Add a rustc flag for disabling the barrier removal optimization

compiler/rustc_mir_transform/src/remove_elidable_drops.rs

@@ -8,6 +8,9 @@ pub struct RemoveElidableDrops;
 
 impl<'tcx> MirPass<'tcx> for RemoveElidableDrops {
     fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
+        if tcx.sess.opts.cg.no_premature_finalizer_prevention_opt {
+            return;
+        }
         trace!("Running RemoveElidableDrops on {:?}", body.source);
 
         let is_gc_crate = tcx

compiler/rustc_session/src/options.rs

@@ -1521,6 +1521,8 @@ options! {
         "disable optimization to remove unnecessary finalizers"),
     no_finalizer_safety_analysis: bool = (false, parse_bool, [TRACKED],
         "disable checking of drop methods for GC soundness"),
+    no_premature_finalizer_prevention_opt: bool = (false, parse_bool, [TRACKED],
+        "disable optimization to remove unnecessary finalization barriers"),
     no_prepopulate_passes: bool = (false, parse_no_flag, [TRACKED],
         "give an empty list of passes to the pass manager"),
     no_redzone: Option<bool> = (None, parse_opt_bool, [TRACKED],

src/bootstrap/src/core/builder.rs

@@ -1524,6 +1524,9 @@ impl<'a> Builder<'a> {
         if stage != 0 && !self.config.finalizer_safety_analysis {
             rustflags.arg("-Cno-finalizer-safety-analysis");
         }
+        if stage != 0 && !self.config.premature_finalizer_prevention_optimize {
+            rustflags.arg("-Cno-premature-finalizer-prevention-opt");
+        }
 
         // Enable compile-time checking of `cfg` names, values and Cargo `features`.
         //

src/bootstrap/src/core/config/config.rs

@@ -311,6 +311,7 @@ pub struct Config {
     pub finalizer_elision: bool,
     pub finalizer_safety_analysis: bool,
     pub premature_finalizer_prevention: bool,
+    pub premature_finalizer_prevention_optimize: bool,
 
     // misc
     pub low_priority: bool,
@@ -1146,6 +1147,7 @@ define_config! {
         finalizer_elision: Option<bool> = "finalizer-elision",
         finalizer_safety_analysis: Option<bool> = "finalizer-safety-analysis",
         premature_finalizer_prevention: Option<bool> = "premature-finalizer-prevention",
+        premature_finalizer_prevention_optimize: Option<bool> = "premature-finalizer-prevention-optimize",
     }
 }
 
@@ -1220,6 +1222,7 @@ impl Config {
             finalizer_elision: true,
             finalizer_safety_analysis: true,
             premature_finalizer_prevention: true,
+            premature_finalizer_prevention_optimize: true,
 
             ..Default::default()
         }
@@ -1779,12 +1782,17 @@ impl Config {
                 finalizer_elision,
                 finalizer_safety_analysis,
                 premature_finalizer_prevention,
+                premature_finalizer_prevention_optimize,
             } = alloy;
 
             set(&mut config.log_stats, log_stats);
             set(&mut config.finalizer_elision, finalizer_elision);
             set(&mut config.finalizer_safety_analysis, finalizer_safety_analysis);
             set(&mut config.premature_finalizer_prevention, premature_finalizer_prevention);
+            set(
+                &mut config.premature_finalizer_prevention_optimize,
+                premature_finalizer_prevention_optimize,
+            );
         }
 
         if let Some(llvm) = toml.llvm {