From 8bd14bc90e38700213d120f4dd601d66a5efce5f Mon Sep 17 00:00:00 2001
From: Tom French <15848336+TomAFrench@users.noreply.github.com>
Date: Mon, 13 Jan 2025 14:27:20 +0000
Subject: [PATCH] feat: avoid inserting `inc_rc` instructions into ACIR (#7036)

---
 compiler/noirc_evaluator/src/ssa/ir/dfg.rs             |  4 +---
 .../noirc_evaluator/src/ssa/opt/constant_folding.rs    |  3 ++-
 compiler/noirc_evaluator/src/ssa/opt/loop_invariant.rs | 10 ++++++----
 3 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/compiler/noirc_evaluator/src/ssa/ir/dfg.rs b/compiler/noirc_evaluator/src/ssa/ir/dfg.rs
index ddc9814a40..6eae291ca4 100644
--- a/compiler/noirc_evaluator/src/ssa/ir/dfg.rs
+++ b/compiler/noirc_evaluator/src/ssa/ir/dfg.rs
@@ -20,7 +20,6 @@ use iter_extended::vecmap;
 use serde::{Deserialize, Serialize};
 use serde_with::serde_as;
 use serde_with::DisplayFromStr;
-use tracing::warn;
 
 /// The DataFlowGraph contains most of the actual data in a function including
 /// its blocks, instructions, and values. This struct is largely responsible for
@@ -238,8 +237,7 @@ impl DataFlowGraph {
         call_stack: CallStackId,
     ) -> InsertInstructionResult {
         if !self.is_handled_by_runtime(&instruction) {
-            warn!("Attempted to insert instruction not handled by runtime: {instruction:?}");
-            return InsertInstructionResult::InstructionRemoved;
+            panic!("Attempted to insert instruction not handled by runtime: {instruction:?}");
         }
 
         match instruction.simplify(self, block, ctrl_typevars.clone(), call_stack) {
diff --git a/compiler/noirc_evaluator/src/ssa/opt/constant_folding.rs b/compiler/noirc_evaluator/src/ssa/opt/constant_folding.rs
index 2c7d6b4f1e..5b75055c09 100644
--- a/compiler/noirc_evaluator/src/ssa/opt/constant_folding.rs
+++ b/compiler/noirc_evaluator/src/ssa/opt/constant_folding.rs
@@ -307,6 +307,7 @@ impl<'brillig> Context<'brillig> {
         let old_results = dfg.instruction_results(id).to_vec();
 
         // If a copy of this instruction exists earlier in the block, then reuse the previous results.
+        let runtime_is_brillig = dfg.runtime().is_brillig();
         if let Some(cache_result) =
             self.get_cached(dfg, dom, &instruction, *side_effects_enabled_var, block)
         {
@@ -314,7 +315,7 @@ impl<'brillig> Context<'brillig> {
                 CacheResult::Cached(cached) => {
                     // We track whether we may mutate MakeArray instructions before we deduplicate
                     // them but we still need to issue an extra inc_rc in case they're mutated afterward.
-                    if matches!(instruction, Instruction::MakeArray { .. }) {
+                    if runtime_is_brillig && matches!(instruction, Instruction::MakeArray { .. }) {
                         let value = *cached.last().unwrap();
                         let inc_rc = Instruction::IncrementRc { value };
                         let call_stack = dfg.get_instruction_call_stack_id(id);
diff --git a/compiler/noirc_evaluator/src/ssa/opt/loop_invariant.rs b/compiler/noirc_evaluator/src/ssa/opt/loop_invariant.rs
index f0f677e5db..125cf3a12c 100644
--- a/compiler/noirc_evaluator/src/ssa/opt/loop_invariant.rs
+++ b/compiler/noirc_evaluator/src/ssa/opt/loop_invariant.rs
@@ -112,10 +112,12 @@ impl<'f> LoopInvariantContext<'f> {
 
                     // If we are hoisting a MakeArray instruction,
                     // we need to issue an extra inc_rc in case they are mutated afterward.
-                    if matches!(
-                        self.inserter.function.dfg[instruction_id],
-                        Instruction::MakeArray { .. }
-                    ) {
+                    if self.inserter.function.runtime().is_brillig()
+                        && matches!(
+                            self.inserter.function.dfg[instruction_id],
+                            Instruction::MakeArray { .. }
+                        )
+                    {
                         let result =
                             self.inserter.function.dfg.instruction_results(instruction_id)[0];
                         let inc_rc = Instruction::IncrementRc { value: result };