feat: remove replacement of boolean range opcodes with AssertZero opcodes

Author: TomAFrench

acvm-repo/acvm/src/compiler/optimizers/redundant_range.rs

@@ -3,8 +3,7 @@ use acir::{
         opcodes::{BlackBoxFuncCall, FunctionInput},
         Circuit, Opcode,
     },
-    native_types::{Expression, Witness},
-    FieldElement,
+    native_types::Witness,
 };
 use std::collections::{BTreeMap, HashSet};
 
@@ -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);
@@ -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},
@@ -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]
@@ -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]