Inline __ieee754__rem_pio2f(). On amd64 (A64) and i386 (A64), this

Inline __ieee754__rem_pio2f().  On amd64 (A64) and i386 (A64), this
gives an average speedup of about 12 cycles or 17% for
9pi/4 < |x| <= 2**19pi/2 and a smaller speedup for larger x, and a
small speeddown for |x| <= 9pi/4 (only 1-2 cycles average, but that
is 4%).

Inlining this is less likely to bust caches than inlining the float
version since it is much smaller (about 220 bytes text and rodata) and
has many fewer branches.  However, the float version was already large
due to its manual inlining of the branches and also the polynomial
evaluations.