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Fixed-arity protocol dispatch shims (#223)

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defprotocol emitted one variadic (fn [this & rest] (protocol-dispatch P m this
(list->cseq rest))) per method, so every protocol call — even a no-extra-arg one
like (area s) — consed a rest list, wrapped it in a cseq, var-deref'd
protocol-dispatch, and jolt-invoke'd it (consing again). On mono-dispatch that was
2.07GB of allocation, ~65% of the benchmark.

Emit one fixed-arity clause per declared arglist instead. The 1/2/3-param arities
call positional protocol-dispatch{1,2,3}, which resolve the impl (by record tag,
reify method, or host-tag extension — factored into protocol-resolve) and apply it
directly; no rest-list, no seq round-trip. The dispatchN entry points are in the
native-op table so the shim calls bind straight to the records.ss procedures
rather than var-deref. 4+ params fall back to the variadic protocol-dispatch.

mono-dispatch 1.5s/2.07GB -> 0.69s/280MB; dispatch 26x -> 12.2x, mono-dispatch
111x -> 51x vs JVM. 5 new corpus rows pin multi-arity methods, host-type args,
and protocol-method-as-value against JVM Clojure.

Co-authored-by: Yogthos <yogthos@gmail.com>
This commit is contained in:
Dmitri Sotnikov 2026-06-26 05:57:42 +00:00 • committed by GitHub
parent 8bea1abe12
commit 0a7e818700
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6 changed files with 663 additions and 625 deletions
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5
test/chez/corpus.edn
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@ -3206,4 +3206,9 @@
{:suite "records / representation" :label "record as a map key" :expected ":v" :actual "(do (defrecord R [a]) (get {(->R 1) :v} (->R 1)))"}
{:suite "records / representation" :label "records dedup in a set by value" :expected "2" :actual "(do (defrecord R [a]) (count (into #{} [(->R 1) (->R 1) (->R 2)])))"}
{:suite "records / representation" :label "nested record field reads" :expected "[2 1]" :actual "(do (defrecord N [l r v]) (let [t (->N (->N nil nil 1) nil 2)] [(:v t) (:v (:l t))]))"}
{:suite "protocols / arity dispatch" :label "multi-arity protocol method on a record" :expected "[\"0:9\" \"1:9::a\" \"2:9::a::b\"]" :actual "(do (defprotocol P (m [this] [this x] [this x y])) (defrecord R [v] P (m [this] (str \"0:\" v)) (m [this x] (str \"1:\" v \":\" x)) (m [this x y] (str \"2:\" v \":\" x \":\" y))) [(m (->R 9)) (m (->R 9) :a) (m (->R 9) :a :b)])"}
{:suite "protocols / arity dispatch" :label "two-arg protocol method" :expected "30" :actual "(do (defprotocol P (addp [this x y])) (defrecord R [n] P (addp [_ x y] (+ n (+ x y)))) (addp (->R 10) 7 13))"}
{:suite "protocols / arity dispatch" :label "protocol method extended to a host type with an arg" :expected "\"S:hi:5\"" :actual "(do (defprotocol Q (mq [this a])) (extend-protocol Q java.lang.String (mq [this a] (str \"S:\" this \":\" a))) (mq \"hi\" 5))"}
{:suite "protocols / arity dispatch" :label "protocol method used as a value" :expected "[1 2]" :actual "(do (defprotocol Z (z [this])) (defrecord ZR [v] Z (z [_] v)) (mapv z [(->ZR 1) (->ZR 2)]))"}
{:suite "protocols / arity dispatch" :label "no-extra-arg method dispatches by type" :expected "[16 25]" :actual "(do (defprotocol Sh (ar [s])) (defrecord Sq [x] Sh (ar [_] (* x x))) (defrecord Sq2 [y] Sh (ar [_] (* y y))) [(ar (->Sq 4)) (ar (->Sq2 5))])"}
]