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fix(cpu): store PC plus six for Thumb empty register lists

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Correct the shared Thumb block-store PC offset from four to six bytes. Retain ARM PC+12, 64-byte empty-list writeback, normal load behavior, alignment, flags, and nominal timing. Correct prior internal expectations and add original regressions for bases, banks, alignment, ROM windows, writeback, clocks, and atomic errors.

The pinned public Thumb ROM now passes its unchanged ARM-state r7 checkpoint after 807 steps and 4170 nominal cycles. The pinned ARM ROM still passes. Neither external ROM nor result assertion is modified.

Validated on Darwin arm64: 848 workspace tests in debug and release; 779 core/demo tests separately; 21 Python adapter tests; both public suites in both profiles; native ROM-window tests; all ten demo window smoke tests; fmt, clippy, rustdoc, and local documentation links.
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0xrsydn 2026-10-05 20:47:20 +07:00
commit 3d67b136ba
12 changed files with 222 additions and 17 deletions
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docs/references.md
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@ -78,7 +78,8 @@ Hardware references used for the core:
- [GBATEK Thumb register operations](https://problemkaputt.de/gbatek-thumb-opcodes-register-operations-alu-bx.htm).
- [GBATEK Thumb loads/stores](https://problemkaputt.de/gbatek-thumb-opcodes-memory-load-store-ldr-str.htm).
- [GBATEK Thumb address calculation](https://problemkaputt.de/gbatek-thumb-opcodes-memory-addressing-add-pc-sp.htm).
- [GBATEK Thumb stack and multiple transfers](https://problemkaputt.de/gbatek-thumb-opcodes-memory-multiple-load-store-push-pop-and-ldm-stm.htm).
- [GBATEK Thumb stack and multiple transfers](https://problemkaputt.de/gbatek-thumb-opcodes-memory-multiple-load-store-push-pop-and-ldm-stm.htm), for empty-list PC transfers and 64-byte writeback.
- [mGBA Thumb transfer implementation](https://github.com/mgba-emu/mgba/blob/master/src/arm/isa-thumb.c) and [shared memory transfers](https://github.com/mgba-emu/mgba/blob/master/src/gba/memory.c), reviewed for empty STM/PUSH routing and the extra Thumb instruction width on the stored pipeline PC. This supports executing PC+6, rather than an ordinary PC+4 operand read.
- [GBATEK Thumb jumps and calls](https://problemkaputt.de/gbatek-thumb-opcodes-jumps-and-calls.htm).
Use [GBATEK](https://problemkaputt.de/gbatek.htm) and ARM7TDMI documentation for further hardware work.