collapseos/forth/xcomp.fs

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( Do dictionary cross compilation.
Include this file right before your cross compilation, then
set XCURRENT to CURRENT and XOFF to H@ - your target hook.
Example: H@ ' _bend - XOFF !
This redefines defining words to achieve cross compilation.
The goal is two-fold:
1. Add an offset to all word references in definitions.
2. Don't shadow important words we need right now.
New defining words establish a new XCURRENT, a copy of
CURRENT. From now on, CURRENT doesn't move. This means that
"'" and friends will *not* find words you're about to
define. Only (xfind) will.
Words overrides like ":", "IMMEDIATE" and "CODE" are not
automatically shadowed to allow the harmless inclusion of
this unit. This shadowing has to take place in your xcomp
configuration.
See example in /emul/forth/xcomp.fs
Note that this cross compilation unit is far from foolproof
and cannot cross compile any kind of code. Cross compliation
of Forth dicts is *tricky*. This unit is designed to cross
compile the core full interpreter, that is, the contents
of the "/forth" folder of the project.
Cross compiling anything else might work, but as soon as
you start defining immediates and using them on-the-fly,
things get icky.
)
VARIABLE XCURRENT
VARIABLE XOFF
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: XCON XCURRENT CURRENT* ! ;
: XCOFF 0x02 RAM+ CURRENT* ! ;
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: (xentry) XCON (entry) XCOFF ;
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: XCODE XCON CODE XCOFF ;
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: XIMM XCON IMMEDIATE XCOFF ;
: XAPPLY
DUP XOFF @ > IF XOFF @ - THEN
;
( Run find in XCURRENT and apply XOFF )
: (xfind)
XCURRENT @ SWAP ( xcur w )
_find ( a f )
IF ( a )
( apply XOFF )
XAPPLY 1
ELSE
0
THEN
;
: X' XCON ' XCOFF XAPPLY ;
: X['] X' LITN ;
( TODO: am I making the word "," stable here? )
: XCOMPILE X' LITN ['] , , ;
: X:
(xentry)
( 0e == compiledWord )
[ 0x0e LITN ] ,
BEGIN
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( DUP is because we need a copy in case it's IMMED )
WORD DUP
( cross compile CURRENT )
XCURRENT @ SWAP ( w xcur w )
_find ( w a f )
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IF
( is word )
DUP IMMED?
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IF ( w a )
( When encountering IMMEDIATE, we exec the *host*
word. )
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DROP ( w )
( system CURRENT )
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0x02 RAM+ @ SWAP ( cur w )
_find ( a f )
NOT IF ABORT THEN ( a )
XCON EXECUTE XCOFF
ELSE
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( not an immed. drop backup w and write, with
offset. )
SWAP DROP ( a )
XAPPLY
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,
THEN
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ELSE ( w a )
( not found? it might be an immediate that isn't yet defined in our
cross-compiled dict. It's alright, we can find-and-execute it. )
DROP ( w )
( system CURRENT )
0x02 RAM+ @ SWAP ( cur w )
_find ( a f )
IF
( found. It *must* be an IMMED )
DUP IMMED? NOT IF ABORT THEN
EXECUTE
ELSE
( not found. maybe number )
(parse*) @ EXECUTE LITN
THEN
THEN
AGAIN
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;