CODEWITHSUNDEEP
assemblymips
spearman008
spearman008

Reputation: 87

Assembly Language implementation of C instruction

I am trying to translate A[2*i]=A[2*k+j]; into assembly language. Array 'A' of ints (four bytes) starts at address Astart (32 bit) and i, j, k are stored in $s0, $s1, $s3.

So if I am understanding the problem correctly, I need to set the address and value of the [2*k+j] element to the [2*i] element? My confusion is modifying the addresses. This is what I have:

add $t0, $s0, $s0       #2*i
add $t1, $s3, $s3       #2*k
add $t2, $t1, $s3       #2*k+j
sw $t2, Astart
sw $t0 4(Astart)

Is this correct?

Upvotes: 1

Views: 1110

Answers (1)

Konrad Lindenbach
Konrad Lindenbach

Reputation: 4961

There are two steps necessary here, first to load from A[2*k+j] and second to store at A[2*i].

You have already calculated 2*i and 2*k+j, but you have forgotten to multiply by 4 (because the offset of each element of a 32 bit integer is 4 bytes).

The corrected code might look like:

add $t0, $s0, $s0       #2*i
add $t1, $s3, $s3       #2*k
add $t2, $t1, $s3       #2*k+j

sll $t1 $t1 2
sll $t2 $t2 2

la $t0 Astart
add $t3 $t0 $t1 #Address of A[2*k]
add $t4 $t0 $t2 #Address of A[2*k+j]

lw $t0 0($t3)
sw $t0 0($t4)

Upvotes: 1

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