RFC: Creating a more efficient sincos interface

[Alexander Monakov]

On Thu, 13 Sep 2018, Wilco Dijkstra wrote:
> What do people think? Ideally I'd like to support this in a generic way so all targets can
> benefit, but it's also feasible to enable it on a per-target basis. Also since not all libraries
> will support the new interface, there would have to be a flag or configure option to switch
> the new interface off if not supported (maybe automatically based on the math.h header).

GCC already has __builtin_cexpi for this, so I think you can introduce cexpi
implementation in libc, and then adjust expand_builtin_cexpi appropriately.

I wonder if it would be possible to add a fallback cexpi implementation to
libgcc.a that would be picked by the linker if there's no such symbol in libm?

Alexander