collapseos/blk/397
Virgil Dupras a7dcb522c2 Make br cells 1 byte wide
The 1 byte limitation has been effective for a while now, but I
hadn't made the move yet, I wanted to see if the limitation would
cause me problems. It doesn't.

Doing this now slightly facilitates the IY->BC move in z80.

Bootstrapping: if you try to recreate the CVM binary from the
previous commit with this code, you'll have bootstrapping problems.
The first bootstrap will compile a binary with 2-bytes wide cells
but branching conditionals that yields 1-byte cells. That's bad.

I got around the issue by temporarily inserting a "397 399 LOADR"
instruction in cvm/xcomp.fs, right before the xcomp overrides. This
way, I force 1-byte cells everywhere on the first compiliation,
which then allows me to apply the logic change in cvm/vm.c and have
a properly running binary.
2020-07-06 07:27:50 -04:00

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( Now we have "as late as possible" stuff. See B70 and B260. )
: _bchk DUP 0x7f + 0xff > IF LIT< br-ovfl (print) ABORT THEN ;
: DO 0x33 ( 2>R ) , H@ ; IMMEDIATE
: LOOP 0x43 ( loop ) , H@ - _bchk C, ; IMMEDIATE
( LEAVE is implemented in low xcomp )
: LITN 0x23 ( n ) , , ;
( 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) 1 ( compiled ) C,
BEGIN
WORD FIND
IF ( is word ) DUP IMMED? IF EXECUTE ELSE , THEN
ELSE ( maybe number ) (parse) LITN THEN
AGAIN ;