Lift ct 2 / ct 3 count-by-predicate to native VM dispatch (PR C of ILO-45)#707
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PR C of ILO-45. Adds a combined `(Builtin::Ct, 2) | (Builtin::Ct, 3)`
compiler arm that emits a per-element OP_CALL_DYN loop with a numeric
counter accumulator. No new opcode or finalizer needed — counter
increments via OP_ADDK_N on the true branch of the bool typecheck,
identical to flt's predicate shape minus the LISTAPPEND.
Argc=1 for plain `ct fn xs`, argc=2 for closure-bind `ct fn ctx xs`.
Both share the same arm; the ctx variant just allocates the extra
contiguous arg1_reg before the loop. Cranelift inherits via the
existing OP_CALL_DYN codegen.
Two entries removed from is_tree_bridge_eligible. After this PR, the
only FnRef-taking entries left on the bridge are gone — the remaining
work for the eval-loop deletion is:
- PR D: audit non-HOF bridge entries for transitive eval_body
reachability, lift any that need it
- PR E: delete eval_body / eval_stmt / eval_expr / Env / trampoline
AOT object baselines updated for the two examples that exercise `ct`
(ct-count-by-predicate, reserved-names). The remaining 134 baselines
are byte-identical to PR B's regen.
Test plan: cargo test --release --features cranelift green.
Smoke test: pos / above-threshold counts give identical output across
default / --vm / --jit. examples/ct-count-by-predicate.@ covers
both ct 2 and ct 3 (closure-bind) — now natively dispatched.
Codecov Report❌ Patch coverage is
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This was referenced May 22, 2026
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Summary
PR C of ILO-45 — third slice of the tree-walker eval-loop deletion. Lifts
ct fn xsandct fn ctx xsoff the tree-bridge to native VM dispatch via a per-element OP_CALL_DYN loop with a numeric counter accumulator. No new opcode needed — counter increments via the existing OP_ADDK_N on the true branch of the bool typecheck.After this PR, every FnRef-taking entry on
is_tree_bridge_eligiblehas been lifted. The remaining bridge entries are all non-HOF builtins (regex, fmt, fs metadata, crypto, calendar, sleep, run, env-all, math constants, jkeys). PR D will audit those for transitiveeval_bodyreachability, and PR E will delete the eval loop itself.What's in the diff
Single commit, two files:
src/vm/mod.rs(Builtin::Ct, 2) | (Builtin::Ct, 3) =>arm incompile_call. Argc=1 (plain) vs argc=2 (closure-bind) handled by conditionally allocating arg1_reg. Same bool-typecheck error shape as flt 2/3 ("ct: predicate must return bool" via WRAPERR + PANIC_UNWRAP).is_tree_bridge_eligible.tests/aot-baselines/obj-baselines.tsvct-count-by-predicateandreserved-names(the only examples exercisingct). Other 134 baselines byte-identical to PR B's regen.Test plan
cargo test --release --features cranelift— full suite greenpos/above-thresholdcounts give identical output across default /--vm/--jitexamples/ct-count-by-predicate.@covers bothct 2andct 3closure-bind — now natively dispatchedsuperpowers:code-reviewersubagent run on the diff — no blockers (flagged a closure-with-captures coverage gap that's shared with PRs A and B's lifts, not new in C)Follow-ups
eval_bodyreachability; lift any that still call into the eval loop internallyeval_body/eval_stmt/eval_expr/Env/ trampoline /ACTIVE_AST_PROGRAM(the headline LoC win)