assembly – Greater than, less than equal, greater than equal in MIPS

assembly – Greater than, less than equal, greater than equal in MIPS

Im assuming that the pseudocode executes sequentially, so an earlier condition being true means you go there and never reach the later if statements. This makes the last branch guaranteed taken if its reached at all, so it doesnt even need to be conditional. (Also assuming that this is a MIPS without a branch-delay slot.)

slt  $t1,$s1,$s0      # checks if $s0 > $s1
bne  $t1,$zero,label1 # if $s0 >  $s1, goes to label1
beq  $s1,$s2,label2   # if $s0 == $s2, goes to label2 
# beq  $t1,$zero,label3 # if $s0 <  $s1, goes to label3
b    label3            # only possibility left

If thats not the case, youll want to implement $s0 >= $s1 as
!($s0 < $s1) with slt $t1, $s0, $s1 / beqz $t1, target, for example,
as shown in Ahmeds answer.

To implement each compare separately, without optimizing across multiple compares with earlier true conditions making later ones unreachable:

slt $at, $s1, $s0           # $s0 > $s1  as ($s1 < $s0) != 0
bne $at, $zero, label1

slt $t0, $s0, $s1           # $s0 >= $s1 as (s0<s1) == 0
beq $t0, $zero, label2

slt $t1, $s1, $s0           # $s0 <= $s1 the same but reversing the inputs
beq $t1, $zero, label3

label1:
label2:
label3:

Related:

• How to do less than or equal in Assembly Language(MIPS)? – branchless compare-into-register for things like C return (z<=y); as an int.

assembly – Greater than, less than equal, greater than equal in MIPS

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