This was originally set to zero out of concern for any application that
is doing anti-emulation, anti-cheat, anti-VM checks.
This concern is likely unwarranted, and if any application/game starts
hitting this as a problem then we can throw an application profile at it
instead.
This makes pressure-vessel emulation checking more optimal by it not
having to do a uname dance.
The latest ARMv8.0 toolchain is implementing fetch_add with a bic rather
than an and. Not sure why they started doing this but support the
remaining logical operations in our unaligned atomics handler.
Fixes the Interpreter ARMv8.0 atomic ops.
Fixes#1742
The pause instruction is architecturally defined to be the `REP NOP`
instruction.
This allows people to use this instruction as a backwards compatible
pause without checking for CPUID support. In fact there is no way to
check if the hardware implements this as a `REP NOP` or a `PAUSE`.
If you have new enough hardware then this just ends up being a PAUSE.
Pass this PAUSE over to our host to help out applications that are
writing spin loops with a PAUSE in it, which we were deleting
previously.
This is an IR op that produces nor consumes any SSA values, but has side
effects.
Turns in to the pause instruction on x86 and yield instruction on
AArch64.
Previously if the instruction was encoded to use rsp, rbp, rsi, or rdi
then due to how these were encoded in modrm this would hit the frontend
path for writing to the high 8 bits of a 16bit register.
This is because it's instruction specific if an 8-bit modrm instruction
chooses to use the high 8-bit region or the upper 4 registers.
See the ModRM.reg section of `ModRM.reg and .r/m Field Encodings`
specifically to see what each encoding stands for. Has four different
meanings per encoding depending on instruction.
This instruction doesn't actually write to registers at 8-bit size, it
extracts an element at 8-bit size and then zero extends it to the full
GPR.
When storing to memory it always stores to memory at the size of the
element extracted.
I grepped around the instruction tables to see if there were any other
instances of this mistake. This was the only one.
Fixes#1472 and also gets Psychonauts 2 running.
