This word puzzles me: The extra l in filll seems to be for "long" according to the patch description. But there's a hardcoded arithmetic with 4 and the parameter is documented as byte yet is being written ucell-wide. That strikes me as inconsistent.
"l" in OF refers to 32-bit memory, like in "la1+" and "rl@" for example. 64-bit is "x".
Honestly, my problem is I was unable to find documentation on filll. This suggests that it may be an non-standard addition by Apple.
It is.
Segher