0xrsydn/gameboy-rust
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fix(cpu): support single-load writeback register aliases

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Allow ARM LDR/LDRB/LDRH/LDRSB/LDRSH to share non-PC base and destination registers with writeback. Keep the loaded value after computing addresses from incoming operands. Preserve PC restrictions, unsupported user transfers, store behavior, and atomic memory diagnostics.

Add original regressions for index modes, offsets, widths, alignment, sign extension, all active banks, timing, I/O/IRQ ordering, and failures. The unchanged pinned public ARM ROM progresses past tests 360 and 361, then fails at test 362 on an unmapped 0x80000000 read; no full-suite pass is claimed.

Verified on Darwin arm64: debug/release workspace and core suites, Python adapter tests, Clippy, rustdoc, native ROM-window checks, and all ten demo smoke tests. Document the new behavior and next memory-access blocker.
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0xrsydn 2026-10-05 20:15:18 +07:00
commit ab625dc55d
11 changed files with 367 additions and 12 deletions
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docs/testing.md
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@ -58,6 +58,9 @@ direnv exec . python3 -B -m unittest discover -s tools -p 'test_*.py' -v
They verify pinned URLs, hashes, sizes, checkpoint validation, offline copies, destination safety, and non-overwriting output.
Compare/status CPU regressions verify saved flags/masks, bank switching, sequential PC/timing, User/System fallback, and atomic diagnostics.
Load-alias regressions cover widths, signed/unaligned values, immediate/register offsets, pre/post-indexing, every non-PC register bank, and address wrapping.
They verify loaded-value precedence, preserved flags, unchanged stores, nominal timing, I/O reads before device progress, deferred IRQ delivery, and atomic errors.
The public ARM ROM progresses past tests 360–361 but still fails on the high-address read in test 362.
ROM-runner tests use temporary files containing original instructions, without Nintendo assets or a desktop session.
They check file-size boundaries, bounded reads, short reads, I/O errors, paths, symlinks, and read-only loading.