A (partial) port of #9481 to ARM64. This commit adds special cases for
immediate values equal to 0 or 0xFFFFFFFF, allowing for more efficient
or no code to be generated.
When a guest register is an immediate, it may be necessary to move this
value into a register. This is handled by gpr.R(), which lacks context
on how the register will be used. This leads to cases where the
immediate is written to a register, only for it to be overwritten. Take
for example this code generated by srwx:
0x5280031b mov w27, #0x18
0x53187edb lsr w27, w22, #24
gpr.BindToRegister() does have this context through the do_load
parameter, but didn't handle immediates. By adding this logic, we can
intelligently skip the write when do_load is false.
Bram Speeckaert