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compiler: PRNG / edge input / palette fade / AxROM / CNROM / FCEUX labels

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Closes seven of the cc65/nesdoug parity gaps catalogued in
docs/future-work.md in a single pass. All of the new features are
gated on marker labels so programs that don't use them produce
byte-identical ROM output (every pre-existing committed .nes file
round-trips unchanged).

Language / runtime additions:
- `rand8()` / `rand16()` / `seed_rand(u16)` intrinsics backed by a
  16-bit Galois LFSR (~30 bytes of runtime, ~40 cycles per draw).
  Reset path seeds state to 0xACE1 so the first draw is useful even
  without explicit seeding.
- `p1.button.a.pressed` / `.released` edge-triggered input via a
  new ReadInputEdge IR op plus an NMI-side prev-frame snapshot into
  $07E6/$07E7, gated on the `__edge_input_used` marker.
- `set_palette_brightness(level)` builtin mapping levels 0..8 to
  PPU mask emphasis bytes (`$2001`) for neslib-style screen fades.
- `mapper: AxROM` (iNES 7) with automatic 32 KB PRG padding so
  emulators that enforce mapper-7's 32 KB page size boot cleanly.
- `mapper: CNROM` (iNES 3) with a reset-time CHR bank 0 select.
- `--fceux-labels <prefix>` CLI flag emitting per-bank `.nl` label
  files and a `.ram.nl` file for FCEUX's debugger.

Tests + examples:
- Five new example programs with committed .nes ROMs and
  pixel+audio goldens: prng_demo, edge_input_demo,
  palette_brightness_demo, axrom_simple, cnrom_simple.
- Seven integration tests covering JSR emission, the
  omitted-when-unused invariant, the NMI prev-input snapshot, the
  correct mapper numbers for AxROM/CNROM, and negative tests for
  unknown button names and bad rand8 arity.
- `is_intrinsic()` now runs in expression-position Call paths too,
  so `var x = rand8(1, 2)` errors at compile time instead of
  silently dropping the extra arguments.
This commit is contained in:
Claude 2026-04-18 18:13:18 +00:00
parent c96135fd86
commit 7507459787
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35 changed files with 1272 additions and 22 deletions
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5
README.md
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@ -61,7 +61,10 @@ start Main
- **Compile-time safety** -- call depth limits, recursion detection, type checking, unused-var warnings
- **IR-based optimizer** -- constant folding, dead code elimination, strength reduction (incl. div/mod by power-of-two), 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)
- **Multiple mappers** -- NROM, MMC1, UxROM, MMC3 (including multi-scanline IRQ dispatch per state), AxROM (mapper 7), CNROM (mapper 3)
- **Runtime PRNG** -- `rand8()`, `rand16()`, `seed_rand(s)` backed by a zero-cost-when-unused xorshift LFSR
- **Edge-triggered input** -- `p1.button.a.pressed` / `.released` for menu / one-shot input handling
- **Palette brightness fades** -- `set_palette_brightness(level)` for cheap neslib-style screen fades
- **Audio subsystem** -- frame-walking pulse driver with user-declared `sfx`/`music` blocks, builtin effects and tracks, period table, and zero-cost elision when unused
- **Palette & background pipeline** -- `palette` and `background` blocks, initial values loaded at reset, vblank-safe `set_palette` / `load_background` runtime swaps
- **Asset pipeline** -- PNG-to-CHR conversion, inline tile data, sfx envelopes, music note streams