When BindToRegister is called, the register cache marks the relevant
guest register as no longer containing an immediate. However, subfcx was
calling GetImm after BindToRegister. This led to a lot of panic alerts
after 2995aa5be4 added an assert to GetImm to check that the passed-in
register is an immediate.
Both before and after 2995aa5be4, the actual value of the immediate
wasn't overwritten by BindForRegister, only the fact that the register
is an immediate. Because of this, the emitted code happened to work
correctly.
Like Jit64, JitArm64 now keeps track of the location of a guest register
using three booleans: Whether it is in ppcState, whether it is in a host
register, and whether it is a known immediate. The RegType enum remains
only for the purpose of keeping track of what format FPRs are stored in
in host registers.
Like the previous commit did for Jit64, JitArm64 can now handle the
combination of a value simultaneously being in a host register and being
a known immediate.
Unlike with Jit64, I've put the codegen-affecting changes in this commit
and the move away from the RegType enum in a follow-up commit. This is
in part because the design of JitArm64 made it easy to implement the
codegen-affecting changes without combining it with a big bang
refactorization, and in part because we need to keep RegType around for
keeping track of different float formats in Arm64FPRCache, complicating
the refactorization a bit.
They're now stored in ConstantPropagation instead.
I've also removed the LocationType enum. The location of each guest
register is now tracked using three booleans: Whether it is in ppcState,
whether it is in a host register, and whether it is a known immediate.
The first two of these booleans are stored in the register cache, and
the last one is stored in ConstantPropagation. This new model allows us
to handle the combination of a value simultaneously being in a host
register and being a known immediate. It also keeps track of which
registers are dirty, which was previously kept track of in X64CachedReg.
The old model maps to the new model as follows:
default host_reg immediate
Default true false false
Discarded false false false
Bound (!dirty) true false
Immediate false false true
SpeculativeImmediate true false true
[previously unrepresentable] (!dirty) true true
This commit makes the JIT set/clear the individual registers of
ConstantPropagation immediately instead of at the end of the
instruction. This is needed to prevent Jit64::ComputeRC, which reads
from a register written to earlier during the same instruction, from
reading back stale register values from ConstantPropagation in the next
commit.
To find out whether a host register needs to be unlocked, FlushRegisters
checks if the guest register is known to be a zero immediate. This works
right now, but it will stop working correctly once we gain the ability
to have a guest register be a known immediate and be in a host register
at the same time, because a register that's known to be a zero immediate
may have had a host register allocated prior to the call to
FlushRegisters. Instead, we should check whether the register is
RegType::Register after we're done calling BindForRead.
Jordan Woyak
Naim2000andJordan Woyak
JosJuiceandGitHub