Only doing the single table for review purposes. Once reviewed I will
hammer out the remaining tables.
Similar to #3320, most of the OpcodeDispatcher tables can be consteval
and made to be a compile time constant. This just requires shuffling the
code slightly. The idea is to get almost all of the table setup out of
the `InstallOpcodeHandlers` function and instead only install the
handlers that change based on 32-bit or 64-bit, just like the x86 tables
we also did.
This works fine on real Windows and is relied on by wine as SystemCall
is set to 1 in KUSER_SHARED_DATA, which causes the ntdll thunks to use
it over `syscall`
When I implemented TSC scaling originally, I chose a scale factor of 128
because it basically covered the range of devices we cared about without
going too high. I also only tested devices that had a TSC scale factor
from 19.2Mhz to 34Mhz. Turns out there is hardware that also has a 48Mhz
cycle counter, which cause them to effectively have a 6.1Ghz cycle
counter, which is kind of absurd.
Instead of a fixed scale, just calculate the amount of scaling we need
to get >= the minimum threshold of 1Ghz. This will change the shift from
7 to 5 or 6 for the faster cycle counter devices.
Of course if someone wants to know the scale factor they can still use
cpuid function 15h to know it.
Fixes#4026
Required by newer insider preview versions, I noticed many crashes with
this exception number and QueryPeformanceCounter in the backtrace,
testing with XTA found it to not be passed through and instead write
the host CNTVCT (unscaled) into RAX. No other registers seem to be
affected.
rotate right by less than 8:
ror(________________7654321076543120, ...)
rotate left by less than 8:
rol(76543210________________76543210, ...)
Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
avoid masking. apparently even modern compilers will do cute tricks with 8-bit
math in hot loops ...
Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Somewhere there was an assumption made that INC and DEC supported the
repeat prefix. This isn't actually the case, while the prefix can be
encoded, it is a nop and should only expect to be used for padding.
Adds a unittest to ensure that behaviour is as expected.
Ryan Houdek