Ben Gamari authored Jan 06, 2020 and Marge Bot committed Jan 19, 2020

Fixes the calling convention for functions passing raw SSE-register
values by adding padding as needed to get the values in the right
registers. This problem cropped up when some args were unused an dropped
from the live list.

This folds together 2e23e1c7 and
73273be4 previously from @kavon.

Metric Increase:
    T12707
    ManyConstructors