Added abs, max, min and parity functions

2026-08-31 01:17:50 +02:00
parent 0d9958e850
commit b99532b980
2 changed files with 68 additions and 0 deletions
@@ -70,3 +70,25 @@ pub popc:
 	add r4, r4, r2
 	and r1, r4, 0xFF ; mask out end result in lowest byte
 	jmp r13
+
+; Calculates the parity of the value provided in the r1 register
+; i.e. 0 means even bits set, 1 means odd bits set
+; Based on Stanford's BitHacks
+; Clobbers r2
+pub parity:
+	; v ^= v >> 16;
+	lsr r2, r1, 16
+	xor r1, r1, r2
+	; v ^= v >> 8;
+	lsr r2, r1, 8
+	xor r1, r1, r2
+	; v ^= v >> 4;
+	lsr r2, r1, 4
+	xor r1, r1, r2
+	; v &= 0xf;
+	and r1, r1, 0x0F
+	; return (0x6996 >> v) & 1;
+	mov r2, 0x6996
+	lsr r1, r2, r1
+	and r1, r1, 0x01
+	jmp r13