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feat(cpu): retain ARM instruction pipeline words

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Buffer ARM sequential fetch results and refill target pairs after branches, PC writes, and machine exception entry. Stage advances transactionally, defer speculative fetch diagnostics, and preserve buffered words across CPU/DMA stores and host edits. Add explicit CPU pipeline invalidation for debugger repair and memory rebinding.

Add 15 original instruction-buffer regressions. Keep full-state rollback equality while distinguishing architectural comparisons in semantic tests. Update the display error test for an already buffered branch. Document evidence and separate remaining Thumb, bus-history, and timing work.

Validated on Darwin arm64: 967 workspace and 898 core/demo tests in each debug/release profile, 39 Python tests, native ROM windows, ten window smoke modes, fmt, clippy, and rustdoc. Public ARM/Thumb/memory/BIOS reports and nominal cycles remain unchanged.
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0xrsydn 2026-10-06 03:57:57 +07:00
commit 47df9d05a7
24 changed files with 629 additions and 37 deletions
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docs/references.md
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@ -147,6 +147,14 @@ DMA resume-timing research:
See [non-sequential CPU resume](research/dma-resume-timing.md) for the nominal subset and unmodeled refill/prefetch details.
The public test was reviewed, not executed. No hardware timing pass is claimed.
ARM instruction-buffer research:
- [ARM7TDMI instruction pipeline](https://developer.arm.com/documentation/dvi0027/b/arm7tdmi/instruction-pipeline) and [technical reference manual](https://documentation-service.arm.com/static/5e8e1323fd977155116a3129), for fetch/decode/execute stages and the visible ARM PC offset.
- The pinned NanoBoyAdvance ARM7TDMI `Run` and `ReloadPipeline32` helpers above, for retained words, pre-execution fetching, and target-pair refill order.
- The ARM branch cycle sequence above, for target and target+instruction-width fetches.
See [persistent ARM instruction buffering](research/arm-instruction-buffer.md). Instruction retention is implemented; per-access timing and Thumb buffering remain incomplete.
Use [GBATEK](https://problemkaputt.de/gbatek.htm) and ARM7TDMI documentation for further hardware work.
Only use game ROMs that you may lawfully use. Do not commit game ROMs, BIOS files, or game assets.
The ignore file excludes `roms/`, common game ROM extensions, and save files.