fix: an own push beats Array.prototype.push on a proven array (#11021) - #11333
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`const a = [1]; a.push = (x) => "own:" + x; a.push(9)` ran the builtin and returned 2. It now calls the own method and returns its value, with nothing appended, across every tier `Expr::ArrayPush` lowers to. No diamond and no cost on the inline store: every inline push tier's admission mask already tests OBJ_FLAG_ARRAY_DESCRIPTORS, which every install of an array's own named property arms, so an array that owns `push` always lands in a slow arm. Each of the five slow arms (spec-order, numeric fallback, forwarded, realloc, local tail) now calls js_array_push_f64_spec_or_own, whose i32 out-flag selects between the new head (the old call, unchanged) and the own method's return, which OwnPushJoin phis in as the expression's value. The runtime answers the common case from the single header probe js_array_push_f64_spec already made, and asks the precise non-allocating question only when the bit is set. `a.push()` (a NativeMethodCall, call-only) joins the #10943 folded-node diamond. `a.push(x, y)` and `a.push(...xs)` remain open.
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Included review availability: Your plan provides up to 8 included reviews per hour; 5 remain after this review. 📝 WalkthroughWalkthroughArray push slow paths now check for an own ChangesArray push own-method handling
Priority: ➖ Normal Estimated code review effort: 4 (Complex) | ~45 minutes Change: Bug fix · Severity of issue fixed: Medium Sequence Diagram(s)sequenceDiagram
participant GeneratedArrayPush
participant js_array_push_f64_spec_or_own
participant array_owning_push
participant invoke_own_user_method
participant js_array_push_f64_spec
GeneratedArrayPush->>js_array_push_f64_spec_or_own: pass array and value
js_array_push_f64_spec_or_own->>array_owning_push: check for own push when plain-array push declines
array_owning_push-->>js_array_push_f64_spec_or_own: return ownership result
js_array_push_f64_spec_or_own->>invoke_own_user_method: invoke own method when present
js_array_push_f64_spec_or_own->>js_array_push_f64_spec: use builtin push when no own method is found
Merge Risk: 🔵 Low · up to An argument that changes an array’s own push method can cause the wrong method to run. This is a narrow edge case, but it should be fixed or explicitly accepted before merging. Security Architecture ReviewSecurity architecture risk: 🔵 Low · up to The change lets a method installed on an array run and supply the call’s result. The inspected path does not show a new privilege or service boundary, but exception recovery and some repeated-call cases are not fully verified. Retained concerns Security review detailsSecurity Blast Radius
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Inline comments:
In `@crates/perry-runtime/src/object/own_override.rs`:
- Around line 447-490: Update the array-push call lowering used with
js_array_push_f64_spec_or_own to resolve and root the push method before
evaluating the argument, following the existing property-call ordering pattern.
Invoke that captured method afterward so argument side effects that replace or
delete push do not change which method is called.
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changelog.d/11333-array-own-push-beats-builtin.mdcrates/perry-codegen/src/expr/array_push.rscrates/perry-codegen/src/expr/array_push_guard_tests.rscrates/perry-codegen/src/expr/array_push_own.rscrates/perry-codegen/src/expr/array_push_own_tests.rscrates/perry-codegen/src/expr/folded_builtin_override.rscrates/perry-codegen/src/expr/mod.rscrates/perry-codegen/src/lower_call/property_get/own_override_guard.rscrates/perry-codegen/src/native_value/verify/raw_f64.rscrates/perry-codegen/src/native_value/verify/tests.rscrates/perry-codegen/src/runtime_decls/arrays.rscrates/perry-runtime/src/array/generic.rscrates/perry-runtime/src/array/mod.rscrates/perry-runtime/src/array/push_pop.rscrates/perry-runtime/src/object/mod.rscrates/perry-runtime/src/object/own_override.rscrates/perry-runtime/src/object/own_override_push_tests.rstest-files/test_parity_own_override_beats_builtin.ts
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Measured on the shipping profile (thin LTO, one codegen unit), the first cut cost a captured receiver +32 instructions per push and an object-push loop +3: * everything past the plain push now lives in a #[cold] out-of-line function, so the entry has no frame of its own (+28 -> 0); * push_spec_if_plain is inline(always), so both entries inline the plain push instead of the second one calling it; * the own-exit branch carries llvm.expect.i1(false), without which the new blocks cost the hot loop three register moves per iteration. Now flat on every row: captured receiver 529.259 -> 529.254, object push 1987.783 -> 1988.531 (within main's own spread), indexOf and element read identical.
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Summary
const a = [1]; a.push = (x) => "own:" + x; a.push(9)ran the builtin and printed2. It now calls the own method, printsown:9and leavesa.lengthat 1, matching Node. This closes #11021, the one case #10958 left out of the #10943 own-override gate, and it does so without a diamond and with no cost on the inline store.The issue assumed an array records nothing in its header that the inline tier can test. It does. Every install of an array's own named property arms
OBJ_FLAG_ARRAY_DESCRIPTORS(0x400): both storages ofarray_named_property_set, and everyObject.definePropertyroute. Every inline push tier's admission mask already tests that bit (0x407/0x3C07/0xF487), so an array that ownspushcan never take the inline store. The missing piece was the second half of what the issue describes. Every slow arm calledjs_array_push_f64_spec, which returns the new head pointer, so none of them could return the own method's result.Changes
perry-runtime/src/object/own_override.rs): newjs_array_push_f64_spec_or_own(arr, value, *own) -> u64.*own = 0it returns the new head, exactly as the old call did. With*own = 1it returns the own method's result bits.js_array_push_f64_specalready makes (push_spec_if_plain, split out of it inarray/push_pop.rs). Everything else is in a#[cold]out-of-line function, which does a non-allocating lookup (does the live head ownpushin its accessor descriptors or named properties?) only when the bit is set.own_overridenow has separate resolve and invoke halves, so this caller skipsPERRY_OWN_NAMED_PROP_INSTALLED. That flag is never armed byjs_array_set_string_key's direct install.value_is_own_user_method) instead of doing a secondGet, so an own accessor's getter runs once.perry-codegen/src/expr/array_push_own.rs,array_push.rs):OwnPushJoingives each of the fiveExpr::ArrayPushslow arms an exit whose value is the method's return, merged in with a phi. The arms are spec-order, typed-feedback numeric fallback, forwarded, realloc and the local tail. The branch to that exit is marked unlikely (llvm.expect.i1). The inline store block is unchanged.a.push()is a call-onlyNativeMethodCall, so it now goes through the existing An own property shadowing a native method is IGNORED on Map/Set/RegExp/Date/Array —m.get = () => x; m.get()runs the native method (wrong value, plain JS, on main) #10943 folded-node diamond (folded_builtin_override.rs).own_override_guard.rsandfolded_builtin_override.rs, added the new consumer to the raw-f64 verifier, and declared the new runtime entry.Still open:
a.push(...xs)(ArrayPushSpread) is not covered.a.push(x, y)is desugared by HIR into oneArrayPushper argument. With an ownpushit now calls the method once per argument, where Node calls it once with both (it previously ran the builtin).pushon an array that had none.Related issue
Fixes #11021 (the remaining case of #10943).
Test plan
Built locally against LLVM 22.1.8. The fixtures were run on the release build with 16 codegen units and again on the shipping
releaseprofile (thin LTO, one codegen unit).cargo test --release -p perry-codegen --lib: 1711 passed.expr/array_push_own_tests.rschecks the emitted IR: both inline slow arms and the spec-order arm call the own-aware push and never the bare one, the own exits reach aphi,apush.inboundshas no trace of the exit, and every admission mask (pointer, number and string pushes) includes 0x400.7) and saw them fail both times.a_metadata_selected_add_keeps_the_runtime_number_guardnow pins the numeric fallback to the own-aware call. There is a newfolded_builtin_overridetest for the zero-argument node.RUST_TEST_THREADS=1 cargo test --release -p perry-runtime --lib -- array:: own_override object::native_call_method: 412 passed. That includes the newobject/own_override_push_tests.rs, covering:push.Parity fixtures:
test_parity_own_override_beats_builtin.tsgains 14 rows across the tiers. All are red on main and byte-identical to Node here.test_parity_11006_noncallable_own_builtin.ts'sarray.pushrow was red on main (2instead ofTypeError) and is green now.push, later implicit-thisreads still match Node.Gap-suite A/B, main vs this branch: all 1019
test_gap_*programs, output compared byte-for-byte. 1018 are identical; the one difference isconsole.timejitter intest_gap_console_methods. 65 tests need theext-http/ext-net/wasm-host archives and didn't compile on either build in my setup, so CI is their only coverage.Instructions per iteration (callgrind,
(Ir(2N) − Ir(N)) / N, shipping profile, main → this branch):a.push(i)s += a.push(i)a.push({v: i})a.indexOf(x)The first version of the fix cost the captured row +46 and then +32, and the object-push loop +3. The
perf:commit removes both costs; its message has the breakdown.cargo fmt --checkon the touched files,check_file_size.sh, and the address-classification, store-site, runtime-root-holder, pin-site, test-registration, global-sink, raw-handle and unrooted-local (vs. merge base) audits all pass.cargo clippyadds nothing in touched files; its errors are pre-existingapprox_constanthits in untouched tests.Checklist
feat:/fix:/docs:/chore:prefix convention used in the log🤖 Generated with Claude Code
https://claude.ai/code/session_01PB3APtR4JW6ksGTunzZuQZ
Summary by CodeRabbit
pushmethod now call it instead of using the built-in behavior. Its return value is preserved, and a non-callable ownpushthrows aTypeErrorwithout appending.pushcontinue to use built-in behavior, including arrays with unrelated custom properties.