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Doesn't use self-modifying code

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The number of bytes is the same as my previous attempt, with 11 more cycles in intoHL, so although I don't feel as clever this time it's still a good optimisation. I found an equivalent method for intoDE, however relying on intoHL still allows for  `ex (sp), hl` to be used in intoIX, which is smaller and faster.
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Clanmaster21 2019-10-10 07:56:15 +01:00 committed by GitHub
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kernel/core.asm
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@ -26,20 +26,21 @@ addDE:
noop: ; piggy backing on the first "ret" we have noop: ; piggy backing on the first "ret" we have
ret ret
; copy (HL) into HL, utilising the optimised HL instructions. The first ld ; copy (HL) into DE, then exchange the two, utilising the optimised HL instructions.
; edits the address of the second ld to now be HL. ; ld must be done little endian, so least significant byte first.
intoHL: intoHL:
ld (.load+1), hl push de
.load: ld e, (hl)
ld hl, (.load) ; (.load) is just a placeholder so the inc hl
; assembler will assemble the correct opcode ld d, (hl)
ex de, hl
pop de
ret ret
intoDE: intoDE:
ex de, hl ex de, hl
call intoHL call intoHL
ex de, hl ; de not affected by intoHL, so no push/pop ex de, hl ; de preserved by intoHL, so no push/pop needed
; is necessary
ret ret
intoIX: intoIX: