>>>>> "DS" == Dan Sugalski <[EMAIL PROTECTED]> writes:
DS> If someone can make a compelling argument for details on how the
DS> registers should be done that should be visible to the bytecode
DS> (Like, say, a variant on SPARC's windowing system, or forcing them
DS> on the stack such that pushes and pops renumber the registers)
DS> that'd be keen. I can see the merits, but I'm not compelled one
DS> way or the other quite yet.
here is an idea. if we use a pure stack design but you can access the
stack values with an index, then the index number can get large. so a
fixed register set would allow us to limit the index to 8 bits. so the
byte code could look something like this:
16 bit op (plenty of room for growth)
8 bit register index of arg 1
8 bit register index of arg 2
...
next op code ...
literal data support is needed (read only)
either each op code knows how many args it has, or we have an end marker
(e.g 0xff which is never used as a register index).
the op code is stored in network endian order and the interpreter will
always build a 16 bit int from the 2 bytes.
we have a simple set of load literal, push/pop (multiple) registers op
codes.
each thread has its own register set.
all registers point to PMC's
passing lists to/from subs is via an array ref. the data list is on the
stack and the array ref is in @_ or passed by return().
special registers ($_, @_, events, etc.) are indexed with a starting
offset of 64, so general registers are 0-63.
this can be mmapped in, executed with NO changes, fairly easily
generated by the compiler front end, optimizable on or offline,
(dis)assembler can be simply written, etc.
simple to translate to TIL code by converting each op code to a call to
the the op function itself and passing in the register indexes or even
the PMC pointers themselves.
uri
--
Uri Guttman --------- [EMAIL PROTECTED] ---------- http://www.sysarch.com
SYStems ARCHitecture and Stem Development ------ http://www.stemsystems.com
Learn Advanced Object Oriented Perl from Damian Conway - Boston, July 10-11
Class and Registration info: http://www.sysarch.com/perl/OOP_class.html
