In order to support code caching of 32-bit libraries, any library-base
relative relocations on the guest must be transformed into FEX
relocations so e.g. absolute jumps or loads refer to the correct
location when the library is loaded at a different base address.
Turns out a simpler way was added to the docs at some point and I never
noticed.
Before:
text data bss dec hex filename
4159895 1471360 4336824 9968079 9819cf Bin/FEX
After:
text data bss dec hex filename
4157159 1471360 4336824 9965343 980f1f Bin/FEX
We were paying a large cost per Literal type that we can special case
for the two class of instructions that use a 64-bit literal.
If we packed this would get to a further 62 bytes but probably not worth
it.
Unity games crash with TSO disabled due to the SPSC GfxDevice
ThreadedStreamBuffer read/write pointer updates missing acq/rel
semantics. Rather than attempting to use heuristics to match cases like
this, which could be overzealous and hit more accesses than necessary, just
target the problem directly as this is consist across 32/64 bit Unity versions
for at least the past 10 years. Gate this behind the existing Unity mono
hacks to avoid false-positives in non-Unity games.
One set of tables for 128-bit and one set of tables for 256-bit.
This one took a bit longer since I needed to convert a few handlers over
to `Bind`. With this all of our x86 tables are costexpr so they end up
in RO mapped memory which is great.
A wild use case of union over a variant because we don't want to
increase the encoding size from 128-bit to 256-bit (because of padding).
The type of operation is encoded with the table operation type, so a
variant is unnecessary and we get to keep the 128-bit encoding.
This allows us to have "recursive" x86 table descriptions. But in
reality this is going to only be one layer deep. As this will allow the
Frontend decoder to select instruction encodings based on arch bitness
once the tables are generated correctly.
Similar to the previous far jmp, if the CS changes operating mode then
things will still explode with other FEX asserts. But this gets another
change out of my stashes.
These instructions go hand-in-hand obviously so they get implemented as
a pair.
Only the last prefix byte is retained when multiple are set. We were
accidentally generating a mask.
Additionally with 64-bit code, the legacy segment prefixes don't
overwrite if FS or GS have been set. So no weird behaviour where FS/GS
is set, a legacy prefix is used for padding, and then it "ignores" a bad
prefix by ignoring only the latest one.
Part of waitpkg is the TPAUSE instruction. This instruction gives an
RDTSC deadline to go in to a low power sleep mode with the CPU.
Semantically we can't implement umonitor and umwait with ARM's exclusive
monitor implementation, but a nop implementation is sane. Just need to
make sure to clear the pre-req flags.
This lowers power consumption of UE5 games since their job handler now
goes to a tpause based implementation instead of a `pause` spinloop
implementation.
These three options are mutually exclusive with each other and could
potentially result in invalid encodings of the table on accident.
Change over to a 2-bit bitfield to encode if the operand that consumes
the VEX option is none, destination, 1st src, or 2nd src.
This ensures the table can't ever be incorrectly encoded.
Tony Wasserka