simon_tatham added inline comments.
================ Comment at: docs/LanguageExtensions.rst:457 +that arithmetic on ``_Float16`` is performed in half-precision, thus it is not +a storage-only format. It is recommended that portable code use the +``_Float16`` type. ---------------- I think the use of "portable" here doesn't really give enough detail. From an ARM-specific perspective, source code using `_Float16` will be compiled into code that uses the hardware FP instructions for arithmetic on 16-bit FP values which were introduced in ARMv8.2, whereas `__fp16` will be compiled into code that only uses the instructions to convert 16-bit to and from 32-bit, from a much earlier architecture revision. So from that perspective, using `_Float16` will //reduce// portability, because it will make your code run (or at least run at full hardware-FP speed) on a smaller set of CPUs. On the other hand, from a source language perspective, `__fp16` is defined in an ARM-specific language extension, whereas `_Float16` is defined by the C standards committee. So if your portability concern is between entire architectures, rather than between versions of the ARM architecture, then using `_Float16` probably does help. So I think it would probably be better to make some of this explicit – don't just say one or the other type is "more portable", but say something more specific about the circumstances in which each one can be expected to work. https://reviews.llvm.org/D35295 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
