Dolphin FPU Inaccuracies - Printable Version +- Mario Kart Wii Gecko Codes, Cheats, & Hacks (https://mariokartwii.com) +-- Forum: Hacks/Modding (https://mariokartwii.com/forumdisplay.php?fid=14) +--- Forum: Coding & Hacking General Discussion (https://mariokartwii.com/forumdisplay.php?fid=23) +--- Thread: Dolphin FPU Inaccuracies (/showthread.php?tid=1886) |
Dolphin FPU Inaccuracies - Vega - 08-13-2021 Dolphin FPU Inaccuracies Below is a code that will show an output on your screen. Due to how Dolphin doesn't emulate the FPRs and certain floating point instructions 100% correctly, the code will produce different results on Real Hardware vs Dolphin. Code is PAL only, start a race/battle, pick up a box. C27BA164 00000021 7D98E2A6 758C2000 418200F8 3FE08000 63FF1500 38600000 907F0008 3C00C020 3C604084 3C804080 60008000 6063C000 60840000 901F0000 907F0004 909F000C C01F0000 D81F0010 C83F0004 D03F0018 C05F000C FC001034 F01F001C 80BF0010 80DF0014 80FF0018 811F001C 813F0020 4800004D 52657375 6C74730A 0A6C6673 2B737466 64206653 3A202530 38582025 3038580A 6C66642B 73746673 2066533A 20253038 580A6672 73717274 65206644 3A202530 38582025 30385800 7C8802A6 387F0030 4CC63182 3D808001 618C1A2C 7D8903A6 4E800421 4800000D FFFFFFFF 000000FF 7C6802A6 38830004 38BF0030 3D80801A 618C4EC4 7D8903A6 4E800420 90770020 00000000 The code manipulates 3 Dolphin Inaccuracies. Those are Dolphin not emulating the stfd, lfd, and frsqrte instructions correctly when the PSE bit is high in the HID2 special purpose register. Nothing to be concerned about as this bug can occur as a result of poorly handwritten assembly. Thus it won't effect how Wii games run on Dolphin, well I assume so at least. Source: Code: #PAL = 807BA164 In conclusion, why it may be easy to blame the devs and/or contributors of Dolphin for these inaccuracies, you have to take into account that the behavior of stfd, lfd, & frsqrte (when HID2 PSE is high), is completely absent within the Broadway Manual (well at least absent in both leaked versions, 0.8 and 1.0). RE: Demonstrating the mishandling of FPRs by Dolphin - Leseratte10 - 08-19-2021 Has this been reported to the Dolphin developers already? Who knows, there might still be obscure games using code like that. Or is it 100% guaranteed that no compiler will emit code like this? RE: Demonstrating the mishandling of FPRs by Dolphin - Vega - 08-19-2021 This exact bug has not been reported afaik. I cannot think of a way on how a compiler can produce botchy/improper Assembly (like the source used in the code) to replicate this bug. |