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Building relocatable code snippets — Parallax Forums

Building relocatable code snippets

ozpropdevozpropdev Posts: 2,793
edited 2013-10-20 20:28 in Propeller 2
Hi All,

Following on from Heaters idea on re-entrant code snippets
See http://forums.parallax.com/showthread.php/150541-Recursive-Reentrant-code-in-COG

It occurred to me that it would be very easy to run 4 x byte code interpreters in 1 cog.
The only problem is that the code snippets are aligned to a single address(codebase).
By placing a simple header in front of all snippets with some count and offset values, the snippets
can be loaded and then relocated before execution. All snippets are compiled with a 0 base address.

The attached code is a simple example of this technique.
The target platform is the DE2 board. (Uses LEDS as status etc.)

Maybe this could be used to combine OBEX code snippets.
spin
spin
quad_interpreter_v1_01.spin
9K

Comments

  • ozpropdevozpropdev Posts: 2,793
    edited 2013-10-20 17:52
    Maybe this can be added to the P3 wish list.

    LOADSNIP D,S

    This would load a snippet from hub ram to cog ram.
    By using a dedicated unused opcode as a end of snippet marker to set length.

    RELOC D,S

    Relocates last loaded snippet using the simple header technique?

    Thoughts?
  • Bill HenningBill Henning Posts: 6,445
    edited 2013-10-20 18:15
    IMHO, too complex to be an instruction
    ozpropdev wrote: »
    Maybe this can be added to the P3 wish list.

    LOADSNIP D,S

    This would load a snippet from hub ram to cog ram.
    By using a dedicated unused opcode as a end of snippet marker to set length.

    RELOC D,S

    Relocates last loaded snippet using the simple header technique?

    Thoughts?
  • SapiehaSapieha Posts: 2,964
    edited 2013-10-20 18:39
    Hi ozpropdev.

    Some time ago I proposed to Chip.

    COGLOAD
    like COGINIT --- But instead of second parameter PLACE and LENGHT to load.

    COGLOAD HubAddres, CogAddres-Lenght

    ozpropdev wrote: »
    Maybe this can be added to the P3 wish list.

    LOADSNIP D,S

    This would load a snippet from hub ram to cog ram.
    By using a dedicated unused opcode as a end of snippet marker to set length.

    RELOC D,S

    Relocates last loaded snippet using the simple header technique?

    Thoughts?
  • ozpropdevozpropdev Posts: 2,793
    edited 2013-10-20 19:03
    Bill Henning wrote: »
    IMHO, too complex to be an instruction

    Yes, RELOC would be tricky but maybe LOAD is possible.
    Sapieha wrote: »
    Hi ozpropdev.

    Some time ago I proposed to Chip.

    COGLOAD
    like COGINIT --- But instead of second parameter PLACE and LENGHT to load.

    COGLOAD HubAddres, CogAddres-Lenght

    That's the sort of thing I was thinking of.
  • Bill HenningBill Henning Posts: 6,445
    edited 2013-10-20 19:40
    How about:
       setptra  hubloc
   reps     #<num longs to load>,#1
   setinda  #cogregaddr
   rdlongc  inda++,ptra++

    Does what you want a load instruction to do, just as fast as a load instruction could :-)

    (I've used this in some of my p2 tests - works great)

    ozpropdev wrote: »
    Yes, RELOC would be tricky but maybe LOAD is possible.

    That's the sort of thing I was thinking of.
  • ozpropdevozpropdev Posts: 2,793
    edited 2013-10-20 20:11
    Bill Henning wrote: »
    Does what you want a load instruction to do, just as fast as a load instruction could :-)

    (I've used this in some of my p2 tests - works great)

    Thanks Bill

    Very elegant, compact and fast! :) I have used this too in some of my P2 stuff.

    What made me mention this idea is when you start introducing multi-tasking into the mix this
    technique starts to grow in size when taking into consideration 4 x tasks, variable length code and
    assorted source addresses. Also with only 2 IND and 2 PTR registers, conventional register indexing has to
    be employed to achieve the same result.

    As small as possible code being the mission. (Larger snippets - I'm greedy :) )

    Cheers
    Brian
  • Bill HenningBill Henning Posts: 6,445
    edited 2013-10-20 20:28
    :)

    I agree that for some cases a LOAD instruction would be nice... but personally (your mileage may vary) I don't know if it is worth the transistors - perhaps there are more general purpose improvements that would be used in more code that would make better use of the transistors?

    I hope to find time to try your invaders soon... been too busy with some other projects so far :(
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