X30 is used in fewer situations than the comment was claiming.
(I think that when I wrote the comment I was counting the use of X30
as a temp variable in the slowmem code as clobbering X30, but that
happens after pushing X30, so it doesn't actually get clobbered.)
This is used when fastmem isn't available. Instead of always falling
back to the C++ code in MMU.cpp, the JIT translates addresses on its
own by looking them up in a table that Dolphin constructs. This is
slower than fastmem, but faster than the old non-fastmem code.
This is primarily useful for iOS, since that's the only major platform
nowadays where you can't reliably get fastmem. I think it would make
sense to merge this feature to master despite this, since there's
nothing actually iOS-specific about the feature. It would be of use
for me when I have to disable fastmem to stop Android Studio from
constantly breaking on segfaults, for instance.
Co-authored-by: OatmealDome <julian@oatmealdome.me>
This refactorization is done just to match the order that I made
WriteToHardware use in 543ed8a. For WriteToHardware, it's important that
things like MMIO and gather pipe are handled before we reach a special
piece of code that only should get triggered for writes that hit memory
directly, but for ReadFromHardware we don't have any code like that.
This fixes a problem where Dolphin could crash if a non-translated
read crossed the end of a physical memory region.
The same change was applied to WriteToHardware in ecbce0a.
In a code block where a guest register is accessed at least twice and the
last access is a write and the register is not discardable immediately
after the second-to-last instruction (perhaps there is an instruction
in between that can cause an exception), currently Dolphin's JITs will
flush the register after the second-to-last instruction.
It would be better if we replaced the flush after the second-to-last
instruction with a flush that only happens if the exception path is
taken. This change accomplishes that by marking guest registers as
"in use" not just when they are used as inputs but also when they are
used as outputs, preventing the loop in DoJit from flushing the
register until after the last access.
This makes codegen faster (by perhaps 10-20% in the case of Jit64,
I didn't measure too closely), which helps speed up NBA Live 2005
a little. But the game still has serious performance issues.
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