collapseos/blk/285
Virgil Dupras d041b91846 Optimize chkPS
Use EXX instead of the stack for HL protection and remove all
spurious uses of chkPS,

I wanted to inline chkPS in next because of its "tight loop" status,
but for reasons I don't understand, doing so breaks Collapse OS.
Later...
2020-05-22 23:12:03 -04:00

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CODE (?br) ( 0x67 )
HL POPqq,
HLZ,
JRZ, L2 BWR ( BR + 2. False, branch )
L1 BSET ( loop will jump here )
( True, skip next 2 bytes and don't branch )
IY INCss, IY INCss,
JPNEXT, NOP, NOP, NOP,
CODE (loop) ( 0x77 )
0 IX+ INC(IXY+), IFZ, 1 IX+ INC(IXY+), THEN, ( I++ )
( Jump if I <> I' )
A 0 IX+ LDrIXY, 2 IX- CP(IXY+), JRNZ, L2 BWR ( branch )
A 1 IX+ LDrIXY, 1 IX- CP(IXY+), JRNZ, L2 BWR ( branch )
( don't branch )
IX DECss, IX DECss, IX DECss, IX DECss, JR, L1 BWR