Thanks for the suggestions and apologies for not being 100% clear at the start.
I'm not looking for a dot product. I'm looking for
a[i] += b[i]*c[i] specifically for floating point
So it would be the equivalent of IPP's ippsAddProduct_32f.
The application is to apply a window to a set of samples before accumulating, to implement a weighted overlap add PFB. In my case the samples are real-valued, but I could also see a case for a and b being complex, or the case for b being 8 or 16-bit ints with a and c being floating point.