Flushing other regs is not necessary, and breaks any ConvertNZCVToX87 use
which relies previously saved NZCV values as the flag-setting NZCV op after
the save could trigger a flush of NZCV.
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.
This has the Frontend and OpcodeDispatcher select their operating mode
depending on the incoming code segment long-mode flag.
Adds some asserts since currently it is unexpected if the configuration
changes at runtime.
This is fairly straightforward for an initial setup but isn't fully
fleshed out.
Right now FEX's x86 tables aren't setup in a way to support choosing a
different instruction decoding depending on runtime operating mode
change, so that would break in interesting ways.
Primarily this just gets FEX setup to start piping the operating mode
through from the frontend to the backend. This is a long term task, so
it is going to take a long time to iron out all the issues.
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.
this will eliminate an annoying special case in post-RA opts.
No difference proven at 95.0% confidence
Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
nothing else does this, and it complicates upcoming refactor to move away from
IR builder helpers doing IR dereferencing.
Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Ensures that blocks always start with the same state independently of predecessors
which allows independent compilation of blocks.
Starting in the X87 state is better than starting in MMX state because
MMX state is more work to initialize.
FEAT_ECV added a new synchronizing cycle counter instruction that
restrict speculation across the cycle counter access. Because it
restricts speculation, it effectively acts like an isb and load dsb.
Luckily for us, this actually matches behaviour for what rdtscp does, so
we can take advantage of it if the host supports FEAT_ECV.
Ryan Houdek