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feat: remove replacement of boolean range opcodes with AssertZero opcodes #4107

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Jan 30, 2024
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feat: remove replacement of boolean range opcodes with AssertZero opcodes #4107

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72 changes: 26 additions & 46 deletions acvm-repo/acvm/src/compiler/optimizers/redundant_range.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -3,8 +3,7 @@ use acir::{
opcodes::{BlackBoxFuncCall, FunctionInput},
Circuit, Opcode,
},
native_types::{Expression, Witness},
FieldElement,
native_types::Witness,
};
use std::collections::{BTreeMap, HashSet};

Expand Down Expand Up @@ -105,9 +104,11 @@ impl RangeOptimizer {
let mut new_order_list = Vec::with_capacity(order_list.len());
let mut optimized_opcodes = Vec::with_capacity(self.circuit.opcodes.len());
for (idx, opcode) in self.circuit.opcodes.into_iter().enumerate() {
let (witness, num_bits) = match extract_range_opcode(&opcode) {
Some(range_opcode) => range_opcode,
None => {
let (witness, num_bits) = match &opcode {
Opcode::BlackBoxFuncCall(BlackBoxFuncCall::RANGE { input }) => {
(input.witness, input.num_bits)
}
_ => {
// If its not the range opcode, add it to the opcode
// list and continue;
optimized_opcodes.push(opcode);
Expand All @@ -131,44 +132,19 @@ impl RangeOptimizer {
if is_lowest_bit_size {
already_seen_witness.insert(witness);
new_order_list.push(order_list[idx]);
optimized_opcodes.push(optimized_range_opcode(witness, num_bits));
optimized_opcodes.push(opcode);
}
}

(Circuit { opcodes: optimized_opcodes, ..self.circuit }, new_order_list)
}
}

/// Extract the range opcode from the `Opcode` enum
/// Returns None, if `Opcode` is not the range opcode.
fn extract_range_opcode(opcode: &Opcode) -> Option<(Witness, u32)> {
match opcode {
Opcode::BlackBoxFuncCall(BlackBoxFuncCall::RANGE { input }) => {
Some((input.witness, input.num_bits))
}
_ => None,
}
}

fn optimized_range_opcode(witness: Witness, num_bits: u32) -> Opcode {
if num_bits == 1 {
Opcode::AssertZero(Expression {
mul_terms: vec![(FieldElement::one(), witness, witness)],
linear_combinations: vec![(-FieldElement::one(), witness)],
q_c: FieldElement::zero(),
})
} else {
Opcode::BlackBoxFuncCall(BlackBoxFuncCall::RANGE {
input: FunctionInput { witness, num_bits },
})
}
}

#[cfg(test)]
mod tests {
use std::collections::BTreeSet;

use crate::compiler::optimizers::redundant_range::{extract_range_opcode, RangeOptimizer};
use crate::compiler::optimizers::redundant_range::RangeOptimizer;
use acir::{
circuit::{
opcodes::{BlackBoxFuncCall, FunctionInput},
Expand Down Expand Up @@ -218,11 +194,12 @@ mod tests {
let (optimized_circuit, _) = optimizer.replace_redundant_ranges(acir_opcode_positions);
assert_eq!(optimized_circuit.opcodes.len(), 1);

let (witness, num_bits) =
extract_range_opcode(&optimized_circuit.opcodes[0]).expect("expected one range opcode");

assert_eq!(witness, Witness(1));
assert_eq!(num_bits, 16);
assert_eq!(
optimized_circuit.opcodes[0],
Opcode::BlackBoxFuncCall(BlackBoxFuncCall::RANGE {
input: FunctionInput { witness: Witness(1), num_bits: 16 }
})
);
}

#[test]
Expand All @@ -240,15 +217,18 @@ mod tests {
let (optimized_circuit, _) = optimizer.replace_redundant_ranges(acir_opcode_positions);
assert_eq!(optimized_circuit.opcodes.len(), 2);

let (witness_a, num_bits_a) =
extract_range_opcode(&optimized_circuit.opcodes[0]).expect("expected two range opcode");
let (witness_b, num_bits_b) =
extract_range_opcode(&optimized_circuit.opcodes[1]).expect("expected two range opcode");

assert_eq!(witness_a, Witness(1));
assert_eq!(witness_b, Witness(2));
assert_eq!(num_bits_a, 16);
assert_eq!(num_bits_b, 23);
assert_eq!(
optimized_circuit.opcodes[0],
Opcode::BlackBoxFuncCall(BlackBoxFuncCall::RANGE {
input: FunctionInput { witness: Witness(1), num_bits: 16 }
})
);
assert_eq!(
optimized_circuit.opcodes[1],
Opcode::BlackBoxFuncCall(BlackBoxFuncCall::RANGE {
input: FunctionInput { witness: Witness(2), num_bits: 23 }
})
);
}

#[test]
Expand Down
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