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; mul 8×8 16 bit result for when you can't afford big tables ; by djmips ; ; inputs are mul1 and mul2 and A should be zero ; output is 16 bit in A : mul1 ; ; total cycles worst case = 113 ; total cycles best case = 97 ; avg = 105 ; inner loop credits supercat

MUL:

   dec mul2	;5  ; decrement mul2 because we will be adding with carry set for speed (an extra one)
   ror mul1	;5      \
   bcc b1	  ;2/3     \  Best case 8 Worst case 10
   adc mul2	;3       /

b1: ror ;2 \

   ror mul1	;5         \
   bcc b2	  ;2/3      /  Best case 10 Worst case 12
   adc mul2	;3       /   

b2: ror

   ror mul1
   bcc b3
   adc mul2  ; 10 or 12

b3: ror

   ror mul1
   bcc b4
   adc mul2  ; 10 or 12

b4: ror

   ror mul1
   bcc b5
   adc mul2   ; 10 or 12 

b5: ror

   ror mul1
   bcc b6
   adc mul2   ; 10 or 12 

b6: ror

   ror mul1
   bcc b7
   adc mul2   ; 10 or 12 

b7: ror

   ror mul1
   bcc b8
   adc mul2  ; 10 or 12

b8: ror ; 2

   ror mul1	 ; 5
   inc mul2  ; 5
   rts