Page 215 - ARM 64 Bit Assembly Language

Integer mathematics 203

⎫
Quotient: 0 0 0 0 0 0 0 0 ⎪
⎪
⎪
Dividend: 0 1 0 1 1 1 1 0 ⎬ Divisor > Dividend: shift Power
Divisor: 0 1 1 1 0 0 0 0 ⎪ right, shift Divisor right
⎪
⎪
Power: 0 0 0 1 0 0 0 0 ⎭
⎫
Quotient: 0 0 0 0 0 0 0 0 ⎪ Divisor ≤ Dividend:
⎪
⎪
Dividend: 0 1 0 1 1 1 1 0 ⎬ Dividend -= Divisor,
Divisor: 0 0 1 1 1 0 0 0 ⎪ Quotient += Power, shift Power
⎪
Power: 0 0 0 0 1 0 0 0 ⎭ right, shift Divisor right
⎪
⎫
Quotient: 0 0 0 0 1 0 0 0 ⎪ Divisor ≤ Dividend:
⎪
⎪
Dividend: 0 0 1 0 0 1 1 0 ⎬ Dividend -= Divisor,
Divisor: 0 0 0 1 1 1 0 0 ⎪ Quotient += Power, shift Power
⎪
Power: 0 0 0 0 0 1 0 0 ⎭ right, shift Divisor right
⎪
⎫
Quotient: 0 0 0 0 1 1 0 0 ⎪
⎪
⎪
Dividend: 0 0 0 0 1 0 1 0 ⎬ Divisor > Dividend: shift Power
Divisor: 0 0 0 0 1 1 1 0 ⎪ right, shift Divisor right
⎪
⎪
Power: 0 0 0 0 0 0 1 0 ⎭

⎫
Quotient: 0 0 0 0 1 1 0 0 ⎪ Divisor ≤ Dividend:
⎪
⎪
Dividend: 0 0 0 0 1 0 1 0 ⎬ Dividend -= Divisor,
Divisor: 0 0 0 0 0 1 1 1 ⎪ Quotient += Power, shift Power
⎪
⎪
Power: 0 0 0 0 0 0 0 1 ⎭ right, shift Divisor right
⎫
Quotient: 0 0 0 0 1 1 0 1 ⎪
⎪
⎪
Dividend: 0 0 0 0 0 0 1 1 ⎬
Power = 0: We are finished
Divisor: 0 0 0 0 0 0 1 1
⎪
⎪
⎪
Power: 0 0 0 0 0 0 0 0 ⎭
As with the previous version, when the algorithm terminates, the quotient register contains
the result of the division, and the modulus (remainder) is in the dividend register. Listing 7.4
shows the AArch64 assembly code to implement this version of the division algorithm for
64-bit numbers, and the counting method for 128-bit numbers.