5.135 · exercise

Predict: vectors

For each snippet, give the exact value left in the named general register. Every snippet works on lanes, then copies one lane or a total out to a w or x register.

0 of 6 correct

Predict the result

mov w9, 5
dup v0.4s, w9
mov w10, 3
dup v1.4s, w10
mul v2.4s, v0.4s, v1.4s
addv s3, v2.4s
mov w19, v3.s[0]

What value does w19 hold after the addv and the last mov? Answer in decimal.

Predict the result

movi v0.16b, 180
movi v1.16b, 90
add v2.16b, v0.16b, v1.16b
umov w19, v2.b[7]

What value does w19 hold after the add and the umov? Answer in decimal.

Predict the result

movi v0.8b, 30
movi v1.8b, 50
uqsub v2.8b, v0.8b, v1.8b
umov w19, v2.b[3]

What value does w19 hold after the uqsub and the umov? Answer in decimal.

Predict the result

// in .data:  primes: .word 7, 11, 13, 17
ldr x9, =primes
ld1 {v0.4s}, [x9]
mov w19, v0.s[1]

What value does w19 hold after the ld1 and the mov? Answer in decimal.

Predict the result

movi v0.16b, 20
addv b1, v0.16b
umov w19, v1.b[0]

What value does w19 hold after the addv of the 16 byte lanes? Answer in decimal.

Predict the result

movi v0.16b, 1
mov x19, v0.d[0]

Write x19 after the mov as 0x followed by sixteen hex digits.