MIPS errors with %hi and %lo - mips

Question

lui $v0,%hi(length)
lw $v1,%lo(length)($v0)
li $v0,3 # 0x3
bne $v0,$zero,1f
div $zero,$v1,$v0
break 7
mfhi $v0
mflo $v0
sw $v0,28($fp)
lw $a1,28($fp)
lui $v0,%hi(game_over)
addiu $a0,$v0,%lo(game_over)
jal printf
nop
When I try running this for my MIPS code, it comes up with this error:
Your program produced these errors:
spim: (parser) Unknown character on line 180 of file measurement.s
lui $v0,%hi(length)
spim: (parser) syntax error on line 181 of file measurement.s
Instruction references undefined symbol at 0x00400038
[0x00400038] 0x0c000000 jal 0x00000000 [init_measure] ; 159: jal init_measure
Do I need to substitute %hi and $lo for something else in the code?
EDIT For the following code:
sw $v0,16($fp)
lui $a0,%hi(grid)
lw $v1,12($fp)
nop
move $v0,$v1
sll $v0,$v0,4
subu $v0,$v0,$v1
addiu $v1,$a0,%lo(grid)
addu $v1,$v0,$v1
lw $v0,16($fp)
And
lui $v0,%hi(column)
lb $v0,%lo(column)($v0)
nop
sw $v0,12($fp)
lui $v0,%hi(column)
addiu $v1,$v0,%lo(column)
lw $v0,8($fp)
nop
addiu $v1,$v0,-1
lui $v0,%hi(growth)
sw $v1,%lo(growth)($v0)
b true
nop
Will I be substituting %hi and % lo it in a similar manner or differently?

Answer 1

Those seem to be operators not supported by spim. %LO(label) should give you the lowest half of the address of label, and %HI(label) the upper half.
You can substitute these two instructions:
lui $v0,%hi(length)
lw $v1,%lo(length)($v0)
with this:
la $v0,length
lw $v1,0($v0)
So we use la pseudoinstruction to load the whole address of the label onto a register (in the example $v0) then you directly load its memory contents using 0 as the lw offset. Note that la pseudoinstruction would use 2 instructions for an arbitrary label address (and leave $at with the upper half address).
Also note that in your code $v0 would still hold the upper half of the label address whereas in the second snippet it will contain the whole address.
Similarily, instead of
lui $v0,%hi(game_over)
addiu $a0,$v0,%lo(game_over)
you can just issue:
la $a0, game_over
In this case, your code would end with $a0 having the address of game_over label (as in the second snippet), and $v0 holding the lower half of that address. la pseudoinstruction will leave the upper half of the label on $at