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mkst / maspsx

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Complete the set of instructions with two-nops afterward #15

Closed bismurphy closed 1 year ago

bismurphy commented 1 year ago

Fixes #14.

As per the CPU manual, https://cgi.cse.unsw.edu.au/~cs3231/doc/R3000.pdf, page 258 or A-46, the MFHI instruction says

"To ensure proper operation in the event of interruptions, the two instructions which follow a MFHI instruction may not be any of the instructions which modify the HI register: MULT, MULTU, DIV, DIVU, MTHI."

I have taken the liberty of adding all of these instructions to the keepout section after mflo and mfhi instructions. I also used Python's any keyword to make the line neater.

I removed mthi from the set because the SOTN decomp does not use that instruction, and because mthi and mtlo would require us to separate some of the logic for handling mflo versus mfhi, rather than the combined approach that is currently used. Therefore, ultimately, all this PR does is add the unsigned versions of mult and div to the keepout-zone.

I have confirmed that, with this change in place, the sotn-decomp project compiles successfully, so this should not introduce any regressions.

mkst commented 1 year ago

Awesome, thanks for finding the bug, and even bigger thanks for fixing it!