Optimised intoXX functions (#19)
* Optimised intoXX functions Rewrote intoXX functions to mainly rely on intoHL, as the HL instructions are smaller and faster. Also removed some redundant push and pop instructions. I edited the given unit tests to test these, and they seem to work as expected. * Doesn't use self-modifying code 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. * Update core.asm * Tried harder to follow coding convention Added tabs between mnemonics and operands, and replaced a new line I accidentally removed.
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@ -27,34 +27,29 @@ addDE:
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noop: ; piggy backing on the first "ret" we have
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ret
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; copy (DE) into DE, little endian style (addresses in z80 are always have
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; their LSB before their MSB)
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intoDE:
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push af
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ld a, (de)
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inc de
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ex af, af'
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ld a, (de)
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ld d, a
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ex af, af'
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ld e, a
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pop af
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; copy (HL) into DE, then exchange the two, utilising the optimised HL instructions.
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; ld must be done little endian, so least significant byte first.
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intoHL:
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push de
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ld e, (hl)
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inc hl
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ld d, (hl)
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ex de, hl
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pop de
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ret
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intoHL:
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push de
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ex de, hl
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call intoDE
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ex de, hl
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pop de
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intoDE:
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ex de, hl
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call intoHL
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ex de, hl ; de preserved by intoHL, so no push/pop needed
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ret
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intoIX:
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push de
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push ix \ pop de
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call intoDE
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push de \ pop ix
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pop de
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push ix
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ex (sp), hl ;swap hl with ix, on the stack
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call intoHL
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ex (sp), hl ;restore hl from stack
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pop ix
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ret
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; add the value of A into HL
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