On Sat, Nov 25, 2023 at 12:03:56PM +0000, Tamar Christina wrote:
> For the C99 versions of copysign, expand_COPYSIGN has optimized expansions
> inplace.
> One of the hooks there forces it to abs/neg. There is also code in place
> for if the target
> prefers integer expansion over floating point one etc.
I thought the simplify-rtx.cc canonicalization of copysign (x, negative) to
(neg (abs ()) was disabled shortly after your change.
> However the issue here is that IFNs at the moment only support direct
> expansion. That is, you need an optab to get the
> rewriting done. So you have a catch 22, unlike the C99 versions which have a
> libcall fallback.
For POPCOUNT I've introduced recently a way to provide custom expand_*
function and decide there what optimizations to use, even when it otherwise
is an integral unary optab ifn.
Jakub
