Assembly multiple conditional jumps
I can't organize jumps for the following pseudo code (to Assembly 8086):
array = ...numbers set...
cl = 2
num = 0
si = 0
while(si != 11)
{
ax = 0
al = arra开发者_开发百科y[si]
// divide with assembly
div cl
if(ah = 0)
{
n+1
}
si+1
}
I've tried something like that:
.data
array db 0Fh, 45h, 0A1h, 78h, 0CFh, 0AAh, 8Fh, 19h ; Array
p db 0 ; Number of even numbers in the array
.code
xor si, si
xor cx, cx
mov cl, 2
again:
xor ax, ax
mov al, array[si]
div cl
cmp ah, 0
je eq
inc si
cmp si, 11
jne again
eq:
inc p
inc si
cmp si, 11
jne again
Do you have any ideas how to fix this code?
One way would be to do the inc p
right under the cmp ah, 0
jump and only jump over it if they're not equal:
...
cmp ah, 0
jne noteq
inc p
noteq:
inc si
cmp si, 11
jne again
Technically, what you are missing is a jump to the end just before the eq
label. Currently, if the last iteration ends in the ah
!=0 branch, it will fall through to the eq
label, increase si
to 12 and jump back to the again
label. You could also reorganize the code such that only the inc p
is jumped over, so both cases would use the same si
comparison (similar to your pseudocode).
Note, if you only want to check for even/odd numbers, just testing the lowest bit is a simpler way.
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