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core: preserve A in cpHLDE

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This commit is contained in:
Virgil Dupras 2019-07-23 22:59:10 -04:00
parent 1c6a7caeae
commit 985d56ca5a
1 changed files with 11 additions and 2 deletions
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13
kernel/core.asm
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@ -84,13 +84,22 @@ subHL:
; Compare HL with DE and sets Z and C in the same way as a regular cp X where
; HL is A and DE is X.
; A is preserved through some register hocus pocus: having cpHLDE destroying
; A bit me too many times.
cpHLDE:
push bc
ld b, a ; preserve A
ld a, h
cp d
ret nz ; if not equal, flags are correct
jr nz, .end ; if not equal, flags are correct
ld a, l
cp e
ret ; flags are correct
; flags are correct
.end:
; restore A but don't touch flags
ld a, b
pop bc
ret
; Write the contents of HL in (DE)
writeHLinDE: