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compiler: audio driver, u16 arithmetic, multi-scanline, slot recycling

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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
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Claude 2026-04-12 22:21:53 +00:00
parent 9ebf58f7db
commit 9a539ea068
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12 changed files with 2108 additions and 144 deletions
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@ -47,8 +47,10 @@ start Main
- **Functions** -- with parameters, return types, `inline` hint, recursion detection
- **State machines** -- `state` with `on enter`, `on exit`, `on frame`, `on scanline(N)` handlers
- **Compile-time safety** -- call depth limits, recursion detection, type checking, unused-var warnings
- **IR-based optimizer** -- constant folding, dead code elimination, strength reduction, copy propagation, peephole passes
- **Multiple mappers** -- NROM, MMC1, UxROM, MMC3 (including scanline IRQ dispatch)
- **IR-based optimizer** -- constant folding, dead code elimination, strength reduction, copy propagation, peephole passes including INC/DEC fold and live-range slot recycling
- **Full 16-bit arithmetic** -- u16 add/sub/compare lower to carry-propagating paired operations
- **Multiple mappers** -- NROM, MMC1, UxROM, MMC3 (including multi-scanline IRQ dispatch per state)
- **Minimal audio driver** -- `play`/`start_music`/`stop_music` drive a builtin APU engine with no per-program cost when unused
- **Asset pipeline** -- PNG-to-CHR conversion, palette definitions, inline tile data
- **Inline assembly** -- `asm { ... }` with `{var}` substitution, plus `raw asm { ... }` for verbatim blocks
- **Hardware intrinsics** -- `poke(addr, value)` / `peek(addr)` for direct register access
@ -76,6 +78,7 @@ start Main
| [`mmc1_banked.ne`](examples/mmc1_banked.ne) | MMC1 mapper, bank declarations, multiply |
| [`structs_enums_for.ne`](examples/structs_enums_for.ne) | Structs, enums, `for` loops, struct literals |
| [`inline_asm_demo.ne`](examples/inline_asm_demo.ne) | Inline asm with `{var}` substitution, `poke`/`peek` |
| [`audio_demo.ne`](examples/audio_demo.ne) | Minimal audio driver: `play`, `start_music`, `stop_music` |
## Compiler Commands