mirror of
https://github.com/imjasonh/nescript
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f49dbce686
Landing bug A from the previous writeup plus two adjacent bugs that the fix exposed. All three miscompile anything that uses a u8[N] global with a literal initializer. 1. Array-literal globals are now actually initialized. `lower_program` only expanded `Expr::StructLiteral` into per- field synthetic globals — `Expr::ArrayLiteral` hit `eval_const`, returned `None`, and the array boot-cleared to zero. `IrGlobal` now carries an `init_array: Vec<u8>` populated by lowering, and the IR codegen startup loop emits one `LDA #byte; STA base+i` pair per element. 2. Local variables no longer overlap array globals. `IrCodeGen::new` advanced `local_ram_next` past `max_global_base + 1` — for an array at `$0300-$0303` it placed the first handler-local at `$0301`, inside the array. The frame handler's stores through the local then corrupted the array mid-frame. The allocator now walks the analyzer's `VarAllocation` list and advances past `address + size` for every RAM global, not just the base. 3. Peephole `remove_redundant_loads` honors indexed LDAs. The pass tracked `LDA Immediate/ZeroPage/Absolute` but let `LDA AbsoluteX/AbsoluteY/ZeroPageX/IndirectX/IndirectY` fall through the match, leaving the A-equivalence tracker unchanged. A later `LDA #v` that happened to match a stale entry from BEFORE the indexed load would then be dropped as "already in A" — a silent miscompile that turned every `draw Sprite at: (arr[i], arr[j])` pattern into garbage (the second array index would be computed from `arr[i]`'s value, reading way out of bounds). Indexed LDAs now clear the tracker. Regression tests: - `src/codegen/peephole.rs`: a synthetic `LDA #0; TAX; LDA AbsX(arr1); STA temp; LDA #0; TAX; LDA AbsX(arr2); ...` sequence asserts both `LDA #0`s survive. - `src/ir/tests.rs`: verifies `var xs: u8[4] = [1,2,3,4]` populates `IrGlobal::init_array` with `[1,2,3,4]`. - `tests/integration_test.rs`: two IR-codegen tests — one checks the startup instructions contain `LDA #v; STA base+i` for every element, the other compiles a handler-local var alongside an array global and asserts no post-init stores land inside the array. Smoke test impact (14/14 still passing, now more visible): - arrays_and_functions: 56 -> 104 nonBlack, now animated - loop_break_continue: 52 -> 208 (player + 3 hazards visible) - structs_enums_for: 52 -> 104 (player + enemy visible) Existing examples unchanged; no remaining work for bug B (static OAM slot allocation in loops) — that's the next PR. https://claude.ai/code/session_014Z5y3Q9krLcAxYpZQJhZ5V |
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| .. | ||
| analyzer | ||
| asm | ||
| assets | ||
| codegen | ||
| debug | ||
| errors | ||
| ir | ||
| lexer | ||
| linker | ||
| optimizer | ||
| parser | ||
| rom | ||
| runtime | ||
| lib.rs | ||
| main.rs | ||