collapseos/blk/398
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

13 lines
327 B
Plaintext

: IF ( -- a | a: br cell addr )
0x3f ( ?br ) , H@ 1 ALLOT ( br cell allot )
; IMMEDIATE
: THEN ( a -- | a: br cell addr )
DUP H@ -^ _bchk SWAP ( a-H a ) C!
; IMMEDIATE
: ELSE ( a1 -- a2 | a1: IF cell a2: ELSE cell )
0x3b ( br ) ,
1 ALLOT
[COMPILE] THEN
H@ 1- ( push a. 1- for allot offset )
; IMMEDIATE