Merge pull request 'Added abs, max, min and parity functions' (#8) from Micha_i

Looks good, will probably have to look how closely it matches the guidelines for documentation once i am done with them
but that will be a quick change

bit.asm

@@ -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

imath.asm

@@ -13,4 +13,50 @@ pub mul_low:
 		jge mull_loop
 	mov r1, r3
 	
+	jmp r13
+
+; Calculates the absolute value of the value provided in the r1 register
+; Based on Stanford's BitHacks
+; Clobbers r2
+pub abs: ; SHOULD BE INLINED
+	; mask = v >> 31
+	asr r2, r1, 31
+	; v + mask
+	add r1, r1, r2
+	; return (v + mask) ^ mask
+	xor r1, r1, r2
+	jmp r13
+
+; Calculates the minimum value of the two values provided in the r1 and r2 registers
+; Based on Stanford's BitHacks
+; Clobbers flags
+pub min: ; SHOULD BE INLINED
+	; x < y
+	cmp r1, r2
+	lsr flags, flags, 2
+	; -(x < y)
+	neg flags, flags
+	; x ^ y
+	xor r1, r1, r2
+	; (x ^ y) & -(x < y)
+	and r1, r1, flags
+	; return y ^ ((x ^ y) & -(x < y))
+	xor r1, r2, r1
+	jmp r13
+
+; Calculates the maximum value of the two values provided in the r1 and r2 registers
+; Based on Stanford's BitHacks
+; Clobbers r2 and flags
+pub max: ; SHOULD BE INLINED
+	; x < y
+	cmp r1, r2
+	lsr flags, flags, 2
+	; -(x < y)
+	neg flags, flags
+	; x ^ y
+	xor r2, r1, r2
+	; (x ^ y) & -(x < y)
+	and r2, r2, flags
+	; return x ^ ((x ^ y) & -(x < y))
+	xor r1, r1, r2
 	jmp r13