collapseos/blk/310
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 PICK
HL POPqq,
( x2 )
L SLAr, H RLr,
SP ADDHLss,
C (HL) LDrr,
HL INCss,
B (HL) LDrr,
( check PS range before returning )
EXDEHL,
HL PS_ADDR LDddnn,
DE SUBHLss,
CC L2 @ JPccnn, ( abortUnderflow-B298 )
BC PUSHqq,
;CODE