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Devirtualize monomorphic protocol calls (#227)

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When the inference proves a protocol call's receiver is one record type, the
back end resolves the impl by that static tag (find-protocol-method) instead of
routing through the protocol var -> jolt-invoke -> protocol-resolve, which
re-derives the tag and walks the type table. Same table lookup, minus the
var-deref, the rest-cons, and the receiver-type computation.

Fires only on a monomorphic site: a megamorphic receiver joins to :any and
carries no :devirt-type, so it keeps ordinary dispatch (the dispatch bench is
unaffected). The annotation comes from the whole-program fixpoint typing a
reduce/HOF element or a ctor return as a specific record.

Modest on the dispatch benchmarks (~6% on mono-dispatch) — float boxing in the
reduce accumulator dominates there, a separate numeric lever — but it removes
the dispatch overhead wherever a typed receiver is known.

run-devirt.ss gate: emitted form uses find-protocol-method, and evaluating it
matches ordinary dispatch for an inline impl, an extend-type impl, and the
non-devirt path. make test / shakesmoke green, 0 new divergences.

Co-authored-by: Yogthos <yogthos@gmail.com>
This commit is contained in:
Dmitri Sotnikov 2026-06-26 11:16:19 +00:00 • committed by GitHub
parent 09712ec575
commit af11aaa7ff
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4 changed files with 167 additions and 78 deletions
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10
Makefile
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@ -4,7 +4,7 @@
# build step. `make test` is the full gate. `make remint` rebuilds the seed after a
# source change.
.PHONY: test ci values corpus unit smoke buildsmoke selfhost sci certify ffi transient infer wp directlink numeric inline shakesmoke remint
.PHONY: test ci values corpus unit smoke buildsmoke selfhost sci certify ffi transient infer wp devirt directlink numeric inline shakesmoke remint
# Full gate (dev machine). Includes the self-host byte-fixpoint, which only holds
# on the same Chez that minted the seed.
@ -15,7 +15,7 @@ test: selfhost ci
# lockfile) — it RUNS correctly on any Chez, but `selfhost` rebuilds it and a
# different Chez version may emit byte-different (gensym/order) output, so the
# byte-fixpoint is a dev-machine check, not a CI one (jolt-8479).
ci: values corpus unit smoke buildsmoke sci ffi transient infer wp directlink numeric inline certify
ci: values corpus unit smoke buildsmoke sci ffi transient infer wp devirt directlink numeric inline certify
@echo "OK: CI gates passed"
# Self-host fixpoint: bootstrap.ss rebuild == checked-in seed.
@ -67,6 +67,12 @@ infer:
wp:
@chez --script host/chez/run-wp.ss
# Protocol-call devirtualization: a monomorphic call resolves its impl by the
# inferred record tag (find-protocol-method) instead of routing through the
# protocol var; the result must match ordinary dispatch.
devirt:
@chez --script host/chez/run-devirt.ss
# Direct-linking emission: a closed-world build binds top-level app defs to jv$
# Scheme bindings and routes app->app calls/refs to them, skipping var-deref +
# jolt-invoke; ^:dynamic/^:redef and nested defs opt out.