Return Spiral Indexes!
JavaScript (ES7), 50 bytes
This is using a slightly modified version of the formula that I've used and explained in this post.

x=&gt;y=&gt;(i=4*(x*x&gt;y*y?x:y)**2)-(x&lt;y||-1)*(i**.5-x-y)

Try it online!
or Try a version that displays the spiral.