fs movs byte [edi], [esi]
movs byte [fs:edi], [esi]
movs byte [edi], [fs:esi]Note that code can jump past some of the prefixes. The C library on Linux does this to bypass prefixes. Reasonable assembly syntax needs to be able to describe this. You need to be able to put a label right after a prefix.
fs rep gs fs ; Note: extraneous prefix
mov eax, [fs:ebx]
> Note that code can jump past some of the prefixes. The C library on Linux does this to bypass prefixes
What's the use case for this?
I wouldn't split the prefix from the instruction and would rather use label+1 where it's absolutely required.