The type `short float`, which is proposed in ISO/IEC JTC 1/SC 22 WG 14
(C WG), is not supported by most compilers yet. But some compilers
(including gcc 7 for AArch64 and clang 6) support `_Float16`, which
is defined in ISO/IEC TS 18661-3:2015 (ISO/IEC JTC 1/SC 22/WG 14 N1945)
as an extensions for C. If it is detected in `configure`, it is used
as an alternate type of `short float` in Open MPI internal code.
This commit adds a `configure` option `--enable-alt-short-float=TYPE`.
It can be used to specify a type other than `short float` and `_Float16`
as the alternate type.
Signed-off-by: KAWASHIMA Takahiro <t-kawashima@jp.fujitsu.com>
