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.

kernel/core.asm

@@ -12,7 +12,6 @@
 ; *** DATA ***
 ; Useful data to point to, when a pointer is needed.
 P_NULL:		.db 0
-
 ; *** REGISTER FIDDLING ***
 
 ; add the value of A into DE
@@ -27,34 +26,28 @@ addDE:
 noop:				; piggy backing on the first "ret" we have
 	ret
 
-; copy (DE) into DE, little endian style (addresses in z80 are always have
+; copy (HL) into HL, utilising the optimised HL instructions. The first ld
-; their LSB before their MSB)
+; edits the address of the second ld to now be HL.
-intoDE:
+intoHL:
-	push	af
+	ld (.load+1), hl
-	ld	a, (de)
+.load:			
-	inc	de
+	ld hl, (.load)		; (.load) is just a placeholder so the
-	ex	af, af'
+				; assembler will assemble the correct opcode
-	ld	a, (de)
-	ld	d, a
-	ex	af, af'
-	ld	e, a
-	pop	af
 	ret
 
-intoHL:
+intoDE:
-	push	de
 	ex de, hl
-	call	intoDE
+	call intoHL
-	ex	de, hl
+	ex de, hl		; de not affected by intoHL, so no push/pop 
-	pop	de
+				; is necessary
 	ret
 
 intoIX:
-	push	de
+	push ix
-	push	ix \ pop de
+	ex (sp), hl		;swap hl with ix, on the stack
-	call	intoDE
+	call intoHL
-	push	de \ pop ix
+	ex (sp), hl		;restore hl from stack
-	pop	de
+	pop ix
 	ret
 
 ; add the value of A into HL