Question

Consider this line of code:

(i > 0) && ((i&(i-1)) == 0)

Express this in MIPS assembler. Assume i is in register $a0. Use $t* registers for temporary storage. Use labels if you need to skip instructions. Leave the result (1 or 0) in register $v0. This can be done in 6 instructions.

Answer 1

Ans=

li $t0,0 #load 0 in $t0

subi &t1,$a0,1 # &t1=Sa0-1 ie $t1=i-1

and $t2,$a0,$t1 #$t2=$a0&$t1 ie $t2=i & (i-1)

sgt $t3,$a0,$t0 #sqt set $t3 to 1 if $a0>0 ie i>0 otherwise 0

and $t4,$t3,$t2 # $t4=$t3 and $t2 ie (i>0)&&((i &(i-1))

seq $v0,$t4,$t0 # seq set $v0 to 1 if $t4==0 otherwise 0