[LLVMdev] [RFC] Add a simple soft-float class

[Bruce Hoult]

On Thu, Jun 19, 2014 at 10:08 AM, Owen Anderson <resistor at mac.com> wrote:

>
> On Jun 18, 2014, at 3:05 PM, Bruce Hoult <bruce at hoult.org> wrote:
>
> On Thu, Jun 19, 2014 at 8:29 AM, Owen Anderson <resistor at mac.com> wrote:
>
>> Numerical analysis is hard.  Every numerics expert I have ever worked
>> with considers trying to re-invent floating point a cardinal sin of
>> numerical analysis.  Just don’t do it.  You will miss important
>> considerations, and you will pay the price for it later.
>>
>
> I don't think anyone is planning to use it to write climate models. Or
> simulate airflow over a 787. Or even invert a near-singular matrix.
>
> This is for jobs that *could* perfectly well be done with a simple integer
> with an implied scale factor, if you could easily and reliably predict in
> advance exactly what scale factor is appropriate for each value.
>
> This simply keeps track of the scale factor for you, so you can't get it
> wrong.
>
>
> If you couldn’t get it wrong, we wouldn’t have had so much difficulty
> getting the current version to work.
>

Non sequitur.

Statically analysing in advance the correct scale factor for all possible
situations and values is super hard.

Given two actual values to be added/multiplied etc, determining the correct
scale factor for that particular result is next to trivial.
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