Atic Atac: Routine at 9EE6

9EE6: The erase path's unrolled shift chain

Seven more ADD HL,HL and ADC A,A pairs, entered part-way down by the jump at ERASE_JR, which SETUP_ERASE patches exactly as SETUP_SPRITE_DRAW patches the one before SHIFT_CHAIN. There are two because the erase and the draw run interleaved, each in its own register bank, with its own shift.
ERASE_SHIFT_CHAIN	9EE6	ADD HL,HL
	9EE7	ADC A,A
	9EE8	ADD HL,HL
	9EE9	ADC A,A
	9EEA	ADD HL,HL
	9EEB	ADC A,A
	9EEC	ADD HL,HL
	9EED	ADC A,A
	9EEE	ADD HL,HL
	9EEF	ADC A,A
	9EF0	ADD HL,HL
	9EF1	ADC A,A
	9EF2	ADD HL,HL
	9EF3	ADC A,A
	9EF4	EX DE,HL
	9EF5	EX (SP),HL
	9EF6	XOR (HL)
	9EF7	LD (HL),A
	9EF8	INC L
This entry point is used by the routine at SHIFT_CHAIN.
XOR_BYTE	9EF9	LD A,D
	9EFA	XOR (HL)
	9EFB	LD (HL),A
	9EFC	INC L
	9EFD	LD A,E
	9EFE	XOR (HL)
	9EFF	LD (HL),A
	9F00	POP DE
	9F01	DEC L
	9F02	DEC L