iter hs.1: static-Str layout migration — packed-struct globals + sentinel rc-header + len
First iter of the heap-Str ABI milestone. Pure codegen refactor; every existing program produces byte-identical stdout.
Static-Str LLVM globals migrate from `[N x i8] c"…\00"` to `<{ i64, i64, [N x i8] }> <{ i64 -1, i64 N-1, [N x i8] c"…\00" }>`, carrying the UINT64_MAX sentinel rc-header (slot exploited in hs.2 via runtime short-circuit) and an explicit byte length. Two parallel intern paths (`intern_string` for raw format scaffolding, new `intern_str_literal` for language Str values) keep format strings untouched in `[N x i8]` shape.
IR-Str pointers now uniformly land on the len-field (offset +8 from rc-header, -8 from bytes). Four codegen sites that hand a Str pointer to a NUL-terminated-bytes C-API consumer now emit a +8 GEP first: `@puts` (io/print_str), `@ail_str_eq` (eq__Str intercept), `@ail_str_compare` (compare__Str intercept), and `@strcmp` (lower_eq Str arm — the 4th site was not in the plan; surfaced by Task-5 e2e regression and fixed inline).
6 new IR-shape pinning tests; `hello.ll` snapshot regenerated; cross_lang.py + compile_check.py + full `cargo test --workspace` green.
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# iter hs.1 — Heap-Str ABI: Static-Str layout migration
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**Date:** 2026-05-12
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**Started from:** 69bb5f9952fb51af7cdf4e36f77cff1b6cd73c40
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**Status:** DONE
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**Tasks completed:** 5 of 5
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## Summary
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First iter of the heap-Str ABI milestone. Pure codegen-side refactor:
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language `Str` literals now emit as packed-struct LLVM globals
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`<{ i64, i64, [N+1 x i8] }> <{ i64 -1, i64 N, [N+1 x i8] c"...\00" }>`
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carrying a `UINT64_MAX` sentinel rc-header in the first slot, an
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explicit byte length in the second, and the bytes plus trailing NUL
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in the array tail. The IR-Str-pointer convention is now uniform: a
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language `Str` value flowing through the IR is a `ptr` landing on the
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`len`-field (offset +8 from the header, -8 from the bytes). Every
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codegen site that hands a `Str` pointer to a `NUL`-terminated-bytes
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C-API consumer emits a `getelementptr inbounds i8, ptr <v>, i64 8`
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immediately before the call. The sentinel slot is hardcoded in the
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global initialiser and not yet observed by any caller — `hs.2` will
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add the `UINT64_MAX` short-circuit to `ailang_rc_inc` /
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`ailang_rc_dec` in `runtime/rc.c` to exploit it. Format strings
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(`%lld\n`, `%g\n`, `true\n`, `false\n`) are unchanged — they are
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runtime-internal scaffolding, never flow as language `Str` values,
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and remain in the raw `[N x i8]` shape via the original
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`intern_string` / `all_strings` path. Acceptance verified
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end-to-end: full `cargo test --workspace` green (no regressions
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across 74 e2e fixtures), `bench/compile_check.py` exit 0,
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`bench/cross_lang.py` exit 0 (byte-identical stdout across all
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ail/c benchmark pairs).
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## Per-task notes
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- iter hs.1.1: introduced parallel `str_literals` interning table on
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`Emitter`, `intern_str_literal` fn, workspace-level
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`all_str_literals` aggregation, and a parallel global-emission
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loop emitting the packed-struct shape. Switched both
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`Literal::Str` arms (`emit_const_def`, `lower_term`) to call
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`intern_str_literal` and materialise a constexpr
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`getelementptr inbounds (<{ i64, i64, [N x i8] }>, ptr @g, i32 0, i32 1)`
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landing on the `len`-field. Two pinning tests added.
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- iter hs.1.2: `io/print_str` arm now emits a `+8 GEP` to land on
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the bytes pointer before calling `@puts`. One pinning test added.
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- iter hs.1.3: `eq__Str` arm of `try_emit_primitive_instance_body`
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now emits `+8 GEP`s on both operands before calling
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`@ail_str_eq`. One pinning test added.
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- iter hs.1.4: `compare__Str` arm of `try_emit_primitive_instance_body`
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now emits `+8 GEP`s on both operands before calling
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`@ail_str_compare`. One pinning test added.
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- iter hs.1.5: regenerated `crates/ail/tests/snapshots/hello.ll`
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via `UPDATE_SNAPSHOTS=1`. Full `cargo test --workspace` revealed
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a regression in `eq_demo` traced to a fourth codegen site not
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enumerated in the plan: `lower_eq`'s `"Str"` arm calls `@strcmp`
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inline (separate from the `eq__Str` instance-method intercept)
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to lower `==` on `Str` literals and Str-pattern desugaring in
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`classify_str`. Fixed inline with the same `+8 GEP` shape; one
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additional pinning test added.
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## Concerns
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- The plan claimed three codegen sites pass a `Str` pointer to a
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`NUL`-terminated-bytes C-API consumer (`@puts`, `@ail_str_eq`,
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`@ail_str_compare`); in fact a fourth site exists in
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`lower_eq`'s `"Str"` arm, calling `@strcmp` directly. This is
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the dispatch path for the surface-level `==` operator on
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`Str` and for `(pat-lit "...")` desugar against a `Str`
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scrutinee. The fourth site is required to meet the iter's
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stated acceptance criterion (byte-identical stdout); fixing it
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was discovered via the e2e regression in `eq_demo` rather than
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via the per-task IR-shape checks. The fix has the same shape
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as Tasks 2-4 and the corresponding pinning test
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(`lower_eq_str_calls_strcmp_with_bytes_pointer`) is added. The
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plan's "Files this plan creates or modifies" enumeration
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should list `crates/ailang-codegen/src/lib.rs:2520-2529` as a
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fifth modify site for any future re-execution.
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- The plan's two test fixtures in Task 1 contained schema-syntax
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errors that prevented compilation: `ConstDef.body` (actual:
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`value`), `Term::App { f, args }` (actual: `callee, args, tail`),
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and `Term::App { Term::Var "io/print_str", ... }` for what is
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actually a `Term::Do` effect op. Tests were adapted to compile
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while preserving the substantive assertions verbatim. Same
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applies to the test in Task 2 (`Term::App` → `Term::Do` for the
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`io/print_str` invocation and added `effects: ["IO"]` on the
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main fn so the typecheck-side dispatch finds the effect).
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These were small per-test fixture adaptations, not changes to
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the asserted IR shape.
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## Known debt
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- The sentinel value `-1` (`UINT64_MAX`) is hardcoded in the
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global initialiser. `hs.2` adds the matching short-circuit
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check in `ailang_rc_inc` / `ailang_rc_dec` so static-Str
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pointers can flow through generic RC paths without
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ref-count traffic. Until `hs.2` lands, no caller actually
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observes the sentinel — static `Str` slabs are still
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invisible to the RC runtime by construction (the call sites
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for `inc` / `dec` against `Str` values are still gated by
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the same uniqueness-inference pass that elided them
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pre-iter).
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## Files touched
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- `crates/ailang-codegen/src/lib.rs` — Emitter field, intern fn,
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workspace aggregation, global emission, two `Literal::Str` arm
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switches, four C-API-callsite `+8 GEP` adjustments
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(`io/print_str`, `eq__Str`, `compare__Str`, `lower_eq` Str arm),
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six new IR-shape pinning tests in the test module.
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- `crates/ail/tests/snapshots/hello.ll` — regenerated snapshot
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showing the new packed-struct global and the `+8 GEP` before
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`@puts`. No other snapshot under
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`crates/ail/tests/snapshots/` changed (other snapshots contain
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only format-string globals which kept the raw `[N x i8]`
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shape).
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## Stats
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`bench/orchestrator-stats/2026-05-12-iter-hs.1.json`
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@@ -30,3 +30,4 @@
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- 2026-05-12 — audit-ms: milestone close (Multi-subject Authoring-Form Test — CodeLlama Replication) — architect clean, bench all-green (same 5-metric latency.explicit_at_rc improvement cluster as audit-cma earlier today, baseline left pristine for second consecutive audit) → 2026-05-12-audit-ms.md
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- 2026-05-12 — iter ext-rename: `.ailx` → `.ail` extension rename across the live toolchain (61 example renames + 35 content edits + experiment-crate cohort rename `ailx → ail`); historical docs (journals, archive, specs, plans, frozen experiment runs) deliberately untouched; cargo+bench all-green; opens follow-up `.ail`-CLI-acceptance iter → 2026-05-12-iter-ext-rename.md
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- 2026-05-12 — iter ext-cli.1: `ail check`/build/run/...all 12 path-taking subcommands now accept `.ail` (Form A) inputs via `ailang_surface::{load_module, load_workspace}` (extension-dispatching loaders + injection point `core::load_workspace_with<F>`); workspace imports prefer `.ail` sibling over `.ail.json`; new `WorkspaceLoadError::SurfaceParse` variant routes surface parse errors as `surface-parse-error` structured diagnostics through `ail check --json`; DESIGN.md §Decision 6 CLI addendum; +7 new tests; closes the loop opened by iter ext-rename → 2026-05-12-iter-ext-cli.1.md
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- 2026-05-12 — iter hs.1: heap-Str ABI iter 1 — static-Str LLVM globals migrate from `[N x i8]` to packed-struct `<{ i64, i64, [N x i8] }>` carrying a `UINT64_MAX` sentinel rc-header + explicit `len`; IR-Str pointers now land on the `len`-field; `@puts` / `@ail_str_eq` / `@ail_str_compare` / `@strcmp` callsites GEP +8 to recover the bytes pointer (4 sites; plan listed 3, Task-5 e2e regression surfaced the 4th); 6 IR-shape pins; format strings stay raw `[N x i8]`; cross_lang.py + compile_check.py + full cargo test --workspace all green; byte-identical stdout across every example → 2026-05-12-iter-hs.1.md
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