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collapseos/blk/298
Virgil Dupras e4a4a9800d z80: Use BC as IP register instead of IY
It's a bit more inconvenient in terms of register protection (BC
is much more generally useful than IY), but it makes tight spots
such as next and execute much faster, so I think it's worth it.
2020-07-06 23:31:00 -04:00

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CODE (loop)
PC ORG @ 0x45 + ! ( stable ABI JP )
0 IX+ INC(IXY+), IFZ, 1 IX+ INC(IXY+), THEN, ( I++ )
( Jump if I <> I' )
A 0 IX+ LDrIXY, 2 IX- CP(IXY+), JRNZ, L1 BWR ( branch )
A 1 IX+ LDrIXY, 1 IX- CP(IXY+), JRNZ, L1 BWR ( branch )
( don't branch )
IX DECd, IX DECd, IX DECd, IX DECd,
BC INCd,
;CODE