Lecture Notes for Computer Architecture II - St. Cloud State University

Lecture 7 Data transfer memory register - two instructions
Manipulate data in memory
lw
load word memory to register Register Memory
sw
store word from register to memory Register Memory
I format
op rs rt address
6 bits 5 bits 5 bits 16 bit
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Problem
Consider the array A[] and the HLL statement
g = h + A[8]
Translate it into assembly language.
g = h + A[8] means Add the eighth array element to content of register h and
store the result in register g.
Solution
Step1 Assign variables to registers
g h A
$S 1 $S 2 $S 3
array A[] is in memory
eighth element of array A A[8] is in memory
starting address of A is in $S 3
Step 2 Do simple translations
lw $t 0 8($S 3 )
add $S 1 $S 2 $t 0
Problem
Translate the HLL statement A[12] = h+A[8] to assembly
A[12] = h + A[8] means Add the content of array element eight to content of
register h and store the result as 12th element of the array
Solution
Step1 Assign variables to registers
A[12] = h+A[8]
$S 3 $S 2 $S 3
Step 2 Do simple translations
lw $t 0 8($S 3 )
add $t 0 $t 0 $S 2
sw $t 0 12($S 3 )