fix: discard ref counts during unrolling

compiler/noirc_evaluator/src/ssa/opt/unrolling.rs

@@ -12,6 +12,8 @@
 //!
 //! Note that this pass also often creates superfluous jmp instructions in the
 //! program that will need to be removed by a later simplify cfg pass.
+//! Note also that unrolling is skipped for Brillig runtime and as a result
+//! we remove reference count instructions because they are only used by Brillig bytecode
 use std::collections::HashSet;
 
 use crate::{
@@ -24,7 +26,7 @@ use crate::{
             dom::DominatorTree,
             function::{Function, RuntimeType},
             function_inserter::FunctionInserter,
-            instruction::TerminatorInstruction,
+            instruction::{Instruction, TerminatorInstruction},
             post_order::PostOrder,
             value::ValueId,
         },
@@ -465,9 +467,14 @@ impl<'f> LoopIteration<'f> {
         // instances of the induction variable or any values that were changed as a result
         // of the new induction variable value.
         for instruction in instructions {
-            self.inserter.push_instruction(instruction, self.insert_block);
+            // Skip reference count instructions since they are only used for brillig, and brillig code is not unrolled
+            if !matches!(
+                self.dfg()[instruction],
+                Instruction::IncrementRc { .. } | Instruction::DecrementRc { .. }
+            ) {
+                self.inserter.push_instruction(instruction, self.insert_block);
+            }
         }
-
         let mut terminator = self.dfg()[self.source_block]
             .unwrap_terminator()
             .clone()

test_programs/execution_success/regression_4709/Nargo.toml

@@ -0,0 +1,6 @@
+[package]
+name = "regression_4709"
+type = "bin"
+authors = [""]
+
+[dependencies]

test_programs/execution_success/regression_4709/Prover.toml

@@ -0,0 +1,2 @@
+x = 1
+y = 2