Brummel
ce6ab8ee44
Closes the 18-arc's stack-recursion limit. Recursive drop cascades from 18c.4 overflow on long ADT chains (Linux's 8 MB default stack maxes out around 1M cells of List). The new opt-in (drop-iterative) annotation on a Def::Type switches the synthesised drop_<m>_<T> body from recursive to iterative-with- explicit-worklist for that type. Schema: - TypeDef.drop_iterative: bool. Default false; serde-skip when false so existing fixtures' canonical JSON hashes stay stable. - Form-A: (drop-iterative) clause inside (data T ...). Worklist runtime (4 new ABI symbols in runtime/rc.c): - ailang_drop_worklist_new(initial_capacity) - ailang_drop_worklist_push(wl, ptr) - ailang_drop_worklist_pop(wl) -> ptr - ailang_drop_worklist_free(wl) Heap stretchy buffer, doubling on overflow, null-filtering on push. Lean 4 / Roc precedent documented in the runtime; the slot-repurposing strategy was considered and rejected because not every box has a free pointer-typed slot to thread the worklist through (Cons head is i64, slot 1 is ptr but it's the field we're following — no free slot). Codegen (emit_iterative_drop_fn_for_type): for a drop_iterative type, drop_<m>_<T>(ptr %p) emits a worklist loop. Fields of the SAME annotated type push onto the worklist (mono-typed); fields of DIFFERENT types call their own drop fn directly (recursive on those, but only if THEY are themselves recursive — i.e. one level of cascade jump maximum). Mono-typed-worklist is sound for the deep-self- recursion case the iter targets (List of List of T just needs the spine flattened). Tests: - examples/rc_drop_iterative_long_list — 1M-cell List of Int with (drop-iterative) annotation. - alloc_rc_drop_iterative_handles_million_cell_list E2E — builds + runs under --alloc=rc, asserts clean exit. With annotation: exits 0. Without annotation (control): SIGSEGV at exit code 139 (verified by hand). Worklist is load- bearing. - iter18e_drop_iterative_emits_worklist_body_no_self_recursion IR-shape: worklist body has br to loop_head AND no direct recursive call into drop_<m>_<T>. - iter18e_no_annotation_keeps_recursive_drop_body — control: unannotated variant still emits the 18c.4 recursive shape. - 3 surface parse-tests for the annotation round-trip. Test deltas: e2e 58 -> 61 (+3), surface 18 -> 21 (+3). All other buckets unchanged. cargo test --workspace green. Known debt (deliberate): - Mono-typed worklist: cross-type drop-iterative fields call the other type's drop fn directly. A heterogeneous worklist would be more general but adds tag tracking complexity for a case (drop-iterative T containing drop-iterative T') that's narrower than the deep-self- recursion target. Documented in emit_iterative_drop_fn_for_type's doc. - Closure / Type::Var / Type::Forall fields fall back to shallow ailang_rc_dec via field_drop_call — same as the recursive variant. - Dynamic-tag partial-drop fallback (head_or_zero epilogue shallow dec when moved_slots non-empty) — out of scope per brief.
1 line
2.4 KiB
JSON
1 line
2.4 KiB
JSON
{"defs":[{"ctors":[{"fields":[],"name":"INil"},{"fields":[{"k":"con","name":"Int"},{"k":"con","name":"IntList"}],"name":"ICons"}],"drop-iterative":true,"kind":"type","name":"IntList"},{"body":{"cond":{"args":[{"name":"n","t":"var"},{"lit":{"kind":"int","value":0},"t":"lit"}],"fn":{"name":"==","t":"var"},"t":"app"},"else":{"args":[{"args":[{"name":"n","t":"var"},{"lit":{"kind":"int","value":1},"t":"lit"}],"fn":{"name":"-","t":"var"},"t":"app"},{"args":[{"name":"n","t":"var"},{"name":"acc","t":"var"}],"ctor":"ICons","t":"ctor","type":"IntList"}],"fn":{"name":"cons_n_acc","t":"var"},"t":"app","tail":true},"t":"if","then":{"name":"acc","t":"var"}},"doc":"Tail-recursive list builder. acc-prepended.","kind":"fn","name":"cons_n_acc","params":["n","acc"],"type":{"effects":[],"k":"fn","params":[{"k":"con","name":"Int"},{"k":"con","name":"IntList"}],"ret":{"k":"con","name":"IntList"}}},{"body":{"args":[{"name":"n","t":"var"},{"args":[],"ctor":"INil","t":"ctor","type":"IntList"}],"fn":{"name":"cons_n_acc","t":"var"},"t":"app"},"doc":"Build [1, 2, ..., n] :: IntList. Order is reverse of build but immaterial for head/sum.","kind":"fn","name":"cons_n","params":["n"],"type":{"effects":[],"k":"fn","params":[{"k":"con","name":"Int"}],"ret":{"k":"con","name":"IntList"}}},{"body":{"arms":[{"body":{"lit":{"kind":"int","value":0},"t":"lit"},"pat":{"ctor":"INil","fields":[],"p":"ctor"}},{"body":{"name":"h","t":"var"},"pat":{"ctor":"ICons","fields":[{"name":"h","p":"var"},{"name":"t","p":"var"}],"p":"ctor"}}],"scrutinee":{"name":"xs","t":"var"},"t":"match"},"doc":"Take ownership of an IntList; return its head if ICons, else 0. The (own ...) signature signals 18d.4 to emit an Own-param drop at fn return — which under the (drop-iterative) annotation is the iterative-worklist body, freeing the entire chain via the heap-allocated worklist instead of recursive cascade.","kind":"fn","name":"head_or_zero","params":["xs"],"type":{"effects":[],"k":"fn","param_modes":["own"],"params":[{"k":"con","name":"IntList"}],"ret":{"k":"con","name":"Int"}}},{"body":{"args":[{"args":[{"args":[{"lit":{"kind":"int","value":1000000},"t":"lit"}],"fn":{"name":"cons_n","t":"var"},"t":"app"}],"fn":{"name":"head_or_zero","t":"var"},"t":"app"}],"op":"io/print_int","t":"do"},"kind":"fn","name":"main","params":[],"type":{"effects":["IO"],"k":"fn","params":[],"ret":{"k":"con","name":"Unit"}}}],"imports":[],"name":"rc_drop_iterative_long_list","schema":"ailang/v0"} |