0xrsydn/gameboy-rust
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feat(memory): add region-dependent Thumb open-bus snapshots

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Repeat the mapped PC+4 halfword for Thumb code in EWRAM, palette RAM, VRAM, and ROM. Use the aligned PC+4 word for BIOS/OAM. Keep retained BIOS history separate from current unused-memory reads. Reuse one instruction snapshot without extra data cycles or host/fetch/DMA fallbacks.

Keep IWRAM and 16 MiB region-crossing fetches diagnostic until prior bus history is modeled. Add original regressions for regions, alignments, mirrors, physical wrap, signed and unaligned loads, block/stack/PC loads, aliases, modes, short ROMs, strict errors, BIOS isolation, and nominal device progression. Record documented rules and remaining limits.

Darwin arm64 validation: 890 workspace tests and 821 core/demo tests in each of debug and release; 39 preparation tests; native ROM windows in both profiles; ten window/graphics smoke modes; fmt, clippy, and rustdoc. Public ARM, Thumb, memory, and BIOS reports remain identical to previous passing results and between profiles. No physical-hardware or independent public Thumb open-bus conformance claim.
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0xrsydn 2026-10-06 01:25:41 +07:00
commit 8360ba4652
11 changed files with 528 additions and 36 deletions
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docs/architecture.md
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@ -29,6 +29,7 @@ The repository is a Cargo workspace with three crates:
| `crates/gba-core/src/cpu/load_alias_tests.rs` | Original single-load alias regressions for indexing, banks, widths, alignment, I/O, timing, and diagnostics |
| `crates/gba-core/src/cpu/bios_access_tests.rs` | Original CPU BIOS protection regressions for retained history, modes, widths, exception returns, and diagnostics |
| `crates/gba-core/src/cpu/thumb_bios_access_tests.rs` | Thumb BIOS aligned-word snapshots, transitions, load lanes, boundaries, diagnostics, and nominal timing |
| `crates/gba-core/src/cpu/thumb_open_bus_tests.rs` | Region-dependent Thumb open bus, mirrors, widths, transfers, source boundaries, isolation, and nominal timing |
| `crates/gba-core/src/cpu/compare_psr_tests.rs` | Original Rd=15 test/compare status restoration, flags, bank, and timing regressions |
| `crates/gba-core/src/cpu/status_tests.rs`, `crates/gba-core/src/cpu/exception_tests.rs` | Status, banking, exception, and return tests |
| `crates/gba-core/src/cpu/thumb_tests.rs` | Thumb instructions, state switching, and decoder checks |