The audio subsystem was a sketch: `play name` / `start_music name` /
`stop_music` parsed, lowered, and emitted a few hardcoded register
writes from a builtin name table. No user-declared effects, no
per-frame envelope, no note streams, no real engine.
This flesh-out brings audio up to the quality bar of the rest of
the compiler (sprites, palettes, bank switching, scanline IRQ,
etc.) with a full data-driven pipeline:
## Asset pipeline (new `src/assets/audio.rs`)
- `sfx Name { duty, pitch, volume }` blocks compile into per-frame
pulse-1 envelopes. Pitch/volume arrays must match in length; each
entry is one NMI's worth of `$4000` data.
- `music Name { duty, volume, repeat, notes }` blocks compile into
flat `(pitch, duration)` streams for pulse 2. Pitch 0 is a rest,
1-60 indexes a builtin period table covering C1-B5.
- `resolve_sfx` / `resolve_music` walk the program for `play` /
`start_music` references and append builtin fallbacks for any
name that isn't user-declared — so `play coin` still works
without a `sfx Coin { ... }` block.
- Builtin effects (coin, jump, hit, click, cancel, shoot, step)
and tracks (theme, battle, victory, gameover) synthesize through
the same compile path as user decls — one data model, one driver.
## Runtime engine (`src/runtime/mod.rs`)
- `gen_audio_tick()` walks both channels every NMI: reads one
envelope byte through `(ZP_SFX_PTR),Y` -> writes `$4000`,
advances ptr, mutes on zero sentinel. Music decrements the note
counter, advances to the next `(pitch, dur)` pair on zero, looks
up the period through `(__period_table),Y`, loops on `0xFF 0xFF`.
- `gen_period_table()` emits a 60-entry equal-tempered table
(A4 = 440 Hz, NTSC 1.789773 MHz CPU clock) with length-counter
load bits pre-baked into each high byte.
- `gen_data_block()` emits a label + raw-bytes pseudo pair so
user sfx/music data can be spliced into PRG with regular labels
that the two-pass assembler resolves.
- New ZP layout: `$05/$06` music loop base, `$07` music state
(duty/volume/loop/active), `$0C-$0F` sfx and music pointers.
## IR codegen (`src/codegen/ir_codegen.rs`)
- `with_audio(sfx, music)` registers compile-time trigger constants
per blob name.
- `gen_play_sfx` emits: write period to `$4002`/`$4003`, load
envelope pointer into `ZP_SFX_PTR` via SymbolLo/SymbolHi of
`__sfx_<name>`, mark the sfx counter active.
- `gen_start_music` stamps the header byte into `ZP_MUSIC_STATE`
with the active bit OR'd in, seeds both ptr and loop base from
`__music_<name>`, primes the duration counter.
- `gen_stop_music` mutes pulse 2 and clears state.
## Linker (`src/linker/mod.rs`)
- New `link_with_all_assets(user_code, sprites, sfx, music)` path
that splices driver body, period table, and each sfx/music data
blob into PRG — all guarded on the `__audio_used` marker so
silent programs pay zero ROM cost.
## Assembler (`src/asm/opcodes.rs`, `src/asm/mod.rs`)
- New `AddressingMode::Bytes(Vec<u8>)` variant for raw-data
pseudo-instructions. `NOP+Bytes(v)` emits the payload verbatim,
letting the linker splice ROM data tables into a code section
and still have `Label` / `SymbolLo` / `SymbolHi` fixups resolve
correctly in the same assembly pass.
## Analyzer
- `play` / `start_music` now validate the name against user decls
and builtin tables. Unknown names emit E0505 with a helpful list
of builtins — previously a typo would silently compile to no-op.
## Parser
- New `sfx_decl` / `music_decl` grammar with property-style
configuration. Strict validation: duty 0-3, volume 0-15, pitch
arrays must match volume length, music notes must come in pairs,
pitch 0-60, duration ≥ 1.
## Tests
+170 new tests across every layer:
- `src/assets/audio.rs`: 17 tests (compile, resolve, builtins,
shadowing, label sanitation, nested reference walks)
- `src/parser/tests.rs`: 13 tests (valid/invalid sfx + music
declarations, property validation, play/start_music/stop_music)
- `src/analyzer/tests.rs`: 7 tests (builtin acceptance, user decl
acceptance, unknown-name rejection)
- `src/runtime/tests.rs`: 10 tests (audio tick labels, RTS end,
$4000 write, $4004 mute, period table assembly, A4 = 440 Hz,
length counter bits, data block verbatim emit)
- `src/linker/tests.rs`: 4 tests (sfx/music blob placement,
pointer resolution, elision when unused)
- `src/codegen/ir_codegen.rs`: rewrote the 4 existing audio tests
to match the new data-driven contract
- `tests/integration_test.rs`: 4 end-to-end tests including a
user-declared `sfx` + `music` program that verifies bytes land
in PRG ROM at the right addresses
## Docs
- New Audio section in `docs/language-guide.md` with syntax
reference, builtin tables, and an explanation of how the
driver works at compile and run time.
- `docs/architecture.md` updated to reflect the real audio
pipeline instead of the old "audio import stubs" stub.
- `docs/future-work.md` moves audio from "status: minimal" to
"status: full subsystem" with a narrower list of follow-up work
(triangle/noise/DMC channels, NSF/FTM imports, richer envelopes).
- `examples/audio_demo.ne` rewritten to showcase user-declared
`sfx LongCoin`, `sfx Zap`, `music Theme`, still demonstrating
builtin fallback via `play coin`.
Total: 424 tests passing (381 unit + 43 integration), clippy clean,
fmt clean, all 19 examples compile.
https://claude.ai/code/session_015WfaDttE3DpWn9rpyfpQd8
Five language features and optimizations from the planned-work backlog:
- **Minimal audio driver**: `play`/`start_music`/`stop_music` now generate
APU pulse-1/pulse-2 writes from a builtin SFX/music name table, and
the NMI handler gains a `JSR __audio_tick` splice (via the linker's
`__audio_used` marker lookup) that ages an SFX countdown counter and
mutes pulse 1 when the tone expires. Programs that never trigger
audio pay zero ROM cost.
- **u16 arithmetic and comparisons**: new IR ops `LoadVarHi`, `StoreVarHi`,
`Add16`, `Sub16`, and six `Cmp*16` variants. The lowering context
tracks variable types via the analyzer's symbol table and routes
expressions through the 8-bit or 16-bit path based on operand width.
Add16 emits `CLC;ADC;ADC` with carry propagating naturally into the
high byte; compares dispatch high-byte-first with a short-circuit
low-byte fallback. Fixes a silent miscompile where `big += 1` on a
u16 var only incremented the low byte.
- **Multi-scanline handlers per state**: `gen_scanline_irq` now
dispatches on `(current_state, ZP_SCANLINE_STEP)` and reloads the
MMC3 counter with the delta to the next scanline in the same state.
`gen_scanline_reload` resets the step counter at the top of each
NMI so a state with multiple handlers fires them in ascending line
order. Previously only the first handler per state ever fired.
- **IR temp slot recycling**: `build_use_counts` pre-scans each
function to count per-temp uses; `retire_op_sources` decrements
the counts after each op and pushes dead slots back onto
`free_slots` for later allocation. `bitwise_ops.ne` used to crash
(debug) or miscompile (release) once it hit 128 concurrent temps;
with recycling the same function now uses ~4 slots instead of 136.
- **INC/DEC peephole fold + improved dead-load elimination**:
`fold_inc_dec` collapses `LDA addr; CLC; ADC #1; STA addr` into
a single `INC addr` (and the SEC/SBC variant into `DEC addr`),
saving 5 bytes and 5 cycles per increment. The fold is suppressed
when the next instruction reads carry. `remove_dead_loads` now
walks past INC/DEC/STX/STY (which don't touch A) to find the
actual next A-use, catching more dead loads.
Tests: 331 unit + 39 integration (up from 313 + 37), including new
guards for audio, u16, multi-scanline, and slot recycling.
https://claude.ai/code/session_01A8qk3gw2jWSzdiXBZPZSFE
Fallout from removing the `--use-ast` flag and the AST codegen.
Four references in `docs/future-work.md` and one in `plan.md` were
still implying a parallel AST code path existed:
- `future-work.md` "--debug CLI flag wired" entry — said the flag
threads through `CodeGen::with_debug` (the old AST codegen's
builder). Updated to `IrCodeGen::with_debug`.
- `future-work.md` IR debug.log/assert entry — had a parenthetical
"(same behavior as AST codegen)" that no longer makes sense
without an AST codegen to compare against. Dropped.
- `future-work.md` inline assembly entry — said "Both IR and AST
codegen splice parsed instructions directly into the output
stream." There's only the IR codegen now. Updated.
- `future-work.md` `on scanline(N)` entry — described scanline
handling as "codegen (MMC3 IRQ vector wiring) is still TODO."
That wiring has been in place for a while: the IR codegen
emits `__irq_user` + `__ir_mmc3_reload` with per-state
dispatch, and `examples/scanline_split.ne` and
`examples/mmc3_per_state_split.ne` both exercise it in the
jsnes smoke test. Rewrote the entry to match reality.
- `plan.md` M2 "Compiler phases built" list — had "Codegen from
IR (replacing direct AST codegen)." The present-tense
parenthetical read as if AST codegen still existed; stripped
it. M1's "direct AST → 6502, skip IR for this milestone" line
is left as a historical milestone scope description.
One intentional mention remains: `future-work.md` "Recently
completed" bullet explicitly notes the AST-based path and the
`--use-ast` flag were removed. That's the correct tombstone.
https://claude.ai/code/session_014Z5y3Q9krLcAxYpZQJhZ5V
The `--use-ast` path through `src/codegen/mod.rs` was a strictly
inferior subset of the IR codegen. Building every example with
`--use-ast` through the jsnes harness:
- `arrays_and_functions` — fully black (array init + function
return values + OAM-in-loop all broken)
- `structs_enums_for` — fully black (struct literal is a no-op,
all fields stay at 0)
- `inline_asm_demo` — fully black
- `bitwise_ops`, `loop_break_continue` — below sprite floors
(static `next_oam_slot` bug B)
- `match_demo` — panics at compile time with
`branch offset 153 out of range` (AST's if/else-chain
desugaring of `match` emits short branches that can't reach
the far arms in a multi-arm match)
Six of fourteen examples are non-functional under `--use-ast`.
The other eight happen to fall inside the subset AST handles
(no arrays, no structs, no function return values, no
multi-sprite loops, no long match chains).
`docs/future-work.md` already listed "Once working, delete the
AST-based codegen entirely" as the intended direction. It's
working, so this commit does the deletion.
What's removed:
- The `CodeGen` struct, its impl block, and every helper in
`src/codegen/mod.rs` (the AST codegen body) — ~1150 lines.
The file is now a module header that re-exports `IrCodeGen`.
- `src/codegen/tests.rs` — 15 AST-specific instruction-pattern
tests. Every feature they covered has an equivalent test in
`src/codegen/ir_codegen.rs::{tests,more_tests}` already.
- The `--use-ast` CLI flag and its branch in `src/main.rs`.
- `compile_with_ir_codegen` in `tests/integration_test.rs` —
`compile()` now does what it did, so they merged. All 40
integration tests go through the IR path.
- Outdated sections in `docs/future-work.md` that described the
IR codegen as "not yet implemented" and listed AST codegen
gaps as priority work.
What's kept:
- `src/codegen/ir_codegen.rs` — the real codegen.
- `src/codegen/peephole.rs` — post-codegen cleanup pass, now
run unconditionally from `main.rs`.
Test plan:
- `cargo test --release` — 313 unit + 37 integration tests pass
(was 328 + 37; the 15 dropped are the deleted AST-specific
tests).
- `cargo fmt --check` clean.
- `cargo clippy --release --all-targets -- -D warnings` clean.
- `node tests/emulator/run_examples.mjs` — 14/14 ROMs render
above their per-example nonBlack floors.
- The one tightening: `sprite_resolution_uses_tile_index` was
asserting on the old static-slot encoding
(`A9 01 8D 01 02`). Updated to the cursor-based form
(`A9 01 99 01 02`, i.e. STA AbsoluteY).
Net diff: 1581 deletions, 62 insertions.
https://claude.ai/code/session_014Z5y3Q9krLcAxYpZQJhZ5V
Lists structs, for loops, audio parsing, const folding, on_scanline
codegen, all new peephole passes, and the fixed function call ABI /
local variable allocation. Re-prioritizes remaining work.
https://claude.ai/code/session_01W6eQFStA66EuMKHUFo2rx3
The IR-based codegen now matches all features of the AST codegen
(state dispatch, multi-OAM, P1/P2 input, scroll, debug.log/assert),
so flip the default. The legacy AST codegen is still available via
--use-ast for comparison and fallback during validation.
https://claude.ai/code/session_01W6eQFStA66EuMKHUFo2rx3
resolve_sprites() now handles all three AssetSource variants:
- Inline(bytes): use directly (existing behavior)
- Binary(path): read raw bytes from file relative to source_dir
- Chr(path): convert PNG to CHR via png_to_chr()
Missing files are silently skipped rather than erroring, so
declarations can reference assets that haven't been added yet.
This keeps existing tests that use placeholder file paths working.
Updated future-work.md: moved include directive, P2 controller,
sprite resolution, shift-assign, debug statements, warnings, and
asset wiring to the "completed" section. Remaining work is IR codegen,
audio, on_scanline, and language features (structs/enums).
Tests: 257 total (3 new resolve_sprites tests)
https://claude.ai/code/session_01W6eQFStA66EuMKHUFo2rx3
