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https://github.com/imjasonh/nescript
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f4968256f4
Follow-up cleanup on the cc65 parity batch. Addresses issues found during a post-commit code review. **Correctness fixes:** - `rand8()` / `rand16()` at statement position (result discarded) were being eliminated by DCE because `op_dest` returned `Some(dest)` for Rand8/Rand16 even though the ops have a visible side effect — advancing the PRNG state. Now `op_dest` returns `None` for both, keeping the JSR regardless of liveness. New regression test `rand8_statement_survives_dce`. - Void-only intrinsics (`poke`, `seed_rand`, `set_palette_brightness`) used in expression position (e.g. `var x = seed_rand(42)`) were panicking the linker with an unresolved `__ir_fn_X` label. The analyzer now emits E0203 with a clear message; new `void_intrinsic_in_expression_position_errors` test covers all three names. - Statement-position `rand8()` / `rand16()` weren't lowered at all (they fell through to the default Call path). Now both lower to their IR op with a fresh temp that nothing reads; the JSR still runs so the PRNG state advances. - `--fceux-labels foo.nes` was producing `foo.0.nl` because `PathBuf::with_extension` replaces instead of appends. Rewritten to literally append `.<bank>.nl` / `.ram.nl` to the OsString, so users get the FCEUX-expected `foo.nes.<bank>.nl` naming. - Linker now asserts CNROM / AxROM don't accept user-declared switchable PRG banks — their page sizes don't fit the 16 KB per bank model, and silently producing a mis-sized ROM is worse than a loud panic. **PRNG cleanup:** - Removed the stream-of-consciousness comment block in `gen_prng` that described three abandoned algorithms before landing on the actual Galois LFSR. - Simplified `__rand16` to a single JSR + LDX instead of two JSRs + TAY/TYA round-trip — a single shift already produces 16 fresh bits, the doubled call just burned ~40 cycles. The golden PNG for `prng_demo` was regenerated to reflect the new sequence. - Rewrote the `gen_prng` doc comment to accurately describe the algorithm as a Galois LFSR (it was mislabelled as xorshift). - Rewrote the `gen_palette_brightness` doc comment with a proper table of level→mask mappings — the prior prose description didn't match the actual table values. **Tests:** - Three new unit tests in `linker::debug_symbols` covering the FCEUX `.nl` renderer: user-facing labels only, empty output when no user labels exist, and deterministic sorting in `.ram.nl`. - Extended `nes2_mapper_high_nibble_in_byte_8_is_zero_for_small_mappers` to cover AxROM + CNROM. - Renumbered priority list in future-work.md after removing the shipped sections (J, K, N, parts of V and Y). All 737 tests + 40/40 emulator goldens still green.
47 lines
1.3 KiB
Text
47 lines
1.3 KiB
Text
// PRNG demo — sprite positions driven by the runtime PRNG.
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//
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// Each frame draws four sprites at pseudorandom coordinates pulled
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// from the Galois-LFSR `rand8()` intrinsic, plus one sprite whose
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// (x, y) pair comes from a single `rand16()` draw. Exercises all
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// three PRNG intrinsics (`rand8`, `rand16`, `seed_rand`) end-to-end.
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// `seed_rand(0x1234)` on the first frame pins the sequence so the
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// committed golden is deterministic.
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game "PRNG Demo" {
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mapper: NROM
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}
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var seeded: u8 = 0
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on frame {
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if seeded == 0 {
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// Pin the seed so the recording is deterministic. The
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// runtime forces bit 0 of the low byte high so a zero
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// seed doesn't stick the LFSR.
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seed_rand(0x1234)
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seeded = 1
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}
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// Four random sprites per frame. Each call pulls fresh
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// entropy from the shared PRNG state, so the positions
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// drift over time instead of staying fixed.
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var x1: u8 = rand8()
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var y1: u8 = rand8()
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draw Ball at: (x1, y1)
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var x2: u8 = rand8()
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var y2: u8 = rand8()
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draw Ball at: (x2, y2)
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// rand16() returns u16; truncate to u8 for the draw.
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var r: u16 = rand16()
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var x3: u8 = r as u8
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var y3: u8 = (r >> 8) as u8
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draw Ball at: (x3, y3)
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var x4: u8 = rand8()
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var y4: u8 = rand8()
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draw Ball at: (x4, y4)
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}
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start Main
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