how to change value at register in MIPS

Question

So currently at $t0 I have a variable x stored. I want $t0 to now store -x. How can I do this?

I tried

sub $t4, 0, $t0 move $t0, $t4

Any pointers as to why this says parser syntax error?

Does this answer your question? https://stackoverflow.com/questions/53568440/about-negate-a-sign-integer-in-mips — noam, Jul 14 '20 at 16:31

score 2 · Answer 1 · answered Jul 14 '20 at 22:35

2

By the formula 0-x = -x , and knowing that $0 is hard-coded to zero.

Try

sub $t0, $0, $t0

This will negate $t0 and then put it back into $t0.

answered Jul 14 '20 at 22:35

Erik Eidt

score 1 · Accepted Answer · answered Jul 14 '20 at 16:31

1

You can store -x in $t0 by using these 2 lines :

not $t0,$t0
addi $t0,$t0,1

These 2 lines basically apply 2's complement to the binary value stored in $t0.

NOTE: This might not be the most optimised choice in MIPS, but it does the job.

answered Jul 14 '20 at 16:31

NickDelta

2 Answers2