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.
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