[llvm] r212638 - AArch64: Better codegen for storing to __fp16.

Jim Grosbach grosbach at apple.com
Thu Jul 10 12:27:02 PDT 2014

> On Jul 10, 2014, at 10:02 AM, Tim Northover <t.p.northover at gmail.com> wrote:
>> Sort-of. It’s not wrong to go through float, but doing so does require care about rounding (which we weren’t doing).
> And vice-versa, surely? If we were asked in the IR to perform a double
> -> float -> fp16 conversion don't we have to do that unless we know
> the result isn't changed?

If we had good support for rounding modes, yes, definitely. As is it’s a bit muddled. Still best to avoid, you’re right. I think what we have now is at least marginally better than before, but we should definitely do more.

> Which is why I think this double-conversion has to be fixed in Clang:
> the input IR *is* saying to do it in two steps.

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