I'm not quite sure why this was merged with the master branch as it breaks a number of games, including my favorite prince of persia. What exactly does this update do besides break a number of games? Why not just revert this change to get the games working again if it can't be fixed?
It fixes Starfox Assault's crashes in JIT. Other than that, yeah, it breaks a ton of games. I'm not sure if the breaks were from the merge, or from glitches being uncovered by more accurate emulation. If that is the case, that's why it hasn't been reverted.
Would it be possible to disable the codes in this branch unless the emulator detects starfox assault being loaded?
Possibly, but that'd be a stupid idea – it'd just make the code more complex in addition to encouraging the devs to be lazy and never fix the actual issues.
Game-specific hacks aren't how you make a good emulator, anyway. It's how you end up with ZSNES and Snes9x instead of bsnes. (And if you don't know that story, you have a fuckton of reading to do.)
That's true, but we still don't know if ppc_fp actually makes it more accurate and that the games are broken due to glitches being uncovered by more accurate emulation or if it was actually more accurate before this merge.
Who is that "we" that you're talking about?
EDIT: Well ok, JMC wasn't sure so I'll just say this more clearly: It's very likely that the previous code was just completely broken and worked by accident. We have a floating point test suite and Dolphin currently fails 20-30% of the tests (even though the test suite really is not all that extensive). So basically to exaggerate a bit to show the point, we now have 95% broken code instead of 99%, and some games apparently want us to be either completely accurate or completely broken, and they'll get confused otherwise.