Answer:
How the given instructions could be rewritten to reuse $t4 and conserve registers, assuming that no temporary values tmp1 and tmp2 are used by later instructions:
# Original instructions:
add $t1, $s0, $s1 # add s0 and s1, store result in t1
sub $t2, $s3, $s2 # subtract s2 from s3, store result in t2
add $t4, $t1, $t2 # add t1 and t2, store result in t4
mul $t3, $t4, $s4 # multiply t4 and s4, store result in t3
# Rewritten instructions:
add $t4, $s0, $s1 # add s0 and s1, store result in t4
sub $t2, $s3, $s2 # subtract s2 from s3, store result in t2
add $t4, $t4, $t2 # add t2 to t4, store result in t4
mul $t3, $t4, $s4 # multiply t4 and s4, store result in t3
Step-by-step explanation:
In this version, the original instruction that stored the result of adding $s0 and $s1 (add $t1, $s0, $s1) has been replaced with an instruction that stores the result directly in $t4. This allows us to reuse $t4 for the subsequent addition operation, rather than introducing a new temporary register like tmp1.
By consolidating the addition operations into a single instruction (add $t4, $t4, $t2), we can further conserve registers and reduce the overall number of instructions required to perform the same computation.