Instruction Prefix EEEE -> Prefix condition PPPP ?
TonyB
Posts: 73
in Propeller 2
I've never used the Propeller and I've been reading the P2 Documentation and Instructions (v18) for the first time today.
Getting rid of CCCC to avoid confusion with carry seems a good idea to me but EEEE doesn't suggest a condition that is prefixed.
Getting rid of CCCC to avoid confusion with carry seems a good idea to me but EEEE doesn't suggest a condition that is prefixed.
Comments
I agree, but what to call it, then?
I used EEEE for 'execution condition'.
Using CCCC or EEEE or PPPP alerts that there are 4 bits in the field, but dos not try to identify individual bits.
Another name could be COND, also 4 char/bits, but tag is now a real word, closer to assembler use.
Whatever is used, is going to need some expansion explanation.
I see Chip uses Instruction Prefix later in the Docs
Adding a header tag to the encoding column may be enough ?
EEEE = Instruction Prefix, see line 385..
or
COND = Conditional Instruction Prefix, see line 385..
or
PRFX = Conditional Instruction Prefix, see line 385..
Choose the easiest to read/scan ?
or simply
PPPP = Prefix
Putting the conditions are the start of the line will be strange at first for a lot of newcomers used to other microprocessors. Moving the bits formerly known as condition codes to the msb's helps reinforces the idea that they are prefixes. P for prefix ...
Maybe, but the Conditional aspect is more important than the Prefix one, P alone makes it sound like some mandatory prefix ?
Most assembler lines have no prefix at all (encoded by assembler with COND = 1111)
That's a good idea.