X-Git-Url: https://git.gir.st/Chiptunes.git/blobdiff_plain/5b1c6cc5356711880dc73cf95813806c2c2ad04d..362b33c918938aadd44c6516c15661c30952a584:/foo.c

diff --git a/foo.c b/foo.c
index ba748ef..fcb07cd 100644
--- a/foo.c
+++ b/foo.c
@@ -17,23 +17,40 @@ u8 o;
 u8 _;
 #define Mh o //mod3 vars
 #define Ml t // -"-
-void mod3(void) { //avail: t, o _
 //http://homepage.divms.uiowa.edu/~jones/bcd/mod.shtml
-    #define tmp _
-    //unsigned short a = ((Mh) + (Ml)) ;//&0x1ff;
-    //    Mh = a>>8; //1 bit
-    //    Ml = a;
+void mod3(void) {
+	// mod3(Mh.Ml) -> t
+	#define tmp _
 	ADD	(Ml, Mh)
 	CLR	(Mh)
-	ADC	(Mh, zero, carry)
-    Ml = (Mh<<4|Ml>>4) + (Ml & 0xF);
-    Ml = (Ml >>  2) + (Ml & 0x3);
-    Ml = (Ml >>  2) + (Ml & 0x3);
-    if (Ml > 2) Ml = Ml - 3;
-    #undef tmp
+	ADC	(Mh, zero, carry) //Mh only holds the carry bit
+	MOV	(tmp, Ml)
+	SWAP	(tmp)
+	ANDI	(tmp, 0x0f)
+	SWAP	(Mh)
+	OR	(tmp, Mh)
+	ANDI	(Ml, 0x0f)
+	ADD	(Ml, tmp)
+	MOV	(tmp, Ml)
+	LSR	(tmp)
+	LSR	(tmp)
+	ANDI	(Ml, 0x03)
+	ADD	(Ml, tmp)
+	MOV	(tmp, Ml)
+	LSR	(tmp)
+	LSR	(tmp)
+	ANDI	(Ml, 0x03)
+	ADD	(Ml, tmp)
+	CPI	(Ml, 3)
+	BRPL	(skip)
+	SUBI	(Ml, 3)
+	skip:;
+	RET
+	#undef tmp
 }
 void g(void) {
-	// g(i, x, t, o) -> t
+	// g(i, t) -> t
+	// tempvars: `x` and `_`
 	#define tmp _
 	ANDI	(t, 0x07)
 	MOV	(tmp, i2)
@@ -50,10 +67,7 @@ void g(void) {
 	  ADC X_hi, zero
 	  LD  t, X         */
 	t = (((i1&0x1f)<<8|i0)*t)>>8; //TODO
-	t >>= o; //NOTE: o == {1, 2, 4}
-	AND	(t, x)
-	ANDI	(t, 3)
-	RET
+	RET //TODO: CALL/RET is expensive; store PC in register and RJMP, then JRMP back
 };
 
 int main(void) {
@@ -84,14 +98,15 @@ int main(void) {
 		#undef tmp
 
 		//voice 1:
-		LDI	(x, 1)
 		MOV	(t, n)
 		LDI	(o, 4)
 		RCALL	g();
+	t >>= o; //NOTE: o == {1, 2, 4}
+	ANDI	(t, 3)
+		ANDI	(t, 1)
 		MOV	(acc, t)
 
 		//voice 2:
-		MOV	(x, s)
 		#define tmp o
 		MOV	(tmp, i2)
 		LSL	(tmp)
@@ -106,9 +121,40 @@ int main(void) {
 		EOR	(t, n)
 		LDI	(o, 2)
 		RCALL	g();
+	t >>= o; //NOTE: o == {1, 2, 4}
+	ANDI	(t, 3)
+		AND	(t, s)
 		ADD	(acc, t)
 
 		//voice 3:
+		MOV	(Ml, i2)
+		SWAP	(Ml)
+		ANDI	(Ml, 0xf0)
+		LSL	(Ml)
+		#define tmp Mh
+		MOV	(tmp, i1)
+		LSR	(tmp)
+		LSR	(tmp)
+		LSR	(tmp)
+		OR	(Ml, tmp)
+		#undef tmp
+		MOV	(Mh, i3)
+		SWAP	(Mh)
+		ANDI	(Mh, 0xf0)
+		LSL	(Mh)
+		#define tmp _
+		MOV	(tmp, i2)
+		LSR	(tmp)
+		LSR	(tmp)
+		LSR	(tmp)
+		OR	(Mh, tmp)
+		#undef tmp
+		RCALL	mod3();
+		ADD	(t, n)
+		LDI	(o, 2)
+		RCALL	g();
+	t >>= o; //NOTE: o == {1, 2, 4}
+	ANDI	(t, 3)
 		MOV	(x, s)
 		INC	(x)
 		#define tmp o
@@ -126,15 +172,40 @@ int main(void) {
 		LSR	(tmp)
                 MOV	(x, tmp)
 		#undef tmp
-		Ml = i2<<5 | i1>>3;
-		Mh = i3<<5 | i2>>3;
-		RCALL	mod3();
-		ADD	(t, n)
-		LDI	(o, 2)
-		RCALL	g();
+		AND	(t, x)
 		ADD	(acc, t)
 
 		//voice 4:
+		MOV	(Ml, i2)
+		SWAP	(Ml)
+		ANDI	(Ml, 0xf0)
+		LSL	(Ml)
+		LSL	(Ml)
+		#define tmp Mh
+		MOV	(tmp, i1)
+		LSR	(tmp)
+		LSR	(tmp)
+		OR	(Ml, tmp)
+		#undef tmp
+		MOV	(Mh, i3)
+		SWAP	(Mh)
+		ANDI	(Mh, 0xf0)
+		LSL	(Mh)
+		LSL	(Mh)
+		#define tmp _
+		MOV	(tmp, i2)
+		LSR	(tmp)
+		LSR	(tmp)
+		OR	(Mh, tmp)
+		#undef tmp
+		RCALL	mod3();
+		SUB	(t, n)
+		NEG	(t)
+		SUBI	(t, -8)
+		LDI	(o, 1)
+		RCALL	g();
+	t >>= o; //NOTE: o == {1, 2, 4}
+	ANDI	(t, 3)
 		MOV	(x, s)
 		INC	(x)
 		#define tmp o
@@ -152,14 +223,7 @@ int main(void) {
 		LSR	(tmp)
                 MOV	(x, tmp)
 		#undef tmp
-		Ml = i2<<6 | i1>>2;
-		Mh = i3<<6 | i2>>2;
-		RCALL	mod3();
-		SUB	(t, n)
-		NEG	(t)
-		SUBI	(t, -8)
-		LDI	(o, 1)
-		RCALL	g();
+		AND	(t, x)
 		ADD	(acc, t)
 
 		putchar(acc<<4); //TODO