) = lhs.split_at_mut(rhs.len());
+
+        let mut carry = false;
+        for (lhs, rhs) in l_lo.iter_mut().zip(rhs) {
+            (*lhs, carry) = lhs.carrying_add(*rhs, carry);
+        }
+
+        if carry {
+            for d in l_hi.iter_mut() {
+                (*d, carry) = d.carrying_add(0, carry);
+                if !carry {
+                    break;
+                }
+            }
+        }
+
+        carry
+    }
+
+    fn parse_bigint(text: impl Iterator<Item = char>, radix: Radix) -> BigInt {
+        let digits = text
+            .filter_map(|c| match c {
+                '_' => None,
+                c => Some(radix.map_digit(c)),
+            })
+            .collect::<Vec<_>>();
+
+        let (max, power) = {
+            let radix = radix.radix() as u64;
+            let mut power = 1;
+            let mut base = radix;
+            while let Some(b) = base.checked_mul(radix) {
+                if b > u32::MAX as u64 {
+                    break;
+                }
+                base = b;
+                power += 1;
+            }
+            (base, power)
+        };
+        let radix = radix.radix() as u32;
+
+        let r = digits.len() % power;
+        let i = if r == 0 { power } else { r };
+        let (head, tail) = digits.split_at(i);
+
+        let first = head
+            .iter()
+            .fold(0, |acc, &digit| acc * radix + digit as u32);
+        let mut data = vec![first];
+
+        for chunk in tail.chunks(power) {
+            if data.last() != Some(&0) {
+                data.push(0);
+            }
+            let mut carry = 0u64;
+            for digit in data.iter_mut() {
+                carry += *digit as u64 * max as u64;
+                *digit = carry as u32;
+                carry >>= u32::BITS;
+            }
+            assert!(carry == 0);
+            let next = chunk
+                .iter()
+                .fold(0, |acc, &digit| acc * radix + digit as u32);
+
+            let (res, mut carry) = data[0].carrying_add(next, false);
+            data[0] = res;
+            if carry {
+                for digit in data[1..].iter_mut() {
+                    (*digit, carry) = digit.carrying_add(0, carry);
+                    if !carry {
+                        break;
+                    }
+                }
+            }
+        }
+        BigInt(data)
+    }
+
+    #[cfg(test)]
+    mod tests {
+        use super::*;
+
+        #[test]
+        fn parse() {
+            let bigint = super::parse_bigint("2_cafe_babe_dead_beef".chars(), Radix::Hex);
+            println!("{:#x?}", bigint);
+            let bigint = super::parse_bigint("f".chars(), Radix::Hex);
+            println!("{:#x?}", bigint);
+        }
+        #[test]
+        fn add() {
+            let a = super::parse_bigint("2_0000_0000_0000_0000".chars(), Radix::Hex);
+            println!("{:#x?}", a);
+            let b = super::parse_bigint("cafebabe".chars(), Radix::Hex);
+            println!("{:#x?}", b);
+            let sum = a + b;
+            println!("{:#x?}", sum);
+        }
+        #[test]
+        fn sub() {
+            let a = super::parse_bigint("deadbeef".chars(), Radix::Hex);
+            println!("{:#x?}", a);
+            let b = super::parse_bigint("56d2c".chars(), Radix::Hex);
+            println!("{:#x?}", b);
+            let sum = a - b;
+            println!("{:#x?}", sum);
+        }
+        #[test]
+        fn overflowing_sub() {
+            let a = super::parse_bigint("2_0000_0000_0000_0000".chars(), Radix::Hex);
+            println!("{:#x?}", a);
+            let b = super::parse_bigint("ffff_ffff".chars(), Radix::Hex);
+            println!("{:#x?}", b);
+            let sum = b - a;
+            println!("{:#x?}", sum);
+        }
+        #[test]
+        fn shr() {
+            let mut a = super::parse_bigint("cafe_babe_0000".chars(), Radix::Hex);
+            print!("{:0>8x?} >> 32 ", a);
+            shr_bitint(&mut a.0, 32);
+            println!("{:0>8x?}", a);
+
+            let mut a = super::parse_bigint("11110000".chars(), Radix::Bin);
+            print!("{:0>8x?} >> 32 ", a);
+            shr_bitint(&mut a.0, 3);
+            println!("{:0>8x?}", a);
+        }
+        #[test]
+        fn shl() {
+            let mut a = super::parse_bigint("ffff_ffff".chars(), Radix::Hex);
+            a.0.extend([0; 4]);
+            println!("{:0>8x?}", a);
+            shl_bitint(&mut a.0, 40);
+            println!("{:0>8x?}", a);
+        }
+        #[test]
+        fn div() {
+            let a = super::parse_bigint("cafebabe".chars(), Radix::Hex);
+            let b = super::parse_bigint("dead".chars(), Radix::Hex);
+            let (div, rem) = div_rem_bigint(a, b);
+            println!("div: {:0>8x?}", div);
+            println!("rem: {:0>8x?}", rem);
+        }
+    }
+}
+
+use std::ops::Add;
+
+use bigint::BigInt;
+
+use crate::ast::IntegralType;
+
+#[derive(Debug, thiserror::Error)]
+enum Error {
+    #[error("Incompatible Comptime Number variants.")]
+    IncompatibleTypes,
+    #[error("Integer overflow.")]
+    IntegerOverflow,
+}
+
+type Result<T> = core::result::Result<T, Error>;
+
+enum ComptimeInt {
+    Native { bits: u64, ty: IntegralType },
+    BigInt { bits: BigInt, ty: IntegralType },
+    Comptime(BigInt),
+}
+
+impl ComptimeInt {
+    pub fn add(self, other: Self) -> Result<Self> {
+        match (self, other) {
+            (Self::Native { bits: a, ty: aty }, Self::Native { bits: b, ty: bty }) => {
+                let bits = if aty != bty {
+                    return Err(Error::IncompatibleTypes);
+                } else if aty.signed {
+                    (a as i64)
+                        .checked_add(b as i64)
+                        .ok_or(Error::IntegerOverflow)? as u64
+                } else {
+                    (a as u64)
+                        .checked_add(b as u64)
+                        .ok_or(Error::IntegerOverflow)? as u64
+                };
+                if bits & !aty.u64_bitmask() != 0 {
+                    return Err(Error::IntegerOverflow);
+                }
+                Ok(Self::Native { bits, ty: aty })
+            }
+            (Self::Comptime(a), Self::Comptime(b)) => Ok(Self::Comptime(a.clone().add(b.clone()))),
+            (Self::Comptime(a), Self::Native { bits, ty })
+            | (Self::Native { bits, ty }, Self::Comptime(a)) => {
+                let b = a.into_u64().ok_or(Error::IncompatibleTypes)?;
+
+                Self::Native { bits, ty }.add(Self::Native { bits: b, ty })
+            }
+            _ => Err(Error::IncompatibleTypes),
+        }
+    }
+    pub fn sub(self, other: Self) -> Result<Self> {
+        match (self, other) {
+            (Self::Native { bits: a, ty: aty }, Self::Native { bits: b, ty: bty }) => {
+                let bits = if aty != bty {
+                    return Err(Error::IncompatibleTypes);
+                } else if aty.signed {
+                    (a as i64)
+                        .checked_sub(b as i64)
+                        .ok_or(Error::IntegerOverflow)? as u64
+                } else {
+                    (a as u64)
+                        .checked_sub(b as u64)
+                        .ok_or(Error::IntegerOverflow)? as u64
+                };
+                if bits & !aty.u64_bitmask() != 0 {
+                    return Err(Error::IntegerOverflow);
+                }
+                Ok(Self::Native { bits, ty: aty })
+            }
+            (Self::Comptime(a), Self::Comptime(b)) => Ok(Self::Comptime(a - b)),
+            (Self::Comptime(a), b @ Self::Native { ty, .. }) => {
+                let a = a.into_u64().ok_or(Error::IncompatibleTypes)?;
+                Self::Native { bits: a, ty }.sub(b)
+            }
+            (a @ Self::Native { ty, .. }, Self::Comptime(b)) => {
+                let b = b.into_u64().ok_or(Error::IncompatibleTypes)?;
+
+                a.sub(Self::Native { bits: b, ty })
+            }
+            _ => Err(Error::IncompatibleTypes),
+        }
+    }
+}
+
+enum ComptimeFloat {
+    Binary32(f32),
+    Binary64(f64),
+}
+
+impl ComptimeFloat {
+    pub fn add(&self, other: &Self) -> Result<ComptimeFloat> {
+        match (self, other) {
+            (ComptimeFloat::Binary32(a), ComptimeFloat::Binary32(b)) => Ok(Self::Binary32(a + b)),
+            (ComptimeFloat::Binary64(a), ComptimeFloat::Binary64(b)) => Ok(Self::Binary64(a + b)),
+            _ => Err(Error::IncompatibleTypes),
+        }
+    }
+    pub fn sub(&self, other: &Self) -> Result<ComptimeFloat> {
+        match (self, other) {
+            (ComptimeFloat::Binary32(a), ComptimeFloat::Binary32(b)) => Ok(Self::Binary32(a - b)),
+            (ComptimeFloat::Binary64(a), ComptimeFloat::Binary64(b)) => Ok(Self::Binary64(a - b)),
+            _ => Err(Error::IncompatibleTypes),
+        }
+    }
+    pub fn mul(&self, other: &Self) -> Result<ComptimeFloat> {
+        match (self, other) {
+            (ComptimeFloat::Binary32(a), ComptimeFloat::Binary32(b)) => Ok(Self::Binary32(a * b)),
+            (ComptimeFloat::Binary64(a), ComptimeFloat::Binary64(b)) => Ok(Self::Binary64(a * b)),
+            _ => Err(Error::IncompatibleTypes),
+        }
+    }
+    pub fn div(&self, other: &Self) -> Result<ComptimeFloat> {
+        match (self, other) {
+            (ComptimeFloat::Binary32(a), ComptimeFloat::Binary32(b)) => Ok(Self::Binary32(a / b)),
+            (ComptimeFloat::Binary64(a), ComptimeFloat::Binary64(b)) => Ok(Self::Binary64(a / b)),
+            _ => Err(Error::IncompatibleTypes),
+        }
+    }
+    pub fn rem(&self, other: &Self) -> Result<ComptimeFloat> {
+        match (self, other) {
+            (ComptimeFloat::Binary32(a), ComptimeFloat::Binary32(b)) => Ok(Self::Binary32(a % b)),
+            (ComptimeFloat::Binary64(a), ComptimeFloat::Binary64(b)) => Ok(Self::Binary64(a % b)),
+            _ => Err(Error::IncompatibleTypes),
+        }
+    }
+    pub fn neg(&self) -> Result<ComptimeFloat> {
+        match self {
+            ComptimeFloat::Binary32(a) => Ok(Self::Binary32(-a)),
+            ComptimeFloat::Binary64(a) => Ok(Self::Binary64(-a)),
+        }
+    }
+}
+
+enum ComptimeNumber {
+    Integral(ComptimeInt),
+    Bool(bool),
+    Floating(ComptimeFloat),
+}
+
+impl ComptimeNumber {}
diff --git a/src/lexer.rs b/src/lexer.rs
index b86f02c..359fd65 100644
--- a/src/lexer.rs
+++ b/src/lexer.rs
@@ -582,266 +582,6 @@ fn try_parse_integral_type(source: &mut Chars) -> Result<Option<()>> {
     Ok(Some(()))
 }
 
-pub mod bigint {
-
-    use super::Radix;
-    pub struct BigInt(Vec<u32>);
-
-    impl BigInt {
-        pub fn parse_digits<C: IntoIterator<Item = char>>(text: C, radix: Radix) -> BigInt {
-            parse_bigint(text.into_iter(), radix)
-        }
-
-        pub fn bit_width(&self) -> u32 {
-            count_bits(&self.0)
-        }
-
-        pub fn from_bytes_le(bytes: &[u8]) -> BigInt {
-            let data = bytes
-                .chunks(4)
-                .map(|chunk| {
-                    let mut int = [0u8; 4];
-                    int[..chunk.len()].copy_from_slice(chunk);
-                    u32::from_le_bytes(int)
-                })
-                .collect::<Vec<_>>();
-
-            BigInt(data)
-        }
-
-        pub fn into_bytes_le(&self) -> Vec<u8> {
-            let mut bytes = Vec::<u8>::new();
-
-            for d in &self.0[..] {
-                bytes.extend(&d.to_le_bytes());
-            }
-
-            let count = bytes.iter().rev().take_while(|&&b| b == 0).count();
-            bytes.truncate(bytes.len() - count);
-
-            bytes
-        }
-    }
-
-    impl core::ops::Add for BigInt {
-        type Output = Self;
-
-        fn add(mut self, mut rhs: Self) -> Self::Output {
-            let (mut digits, carry) = if self.0.len() > rhs.0.len() {
-                let c = add_bigint(&mut self.0, &rhs.0);
-                (self.0, c)
-            } else {
-                let c = add_bigint(&mut rhs.0, &self.0);
-                (rhs.0, c)
-            };
-
-            if carry {
-                digits.push(u32::from(carry));
-            }
-
-            BigInt(digits)
-        }
-    }
-
-    impl core::ops::Sub for BigInt {
-        type Output = Self;
-
-        fn sub(mut self, rhs: Self) -> Self::Output {
-            if self.0.len() < rhs.0.len() {
-                println!("extending self by {} zeroes", rhs.0.len() - self.0.len());
-                self.0
-                    .extend(core::iter::repeat(0).take(rhs.0.len() - self.0.len()));
-                println!("self: {self:?}");
-            }
-            sub_bigint(&mut self.0, &rhs.0);
-
-            self
-        }
-    }
-
-    impl core::fmt::Debug for BigInt {
-        fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-            let mut list = f.debug_list();
-            list.entries(self.0.iter()).finish()
-        }
-    }
-
-    /// counts used bits in a u32 slice, discards leading zeros in MSB.
-    /// `[0xff,0xff,0x00,0x00]` -> 16
-    /// `[0xff,0xff,0x00]` -> 16
-    /// `[0xff,0xff,0x0f]` -> 20
-    pub fn count_bits(bytes: &[u32]) -> u32 {
-        let mut bits = bytes.len() as u32;
-
-        for d in bytes.iter().rev() {
-            if *d == 0 {
-                bits -= u32::BITS;
-            } else {
-                bits -= d.leading_zeros();
-                break;
-            }
-        }
-
-        bits
-    }
-
-    #[test]
-    fn test_count_bits() {
-        assert_eq!(count_bits(&[0xffffffff, 0x00, 0x00]), 32);
-        assert_eq!(count_bits(&[0xffffffff, 0xff, 0x00]), 40);
-        assert_eq!(count_bits(&[0xffffffff, 0xff]), 40);
-        assert_eq!(count_bits(&[0xffffffff, 0xff, 0xffff]), 64 + 16);
-    }
-
-    #[allow(unused)]
-    /// lhs must be bigger than rhs
-    fn sub_bigint(lhs: &mut [u32], rhs: &[u32]) {
-        let len = lhs.len().min(rhs.len());
-        let (l_lo, l_hi) = lhs.split_at_mut(len);
-        let (r_lo, r_hi) = rhs.split_at(len);
-
-        println!("lhs: {{ lo: {l_lo:?}, hi: {l_hi:?} }}");
-        println!("rhs: {{ lo: {r_lo:?}, hi: {r_hi:?} }}");
-
-        let mut borrow = false;
-        for (lhs, rhs) in l_lo.iter_mut().zip(r_lo) {
-            (*lhs, borrow) = lhs.borrowing_sub(*rhs, borrow);
-        }
-
-        if borrow {
-            for lhs in l_hi {
-                (*lhs, borrow) = lhs.borrowing_sub(0, borrow);
-            }
-        }
-
-        if borrow || !r_hi.iter().all(|&v| v == 0) {
-            panic!("sub failed: borrow: {borrow}");
-        }
-    }
-
-    /// lhs must be bigger than rhs
-    fn add_bigint(lhs: &mut [u32], rhs: &[u32]) -> bool {
-        let (l_lo, l_hi) = lhs.split_at_mut(rhs.len());
-
-        let mut carry = false;
-        for (lhs, rhs) in l_lo.iter_mut().zip(rhs) {
-            (*lhs, carry) = lhs.carrying_add(*rhs, carry);
-        }
-
-        if carry {
-            for d in l_hi.iter_mut() {
-                (*d, carry) = d.carrying_add(0, carry);
-                if !carry {
-                    break;
-                }
-            }
-        }
-
-        carry
-    }
-
-    fn parse_bigint(text: impl Iterator<Item = char>, radix: Radix) -> BigInt {
-        let digits = text
-            .filter_map(|c| match c {
-                '_' => None,
-                c => Some(radix.map_digit(c)),
-            })
-            .collect::<Vec<_>>();
-
-        let (max, power) = {
-            let radix = radix.radix() as u64;
-            let mut power = 1;
-            let mut base = radix;
-            while let Some(b) = base.checked_mul(radix) {
-                if b > u32::MAX as u64 {
-                    break;
-                }
-                base = b;
-                power += 1;
-            }
-            (base, power)
-        };
-        let radix = radix.radix() as u32;
-
-        let r = digits.len() % power;
-        let i = if r == 0 { power } else { r };
-        let (head, tail) = digits.split_at(i);
-
-        let first = head
-            .iter()
-            .fold(0, |acc, &digit| acc * radix + digit as u32);
-        let mut data = vec![first];
-
-        for chunk in tail.chunks(power) {
-            if data.last() != Some(&0) {
-                data.push(0);
-            }
-            let mut carry = 0u64;
-            for digit in data.iter_mut() {
-                carry += *digit as u64 * max as u64;
-                *digit = carry as u32;
-                carry >>= u32::BITS;
-            }
-            assert!(carry == 0);
-            let next = chunk
-                .iter()
-                .fold(0, |acc, &digit| acc * radix + digit as u32);
-
-            let (res, mut carry) = data[0].carrying_add(next, false);
-            data[0] = res;
-            if carry {
-                for digit in data[1..].iter_mut() {
-                    (*digit, carry) = digit.carrying_add(0, carry);
-                    if !carry {
-                        break;
-                    }
-                }
-            }
-        }
-        BigInt(data)
-    }
-
-    #[cfg(test)]
-    mod tests {
-        use super::*;
-
-        #[test]
-        fn parse() {
-            let bigint = super::parse_bigint("2_cafe_babe_dead_beef".chars(), Radix::Hex);
-            println!("{:#x?}", bigint);
-            let bigint = super::parse_bigint("f".chars(), Radix::Hex);
-            println!("{:#x?}", bigint);
-        }
-        #[test]
-        fn add() {
-            let a = super::parse_bigint("2_0000_0000_0000_0000".chars(), Radix::Hex);
-            println!("{:#x?}", a);
-            let b = super::parse_bigint("cafebabe".chars(), Radix::Hex);
-            println!("{:#x?}", b);
-            let sum = a + b;
-            println!("{:#x?}", sum);
-        }
-        #[test]
-        fn sub() {
-            let a = super::parse_bigint("2_0000_0000_0000_0000".chars(), Radix::Hex);
-            println!("{:#x?}", a);
-            let b = super::parse_bigint("ffff_ffff".chars(), Radix::Hex);
-            println!("{:#x?}", b);
-            let sum = a - b;
-            println!("{:#x?}", sum);
-        }
-        #[test]
-        fn overflowing_sub() {
-            let a = super::parse_bigint("2_0000_0000_0000_0000".chars(), Radix::Hex);
-            println!("{:#x?}", a);
-            let b = super::parse_bigint("ffff_ffff".chars(), Radix::Hex);
-            println!("{:#x?}", b);
-            let sum = b - a;
-            println!("{:#x?}", sum);
-        }
-    }
-}
-
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub enum Radix {
     Hex,
@@ -873,7 +613,7 @@ impl Radix {
     }
 
     #[allow(unused)]
-    fn radix(self) -> u8 {
+    pub fn radix(self) -> u8 {
         match self {
             Radix::Hex => 16,
             Radix::Bin => 2,
diff --git a/src/lib.rs b/src/lib.rs
index 2679f9d..e63e914 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -4,13 +4,16 @@
     box_into_inner,
     hash_extract_if,
     bigint_helper_methods,
-    map_try_insert
+    map_try_insert,
+    iter_intersperse,
+    int_roundings
 )]
 #![allow(unused_macros)]
 
 pub mod asm;
 pub mod ast;
 pub mod common;
+pub mod comptime;
 pub mod error;
 pub mod lexer;
 pub mod mir;
diff --git a/src/parser.rs b/src/parser.rs
index ce9cd04..f81583f 100644
--- a/src/parser.rs
+++ b/src/parser.rs
@@ -5,12 +5,12 @@ use itertools::Itertools;
 use crate::{
     ast::{FloatingType, IntegralType, LetOrVar, Node, PrimitiveType, Tag, Type},
     common::NextIf,
+    comptime::bigint::{self, BigInt},
     error::{AnalysisError, AnalysisErrorTag},
-    lexer::{bigint::BigInt, Radix, TokenIterator},
+    lexer::{Radix, TokenIterator},
     string_table::{ImmOrIndex, Index, StringTable},
     symbol_table::{SymbolKind, SymbolTable},
     tokens::Token,
-    variant,
 };
 
 #[derive(Debug, thiserror::Error)]
@@ -251,7 +251,7 @@ impl Tree {
             .map(|(_, c)| c)
             .collect::<Vec<_>>();
 
-        let value = crate::lexer::bigint::BigInt::parse_digits(digits, radix);
+        let value = BigInt::parse_digits(digits, radix);
 
         let ty = match iter.clone().next() {
             Some((_, 'u')) | Some((_, 'i')) => {
diff --git a/src/string_table.rs b/src/string_table.rs
index bc837cd..88197f8 100644
--- a/src/string_table.rs
+++ b/src/string_table.rs
@@ -57,7 +57,7 @@ impl StringTable {
                 let ints = unsafe {
                     core::slice::from_raw_parts(bytes.as_ptr().cast::<u32>(), bytes.len() / 4)
                 };
-                crate::lexer::bigint::count_bits(ints)
+                bigint::count_bits(ints) as u32
             }
         }
     }
@@ -151,3 +151,5 @@ mod display {
 }
 
 pub use display::ImmOrIndexDisplay;
+
+use crate::comptime::bigint;