Using st1 to copy 3 floats from NEON register

Hi,

I am trying to copy 3 floats from NEON register v8 to a c array pOutVertex2. Unfortunately, I didn't really understand the documentation about post-index stuff. 

This is what I have; 

"st1    {v8.d}[0], [%[pOutVertex2]], #8    \t\n"    // double value output to pOutVertex2
"st1    {v8.s}[2], [%[pOutVertex2]]        \t\n"    // pOutVertex2[2]

I was expecting that the "#8" would advance the address by 2 bytes, but it doesn't.

If anyone could give me advice how to do this I would be extremely grateful,

Ed