GP doesn't support ftrunc natively and unfortunately one in generic
opt_algebraic is not GP-friendly either. Introduce our own lowering
that utilizes fsign() that GP supports:
ftrunc(a) = fmul(fsign(a), ffloor(fmax(a, -a)))
Tested-by: Andreas Baierl <ichgeh@imkreisrum.de>
Reviewed-by: Andreas Baierl <ichgeh@imkreisrum.de>
Signed-off-by: Vasily Khoruzhick <anarsoul@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4126>