control-flow instructions

beq src1, src2, label # if (src1 == src2) goto label

bne src1, src2, label # if (src1 != src2) goto label

j label # goto label

slt dest, src1, src2 # if (src1 < src2) dest <- 1

blt src1, src2, label # if (src1 < src2) goto label

# is translated to
slt tmp, src1, src2
bne tmp, $0, label 

if (a == b) {
	c += 5;
} else {
	c += 10;
}

# variable mapping
# a -> $s0
# b -> $s1
# c -> $s2
beq $s0, $s1, Equal
addi $s2, $s2, 10 # runs if not branched
j Exit # we don't want it to execute the other branch
Equal: addi $s2, $s2, 5
Exit:

# or
bne $s0, $s1, NotEqual
addi $s2, $s2, 5
j Exit
NotEqual: addi $s2, $s2, 10
Exit:

while (a == b) { // infinite loop
	c += 5;
}

# variable mapping
# a -> $s0
# b -> $s1
# c -> $s2
Loop: bne $s0, $s1, Exit # check condition on every iteration
addi $s2, $s2, 5
j Loop # go back and repeat
Exit:

for (int i = 0; i < 10; i++) {
	a += 5;
}
// can be thought of as
int i = 0;
while (i < 10) {
	a += 5;
	i++;
}

# variable mapping
# a -> $s0
# i -> $t0
add $t0, $0, $0 # initialize i to 0
addi $t1, $0, 10 # store 10 in an arbitrary register
Loop: beq $t0, $t1, Exit
addi $s0, $s0, 5
addi $t0, $t0, 1
j Loop
Exit:

do {
	a += 5;
} while (a <= b);

# variable mapping
# a -> $s0
# b -> $s1
Loop: addi $s20, $s0, 5
slt $t0, $s1, $s0 # if b < a thats our condition to exit, sets 1 if exit, 0 if repeat
beq $t0, $0, Loop # if 0 repeat

bgt r1, r2, L # r1 > r2 => r2 < r1

stl $at, r2, r1
bne $at, $0, L

bge r1, r2, L # r1 >= r2 => !(r1 < r2)

slt $at, r1, r2
beq $at, $0, L

ble r1, r2, L # r1 <= r2 => !(r2 < r1)

stl $at, r2, r1
beq $at, $0, L