[Libre-soc-dev] qemu cosimulation

Luke Kenneth Casson Leighton lkcl at lkcl.net
Fri Jun 4 03:05:38 BST 2021

crowd-funded eco-conscious hardware: https://www.crowdsupply.com/eoma68

On Fri, Jun 4, 2021 at 1:34 AM Jacob Lifshay <programmerjake at gmail.com>

> I used the test case you have in that unit test, demonstrating that doing
> the multiplication as f32 gives exactly the same answer as doing the
> multiplication as f64 then rounding to f32 (this only works for some fp
> ops):
> See the fmuls_1 and fmuls_2 functions:
> https://rust.godbolt.org/z/6asaf6Mq6 (note the dbgf! macro prints the
> input
> then returns it unmodified)
> I also tested on a Power9 and it gives identical results.

arse.  qemu.  then that's a non-compliance bug in qemu.

this is going to be a damn nuisance.  may have to get
power-gem5 operational instead. which i didn't want to do
right now.

So, I don't know what weird stuff you thought gave different results, but
> it does work the way I am advocating (doing the arithmetic as f32).
> Note this is an exactly half-way rounding case, so if your using
> ieee754fpu.git it may have bugs.

no hardware involved.


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