Brummel
307a3ea848
Ends the leak-everything era under --alloc=rc. Codegen now emits
ailang_rc_inc at every Term::Clone site and ailang_rc_dec at
end-of-scope of trackable RC-allocated let-binders. Default
--alloc=boehm path is byte-identical to before this iter.
Two parts:
(A) New module ailang-check::uniqueness — post-typecheck
dataflow producing UniquenessTable: BTreeMap<(def, binder),
UniquenessInfo>. consume_count is max-over-paths: at if/match
the walker saves state, walks each arm against the snapshot,
and merges by taking the per-binder max. Term::Clone is a
Borrow on its inner term — the explicit clone is the user's
signal that a fresh ref is being produced via inc.
(B) Codegen emission in ailang-codegen. Term::Clone emits inc
under --alloc=rc, gated on val_ty == "ptr" and
!val_ssa.starts_with('@') (top-level fn closure-pair globals
live in the LLVM data segment, not in runtime/rc.c's heap).
Term::Let emits dec at scope close iff the value is
rc_alloc'd (Term::Ctor / Term::Lam in escape set under
--alloc=rc), val_ty == "ptr", consume_count == 0 (no callee
or outer site already took ownership), body's tail SSA is
not the binder itself (caller-takes-ownership case), and the
block isn't already terminated.
Header declares of @ailang_rc_inc / @ailang_rc_dec are gated on
--alloc=rc so Boehm/Bump IR shape is unchanged.
Fixture examples/rc_box_drop.ail.json: single-cell Box(Int) ADT
where shallow free is sufficient (no boxed children). E2E test
alloc_rc_emits_dec_for_unique_let_bound_box runs it under both
gc and rc, asserts byte-identical stdout, clean exit, expected
output (42).
Scope cuts deferred to 18c.4: per-type drop fn / recursive dec
cascades for ADTs with boxed children (List, Tree still leak
their tails). Fn params have no dec emission yet (no static
"caller handed off ownership" signal under Implicit mode);
under explicit (own T) the signal exists but wiring is 18d.
Tests: E2E 52 -> 53, ailang-check unit 38 -> 43 (+5 uniqueness),
all other buckets unchanged. cargo test --workspace green.
60 lines
1.7 KiB
JSON
60 lines
1.7 KiB
JSON
{
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"schema": "ailang/v0",
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"name": "rc_box_drop",
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"imports": [],
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"defs": [
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{
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"kind": "type",
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"name": "Box",
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"vars": [],
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"doc": "Single-cell ADT around an Int. Iter 18c.3 RC fixture: shallow free is sufficient because Box has no boxed children.",
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"ctors": [
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{
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"name": "MkBox",
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"fields": [{ "k": "con", "name": "Int" }]
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}
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]
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},
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{
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"kind": "fn",
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"name": "main",
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"type": {
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"k": "fn",
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"params": [],
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"ret": { "k": "con", "name": "Unit" },
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"effects": ["IO"]
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},
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"params": [],
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"doc": "Bind a heap-allocated MkBox to `b`, read its Int via match, print it. Under --alloc=rc, codegen emits `ailang_rc_dec(b)` at the let scope close: `b` is unique, has zero consume uses (only the match scrutinee, a borrow), and the body's tail value is the printed Unit, not `b` itself. The Box has no boxed children so shallow `free()` is correct.",
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"body": {
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"t": "let",
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"name": "b",
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"value": {
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"t": "ctor",
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"type": "Box",
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"ctor": "MkBox",
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"args": [{ "t": "lit", "lit": { "kind": "int", "value": 42 } }]
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},
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"body": {
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"t": "match",
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"scrutinee": { "t": "var", "name": "b" },
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"arms": [
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{
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"pat": {
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"p": "ctor",
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"ctor": "MkBox",
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"fields": [{ "p": "var", "name": "x" }]
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},
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"body": {
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"t": "do",
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"op": "io/print_int",
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"args": [{ "t": "var", "name": "x" }]
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}
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}
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]
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}
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}
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}
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]
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}
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