RISC-V has a draft extension for half-precision proposed last year,
so we think adding a new type for that would be great to make this
easier to use that extension.
We found there is _Float16 and __fp16 types are supported on GCC and
Clang, but _Float16 has C++ supporting issue on GCC site, so we think
support both type is a reasonable choice to us.
However we would like have slight different behavior for __fp16 other
than ACLE: The evaluation format of __fp16 set same as _Float16,
which means no promotion are performed if there is no hardware half-precision
The only concern to us is it's defined differnt with clang's document,
so we would put this RFC patch here, to make sure it's OK for make
__fp16 has differnt behavior between differnt targets.
This patch contain document change only, implementation would be in
Co-authored-by: Evandro Menezes <email@example.com>