Consider replacing ternary expressions with multiplicative conditionals

[jhp-lanl]

Per @Yurlungur we may want to replace

x = cond ? a : b

with

x = (cond) * a + (1 - cond) * b

to reduce branching and improve GPU performance.

This might be premature optimization, but it also might be a good way to specify default handling of NaNs as well.

[dholladay00]

This definitely seems like a premature optimization and I'd really want to see performance data to know which method to prefer. I'm not convinced that one expression is better than the other WRT performance.

[Yurlungur]

I am fine not acting on this now. That transformation has shown good performance in riot, so that's where my intuition is coming from.

That said the improvement was actually on intel, not GPUs.