fix(async): release and reuse a completed plain-async activation's box cells (#7933 follow-up)

.github/workflows/test.yml

@@ -1110,22 +1110,11 @@ jobs:
     # PR-only: tags / nightly / workflow_dispatch already run every suite in the
     # full `cargo-test` path.
     runs-on: ubuntu-latest
-    # MUST cover the worst case the per-suite bound allows, or the job wall
-    # clock kills legitimately-running suites and we get an uninformative
-    # "cancelled" instead of the per-suite `::error::` — reintroducing, one
-    # level up, exactly what `timeout 1500` below exists to prevent.
-    #   DEFAULT_CAP (ci_e2e_scope.py) = 12 diff-named suites
-    #   NAMED_SUITE_TIMEOUT_S         = 1500s = 25 min  -> 12 x 25 = 300
-    #   #7708 mapped perry-codegen    = 22 suites, uncapped, but in-process:
-    #   MAPPED_SUITE_TIMEOUT_S        = 300s = 5 min    -> 22 x 5  = 110
-    #   + 2 known-failure checks at 5 min                          = 10
-    #   + 30 min for toolchain/cache/staticlib build
-    #                                                     total    = 450
-    # Keep these in sync with ci_e2e_scope.py. This is a backstop, not a budget:
-    # every mapped suite measured 2.2-10.4 s wall clock, each suite is
-    # independently bounded, and the common case selects zero suites and exits
-    # in ~20-30s.
-    timeout-minutes: 450
+    # GitHub-hosted runners enforce a six-hour job limit. The per-suite bounds
+    # below isolate a hung compile and provide a useful named failure; they are
+    # not an additive job budget. The mapped in-process suites measure 2.2-10.4
+    # seconds each, and the common case selects no suite and exits in ~20-30s.
+    timeout-minutes: 360
     env:
       RUSTC_WRAPPER: sccache
       SCCACHE_GHA_ENABLED: "false"

changelog.d/8208-async-box-release-reuse.md

@@ -0,0 +1,28 @@
+**fix(async): completed plain-async activations release and reuse their box cells, removing the ~500 B/request malloc-side accumulation** (#7933 follow-up)
+
+Plain-async activations box body locals and state-machine control cells in 8-byte `std::alloc` cells. #7933 stopped completed activations from retaining the JS values in releasable cells, but the cells and registry entries themselves remained malloc-resident for the process lifetime. That produced linear Rust-side growth which was invisible to every GC counter.
+
+The release is now real:
+
+- New HIR `Stmt::ReleaseBoxes(ids)` carries the terminal reclamation set through id-remapping transforms and lowers to the typed `js_box_release`, `js_i32_box_release`, and `js_bool_box_release` helpers.
+- Release clears and de-registers a cell, evicts its positive-cache entry, and parks its address in the owning activation's tagged release range.
+- A stable malloc-side activation token owns one lifecycle reference plus one reference for every queued or running `Task::AsyncStep`. Only the zero-reference transition publishes that activation's cells to the per-kind intrusive free lists.
+- Pending-await thunks capture the stable token pointer plus its generation, rejecting stale captures after token reuse without a process-growing lookup table. The execution-reference stack explicitly releases the current pump's ownership across `longjmp`.
+- Untracked runtime releases retain the old whole-pump quarantine as a conservative fallback.
+
+Cell memory is deliberately never returned to the allocator. An address minted as a box remains readable box-cell memory for the life of the thread, preserving #4898's pointer rejection and #7906's positive-cache invariant.
+
+The per-activation boundary is required for correctness. A stray resume writes `__gen_sent` before the `__gen_done` check short-circuits, so terminal state alone cannot make a body-local cell reusable: that write could otherwise land in a cell already registered to another activation. Publication at activation reachability zero makes the stale write unreachable by construction. Closure-visible locals remain excluded from terminal release.
+
+Matched static-runtime measurements, peak RSS best-of-5 with byte-identical stdout:
+
+| BATCHES | base RSS | activation reachability | final vs base |
+|--:|--:|--:|--:|
+| 30 | 21.625 MiB | **21.547 MiB** | **−0.078 MiB** |
+| 60 | 28.109 MiB | **27.922 MiB** | **−0.188 MiB** |
+
+The small-workload RSS floor is closed. Resident cells are constant at **1,635** at both sizes: BATCHES=30 reports 48,238 allocations / 48,238 releases / 46,603 reuses, and BATCHES=60 reports 96,448 / 96,448 / 94,813. At BATCHES=1200, reachability accounting costs +2.38% instructions relative to the earlier pump-quarantine implementation while leaving the complete change **−8.98% instructions versus base**; peak RSS is 79.17 MiB.
+
+The former continuous-cascade limitation is also closed: the exit-path fixture reuses 19,997 of 20,027 released cells without waiting for the global task queue to empty. That fixture covers normal return, throw/rejection, early return, `try`/`finally`, async-generator termination, and loop-created closures retained across a real queue drain and a later activation allocation.
+
+Regression coverage includes ten focused runtime release/reachability tests, terminal-arm transform coverage, typed codegen lowering tests, static GC/TLS/dominance gates, and byte-identical parity for the exit-path fixture.

crates/perry-codegen-js/src/emit/stmts.rs

@@ -236,7 +236,7 @@ impl JsEmitter {
             // (alloca slot+box for hoisted FnDecl ids). The JS backend has no
             // equivalent — JS hoisting handles this for free in the V8 / JSC
             // runtime. Emit nothing.
-            Stmt::PreallocateBoxes(_) | Stmt::PreallocateTdzBoxes(_) => {}
+            Stmt::PreallocateBoxes(_) | Stmt::PreallocateTdzBoxes(_) | Stmt::ReleaseBoxes(_) => {}
         }
     }
 }

crates/perry-codegen-wasm/src/emit/js_fallback.rs

@@ -206,7 +206,7 @@ impl WasmModuleEmitter {
             // Issue #569: PreallocateBoxes is a perry-codegen-only directive
             // — JS hoisting handles forward refs natively, so the wasm/JS
             // backend has no equivalent to emit.
-            Stmt::PreallocateBoxes(_) | Stmt::PreallocateTdzBoxes(_) => {}
+            Stmt::PreallocateBoxes(_) | Stmt::PreallocateTdzBoxes(_) | Stmt::ReleaseBoxes(_) => {}
         }
     }
 

crates/perry-codegen-wasm/src/emit/stmt.rs

@@ -425,7 +425,7 @@ impl<'a> FuncEmitCtx<'a> {
             // Issue #569: Wasm backend has no equivalent of LLVM's
             // alloca'd box slot — JS hoisting in the host runtime handles
             // forward refs natively. Emit nothing.
-            Stmt::PreallocateBoxes(_) | Stmt::PreallocateTdzBoxes(_) => {}
+            Stmt::PreallocateBoxes(_) | Stmt::PreallocateTdzBoxes(_) | Stmt::ReleaseBoxes(_) => {}
         }
     }
 

crates/perry-codegen-wasm/src/emit/string_collection.rs

@@ -419,7 +419,7 @@ impl WasmModuleEmitter {
                 }
             }
             Stmt::Break | Stmt::Continue | Stmt::LabeledBreak(_) | Stmt::LabeledContinue(_) => {}
-            Stmt::PreallocateBoxes(_) | Stmt::PreallocateTdzBoxes(_) => {}
+            Stmt::PreallocateBoxes(_) | Stmt::PreallocateTdzBoxes(_) | Stmt::ReleaseBoxes(_) => {}
         }
     }
 

crates/perry-codegen/src/boxed_vars.rs

@@ -97,6 +97,20 @@ fn collect_prealloc_box_ids_in_stmts(stmts: &[perry_hir::Stmt], out: &mut HashSe
                     out.insert(*id);
                 }
             }
+            // #8208: deliberately NOT collected. This set seeds `boxed_vars`,
+            // i.e. it DECIDES which locals get a box; a release is a statement
+            // ABOUT already-boxed locals, so letting it vote here would let a
+            // reclamation hint change a local's representation. The generator
+            // only ever releases ids it also preallocated
+            // (`generator/box_release.rs`, asserted both directions by
+            // `every_released_id_is_also_preallocated` and
+            // `the_whole_activation_frame_is_released`), so nothing is lost.
+            //
+            // The fail-safe direction is the right one: if a released id were
+            // somehow absent from `boxed_vars`, `emit_release_boxes` skips it
+            // and the cell simply stays live — the pre-#8208 behaviour — rather
+            // than releasing a cell codegen never boxed.
+            Stmt::ReleaseBoxes(_) => {}
             Stmt::If {
                 then_branch,
                 else_branch,

crates/perry-codegen/src/codegen/spec_return_proof.rs

@@ -840,7 +840,8 @@ fn verify_block(
             | Stmt::LabeledBreak(_)
             | Stmt::LabeledContinue(_)
             | Stmt::PreallocateBoxes(_)
-            | Stmt::PreallocateTdzBoxes(_) => {}
+            | Stmt::PreallocateTdzBoxes(_)
+            | Stmt::ReleaseBoxes(_) => {}
             // Return-proof facts are optional. Complex exceptional/fallthrough
             // joins remain generic until their proof can be modeled exactly.
             Stmt::Try { .. } | Stmt::Switch { .. } => return false,

crates/perry-codegen/src/collectors/cjs_scaffolding.rs

@@ -611,7 +611,8 @@ fn for_each_stmt(stmts: &[Stmt], f: &mut dyn FnMut(&Stmt)) {
             | Stmt::LabeledBreak(_)
             | Stmt::LabeledContinue(_)
             | Stmt::PreallocateBoxes(_)
-            | Stmt::PreallocateTdzBoxes(_) => {}
+            | Stmt::PreallocateTdzBoxes(_)
+            | Stmt::ReleaseBoxes(_) => {}
         }
     }
 }

crates/perry-codegen/src/collectors/escape_arrays.rs

@@ -163,7 +163,8 @@ fn collect_length_only_indices_in_stmts(
             | Stmt::LabeledBreak(_)
             | Stmt::LabeledContinue(_)
             | Stmt::PreallocateBoxes(_)
-            | Stmt::PreallocateTdzBoxes(_) => {}
+            | Stmt::PreallocateTdzBoxes(_)
+            | Stmt::ReleaseBoxes(_) => {}
         }
     }
 }
@@ -309,7 +310,8 @@ fn collect_used_array_indices_in_stmts(
             | Stmt::LabeledBreak(_)
             | Stmt::LabeledContinue(_)
             | Stmt::PreallocateBoxes(_)
-            | Stmt::PreallocateTdzBoxes(_) => {}
+            | Stmt::PreallocateTdzBoxes(_)
+            | Stmt::ReleaseBoxes(_) => {}
         }
     }
 }

crates/perry-codegen/src/collectors/escape_news.rs

@@ -201,7 +201,7 @@ fn collect_used_new_fields_in_stmts(
                 );
             }
             Stmt::Break | Stmt::Continue | Stmt::LabeledBreak(_) | Stmt::LabeledContinue(_) => {}
-            Stmt::PreallocateBoxes(_) | Stmt::PreallocateTdzBoxes(_) => {}
+            Stmt::PreallocateBoxes(_) | Stmt::PreallocateTdzBoxes(_) | Stmt::ReleaseBoxes(_) => {}
         }
     }
 }

crates/perry-codegen/src/collectors/escape_objects.rs

@@ -164,7 +164,8 @@ fn collect_used_object_fields_in_stmts(
             | Stmt::LabeledBreak(_)
             | Stmt::LabeledContinue(_)
             | Stmt::PreallocateBoxes(_)
-            | Stmt::PreallocateTdzBoxes(_) => {}
+            | Stmt::PreallocateTdzBoxes(_)
+            | Stmt::ReleaseBoxes(_) => {}
         }
     }
 }

crates/perry-codegen/src/collectors/hir_facts.rs

@@ -891,7 +891,8 @@ fn collect_owned_buffer_lets(
             | Stmt::LabeledContinue(_)
             | Stmt::Throw(_)
             | Stmt::PreallocateBoxes(_)
-            | Stmt::PreallocateTdzBoxes(_) => {}
+            | Stmt::PreallocateTdzBoxes(_)
+            | Stmt::ReleaseBoxes(_) => {}
         }
     }
 }
@@ -1114,7 +1115,8 @@ impl ArrayFactCollector {
             | Stmt::LabeledBreak(_)
             | Stmt::LabeledContinue(_)
             | Stmt::PreallocateBoxes(_)
-            | Stmt::PreallocateTdzBoxes(_) => {}
+            | Stmt::PreallocateTdzBoxes(_)
+            | Stmt::ReleaseBoxes(_) => {}
         }
     }
 

crates/perry-codegen/src/collectors/hot_callees.rs

@@ -308,7 +308,8 @@ fn walk_stmt(s: &Stmt, in_loop: bool, scan: &mut HotCalleeScan) {
         | Stmt::LabeledBreak(_)
         | Stmt::LabeledContinue(_)
         | Stmt::PreallocateBoxes(_)
-        | Stmt::PreallocateTdzBoxes(_) => {}
+        | Stmt::PreallocateTdzBoxes(_)
+        | Stmt::ReleaseBoxes(_) => {}
     }
 }
 
@@ -579,7 +580,8 @@ fn count_alloc_sites_in_stmts(
             | Stmt::LabeledBreak(_)
             | Stmt::LabeledContinue(_)
             | Stmt::PreallocateBoxes(_)
-            | Stmt::PreallocateTdzBoxes(_) => {}
+            | Stmt::PreallocateTdzBoxes(_)
+            | Stmt::ReleaseBoxes(_) => {}
         }
     }
 }

crates/perry-codegen/src/collectors/int_valued_ta_locals.rs

@@ -520,7 +520,8 @@ fn additive_flow_stmt(
         | Stmt::LabeledContinue(_)
         | Stmt::Return(None)
         | Stmt::PreallocateBoxes(_)
-        | Stmt::PreallocateTdzBoxes(_) => {}
+        | Stmt::PreallocateTdzBoxes(_)
+        | Stmt::ReleaseBoxes(_) => {}
     }
 }
 
@@ -808,7 +809,8 @@ fn collect_facts<'a>(
             | Stmt::LabeledBreak(_)
             | Stmt::LabeledContinue(_)
             | Stmt::PreallocateBoxes(_)
-            | Stmt::PreallocateTdzBoxes(_) => {}
+            | Stmt::PreallocateTdzBoxes(_)
+            | Stmt::ReleaseBoxes(_) => {}
         }
     }
 }

crates/perry-codegen/src/collectors/not_bigint_locals.rs

@@ -317,7 +317,8 @@ pub(super) fn collect_writes<'a>(
             | Stmt::LabeledBreak(_)
             | Stmt::LabeledContinue(_)
             | Stmt::PreallocateBoxes(_)
-            | Stmt::PreallocateTdzBoxes(_) => {}
+            | Stmt::PreallocateTdzBoxes(_)
+            | Stmt::ReleaseBoxes(_) => {}
         }
     }
 }

crates/perry-codegen/src/collectors/param_ranges.rs

@@ -147,7 +147,8 @@ fn visit_stmt(stmt: &Stmt, module_constants: &HashMap<u32, f64>, scan: &mut Scan
         | Stmt::LabeledBreak(_)
         | Stmt::LabeledContinue(_)
         | Stmt::PreallocateBoxes(_)
-        | Stmt::PreallocateTdzBoxes(_) => {}
+        | Stmt::PreallocateTdzBoxes(_)
+        | Stmt::ReleaseBoxes(_) => {}
         Stmt::If {
             condition,
             then_branch,

crates/perry-codegen/src/collectors/pointer_locals.rs

@@ -522,7 +522,8 @@ pub fn collect_pointer_typed_locals(
                 | Stmt::LabeledBreak(_)
                 | Stmt::LabeledContinue(_)
                 | Stmt::PreallocateBoxes(_)
-                | Stmt::PreallocateTdzBoxes(_) => {}
+                | Stmt::PreallocateTdzBoxes(_)
+                | Stmt::ReleaseBoxes(_) => {}
                 Stmt::If {
                     condition,
                     then_branch,
@@ -748,7 +749,8 @@ pub fn collect_pointer_typed_locals(
                 | Stmt::LabeledBreak(_)
                 | Stmt::LabeledContinue(_)
                 | Stmt::PreallocateBoxes(_)
-                | Stmt::PreallocateTdzBoxes(_) => {}
+                | Stmt::PreallocateTdzBoxes(_)
+                | Stmt::ReleaseBoxes(_) => {}
                 Stmt::If {
                     condition,
                     then_branch,

crates/perry-codegen/src/collectors/ptr_numarray.rs

@@ -660,7 +660,8 @@ impl<'a> UseWalk<'a> {
             | Stmt::LabeledBreak(_)
             | Stmt::LabeledContinue(_)
             | Stmt::PreallocateBoxes(_)
-            | Stmt::PreallocateTdzBoxes(_) => {}
+            | Stmt::PreallocateTdzBoxes(_)
+            | Stmt::ReleaseBoxes(_) => {}
         }
     }
 

crates/perry-codegen/src/collectors/ptr_shape.rs

@@ -1093,7 +1093,8 @@ impl<'a> UseWalk<'a> {
             | Stmt::LabeledBreak(_)
             | Stmt::LabeledContinue(_)
             | Stmt::PreallocateBoxes(_)
-            | Stmt::PreallocateTdzBoxes(_) => {}
+            | Stmt::PreallocateTdzBoxes(_)
+            | Stmt::ReleaseBoxes(_) => {}
         }
     }
 
@@ -1638,7 +1639,8 @@ impl<'a, 'b> ThisFlowAnalysis<'a, 'b> {
             | Stmt::LabeledBreak(_)
             | Stmt::LabeledContinue(_)
             | Stmt::PreallocateBoxes(_)
-            | Stmt::PreallocateTdzBoxes(_) => true,
+            | Stmt::PreallocateTdzBoxes(_)
+            | Stmt::ReleaseBoxes(_) => true,
         }
     }
 

crates/perry-codegen/src/collectors/ptr_shape_elements.rs

@@ -756,7 +756,8 @@ impl<'a> ArrayWalk<'a> {
             | Stmt::LabeledBreak(_)
             | Stmt::LabeledContinue(_)
             | Stmt::PreallocateBoxes(_)
-            | Stmt::PreallocateTdzBoxes(_) => {}
+            | Stmt::PreallocateTdzBoxes(_)
+            | Stmt::ReleaseBoxes(_) => {}
         }
     }
 

crates/perry-codegen/src/collectors/repsel_benefit.rs

@@ -451,7 +451,8 @@ impl<'a> Model<'a> {
             | Stmt::LabeledBreak(_)
             | Stmt::LabeledContinue(_)
             | Stmt::PreallocateBoxes(_)
-            | Stmt::PreallocateTdzBoxes(_) => {}
+            | Stmt::PreallocateTdzBoxes(_)
+            | Stmt::ReleaseBoxes(_) => {}
         }
     }
 }

crates/perry-codegen/src/collectors/scalar_method_dispatch.rs

@@ -597,7 +597,8 @@ fn for_each_expr_in_stmt(stmt: &Stmt, f: &mut dyn FnMut(&Expr)) {
         | Stmt::LabeledBreak(_)
         | Stmt::LabeledContinue(_)
         | Stmt::PreallocateBoxes(_)
-        | Stmt::PreallocateTdzBoxes(_) => {}
+        | Stmt::PreallocateTdzBoxes(_)
+        | Stmt::ReleaseBoxes(_) => {}
     }
 }
 

crates/perry-codegen/src/collectors/scalar_methods.rs

@@ -490,7 +490,8 @@ fn stmt_writes_this_property(stmt: &Stmt, property: &str) -> bool {
         | Stmt::LabeledBreak(_)
         | Stmt::LabeledContinue(_)
         | Stmt::PreallocateBoxes(_)
-        | Stmt::PreallocateTdzBoxes(_) => false,
+        | Stmt::PreallocateTdzBoxes(_)
+        | Stmt::ReleaseBoxes(_) => false,
     }
 }
 

crates/perry-codegen/src/collectors/shadow_slots.rs

@@ -135,6 +135,7 @@ pub fn collect_declared_shadow_locals_in_stmt(
         | Stmt::LabeledContinue(_)
         | Stmt::Throw(_)
         | Stmt::PreallocateBoxes(_)
-        | Stmt::PreallocateTdzBoxes(_) => {}
+        | Stmt::PreallocateTdzBoxes(_)
+        | Stmt::ReleaseBoxes(_) => {}
     }
 }

crates/perry-codegen/src/collectors/spec_abi_sites.rs

@@ -377,7 +377,7 @@ fn walk_stmt(s: &Stmt, depth: u32, scan: &mut ModuleScan) {
         }
         Stmt::Expr(e) | Stmt::Throw(e) => record_expr_use(e, depth, scan),
         Stmt::Return(Some(e)) => record_expr_use(e, depth, scan),
-        Stmt::PreallocateBoxes(ids) | Stmt::PreallocateTdzBoxes(ids) => {
+        Stmt::PreallocateBoxes(ids) | Stmt::PreallocateTdzBoxes(ids) | Stmt::ReleaseBoxes(ids) => {
             scan.boxed_prealloc.extend(ids.iter().copied());
         }
         Stmt::Return(None)

crates/perry-codegen/src/collectors/this_as_value.rs

@@ -273,7 +273,9 @@ pub fn stmts_use_this_as_value(stmts: &[perry_hir::Stmt], fields: &HashSet<Strin
             Stmt::Break | Stmt::Continue | Stmt::LabeledBreak(_) | Stmt::LabeledContinue(_) => {
                 false
             }
-            Stmt::PreallocateBoxes(_) | Stmt::PreallocateTdzBoxes(_) => false,
+            Stmt::PreallocateBoxes(_) | Stmt::PreallocateTdzBoxes(_) | Stmt::ReleaseBoxes(_) => {
+                false
+            }
         };
         if bad {
             return true;

crates/perry-codegen/src/collectors/uppercase_strings.rs

@@ -395,7 +395,8 @@ fn check_uses_in_stmt(
         | Stmt::LabeledBreak(_)
         | Stmt::LabeledContinue(_)
         | Stmt::PreallocateBoxes(_)
-        | Stmt::PreallocateTdzBoxes(_) => {}
+        | Stmt::PreallocateTdzBoxes(_)
+        | Stmt::ReleaseBoxes(_) => {}
     }
 }