[maglev] Don't deopt-for-osr when Turbofan is disabled

Bug: v8:7700
Change-Id: I784d28b8ee043a4fa2478dbaaf7412a0708b811c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3867732Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Jakob Linke <jgruber@chromium.org>
Auto-Submit: Jakob Linke <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/main@{#82894}

src/maglev/maglev-ir.cc

@@ -3358,8 +3358,15 @@ void AttemptOnStackReplacement(MaglevCodeGenState* code_gen_state,
   }
 
   __ bind(&deopt);
+  if (V8_LIKELY(FLAG_turbofan)) {
     EmitEagerDeopt(code_gen_state, node,
                    DeoptimizeReason::kPrepareForOnStackReplacement);
+  } else {
+    // Fall through. With TF disabled we cannot OSR and thus it doesn't make
+    // sense to start the process. We do still perform all remaining
+    // bookkeeping above though, to keep Maglev code behavior roughly the same
+    // in both configurations.
+  }
 }
 
 }  // namespace