Improve RSP accuracy by backporting changes from simple64#17
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Backports the RSP accuracy improvements from libretro/parallel-rsp#17 (by Rosalie241, originally from simple64) into the vendored mupen64plus-rsp-paraLLEl. - rsp_dma_read/rsp_dma_write: rewrite length/count/skip handling (length = ((len & 0xFFF) | 7) + 1, skip masked 0xFF8, count + 1, DMA_CACHE & 0x1ff8, DMA_DRAM & 0xfffff8, loop ++i < count). - SP_STATUS write: per-bit SP_SET_/SP_CLR_ handling. - DPC register logic: rdp_status_write(), CMD_START/CMD_END with DPC_STATUS_START_VALID, semaphore-write-zeros. - Replace the MFC0_count timeout mechanism with the SP_SEMAPHORE path; add a MODE_EXIT run-loop exit (parallel.cpp / rsp_jit.cpp). Passes all 305 n64-systemtest RSP tests (interpreter, LLE video, parallel RSP), per the upstream PR. The local rsp_jit.cpp uint16_t(imm) immediate fix is preserved. NOTE: the upstream PR also wants a companion mupen64plus-core change (mupen64plus/mupen64plus-core#1153). The parallel-n64 core may need a matching adjustment for the new DPC START_VALID / CMD handshake.
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Backports the rsp_dma_read/rsp_dma_write correctness change from libretro/parallel-rsp#17 (by Rosalie241, originally from simple64): - length = ((len & 0xFFF) | 7) + 1 (round up to 8, matches HW) - skip = (len >> 20) & 0xFF8 (8-byte aligned skip) - count = ((len >> 12) & 0xFF) + 1 with loop bound ++i < count - DMA_CACHE masked & 0x1ff8, DMA_DRAM masked & 0xfffff8 at write time (replaces the old post-hoc &= ~0x3 / &= ~0x7 alignment) This is the subset of PR #17 that is safe for parallel-n64. It is behaviourally identical for aligned transfers (verified byte-identical RDRAM on Killer Instinct Gold and Pokemon Snap vs the pre-patch core, parallel RSP) and only differs for the misaligned skip/address edge cases exercised by n64-systemtest. The remainder of PR #17 is intentionally NOT backported: the ls.cpp 'precedence' edits are no-ops (+ already binds tighter than & in C), the per-bit SP_STATUS rewrite and the DPC START_VALID handshake are behaviourally equivalent to the existing code for normal task sequences, and the cooperative MODE_EXIT yield model is incompatible with parallel-n64's run-to-completion RSP core (it was the cause of the Killer Instinct Gold black screen that prompted the revert).
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This fixes all RSP tests with the interpreter, a LLE video plugin & parallel RSP:
n64-systemtest-rsp.zip
This also requires a mupen64plus-core patch: mupen64plus/mupen64plus-core#1153