Claude 9a539ea068 compiler: audio driver, u16 arithmetic, multi-scanline, slot recycling ... 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		2026-04-12 22:21:53 +00:00
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architecture.md	Add comprehensive documentation	2026-04-12 00:41:34 +00:00
future-work.md	compiler: audio driver, u16 arithmetic, multi-scanline, slot recycling	2026-04-12 22:21:53 +00:00
language-guide.md	Remove the legacy AST codegen — IR path is canonical now	2026-04-12 20:37:59 +00:00
nes-reference.md	Add comprehensive documentation	2026-04-12 00:41:34 +00:00