Dan Sugalski <[EMAIL PROTECTED]> writes:
> Ah, this is incorrect. goto ADDRESS should go to an absolute address,
> period. It's for use in those times when you *have* an absolute
> address--for example when you've just fetched the address of a
> subroutine from a symbol table.
but what do i put in the symbol table? every address i have in the
symbol is, unless my understanding is severly flawed, determined at
compile time by the assembler and is relative to the start of the byte
code.
if i have code like (perl5 syntax to avoid confusion)
my $f = sub { print "hello" };
$f->();
i imagine that will become more or less: (in pseudo pasm)
closure_000:
print "hello"
ret
main:
set_sym P0, '$f', [closure_000]
fetch_sym I0, P0, '$f'
jsr I0
> Jumping from the start of the
> bytecode segment is an interesting idea, but since it's only valid
> when used to transfer control from within the current segment, you
> might as well just use goto OFFSET instead.
sorry, but i don't understand.
> --
all i want to be able to do is:
set I0, [whatever]
....
jsr I0
or
set I0, [wherever]
....
jump I0
and as far as i know i can't currently do this. and i can't use goto
OFFSET() because the pc at the time of the jump isn't known when the
register is set, although jsr [I0 - @] might sort of work, but it
can't. although the ever so contorted
set I0, [wherever]
....
add I0, I0, [-@ - 4]
bsr I0
works, i find jsr I0 slightly cleaner.
i really shouldn't be modifying goto ADDRESS(), but i should just
modify jump and jsr, hence the following patch to core.ops. This patch
has the happy side effect of giving Piers Cawley what he wants, i say
this as proof that i'm not the only lunatic who thinks this may be a
good idea :)
--
-Marco
Ring the bells that still can ring.
Forget the perfect offering.
There's a crack in everything.
It's how the light gets in.
-Isonard Cohen
post scriptum - did my patch to lib/Parrot/Assembler get lost in the haze or
was there something wrong with it?
post post scriptum - i noticed a mention of #parrot in some email,
which network is that on?
Index: core.ops
===================================================================
RCS file: /cvs/public/parrot/core.ops,v
retrieving revision 1.124
diff -u -r1.124 core.ops
--- core.ops 19 Apr 2002 01:32:40 -0000 1.124
+++ core.ops 19 Apr 2002 17:05:03 -0000
@@ -2601,8 +2601,8 @@
=item B<bsr>(in INT)
-Branch to the location specified by $1. Push the current location onto the call
-stack for later returning.
+Branch forward or backward by the amount in $1. Push the current
+location onto the call stack for later returning.
=cut
@@ -2614,26 +2614,33 @@
########################################
+=item B<jsr>(in INT)
+
=item B<jsr>()
-Jump to the location specified by register X. Push the current
-location onto the call stack for later returning.
+Jump to the address held in register $1. Push the current location
+onto the call stack for later returning.
TODO: Implement this, or delete the entry.
+inline op jsr (in INT) {
+ stack_push(interpreter, interpreter->control_stack, expr NEXT(),
+STACK_ENTRY_DESTINATION, STACK_CLEANUP_NULL);
+ goto ADDRESS(interpreter->code->byte_code + $1);
+}
+
=cut
########################################
-=item B<jump>(out INT)
+=item B<jump>(in INT)
Jump to the address held in register $1.
=cut
inline op jump(in INT) {
- goto OFFSET($1);
+ goto ADDRESS(interpreter->code->byte_code + $1);
}
=back
