dp4 timings

gistfile1.txt

a*x + b*y + c*z + d*w

1 MUL A, X	(4, 0.5)
2 MOV X, A
3 SHUFPS A, A	(1, 1)
4 ADD A, X	(4, 0.5)
5 MOV X, A
6 SHUFPS A, A	(1, 1)
7 ADD A, X	(4, 0.5)

end-to-end latency: 14
max tput: 1 -> 1 dot

1 MUL a, x	(4, 0.5)
2 FMA a, b, y	(4, 0.5)
3 FMA a, c, z	(4, 0.5)
4 FMA a, d, w	(4, 0.5)

end-to-end latency: 16
max tput: 0.5 (2 per cycle) -> 8 dots
can trivially (just change emitted instructions) use AVX to get 16 dots with full-rate AVX

1 MUL a, x
2 MUL c, z
3 FMA a, b, y
4 FMA c, d, w
5 ADD a, c

e2e latency: 12
max tput: 1 -> 4 dots

1 MUL A, X	(4, 0.5)
2 HADD A, A	(6, 2)
3 HADD A, A	(6, 2)

e2e latency: 16
max tput: 2 -> 0.5 dots

1 DPPS A, X	(13, 1.5)

e2e latency: 13
tput: 1.5 -> 0.66 dots