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
Updates the feature list to mention structs, enums, for loops,
match, inline asm + \`{var}\` substitution, \`poke\`/\`peek\`
intrinsics, and the new \`--memory-map\` / \`--call-graph\`
diagnostics. Adds the two new examples (structs_enums_for and
inline_asm_demo) to the table.
https://claude.ai/code/session_01W6eQFStA66EuMKHUFo2rx3
README: project overview, quick start, feature list, example table
LICENSE: MIT
4 new examples covering all language features:
- arrays_and_functions: arrays, while loops, inline/regular functions
- state_machine: multi-state flow with on enter/exit handlers
- sprites_and_palettes: inline CHR data, palette switching, scroll, cast
- mmc1_banked: MMC1 mapper, bank declarations, software multiply
Parser fix: draw statement keyword-arg parsing now checks for ':'
lookahead before consuming an identifier, preventing it from eating
the next statement as a keyword argument (e.g., `i += 1` after a draw).
https://claude.ai/code/session_01W6eQFStA66EuMKHUFo2rx3
