Some computer have explicit instructions to extract an arbitrary field from a 32-bit register and to place it in the least significant bits of a register. The figure below shows the desired operation:
Find the shortest sequence of MIPS instructions that extracts a field for the constant values i = 5 and j = 22 from register $t3 and places it in register $t0. (Hint: it can be done in two instructions.)
Construct a control flow graph (like the one shown in Figure 2.9) for the following section of C/C++/Java code:
for( i = 0; i < x; i = i + 1 ) {
y = y + i;
}
Add comments to the following MIPS code and describe in one sentence what it computes. Assume that $a0 and $a1 are used for the input and both initially contain the integers a and b, respectively. Assume that $v0 is used for the output.
add $t0, $zero, $zero
loop: beq $a1, $zero, finish
add $t0, $t0, $a0
addi $a1, $a1, -1
j loop
finish: addi $t0, $t0, 100
add $v0, $t0, $zero
The following code fragment processes two arrays and produces an important value in register $v0. Assume that each array contains 2500 words indexed 0 through 2499, that the base addresses of the arrays are held in $a0 and $a1, respectively, and that their sizes are held in $a2 and $a3, respectively. Add comments to the code and describe in one sentence what this code does. Specifically, what will be returned in $v0?
sll $a2, $a2, 2
sll $a3, $a3, 2
add $v0, $zero, $zero
add $t0, $zero, $zero
outer: add $t4, $a0, $t0
lw $t4, 0($t4)
add $t1, $zero, $zero
inner: add $t3, $a1, $t1
lw $t3, 0($t3)
bne $t3, $t4, skip
addi $v0, $v0, 1
skip: addi $t1, $t1, 4
bne $t1, $a3, inner
addi $t0, $t0, 4
bne $t0, $a2, outer