Re: [RFC PATCH 0/4] Idea for using hardfloat in PPC

[Alex Bennée]

Richard Henderson <richard.henderson@linaro.org> writes:

> On 10/5/22 07:37, Víctor Colombo wrote:
>> However, the impact in performance was not the expected. In x86_64 I
>> had a small 3% improvement, while in a Power9 machine there was a small
>> performance loss, as can be seem below (100 executions).
>> |        | min [s] | max [s] | avg [s] |
>> | before | 122.309 | 123.459 | 122.747 |
>> | after  | 123.906 | 125.016 | 124.373 |
>
> I hope this is because you didn't handle the most common cases: add, sub, 
> mul, div.
>
> The logic seems plausible, as far as it goes, and would work for the
> FR bit as well which afair isn't handled at all at the moment.  I'll
> review properly in a little while.

I wonder if this is something that could be generalised and pushed up
into the fpu stuff itself. We could after all cache the op and
decomposed parameters here in a generic way. The trick would be working
out how to do that without slowing down the current common case.

Is ppc unique in not persisting the inexact flag from previous
operations?

>
>
> r~


-- 
Alex Bennée