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collapseos/blk/397
Virgil Dupras ed2b91411a Limit ourselves to 8-bit branching
I'm planning on going back to 8-bit branching. 16-bit br cells incur
a non-negligible penalty and, while at first 64 words (128 bytes
forward or backward) seemed a bit limiting, I now don't see why one
would ever construct such a big branch. It would be un-forthy.

Also, I looked at using BC instead of IY to hold IP and the transition
would be a lot easier with 8-bit branching.

In this commit, all I do is add overflow checks in IF. The mechanic
below doesn't change. I'll give myself some time to think it over so
that I avoid yet another back and forth.
2020-05-24 10:16:25 -04:00

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( Now we have "as late as possible" stuff )
: _bchk DUP 0x7f + 0xff > IF LIT< br-ovfl (print) ABORT THEN ;
: DO COMPILE 2>R H@ ; IMMEDIATE
: LOOP COMPILE (loop) H@ - _bchk , ; IMMEDIATE
( LEAVE is implemented in low xcomp )
: LITN 32 , , ( 32 == NUMBER ) ;
( gets its name at the very end. can't comment afterwards )
: _ BEGIN LIT< ) WORD S= UNTIL ; IMMEDIATE
: _ ( : will get its name almost at the very end )
(entry)
[ 14 ( == compiledWord ) LITN ] C,
BEGIN
WORD FIND
IF ( is word ) DUP IMMED? IF EXECUTE ELSE , THEN
ELSE ( maybe number ) (parse) LITN THEN
AGAIN ;