feat: replace boolean ANDs with multiplication

crates/noirc_evaluator/src/ssa_refactor/ir/dfg.rs

@@ -158,7 +158,12 @@ impl DataFlowGraph {
                 SimplifiedToMultiple(simplification)
             }
             SimplifyResult::Remove => InstructionRemoved,
-            SimplifyResult::None => {
+            result @ (SimplifyResult::SimplifiedToInstruction(_) | SimplifyResult::None) => {
+                let instruction = match result {
+                    SimplifyResult::SimplifiedToInstruction(new_instruction) => new_instruction,
+                    SimplifyResult::None => instruction,
+                    _ => unreachable!("handled by above match statement"),
+                };
                 let id = self.make_instruction(instruction, ctrl_typevars);
                 self.blocks[block].insert_instruction(id);
                 if let Some(location) = location {

crates/noirc_evaluator/src/ssa_refactor/ir/instruction.rs

@@ -737,6 +737,11 @@ impl Binary {
                     let zero = dfg.make_constant(FieldElement::zero(), operand_type);
                     return SimplifyResult::SimplifiedTo(zero);
                 }
+                if operand_type == Type::bool() {
+                    // Boolean AND is equivalent to multiplication, which is a cheaper operation.
+                    let instruction = Instruction::binary(BinaryOp::Mul, self.lhs, self.rhs);
+                    return SimplifyResult::SimplifiedToInstruction(instruction);
+                }
             }
             BinaryOp::Or => {
                 if lhs_is_zero {
@@ -910,6 +915,9 @@ pub(crate) enum SimplifyResult {
     /// a function such as a tuple
     SimplifiedToMultiple(Vec<ValueId>),
 
+    /// Replace this function with an simpler but equivalent function.
+    SimplifiedToInstruction(Instruction),
+
     /// Remove the instruction, it is unnecessary
     Remove,