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.
This commit is contained in:
Clanmaster21 2019-10-10 19:44:23 +01:00 committed by Virgil Dupras
parent e259e3d02e
commit 6281e2036f

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@ -27,34 +27,29 @@ addDE:
noop: ; piggy backing on the first "ret" we have
ret
; copy (DE) into DE, little endian style (addresses in z80 are always have
; their LSB before their MSB)
intoDE:
push af
ld a, (de)
inc de
ex af, af'
ld a, (de)
ld d, a
ex af, af'
ld e, a
pop af
; copy (HL) into DE, then exchange the two, utilising the optimised HL instructions.
; ld must be done little endian, so least significant byte first.
intoHL:
push de
ld e, (hl)
inc hl
ld d, (hl)
ex de, hl
pop de
ret
intoHL:
push de
ex de, hl
call intoDE
ex de, hl
pop de
intoDE:
ex de, hl
call intoHL
ex de, hl ; de preserved by intoHL, so no push/pop needed
ret
intoIX:
push de
push ix \ pop de
call intoDE
push de \ pop ix
pop de
push ix
ex (sp), hl ;swap hl with ix, on the stack
call intoHL
ex (sp), hl ;restore hl from stack
pop ix
ret
; add the value of A into HL