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7b4570eee5
Another batch from the cc65/nesdoug catalogue. All gated on
parser-level opt-in or default-false attributes so existing
programs produce byte-identical ROMs (no committed .nes file
changed).
**§A — `i16` signed 16-bit type:**
- New `KwI16` lexer token, `NesType::I16` AST variant, parser
case in `parse_type`. Type-size and integer-type tables
treat `i16` like `u16` (2 bytes, integer).
- IR lowering accepts `i16` everywhere it accepts `u16` for
wide-load / wide-store / widen-narrow paths.
- New constant fold for `UnaryOp::Negate(IntLiteral(v))` that
emits the wide two's-complement form. Without it, `var vy:
i16 = -10` would zero-extend to `$00F6` (= 246) instead of
sign-extending to `$FFF6` (= -10). Negative literals now
store the right bytes.
- Comparisons reuse the existing unsigned 16-bit compare ops
(matching the existing `i8` behaviour). Documented in the
`NesType::I16` doc comment and in `future-work.md` §A.
- Example `examples/i16_demo.ne` with committed golden.
- Tests cover the literal-fold sign-extension and end-to-end
compile of the example.
**§S — SRAM / battery-backed saves:**
- New `save { var ... }` top-level block. Lexer + parser opt
into a dedicated `KwSave` token. Analyzer allocates save
vars from a separate `next_sram_addr` bump pointer starting
at `$6000`, capped at `$8000` (8 KB cartridge SRAM window).
- Linker reads `analysis.has_battery_saves` and flips iNES
byte-6 bit-1 via the new `RomBuilder::set_battery` /
`Linker::with_battery` chain.
- New `W0111` warning for save-var initializers — SRAM is
preserved across power cycles, so an init expression would
either silently never run or clobber persisted data on
every boot. The warning teaches the user about the
magic-byte sentinel pattern.
- Struct fields in save blocks are explicitly rejected for now
(the field-flattening path uses the main-RAM allocator).
- Example `examples/sram_demo.ne` with committed golden, plus
4 integration tests.
**§D (partial) — inline-asm `.label:` syntax:**
- Codegen-side mangler rewrites `.IDENT` → `__ilab_<N>_IDENT`
per inline-asm block, where `<N>` is the call site's
monotonic suffix. Two `asm { .loop: ... }` blocks in the
same function now coexist without colliding in the linker's
label table.
- Bounds checks on `.` placement: `$2002` and `name.field`
are unaffected; only `.IDENT` in label / branch context
triggers the rewrite. Two integration tests pin the
uniqueness and dollar-vs-dot disambiguation.
**§X follow-up — Mesen trace-log docs:**
- New "Debugger-assisted workflows" section in
`docs/nes-reference.md` walking through the Mesen / FCEUX
log workflows alongside the new `debug_port:` attribute.
**Misc:**
- `future-work.md` updated to mark the shipped items out of
the catalogue and reshuffle the priority ranking. Remaining
niche follow-ups (signedness on Cmp16, struct save fields,
inline-asm format specifiers) documented inline so future
passes know the design.
All 757 tests pass. Clippy clean. 46/46 emulator goldens match.
48 lines
1.6 KiB
Text
48 lines
1.6 KiB
Text
// SRAM demo — a `save { var ... }` block declares battery-backed
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// state in the iNES `$6000-$7FFF` SRAM window. The compiler:
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// * allocates `high_score`, `coins`, and `initials` at $6000+
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// instead of main RAM,
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// * sets the iNES header byte-6 bit-1 (battery flag), and
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// * emits absolute-mode loads/stores that target SRAM directly.
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//
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// Real cartridge boards persist this region to a `.sav` file; in
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// most emulators (FCEUX, Mesen, Nestopia) the file lives next to
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// the ROM. SRAM is uninitialized at first power-on, so production
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// games should reserve a magic-byte sentinel and validate it
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// before trusting the rest of the data — this demo skips the
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// validation step for brevity.
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game "SRAM Demo" {
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mapper: NROM
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}
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// Save vars don't take initializers — SRAM is preserved across
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// power cycles, so an init expression would either silently
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// never run or clobber the player's saved data on every boot.
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// Production games guard their save data with a magic-byte
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// sentinel: check a known signature on boot and only seed
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// defaults if it's missing.
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save {
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var high_score: u16
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var coins: u8
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}
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var px: u8 = 64
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on frame {
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// Bump the in-SRAM coin counter every frame; when it wraps
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// past 256 we treat that as "scored a power-up" and bump
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// the high score.
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coins += 1
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if coins == 0 {
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high_score += 1
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}
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// Move a sprite so the demo has visible output for the
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// emulator golden — frame 180 captures the sprite at
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// x = 64 + 180 (mod 256) = 244.
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px += 1
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draw Ball at: (px, 100)
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}
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start Main
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