[libre-riscv-dev] fp special functions

Luke Kenneth Casson Leighton lkcl at lkcl.net
Tue Aug 6 00:25:07 BST 2019

On Monday, August 5, 2019, Luke Kenneth Casson Leighton <lkcl at lkcl.net>

>>> note that atan(x) and atanpi(x) are just atan2(x, 1.0) and atan2pi(x,
>>> 1.0),
>>> so the atan and atanpi instructions are not needed
>> Ok great, will move them to pseudo op aliases.
> Hang on... there's no immed for loading 1.0 into an FP reg, it's one of
> the downsides of RISCV, a FLD is a hard requirement.
> Hmmm....

"Hmm" means, depending on what an implementor chooses to do, cospi may be
more efficient than cos, or vice-versa.

As a standard, we don't know which, therefore, to not impose that on
implementors, we need both (mandatory)

Does that make sense?


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