[libre-riscv-dev] [isa-dev] Re: FP transcendentals (trigonometry, root/exp/log) proposal

[Allen Baum]

Argument reduction is a huge pain; maybe even slower than the evaluation
once it's finished?
HP calculators guaranteed  accuracy to 1 LSdigit in the *input* argument
(which is much, much larger than 2pi), not in the output

On Wed, Sep 11, 2019 at 12:23 PM Jacob Lifshay <programmerjake at gmail.com>
wrote:

> On Wed, Sep 11, 2019, 04:43 lkcl <luke.leighton at gmail.com> wrote:
>
>>
>> https://gpuopen.com/wp-content/uploads/2019/08/RDNA_Shader_ISA_5August2019.pdf
>>
>>>
>> someone kindly (privately) pointed out the above - table 22, p44 - and
>> apart from updating to include F16 and in some cases F64, the opcodes
>> provided *have not changed* in 11 years since the R500.
>>
>
> looking through it again, the sin/cos instructions for Radeon are actually
> sin(x * 2 * pi) and cos(x * 2 * pi), reinforcing my idea to just implement
> sinpi/cospi for GPU applications, though there is a V_TRIG_PREOP_F64
> instruction to accelerate argument reduction for f64 sin/cos.
>
> Jacob
>
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