Question

I’m trying to learn MIPS Assembly by learning MIPS Assembly Language Programming. In the book I have this code(extracted from the page 37 of the book):

.data
prompt: .asciiz "\n Please Input a Value: "
bye: .asciiz "\n Bye!"
.globl main
.text

main:
   li $v0, 4
   la $a0, prompt
   syscall

   li $v0, 5
   syscall
   beqz $v0, end
   move $a0, $v0
   li $v0, 1
   syscall
   b main


end:
   li $v0, 4
   la $a0, bye
   syscall

   li $v0, 10
   syscall

I have a cross-compiled binutils targeted to mips-elf, but when I’ve tried to Assemble the code, I got some errors

ubuntu@eeepc:~/Desktop$ mips-elf-as test-mips.asm
test-mips.asm: Assembler messages:
test-mips.asm:8: Error: illegal operands ‘li’
test-mips.asm:9: Error: illegal operands ‘la’
test-mips.asm:12: Error: illegal operands ‘li’
test-mips.asm:14: Error: illegal operands ‘beqz’
test-mips.asm:15: Error: illegal operands ‘move’
test-mips.asm:16: Error: illegal operands ‘li’
test-mips.asm:22: Error: illegal operands ‘li’
test-mips.asm:23: Error: illegal operands ‘la’
test-mips.asm:26: Error: illegal operands ‘li’
ubuntu@eeepc:~/Desktop$

I’m using x86 Ubuntu Hardy Herron to cross-compile to MIPS

What is wrong?

Answer 1

I think the problem is that you’re using an older version of binutils which does not support the symbolic names for MIPS registers.

binutils 2.17 (as referenced in the cross-compilation instructions you linked to) does not understand $v0, $a0 etc. (see this question).

However, if you are building the tools yourself anyway, a good solution would be to move to a later version of binutils: versions from 2.18 onwards do support symbolic register names. Your example assembles correctly with either 2.18 or the latest version, 2.20.