[PATCH] D130964: [X86][BF16] Enable __bf16 for x86 targets.

[Benjamin Kramer via Phabricator via llvm-commits]

bkramer added a comment.

In D130964#3694473 <https://reviews.llvm.org/D130964#3694473>, @rjmccall wrote:

> How are you actually implementing `__bf16` on these targets?  There isn't even hardware support for conversions.

`bf16` -> `float` is really just a bit shift. The other direction gets lowered to a libcall, compiler-rt has a conversion function with proper rounding. I added some support to make the backend promote all other arithmetic to float, but I think that's only enabled on x86 so far.


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