From b9146edc799af449708a14eb266e399cbb91458d Mon Sep 17 00:00:00 2001
From: "google-labs-jules[bot]"
 <161369871+google-labs-jules[bot]@users.noreply.github.com>
Date: Sun, 13 Sep 2026 05:23:17 +0000
Subject: [PATCH] perf: avoid intermediate string allocation in VM debugger
 loop

Co-authored-by: Tcode-Motion <188012755+Tcode-Motion@users.noreply.github.com>
---
 runtime/vm/src/debugger.rs | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/runtime/vm/src/debugger.rs b/runtime/vm/src/debugger.rs
index 3817852f..df290a0b 100644
--- a/runtime/vm/src/debugger.rs
+++ b/runtime/vm/src/debugger.rs
@@ -55,7 +55,9 @@ impl VMDebugger {
             return;
         }
 
-        let op_str = format!("{:?}", op_code);
+        // Bolt performance optimization: Avoid unnecessary string allocation for op_code.
+        // `op_code` implements `Debug`, so we can format it directly into the final string
+        // instead of pre-allocating an intermediate String with `format!`.
         let mut operands_str = String::new();
 
         for op in operands {
@@ -93,8 +95,8 @@ impl VMDebugger {
         }
 
         println!(
-            "[{:04}]  {:<15} {}  | Stack: {:?}",
-            ip, op_str, operands_str, stack_dump
+            "[{:04}]  {:<15?} {}  | Stack: {:?}",
+            ip, op_code, operands_str, stack_dump
         );
     }
 }