cpHLDE and writeHLinDE improvements (#33)
Pretty major improvements to both of these, cpHLDE is now 5 bytes shorter and between 9 and 12 cycles faster due to branching, and writeHLinDE is now 2 bytes shorter and 21 cycles faster.
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@ -79,33 +79,22 @@ subHL:
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; Compare HL with DE and sets Z and C in the same way as a regular cp X where
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; HL is A and DE is X.
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; A is preserved through some register hocus pocus: having cpHLDE destroying
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; A bit me too many times.
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cpHLDE:
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push bc
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ld b, a ; preserve A
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ld a, h
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cp d
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jr nz, .end ; if not equal, flags are correct
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ld a, l
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cp e
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; flags are correct
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.end:
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; restore A but don't touch flags
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ld a, b
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pop bc
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push hl
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or a ;reset carry flag
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sbc hl, de ;There is no 'sub hl, de', so we must use sbc
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pop hl
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ret
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; Write the contents of HL in (DE)
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; de and hl are preserved, so no pushing/popping necessary
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writeHLinDE:
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push af
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ld a, l
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ld (de), a
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inc de
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ld a, h
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ld (de), a
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dec de
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pop af
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ex de, hl
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ld (hl), e
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inc hl
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ld (hl), d
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dec hl
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ex de, hl
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ret
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; Call the method (IX) is a pointer to. In other words, call intoIX before
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