git.y1.nz

commit b8dc03dcd522860e7f2809532d4b7520ec1767bb
parent 375bc8cbb59bfb366260fe2a157275db84a5b320
Author: Toxa <untoxa@mail.ru>
Date:   Tue, 13 Jul 2021 13:02:05 +0300

save a bunch of bytes in delay.s

Diffstat:
M
gbdk-lib/libc/gb/delay.s
59
++++++++++++++++++++++++++++++-----------------------------

1 file changed, 30 insertions(+), 29 deletions(-)
diff --git a/gbdk-lib/libc/gb/delay.s b/gbdk-lib/libc/gb/delay.s
@@ -10,18 +10,25 @@
 	;; 
 	;; Register used: AF, DE
 	.CPMS	= 4194/4	; 4.194304 MHz
+
+_delay::
+	LDA	HL,2(SP)	; Skip return address
+	LD	E,(HL)		; DE = delay
+	INC	HL
+	LD	D,(HL)
+
 .delay::			; 6 cycles for the CALL
 	PUSH	BC		; 4 cycles
 	CALL	.dly		; 12 cycles to return from .dly (6+1+5)
-	LD	B,#.CPMS/20-2 ; 2 cycles
+	LD	B,#.CPMS/20-2	; 2 cycles
 				; =========
 				; 24 cycles
 .ldlp:
-	JR	1$		; 3 cycles
-1$:	JR	2$		; 3 cycles
-2$:	JR	3$		; 3 cycles
-3$:	JR	4$		; 3 cycles
-4$:	JR	5$		; 3 cycles
+	PUSH	BC		; 4 cycles
+	POP	BC		; 3 cycles
+	PUSH	BC		; 4 cycles
+	POP	BC		; 3 cycles
+	NOP			; 1 cycles
 5$:	DEC	B		; 1 cycles
 	JP	NZ,.ldlp	; 3 cycles (if TRUE: 4 cycles)
 	NOP			; 1 cycles
@@ -29,10 +36,11 @@
 				; 20 cycles
 	;; Exit in 16 cycles
 	POP	BC		; 3 cycles
-	JR	6$		; 3 cycles
-6$:	JR	7$		; 3 cycles
-7$:	JR	8$		; 3 cycles
-8$:	RET			; 4 cycles
+	PUSH	BC		; 4 cycles
+	POP	BC		; 3 cycles
+	NOP			; 1 cycles
+	NOP			; 1 cycles
+	RET			; 4 cycles
 				; =========
 				; 16 cycles
 
@@ -42,32 +50,25 @@
 	LD	A,E		; 1 cycles
 	OR	D		; 1 cycles
 	RET	Z		; 2 cycles (upon return: 5 cycles)
-	LD	B,#.CPMS/20-1   ; 2 cycles
+	LD	B,#.CPMS/20-1	; 2 cycles
 				; =========
 				; 8 cycles
 .dlp:
-	JR	1$		; 3 cycles
-1$:	JR	2$		; 3 cycles
-2$:	JR	3$		; 3 cycles
-3$:	JR	4$		; 3 cycles
-4$:	JR	5$		; 3 cycles
-5$:	DEC	B		; 1 cycles
+	PUSH	BC		; 4 cycles
+	POP	BC		; 3 cycles
+	PUSH	BC		; 4 cycles
+	POP	BC		; 3 cycles
+	NOP			; 1 cycles
+	DEC	B		; 1 cycles
 	JP	NZ,.dlp		; 3 cycles (if TRUE: 4 cycles)
 	NOP			; 1 cycles
 				; =========
 				; 20 cycles
 	;; Exit in 15 cycles
-	JR	6$		; 3 cycles
-6$:	JR	7$		; 3 cycles
-7$:	JR	8$		; 3 cycles
-8$:	JR	.dly		; 3 cycles
+	PUSH	BC		; 4 cycles
+	POP	BC		; 3 cycles
+	NOP			; 1 cycles
+	NOP			; 1 cycles
+	JR	.dly		; 3 cycles
 				; =========
 				; 12 cycles
-
-_delay::
-	LDA	HL,2(SP)	; Skip return address
-	LD	E,(HL)		; DE = delay
-	INC	HL
-	LD	D,(HL)
-	CALL	.delay
-	RET

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