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14a91f0ae588b515e0e40853088e1f0d252439c1
AILang/examples/bench_latency_explicit.ail
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Brummel 14a91f0ae5 iter boehm-retirement.1 (DONE 10/10): retire the transitional Boehm GC backend 
Closes Gitea #4. Removes the Boehm-Demers-Weiser conservative GC
backend wholesale across six layers in one atomic iteration. After
this iter, `AllocStrategy` has two variants (`Rc`, `Bump`),
`--alloc=gc` is rejected at CLI parse with `unknown --alloc value`,
the libgc link arm is gone, and the design ledger describes RC
(canonical) + bump (raw-alloc bench-floor) as the only allocators.

Layer-by-layer summary:

  CLI surface — `crates/ail/src/main.rs`:
    `parse_alloc_strategy` arm `"gc" => Ok(AllocStrategy::Gc)`
    removed; error wording updated to `(expected `rc` or `bump`)`;
    clap-derive `value_parser = ["gc","bump","rc"]` allowlist on
    BOTH `Build` and `Run` subcommands DROPPED so that
    `parse_alloc_strategy` remains the sole gatekeeper for the
    unknown-value diagnostic (otherwise clap shadows the runtime
    diagnostic with `invalid value 'gc' for '--alloc'`, which would
    miss the milestone-pin's stderr substring check). The
    `default_value = "rc"` stays.

  Codegen — `crates/ailang-codegen/src/lib.rs`:
    `AllocStrategy::Gc` variant + `Default` derive removed (no
    caller of `AllocStrategy::default()` existed in the workspace,
    so the trait derivation was dead). `fn_name` (spec called it
    `runtime_alloc_fn` loosely; actual identifier is `fn_name`)
    drops the `Gc => "GC_malloc"` arm. `lower_workspace` and
    `lower_workspace_staticlib` defaults flip from `Gc` to `Rc`.
    In-source negative-complement codegen test (mod tests, lib.rs:3571ff)
    retargets from `AllocStrategy::Gc` to `AllocStrategy::Bump`
    (bump also doesn't emit per-type drop fns; the test's semantic
    "no drop fns under non-RC" is preserved).

  Link branch — `crates/ail/src/main.rs:2389ff`:
    The `match strategy { AllocStrategy::Gc => { ... cmd.arg("-lgc"); ... } }`
    arm and its libgc-link block are entirely gone. The surviving
    match exhausts on `Bump` and `Rc` (Rust's exhaustiveness check
    confirms; no `error[E0004]`). Staticlib-guard diagnostic
    rewritten to drop the "shared Boehm collector" phrasing while
    preserving the prefix `staticlib (swarm) artefact is RC-only`
    verbatim (the surviving `staticlib_bump_is_rejected` test
    depends on that substring).

  Test suite — 3 pure-differential e2e tests deleted
    (`gc_handles_recursive_list_construction`,
    `alloc_rc_produces_same_stdout_as_gc`,
    `alloc_rc_matches_gc_on_std_list_demo`); 9 RC-feature tests
    stripped of their `stdout_gc` build call and differential
    `assert_eq!(stdout_gc, stdout_rc, ...)` (absolute
    `assert_eq!(stdout_rc.trim(), "<n>")` pin retained as
    correctness oracle); `staticlib_gc_is_rejected` deleted; new
    milestone-pin `crates/ail/tests/boehm_retirement_pin.rs`
    asserts `ail build --alloc=gc` exits ≠ 0 with stderr containing
    `unknown --alloc value` and `\`gc\``; `examples/gc_stress.ail`
    fixture deleted (no remaining references).

    Implementer expansion (not in plan): `iter17a_local_box_alloca`
    (in `e2e.rs`) carried an IR-shape assertion against
    `@GC_malloc`-absence as the witness for non-escaping
    allocation. After the Task-2 codegen default flip, the witness
    shifts to `@ailang_rc_alloc`-absence in escape-targeted
    positions; assertion + doc-comment updated. Property
    protected ("no heap allocation in non-escaping contexts") is
    unchanged; only the named allocator shifts.

  Bench harness — `bench/run.sh` 9→6 column compaction
    (workload + bump(s) + rc(s) + rc/bump + bump RSS + rc RSS);
    gc-arm `bench_latency_implicit_gc` build call + harness
    invocation dropped from latency block; header comment reframed
    from "GC-overhead bench harness" to "RC-overhead bench
    harness"; "Decision 10's Boehm-retirement target (1.3x)"
    rewording to "RC-overhead-vs-bump bench-health regression gate".

    `bench/check.py:62` header-sentinel changes from
    `"gc(s)" in line` to `"bump(s)" in line`; column-count check
    at `:72` flips from `!= 9` to `!= 6`; per-workload field set
    drops `gc_s`/`gc_over_bump`/`gc_rss_kb`; `ARM_LABEL_TO_KEY`
    drops the `"implicit @ gc": "implicit_at_gc"` entry.
    `bench/baseline.json` regenerated via `--update-baseline`.

    Implementer note (planner-defect): `write_new_baseline`
    iterated over the *existing* baseline's metric list when
    emitting the regenerated file, so even after parser-level
    `gc_*` removal, the fallback emitted them back into the JSON.
    Scrubbed post-update; the cleaner fix (have
    `write_new_baseline` emit only keys present in
    `parsed_throughput[workload]`) is a follow-up if the script
    becomes load-bearing for further allocator changes.

  Design ledger — `design/models/rc-uniqueness.md` excises the
    `## Dual allocator — RC canonical, Boehm parity oracle`
    section and the `Boehm-Demers-Weiser conservative GC` choice
    block + rationale + trade-offs; the per-fn-alloca section
    generalises Boehm-specific language to allocator-agnostic;
    the memory-model section's `## Choice.` paragraph reframes the
    1.3× target from "Boehm-retirement gate" to "bench-health
    regression gate".

    `design/models/pipeline.md` drops the `--alloc=gc → links libgc`
    arm of the pipeline diagram and replaces it with
    `--alloc=bump → links bump-floor`; the accompanying prose
    rewrites accordingly.

    `design/contracts/scope-boundaries.md` rewrites the
    "Memory management via Boehm conservative GC" bullet to
    describe RC + per-fn-arena present-tense; the dead reference
    to `examples/gc_stress.ail.json` (file never existed; the
    fixture only ever had a `.ail` form, deleted by this iter) is
    dropped along with the `examples/std_list_stress.ail.json`
    reference whose purpose was Boehm-only soak testing.
    `:67`'s `@printf` / `@GC_malloc` parenthetical updated.

    `design/contracts/memory-model.md:232` drops the
    "leaks like the pre-Boehm era" phrase; the RC inc/dec
    instrumentation is wired up, so the "until then" conditional
    that referenced pre-Boehm is closed.

    `design/contracts/embedding-abi.md:42-44` rewrites the
    staticlib-guard prose to drop the `--alloc=gc` clause (gc is
    now a CLI-parser-level unknown-value, not a staticlib-guard
    rejection) and reframe the swarm-safety justification around
    `--alloc=bump` (leak-only bench instrument) rather than the
    historical Boehm collector.

  Honesty pin — `crates/ailang-core/tests/docs_honesty_pin.rs`
    inverts the polarity: the present-tense Boehm-anchor assertion
    on `pipeline.md` (`:116-117`) is deleted, and four
    absence-pins are added to `design_md_has_no_wunschdenken`
    against the Boehm-zombie strings `transitional Boehm`,
    `parity oracle`, `GC_malloc`, `libgc`. The
    `design_corpus()` already includes `rc-uniqueness.md` so no
    path-list change was needed for the new pins to scan.

    `crates/ailang-core/tests/design_index_pin.rs:166` drops the
    `"pre-Boehm"` token from the protected-exception comment list
    (the phrase no longer appears in `memory-model.md` after this
    iter, so the exception is dead).

  Runtime docs — `runtime/bump.c`, `runtime/rc.c`, `runtime/str.c`
    header comments scrubbed of Boehm/`GC_malloc`/`libgc`
    references. `bump.c`'s function signature description still
    documents `void *bump_malloc(size_t)` as the bench-floor
    allocator interface, but no longer cross-references libgc.

  Example fixtures — `examples/bench_latency_implicit.ail`,
    `bench_latency_explicit.ail`, `escape_local_demo.ail`,
    `reuse_as_demo.ail`, `rc_pin_recurse_implicit.ail` doc-comment
    headers scrubbed of `--alloc=gc` / Boehm references. The
    `.ail` surface (AST) is untouched in every case; round-trip
    invariant holds (`cargo test -p ailang-surface --test round_trip`
    green).

  Skill / agent prompts — `skills/audit/agents/ailang-bencher.md`
    rewritten to use an RC-vs-bump worked example pattern for the
    hypothesis-driven bench tutorial, replacing the recurring
    "RC vs Boehm under heap pressure" example.
    `skills/implement/agents/ailang-implementer.md` Decision-10 /
    Boehm references replaced with present-tense RC-commitment
    framing.

  IR snapshots — the 5 checked-in snapshots
    (`crates/ail/tests/snapshots/{hello,list,max3,sum,ws_main}.ll`)
    regenerated via `UPDATE_SNAPSHOTS=1 cargo test -p ail --test
    ir_snapshot`. Each previously contained
    `declare ptr @GC_malloc(i64)` and (for `list.ll`) a `call ptr
    @GC_malloc(...)` invocation; post-flip the snapshots contain
    `declare ptr @ailang_rc_alloc(i64)` plus the rc inc/dec runtime
    declarations.

Spec-vs-acceptance addendum (caught at orchestrator end-report,
absorbed here rather than in a follow-up spec edit): spec §6
acceptance criteria said "Boehm-grep returns matches ONLY in
docs_honesty_pin.rs". The plan itself prescribed historical Boehm
references in 3 additional files: (a) the new milestone-pin
`boehm_retirement_pin.rs` (must literally invoke `--alloc=gc` to
assert its rejection), (b) `embed_staticlib_alloc_guard.rs` file
doc-comment historical note ("`--alloc=gc` no longer exists as a
CLI value"), (c) `embedding-abi.md:44-45` contract historical
clause ("see the Boehm-retirement iter"). All three are
prescribed; the spec's grep wording was too narrow. The four
absence-pins in `docs_honesty_pin.rs` catch the actual zombies
(Boehm-narrative re-emerging in the design ledger), which is the
substantive intent the spec was aiming at — the four extra
documented-by-design exceptions are the cost of having an
explicit milestone-pin and contract-level historical anchors.

Net delta:
  - 32 files modified, 2 new (boehm_retirement_pin.rs + stats),
    1 deleted (gc_stress.ail);
  - workspace tests: every binary `0 failed`. Pass-count delta:
    -3 net (4 e2e tests deleted, 1 new milestone-pin test added);
  - boehm-grep state: hits only in the four by-design exceptions
    documented above;
  - `bench/check.py` exit 0 against regenerated baseline;
  - CLI must-fail fixture: `ail build --alloc=gc examples/hello.ail`
    exits non-zero with stderr containing `unknown --alloc value`
    and `\`gc\``;
  - design ledger present-tense honest (Boehm-narrative gone from
    `rc-uniqueness.md` + `pipeline.md`; the few historical
    references in `embedding-abi.md` / `boehm_retirement_pin.rs` /
    `embed_staticlib_alloc_guard.rs` are explicit milestone-pins
    or contract anchors, not silent ledger residue).

Bench measurement variance noted: closure-chain and hof-pipeline
are ±1-5% jittery between runs; one regeneration flagged 2
metrics as `regressed` before a second run returned 0. The
captured baseline is within self-comparison range. Existing
per-metric tolerances absorb the jitter.

Stats file:
`bench/orchestrator-stats/2026-05-20-iter-boehm-retirement.1.json`.

closes #4
2026-05-20 20:51:53 +02:00

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; Latency-distribution bench fixture — explicit-mode variant.
;
; Companion to bench_latency_implicit. Same algorithm, with
; `(borrow T)` / `(own T)` annotations so that under --alloc=rc the
; codegen emits proper inc/dec instrumentation: the persistent tree
; cache is borrowed (no inc/dec on pin_root's hot path), the per-op
; IntList is owned by sum_list (param drop at fn return frees the
; chain). The drop-iterative annotation on IntList keeps the per-op
; deallocation O(1)-stack regardless of list length.
;
; This is the "RC-fair" arm of the latency bench; together with
; bench_latency_implicit (the implicit-mode control arm at rc) it
; tests the hypothesis "RC under explicit-mode has p99
; per-operation latency within a small constant factor of the
; median, even under continuous alloc pressure with a large
; persistent live working set".
;
; Workload (must match bench_latency_implicit's parameters exactly
; for the comparison to be fair):
; - Live cache: balanced binary tree of depth 19 (524_287 nodes,
; ~16 MB), borrowed throughout the loop.
; - Per-op: build a CHUNK_LEN-cell IntList of 0..CHUNK_LEN-1, sum
; it, drop it. CHUNK_LEN, NUM_OPS, PRINT_K hardcoded to match
; the implicit variant.
; - Same stdout shape: one READY (8888), N_PRINT timing markers
; each containing the per-op sum (validatable, always equal),
; one DONE (9999).
(module bench_latency_explicit
(data Tree
(doc "Balanced binary tree, 32-byte cells. Borrowed across the bench loop; tree-depth recursion at scope close is bounded (depth 19) so no drop-iterative needed.")
(ctor TLeaf)
(ctor TNode (con Int) (con Tree) (con Tree)))
(data IntList
(doc "Singly-linked Int list. Per-op chains are CHUNK_LEN long; (drop-iterative) keeps Own-param drop O(1) stack regardless of length.")
(ctor LNil)
(ctor LCons (con Int) (con IntList))
(drop-iterative))
; ---------- Live cache: balanced tree of given depth ----------
(fn build_tree
(doc "Build a balanced tree of given depth, every value = 1. Returns owned Tree; main holds it across the loop and the final drop fires at main's scope close.")
(type
(fn-type
(params (con Int))
(ret (own (con Tree)))))
(params depth)
(body
(if (app == depth 0)
(term-ctor Tree TLeaf)
(term-ctor Tree TNode
1
(app build_tree (app - depth 1))
(app build_tree (app - depth 1))))))
(fn pin_root
(doc "Constant-time tree liveness pin — read root tag, return 1 (TNode) or 0 (TLeaf). Borrows t so the persistent cache is not inc/dec'd on every op.")
(type
(fn-type
(params (borrow (con Tree)))
(ret (con Int))))
(params t)
(body
(match t
(case (pat-ctor TLeaf) 0)
(case (pat-ctor TNode v l r) 1))))
; ---------- Per-op work: build/sum an N-cell list ----------
(fn cons_n_acc
(doc "Tail-recursive list builder. Returns owned chain; caller is sum_list which owns and drops it.")
(type
(fn-type
(params (con Int) (own (con IntList)))
(ret (own (con IntList)))))
(params n acc)
(body
(if (app == n 0)
acc
(tail-app cons_n_acc
(app - n 1)
(term-ctor IntList LCons (app - n 1) acc)))))
(fn cons_n
(doc "Build [0,1,...,n-1] :: IntList. Returns owned chain.")
(type
(fn-type
(params (con Int))
(ret (own (con IntList)))))
(params n)
(body
(app cons_n_acc n (term-ctor IntList LNil))))
(fn sum_list_acc
(doc "Tail-recursive sum. Owns xs; consumes it via the LCons arm's t binder (move-into-tail-call).")
(type
(fn-type
(params (own (con IntList)) (con Int))
(ret (con Int))))
(params xs acc)
(body
(match xs
(case (pat-ctor LNil) acc)
(case (pat-ctor LCons h t)
(tail-app sum_list_acc t (app + acc h))))))
(fn sum_list
(doc "Sum every element. Owns xs, hands it to sum_list_acc which consumes it.")
(type
(fn-type
(params (own (con IntList)))
(ret (con Int))))
(params xs)
(body
(app sum_list_acc xs 0)))
(fn one_op
(doc "One bench operation: build+sum a fresh CHUNK_LEN-cell list, pin the tree's root, return their sum so the value chain stays observable. Tree is borrowed; no inc/dec on the hot path against the persistent cache.")
(type
(fn-type
(params (con Int) (borrow (con Tree)))
(ret (con Int))))
(params chunk_len t)
(body
(app + (app sum_list (app cons_n chunk_len)) (app pin_root t))))
; ---------- Bench loop ----------
(fn loop
(doc "Tail-recursive bench loop. Tree is borrowed across all iterations.")
(type
(fn-type
(params (con Int) (con Int) (con Int) (con Int) (borrow (con Tree)))
(ret (con Unit))
(effects IO)))
(params remaining print_countdown chunk_len print_k t)
(body
(if (app == remaining 0)
(app print 9999)
(if (app == print_countdown 0)
(seq
(app print (app one_op chunk_len t))
(tail-app loop
(app - remaining 1)
(app - print_k 1)
chunk_len
print_k
t))
(let _v (app one_op chunk_len t)
(tail-app loop
(app - remaining 1)
(app - print_countdown 1)
chunk_len
print_k
t))))))
(fn main
(doc "Top-level: build tree, signal READY (8888), run loop, signal DONE (9999 emitted by loop).")
(type (fn-type (params) (ret (con Unit)) (effects IO)))
(params)
(body
(let t (app build_tree 19)
(let _root (app pin_root t)
(seq
(app print 8888)
(app loop 20000 0 500 20 t)))))))
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