MIPS loading values from address

Question

I am learning MIPS Assembly language and I was wondering how I can load values from an address. For example I want to store the memory address 0x10010000 in $t2. 0x10010000 has in it values 12,33,70,70(0x10010000 - 0x10010003). 0x10010004 would have something like F4,A6, 12,99((0x10010004 - 0x10010007).

I have this so far

add $t3, $t2, $zero
lw $t4, 0($t3)
add $t5, $t4, -6
sw $t5, 4($t2)

but don't know how I would "initialize" $t2

Erik Eidt Erik Eidt · Accepted Answer · 2020-10-16T03:53:39

Put a label on your data, and use la $t2, labelName.

Alternately you can load 0x10010000 into $t2 using lui, which loads 16-bits worth of constant into the upper part of the registers — here you'd use lui $t2, 0x1001.

If you needed non-zero for the low 16 bits (as in, say, for 0x10010400), you finish them after the lui with an ori (e.g. ori $t2, $t2, 0x0400).

Also, la is a pseudo instruction. It will generally expand into two instructions, and, you'll be able to see that when you assemble your code (e.g. in MARS or QtSPIM).

MIPS loading values from address

1 Answers