MIPS assembly: how to declare integer values in the .data section?

assembly mips
Barney picture Barney · Apr 12, 2010 · Viewed 53.4k times · Source

I'm trying to get my feet wet with MIPS assembly language using the MARS simulator.

My main problem now is how do I initialize a set of memory locations so that I can access them later via assembly language instructions?

For example, I want to initialize addresses 0x1001000 - 0x10001003 with the values 0x99, 0x87, 0x23, 0x45. I think this can be done in the data declaration (.data) section of my assembly program but I'm not sure of the syntax. Is this possible?

Alternatively, in the .data section, how do I specify storing the integer values in some memory location (I don't care where, but I just want to reference them somewhere). So I'm looking for the C equivalent of "int x = 20, y=30, z=90;" I know how to do that using MIPS instructions but is it possible to declare something like that in the .data section of a MIPS assembly program?

Answer

Michael Mrozek picture Michael Mrozek · Apr 12, 2010

You don't usually initialize specific memory locations; each section (including .data) is positioned at link time, and relocations are resolved then

To make a relocation on a data entry, you choose a name and put name: before it, so you can refer to it by name later. You specify a data block using .size value. For example:

.data
    x: .word 20
    y: .word 30
    z: .word 90

Then you can use the labels in your assembly:

.text
    lw $t0, x

Related questions

Difference between "move" and "li" in MIPS assembly language

I was practicing converting C code into MIPS assembly language, and am having trouble understanding the usage of move and li in variable assignment. For example, to implement the following C line in MIPS: int x = 0; If I understand it …

Read More
How to Calculate Jump Target Address and Branch Target Address?

I am new to Assembly language. I was reading about MIPS architecture and I am stuck with Jump Target Address and Branch Target Address and how to calculate each of them.

Read More
Greater than, less than equal, greater than equal in MIPS

Given two registers $s0, $s1, how can I convert the following pseudocode into MIPS assembly language using only the slt (set on less than) and beq and bne (branch if equal, branch if not equal) instructions. if ($s0 > $s1) { …

Read More