openvm_native_compiler/ir/

builder.rs

use std::{iter::Zip, vec::IntoIter};

use backtrace::Backtrace;
use openvm_stark_backend::p3_field::AbstractField;
use serde::{Deserialize, Serialize};

use super::{
    Array, Config, DslIr, Ext, Felt, FromConstant, MemIndex, MemVariable, RVar, SymbolicExt,
    SymbolicFelt, SymbolicVar, Usize, Var, Variable,
};

/// TracedVec is a Vec wrapper that records a trace whenever an element is pushed. When extending
/// from another TracedVec, the traces are copied over.
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct TracedVec<T> {
    pub vec: Vec<T>,
    pub traces: Vec<Option<Backtrace>>,
}

impl<T> Default for TracedVec<T> {
    fn default() -> Self {
        Self::new()
    }
}

impl<T> From<Vec<T>> for TracedVec<T> {
    fn from(vec: Vec<T>) -> Self {
        let len = vec.len();
        Self {
            vec,
            traces: vec![None; len],
        }
    }
}

impl<T> TracedVec<T> {
    pub const fn new() -> Self {
        Self {
            vec: Vec::new(),
            traces: Vec::new(),
        }
    }

    pub fn push(&mut self, value: T) {
        self.vec.push(value);
        self.traces.push(None);
    }

    /// Pushes a value to the vector and records a backtrace if RUST_BACKTRACE is enabled
    pub fn trace_push(&mut self, value: T) {
        self.vec.push(value);
        if std::env::var_os("RUST_BACKTRACE").is_none() {
            self.traces.push(None);
        } else {
            self.traces.push(Some(Backtrace::new_unresolved()));
        }
    }

    pub fn extend<I: IntoIterator<Item = (T, Option<Backtrace>)>>(&mut self, iter: I) {
        let iter = iter.into_iter();
        let len = iter.size_hint().0;
        self.vec.reserve(len);
        self.traces.reserve(len);
        for (value, trace) in iter {
            self.vec.push(value);
            self.traces.push(trace);
        }
    }

    pub fn is_empty(&self) -> bool {
        self.vec.is_empty()
    }
}

impl<T> IntoIterator for TracedVec<T> {
    type Item = (T, Option<Backtrace>);
    type IntoIter = Zip<IntoIter<T>, IntoIter<Option<Backtrace>>>;

    fn into_iter(self) -> Self::IntoIter {
        self.vec.into_iter().zip(self.traces)
    }
}

#[derive(Debug)]
pub struct BreakLoop;
impl std::fmt::Display for BreakLoop {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "Break Loop")
    }
}
impl std::error::Error for BreakLoop {}

#[derive(Debug, Copy, Clone, Default)]
pub struct BuilderFlags {
    pub debug: bool,
    /// If true, `builder.break_loop` will take control flow instead of pushing an instruction.
    pub(crate) static_loop: bool,
    /// If true, panic when `builder.break_loop` is called.
    pub(crate) disable_break: bool,
    /// If true, branching/looping/heap memory is disabled.
    pub static_only: bool,
}

/// A builder for the DSL.
///
/// Can compile to both assembly and a set of constraints.
#[derive(Debug, Clone, Default)]
pub struct Builder<C: Config> {
    pub(crate) var_count: u32,
    pub(crate) felt_count: u32,
    pub(crate) ext_count: u32,
    pub operations: TracedVec<DslIr<C>>,
    pub(crate) nb_public_values: Option<Var<C::N>>,
    pub(crate) witness_var_count: u32,
    pub(crate) witness_felt_count: u32,
    pub(crate) witness_ext_count: u32,
    pub flags: BuilderFlags,
    pub is_sub_builder: bool,
}

impl<C: Config> Builder<C> {
    /// Creates a new builder with a given number of counts for each type.
    pub fn create_sub_builder(&self) -> Self {
        Self {
            var_count: self.var_count,
            felt_count: self.felt_count,
            ext_count: self.ext_count,
            // Witness counts are only used when the target is a gnark circuit.  And sub-builders are
            // not used when the target is a gnark circuit, so it's fine to set the witness counts to 0.
            witness_var_count: 0,
            witness_felt_count: 0,
            witness_ext_count: 0,
            operations: Default::default(),
            nb_public_values: self.nb_public_values,
            flags: self.flags,
            is_sub_builder: true,
        }
    }

    /// Set whether all loops must be static and unrolled
    pub fn set_static_loops(&mut self, static_loop: bool) {
        self.flags.static_loop = static_loop;
    }

    /// Pushes an operation to the builder.
    pub fn push(&mut self, op: DslIr<C>) {
        self.operations.push(op);
    }

    /// Pushes an operation to the builder and records a trace if RUST_BACKTRACE=1.
    pub fn trace_push(&mut self, op: DslIr<C>) {
        self.operations.trace_push(op);
    }

    /// Creates an uninitialized variable.
    pub fn uninit<V: Variable<C>>(&mut self) -> V {
        V::uninit(self)
    }

    /// Evaluates an expression and returns a variable.
    pub fn eval<V: Variable<C>, E: Into<V::Expression>>(&mut self, expr: E) -> V {
        V::eval(self, expr)
    }

    /// Evaluates an expression and returns a right value.
    pub fn eval_expr(&mut self, expr: impl Into<SymbolicVar<C::N>>) -> RVar<C::N> {
        let expr = expr.into();
        match expr {
            SymbolicVar::Const(c, _) => RVar::Const(c),
            SymbolicVar::Val(val, _) => RVar::Val(val),
            _ => {
                let ret: Var<_> = self.eval(expr);
                RVar::Val(ret)
            }
        }
    }

    /// Increments Usize by one.
    pub fn inc(&mut self, u: &Usize<C::N>) {
        self.assign(u, u.clone() + RVar::one());
    }

    /// Evaluates a constant expression and returns a variable.
    pub fn constant<V: FromConstant<C>>(&mut self, value: V::Constant) -> V {
        V::constant(value, self)
    }

    /// Assigns an expression to a variable.
    pub fn assign<V: Variable<C>, E: Into<V::Expression>>(&mut self, dst: &V, expr: E) {
        dst.assign(expr.into(), self);
    }

    /// Casts a Felt to a Var.
    pub fn cast_felt_to_var(&mut self, felt: Felt<C::F>) -> Var<C::N> {
        let var: Var<_> = self.uninit();
        self.operations.push(DslIr::CastFV(var, felt));
        var
    }
    /// Casts a Var to a Felt.
    pub fn unsafe_cast_var_to_felt(&mut self, var: Var<C::N>) -> Felt<C::F> {
        assert!(!self.flags.static_only, "dynamic mode only");
        let felt: Felt<_> = self.uninit();
        self.operations.push(DslIr::UnsafeCastVF(felt, var));
        felt
    }

    /// Asserts that two expressions are equal.
    pub fn assert_eq<V: Variable<C>>(
        &mut self,
        lhs: impl Into<V::Expression>,
        rhs: impl Into<V::Expression>,
    ) {
        V::assert_eq(lhs, rhs, self);
    }

    /// Asserts that two expressions are not equal.
    pub fn assert_ne<V: Variable<C>>(
        &mut self,
        lhs: impl Into<V::Expression>,
        rhs: impl Into<V::Expression>,
    ) {
        V::assert_ne(lhs, rhs, self);
    }

    /// Assert that two vars are equal.
    pub fn assert_var_eq<LhsExpr: Into<SymbolicVar<C::N>>, RhsExpr: Into<SymbolicVar<C::N>>>(
        &mut self,
        lhs: LhsExpr,
        rhs: RhsExpr,
    ) {
        self.assert_eq::<Var<C::N>>(lhs, rhs);
    }

    /// Assert that two vars are not equal.
    pub fn assert_var_ne<LhsExpr: Into<SymbolicVar<C::N>>, RhsExpr: Into<SymbolicVar<C::N>>>(
        &mut self,
        lhs: LhsExpr,
        rhs: RhsExpr,
    ) {
        self.assert_ne::<Var<C::N>>(lhs, rhs);
    }

    /// Assert that two felts are equal.
    pub fn assert_felt_eq<LhsExpr: Into<SymbolicFelt<C::F>>, RhsExpr: Into<SymbolicFelt<C::F>>>(
        &mut self,
        lhs: LhsExpr,
        rhs: RhsExpr,
    ) {
        self.assert_eq::<Felt<C::F>>(lhs, rhs);
    }

    /// Assert that two felts are not equal.
    pub fn assert_felt_ne<LhsExpr: Into<SymbolicFelt<C::F>>, RhsExpr: Into<SymbolicFelt<C::F>>>(
        &mut self,
        lhs: LhsExpr,
        rhs: RhsExpr,
    ) {
        self.assert_ne::<Felt<C::F>>(lhs, rhs);
    }

    /// Assert that two exts are equal.
    pub fn assert_ext_eq<
        LhsExpr: Into<SymbolicExt<C::F, C::EF>>,
        RhsExpr: Into<SymbolicExt<C::F, C::EF>>,
    >(
        &mut self,
        lhs: LhsExpr,
        rhs: RhsExpr,
    ) {
        self.assert_eq::<Ext<C::F, C::EF>>(lhs, rhs);
    }

    /// Assert that two exts are not equal.
    pub fn assert_ext_ne<
        LhsExpr: Into<SymbolicExt<C::F, C::EF>>,
        RhsExpr: Into<SymbolicExt<C::F, C::EF>>,
    >(
        &mut self,
        lhs: LhsExpr,
        rhs: RhsExpr,
    ) {
        self.assert_ne::<Ext<C::F, C::EF>>(lhs, rhs);
    }

    /// Assert that two arrays are equal.
    pub fn assert_var_array_eq(&mut self, lhs: &Array<C, Var<C::N>>, rhs: &Array<C, Var<C::N>>) {
        self.assert_var_eq(lhs.len(), rhs.len());
        self.range(0, lhs.len()).for_each(|i, builder| {
            let l = builder.get(lhs, i);
            let r = builder.get(rhs, i);
            builder.assert_var_eq(l, r);
        });
    }

    /// Compares two variables.
    pub fn lt<LhsExpr: Into<SymbolicVar<C::N>>, RhsExpr: Into<SymbolicVar<C::N>>>(
        &mut self,
        lhs: LhsExpr,
        rhs: RhsExpr,
    ) -> RVar<C::N> {
        let lhs = lhs.into();
        let rhs = rhs.into();
        match (&lhs, &rhs) {
            (SymbolicVar::Const(lhs, _), SymbolicVar::Const(rhs, _)) => {
                if rhs < lhs {
                    RVar::one()
                } else {
                    RVar::zero()
                }
            }
            _ => {
                let result = self.uninit();
                let lhs = self.eval(lhs);
                let rhs = self.eval(rhs);
                self.operations.push(DslIr::LessThanV(result, lhs, rhs));
                RVar::Val(result)
            }
        }
    }

    /// Evaluate a block of operations if two expressions are equal.
    pub fn if_eq<LhsExpr: Into<SymbolicVar<C::N>>, RhsExpr: Into<SymbolicVar<C::N>>>(
        &mut self,
        lhs: LhsExpr,
        rhs: RhsExpr,
    ) -> IfBuilder<C> {
        IfBuilder {
            lhs: lhs.into(),
            rhs: rhs.into(),
            is_eq: true,
            builder: self,
        }
    }

    /// Evaluate a block of operations if two expressions are not equal.
    pub fn if_ne<LhsExpr: Into<SymbolicVar<C::N>>, RhsExpr: Into<SymbolicVar<C::N>>>(
        &mut self,
        lhs: LhsExpr,
        rhs: RhsExpr,
    ) -> IfBuilder<C> {
        IfBuilder {
            lhs: lhs.into(),
            rhs: rhs.into(),
            is_eq: false,
            builder: self,
        }
    }

    /// Evaluate a block of operations over a range from start to end.
    pub fn range(
        &mut self,
        start: impl Into<RVar<C::N>>,
        end: impl Into<RVar<C::N>>,
    ) -> RangeBuilder<C> {
        let start = start.into();
        let end = end.into();
        RangeBuilder {
            start,
            end,
            builder: self,
            step_size: 1,
        }
    }

    /// Evaluate a block of operations repeatedly (until a break).
    pub fn do_loop(&mut self, mut f: impl FnMut(&mut Builder<C>) -> Result<(), BreakLoop>) {
        let mut loop_body_builder = self.create_sub_builder();

        f(&mut loop_body_builder).expect("should not be break issues in dynamic loop");

        let loop_instructions = loop_body_builder.operations;

        let op = DslIr::Loop(loop_instructions);
        self.operations.push(op);
    }

    /// Break out of a loop.
    pub fn break_loop(&mut self) -> Result<(), BreakLoop> {
        if self.flags.disable_break {
            panic!("BreakLoop was called but it was disabled")
        }
        if self.flags.static_loop {
            return Err(BreakLoop);
        }
        self.operations.push(DslIr::Break);
        Ok(())
    }

    pub fn print_debug(&mut self, val: usize) {
        let constant = self.eval(C::N::from_canonical_usize(val));
        self.print_v(constant);
    }

    /// Print a variable.
    pub fn print_v(&mut self, dst: Var<C::N>) {
        self.operations.push(DslIr::PrintV(dst));
    }

    /// Print a felt.
    pub fn print_f(&mut self, dst: Felt<C::F>) {
        self.operations.push(DslIr::PrintF(dst));
    }

    /// Print an ext.
    pub fn print_e(&mut self, dst: Ext<C::F, C::EF>) {
        self.operations.push(DslIr::PrintE(dst));
    }

    pub fn hint_var(&mut self) -> Var<C::N> {
        let arr = self.hint_vars();
        self.get(&arr, RVar::zero())
    }

    pub fn hint_felt(&mut self) -> Felt<C::F> {
        let arr = self.hint_felts();
        self.get(&arr, RVar::zero())
    }

    pub fn hint_ext(&mut self) -> Ext<C::F, C::EF> {
        let arr = self.hint_exts();
        self.get(&arr, RVar::zero())
    }

    /// Hint a vector of variables.
    ///
    /// Writes the next element of the witness stream into memory and returns it.
    pub fn hint_vars(&mut self) -> Array<C, Var<C::N>> {
        self.hint_words()
    }

    /// Hint a vector of felts.
    pub fn hint_felts(&mut self) -> Array<C, Felt<C::F>> {
        self.hint_words()
    }

    /// Hints an array of V and assumes V::size_of() == 1.
    fn hint_words<V: MemVariable<C>>(&mut self) -> Array<C, V> {
        assert_eq!(V::size_of(), 1);

        // Allocate space for the length variable. We assume that mem[ptr..] is empty.
        let ptr = self.alloc(RVar::one(), 1);

        // Prepare length + data for hinting.
        self.operations.push(DslIr::HintInputVec());

        // Write and retrieve length hint.
        let index = MemIndex {
            index: RVar::zero(),
            offset: 0,
            size: 1,
        };
        // MemIndex.index share the same pointer, but it doesn't matter.
        self.operations.push(DslIr::StoreHintWord(ptr, index));

        let vlen: Var<C::N> = self.uninit();
        self.load(vlen, ptr, index);

        let arr = self.dyn_array(vlen);

        // Write the content hints directly into the array memory.
        self.range(0, vlen).for_each(|i, builder| {
            let index = MemIndex {
                index: i,
                offset: 0,
                size: 1,
            };
            builder
                .operations
                .push(DslIr::StoreHintWord(arr.ptr(), index));
        });

        arr
    }

    /// Hint a vector of exts.
    ///
    /// Emits two hint opcodes: the first for the number of exts, the second for the list of exts
    /// themselves.
    pub fn hint_exts(&mut self) -> Array<C, Ext<C::F, C::EF>> {
        let len = self.hint_var();
        let flattened = self.hint_felts();

        let size = <Ext<C::F, C::EF> as MemVariable<C>>::size_of();
        self.assert_eq::<Usize<_>>(flattened.len(), len * C::N::from_canonical_usize(size));

        // Simply recast memory as Array<Ext>.
        match flattened {
            Array::Fixed(_) => unreachable!(),
            Array::Dyn(ptr, _) => Array::Dyn(ptr, Usize::Var(len)),
        }
    }

    pub fn witness_var(&mut self) -> Var<C::N> {
        assert!(
            !self.is_sub_builder,
            "Cannot create a witness var with a sub builder"
        );
        let witness = self.uninit();
        self.operations
            .push(DslIr::WitnessVar(witness, self.witness_var_count));
        self.witness_var_count += 1;
        witness
    }

    pub fn witness_felt(&mut self) -> Felt<C::F> {
        assert!(
            !self.is_sub_builder,
            "Cannot create a witness var with a sub builder"
        );
        let witness = self.uninit();
        self.operations
            .push(DslIr::WitnessFelt(witness, self.witness_felt_count));
        self.witness_felt_count += 1;
        witness
    }

    pub fn witness_ext(&mut self) -> Ext<C::F, C::EF> {
        assert!(
            !self.is_sub_builder,
            "Cannot create a witness var with a sub builder"
        );
        let witness = self.uninit();
        self.operations
            .push(DslIr::WitnessExt(witness, self.witness_ext_count));
        self.witness_ext_count += 1;
        witness
    }

    /// Throws an error.
    pub fn error(&mut self) {
        self.operations.trace_push(DslIr::Error());
    }

    /// Materializes a usize into a variable.
    pub fn materialize(&mut self, num: RVar<C::N>) -> Var<C::N> {
        match num {
            RVar::Const(num) => self.eval(num),
            RVar::Val(num) => num,
        }
    }

    fn get_nb_public_values(&mut self) -> Var<C::N> {
        assert!(
            !self.is_sub_builder,
            "Cannot commit to public values with a sub builder"
        );
        if self.nb_public_values.is_none() {
            self.nb_public_values = Some(self.eval(C::N::ZERO));
        }
        *self.nb_public_values.as_ref().unwrap()
    }

    fn commit_public_value_and_increment(&mut self, val: Felt<C::F>, nb_public_values: Var<C::N>) {
        assert!(
            !self.flags.static_only,
            "Static mode should use static_commit_public_value"
        );
        self.operations.push(DslIr::Publish(val, nb_public_values));
        self.assign(&nb_public_values, nb_public_values + C::N::ONE);
    }

    /// Commits a Var as public value. This value will be constrained when verified. This method should only be used in static mode.
    pub fn static_commit_public_value(&mut self, index: usize, val: Var<C::N>) {
        assert!(
            self.flags.static_only,
            "Dynamic mode should use commit_public_value instead."
        );
        self.operations.push(DslIr::CircuitPublish(val, index));
    }

    /// Register and commits a felt as public value.  This value will be constrained when verified.
    pub fn commit_public_value(&mut self, val: Felt<C::F>) {
        let nb_public_values = self.get_nb_public_values();
        self.commit_public_value_and_increment(val, nb_public_values);
    }

    /// Commits an array of felts in public values.
    pub fn commit_public_values(&mut self, vals: &Array<C, Felt<C::F>>) {
        let nb_public_values = self.get_nb_public_values();
        let len = vals.len();
        self.range(0, len).for_each(|i, builder| {
            let val = builder.get(vals, i);
            builder.commit_public_value_and_increment(val, nb_public_values);
        });
    }

    pub fn commit_vkey_hash_circuit(&mut self, var: Var<C::N>) {
        self.operations.push(DslIr::CircuitCommitVkeyHash(var));
    }

    pub fn commit_commited_values_digest_circuit(&mut self, var: Var<C::N>) {
        self.operations
            .push(DslIr::CircuitCommitCommitedValuesDigest(var));
    }

    pub fn cycle_tracker_start(&mut self, name: &str) {
        self.operations
            .push(DslIr::CycleTrackerStart(name.to_string()));
    }

    pub fn cycle_tracker_end(&mut self, name: &str) {
        self.operations
            .push(DslIr::CycleTrackerEnd(name.to_string()));
    }

    pub fn halt(&mut self) {
        self.operations.push(DslIr::Halt);
    }
}

/// A builder for the DSL that handles if statements.
pub struct IfBuilder<'a, C: Config> {
    lhs: SymbolicVar<C::N>,
    rhs: SymbolicVar<C::N>,
    is_eq: bool,
    pub(crate) builder: &'a mut Builder<C>,
}

/// A set of conditions that if statements can be based on.
enum IfCondition<N> {
    EqConst(N, N),
    NeConst(N, N),
    Eq(Var<N>, Var<N>),
    EqI(Var<N>, N),
    Ne(Var<N>, Var<N>),
    NeI(Var<N>, N),
}

impl<C: Config> IfBuilder<'_, C> {
    pub fn then(&mut self, mut f: impl FnMut(&mut Builder<C>)) {
        self.then_may_break(|builder| {
            f(builder);
            Ok(())
        })
        .expect("Use then_may_break if you want to break inside a then closure");
    }

    pub fn then_may_break(
        &mut self,
        mut f: impl FnMut(&mut Builder<C>) -> Result<(), BreakLoop>,
    ) -> Result<(), BreakLoop> {
        // Get the condition reduced from the expressions for lhs and rhs.
        let condition = self.condition();
        // Early return for const branches.
        match condition {
            IfCondition::EqConst(lhs, rhs) => {
                if lhs == rhs {
                    return f(self.builder);
                }
                return Ok(());
            }
            IfCondition::NeConst(lhs, rhs) => {
                if lhs != rhs {
                    return f(self.builder);
                }
                return Ok(());
            }
            _ => (),
        }
        assert!(
            !self.builder.flags.static_only,
            "Cannot use dynamic branch in static mode"
        );

        // Execute the `then` block and collect the instructions.
        let mut f_builder = self.builder.create_sub_builder();
        f(&mut f_builder).expect("BreakLoop should never be returned in a dynamic if");
        let then_instructions = f_builder.operations;

        // Dispatch instructions to the correct conditional block.
        match condition {
            IfCondition::Eq(lhs, rhs) => {
                let op = DslIr::IfEq(lhs, rhs, then_instructions, Default::default());
                self.builder.operations.push(op);
            }
            IfCondition::EqI(lhs, rhs) => {
                let op = DslIr::IfEqI(lhs, rhs, then_instructions, Default::default());
                self.builder.operations.push(op);
            }
            IfCondition::Ne(lhs, rhs) => {
                let op = DslIr::IfNe(lhs, rhs, then_instructions, Default::default());
                self.builder.operations.push(op);
            }
            IfCondition::NeI(lhs, rhs) => {
                let op = DslIr::IfNeI(lhs, rhs, then_instructions, Default::default());
                self.builder.operations.push(op);
            }
            _ => unreachable!("Const if should have returned early"),
        }
        Ok(())
    }

    pub fn then_or_else(
        &mut self,
        mut then_f: impl FnMut(&mut Builder<C>),
        mut else_f: impl FnMut(&mut Builder<C>),
    ) {
        self.then_or_else_may_break(
            |builder| {
                then_f(builder);
                Ok(())
            },
            |builder| {
                else_f(builder);
                Ok(())
            },
        )
        .expect("Use then_may_break if you want to break inside the then closure");
    }

    pub fn then_or_else_may_break(
        &mut self,
        mut then_f: impl FnMut(&mut Builder<C>) -> Result<(), BreakLoop>,
        mut else_f: impl FnMut(&mut Builder<C>) -> Result<(), BreakLoop>,
    ) -> Result<(), BreakLoop> {
        // Get the condition reduced from the expressions for lhs and rhs.
        let condition = self.condition();
        // Early return for const branches.
        match condition {
            IfCondition::EqConst(lhs, rhs) => {
                if lhs == rhs {
                    return then_f(self.builder);
                }
                return else_f(self.builder);
            }
            IfCondition::NeConst(lhs, rhs) => {
                if lhs != rhs {
                    return then_f(self.builder);
                }
                return else_f(self.builder);
            }
            _ => (),
        }
        assert!(
            !self.builder.flags.static_only,
            "Cannot use dynamic branch in static mode"
        );
        let mut then_builder = self.builder.create_sub_builder();

        // Execute the `then` and `else_then` blocks and collect the instructions.
        then_f(&mut then_builder).expect("BreakLoop should never be returned in a dynamic if");
        let then_instructions = then_builder.operations;

        let mut else_builder = self.builder.create_sub_builder();
        else_f(&mut else_builder).expect("BreakLoop should never be returned in a dynamic if");
        let else_instructions = else_builder.operations;

        // Dispatch instructions to the correct conditional block.
        match condition {
            IfCondition::Eq(lhs, rhs) => {
                let op = DslIr::IfEq(lhs, rhs, then_instructions, else_instructions);
                self.builder.operations.push(op);
            }
            IfCondition::EqI(lhs, rhs) => {
                let op = DslIr::IfEqI(lhs, rhs, then_instructions, else_instructions);
                self.builder.operations.push(op);
            }
            IfCondition::Ne(lhs, rhs) => {
                let op = DslIr::IfNe(lhs, rhs, then_instructions, else_instructions);
                self.builder.operations.push(op);
            }
            IfCondition::NeI(lhs, rhs) => {
                let op = DslIr::IfNeI(lhs, rhs, then_instructions, else_instructions);
                self.builder.operations.push(op);
            }
            _ => unreachable!("Const if should have returned early"),
        }
        Ok(())
    }

    fn condition(&mut self) -> IfCondition<C::N> {
        match (self.lhs.clone(), self.rhs.clone(), self.is_eq) {
            (SymbolicVar::Const(lhs, _), SymbolicVar::Const(rhs, _), true) => {
                IfCondition::EqConst(lhs, rhs)
            }
            (SymbolicVar::Const(lhs, _), SymbolicVar::Const(rhs, _), false) => {
                IfCondition::NeConst(lhs, rhs)
            }
            (SymbolicVar::Const(lhs, _), SymbolicVar::Val(rhs, _), true) => {
                IfCondition::EqI(rhs, lhs)
            }
            (SymbolicVar::Const(lhs, _), SymbolicVar::Val(rhs, _), false) => {
                IfCondition::NeI(rhs, lhs)
            }
            (SymbolicVar::Const(lhs, _), rhs, true) => {
                let rhs: Var<C::N> = self.builder.eval(rhs);
                IfCondition::EqI(rhs, lhs)
            }
            (SymbolicVar::Const(lhs, _), rhs, false) => {
                let rhs: Var<C::N> = self.builder.eval(rhs);
                IfCondition::NeI(rhs, lhs)
            }
            (SymbolicVar::Val(lhs, _), SymbolicVar::Const(rhs, _), true) => {
                let lhs: Var<C::N> = self.builder.eval(lhs);
                IfCondition::EqI(lhs, rhs)
            }
            (SymbolicVar::Val(lhs, _), SymbolicVar::Const(rhs, _), false) => {
                let lhs: Var<C::N> = self.builder.eval(lhs);
                IfCondition::NeI(lhs, rhs)
            }
            (lhs, SymbolicVar::Const(rhs, _), true) => {
                let lhs: Var<C::N> = self.builder.eval(lhs);
                IfCondition::EqI(lhs, rhs)
            }
            (lhs, SymbolicVar::Const(rhs, _), false) => {
                let lhs: Var<C::N> = self.builder.eval(lhs);
                IfCondition::NeI(lhs, rhs)
            }
            (SymbolicVar::Val(lhs, _), SymbolicVar::Val(rhs, _), true) => IfCondition::Eq(lhs, rhs),
            (SymbolicVar::Val(lhs, _), SymbolicVar::Val(rhs, _), false) => {
                IfCondition::Ne(lhs, rhs)
            }
            (SymbolicVar::Val(lhs, _), rhs, true) => {
                let rhs: Var<C::N> = self.builder.eval(rhs);
                IfCondition::Eq(lhs, rhs)
            }
            (SymbolicVar::Val(lhs, _), rhs, false) => {
                let rhs: Var<C::N> = self.builder.eval(rhs);
                IfCondition::Ne(lhs, rhs)
            }
            (lhs, SymbolicVar::Val(rhs, _), true) => {
                let lhs: Var<C::N> = self.builder.eval(lhs);
                IfCondition::Eq(lhs, rhs)
            }
            (lhs, SymbolicVar::Val(rhs, _), false) => {
                let lhs: Var<C::N> = self.builder.eval(lhs);
                IfCondition::Ne(lhs, rhs)
            }
            (lhs, rhs, true) => {
                let lhs: Var<C::N> = self.builder.eval(lhs);
                let rhs: Var<C::N> = self.builder.eval(rhs);
                IfCondition::Eq(lhs, rhs)
            }
            (lhs, rhs, false) => {
                let lhs: Var<C::N> = self.builder.eval(lhs);
                let rhs: Var<C::N> = self.builder.eval(rhs);
                IfCondition::Ne(lhs, rhs)
            }
        }
    }
}

/// A builder for the DSL that handles for loops.
pub struct RangeBuilder<'a, C: Config> {
    start: RVar<C::N>,
    end: RVar<C::N>,
    step_size: usize,
    builder: &'a mut Builder<C>,
}

impl<'a, C: Config> RangeBuilder<'a, C> {
    pub const fn may_break(self) -> RangeBuilderWithBreaks<'a, C> {
        RangeBuilderWithBreaks(self)
    }

    pub const fn step_by(mut self, step_size: usize) -> Self {
        self.step_size = step_size;
        self
    }

    /// No breaks allowed.
    pub fn for_each(&mut self, mut f: impl FnMut(RVar<C::N>, &mut Builder<C>)) {
        // If constant loop, unroll it.
        if self.start.is_const() && self.end.is_const() {
            self.for_each_unrolled(|var, builder| {
                f(var, builder);
                Ok(())
            });
            return;
        }
        // Otherwise, dynamic
        let old_disable_break = self.builder.flags.disable_break;
        self.builder.flags.disable_break = true;
        self.for_each_dynamic(|var, builder| {
            f(var, builder);
            Ok(())
        });
        self.builder.flags.disable_break = old_disable_break;
    }

    /// Compiler unrolls for loops, and currently can only handle breaks
    /// based on compile-time branching conditions.
    fn for_each_unrolled(
        &mut self,
        mut f: impl FnMut(RVar<C::N>, &mut Builder<C>) -> Result<(), BreakLoop>,
    ) {
        let old_static_loop = self.builder.flags.static_loop;
        self.builder.flags.static_loop = true;

        let start = self.start.value();
        let end = self.end.value();
        for i in (start..end).step_by(self.step_size) {
            if f(i.into(), self.builder).is_err() {
                break;
            }
        }
        self.builder.flags.static_loop = old_static_loop;
    }

    /// Internal function
    fn for_each_dynamic(
        &mut self,
        mut f: impl FnMut(RVar<C::N>, &mut Builder<C>) -> Result<(), BreakLoop>,
    ) {
        assert!(
            !self.builder.flags.static_only,
            "Cannot use dynamic loop in static mode"
        );
        let step_size = C::N::from_canonical_usize(self.step_size);
        let loop_variable: Var<C::N> = self.builder.uninit();
        let mut loop_body_builder = self.builder.create_sub_builder();

        f(loop_variable.into(), &mut loop_body_builder)
            .expect("BreakLoop should never be returned in a dynamic loop");

        let loop_instructions = loop_body_builder.operations;

        let op = DslIr::For(
            self.start,
            self.end,
            step_size,
            loop_variable,
            loop_instructions,
        );
        self.builder.operations.push(op);
    }
}

/// A builder for the DSL that handles for loops with breaks.
pub struct RangeBuilderWithBreaks<'a, C: Config>(RangeBuilder<'a, C>);

impl<C: Config> RangeBuilderWithBreaks<'_, C> {
    pub const fn step_by(mut self, step_size: usize) -> Self {
        self.0 = self.0.step_by(step_size);
        self
    }

    /// Does not unroll for loops unless builder flag `static_loop` is set.
    pub fn for_each(
        &mut self,
        f: impl FnMut(RVar<C::N>, &mut Builder<C>) -> Result<(), BreakLoop>,
    ) {
        let old_disable_break = self.0.builder.flags.disable_break;
        self.0.builder.flags.disable_break = false;
        // To handle breaks based on dynamic branching conditions, we do not
        // unroll constant loops unless the builder is in static_loop mode.
        if self.0.start.is_const() && self.0.end.is_const() && self.0.builder.flags.static_loop {
            self.0.for_each_unrolled(f);
        } else {
            // Dynamic
            self.0.for_each_dynamic(f);
        }
        self.0.builder.flags.disable_break = old_disable_break;
    }
}