AMD Typewriter x86 사용자 설명서

22007E/0—November 1999

;In: 

EDX = dividend

;Out:

EDX = quotient

XOR EDX, EDX;0
CMP EAX, d

;CF = (dividend < divisor) ? 1 : 0

SBB EDX, -1 ;quotient = 0+1-CF = (dividend < divisor) ? 0 : 1

In cases where the dividend does not need to be preserved, the
division can be accomplished without the use of an additional
register, thus reducing register pressure. This is shown in
example 2 below:

:

;In:  EDX = dividend
;Out: EAX = quotient
CMP EDX, d  ;CF = (dividend < divisor) ? 1 : 0
MOV EAX, 0  ;0
SBB EAX, -1 ;quotient = 0+1-CF = (dividend < divisor) ? 0 : 1

Integer division by a constant can be made faster if the range of
the dividend is limited, which removes a shift associated with
most divisors. For example, for a divide by 10 operation, use the
following code if the dividend is less than 40000005h:

MOV

EAX, dividend

MOV

EDX, 01999999Ah

MUL

EDX

MOV

quotient, EDX

These algorithms work if the divisor is positive. If the divisor is
negative, use abs(d) instead of d, and append a ‘NEG EDX’ to
the code. The code makes use of the fact that n/–d = –(n/d).

;IN:

d = divisor, 2 <= d < 2^31

;OUT: a = algorithm
;

m = multiplier

;

s = shift count

;algorithm 0
MOV   EAX, m 
MOV   EDX, dividend
MOV   ECX, EDX
IMUL  EDX   
SHR   ECX, 31
SAR   EDX, s
ADD   EDX, ECX           ;quotient in EDX