[libre-riscv-dev] daily kan-ban update 18may2020

Tobias Platen libre-soc at platen-software.de
Mon May 18 19:18:40 BST 2020

Today I was reading and trying to understand Chapter 2. Branch Facility.


On Mon, 18 May 2020 12:45:26 +0100
Luke Kenneth Casson Leighton <lkcl at lkcl.net> wrote:

> over the weekend i:
> * continued to help michael with the pipelines (and moved them to
> soc.fu this morning).
> * also helped cole.
> * and a new team member cesar (welcome!).
> * and got LDSTCompUnit working (maybe).
> * and had a fascinating conversation thanks to yehowshua and jeremy
> (also welcome!), which resulted in this
> (https://libre-soc.org/3d_gpu/architecture/tomasulo_transformation/).
> * and did a preliminary first cut at a pinmux for the 180nm chip.
> * and probably some other things i've forgotten about as i was up late
> enough that my neuro-electrical memory is slightly shot.
> * also this morning i reviewed the XER register and added some tables
> from p45-6 of V3.0B spec to determine when the bits are set.
> documented here https://libre-soc.org/openpower/pipeline_operands/
> this latter is going to be a bit of a pig.  if we don't treat the XER
> bits - each *bit* - as an actual separate and distinct "register" -
> protected by a Dependency Matrix column - we might as well give up -
> and no, doing an in-order design will not help on any level of
> performance because all of those operations which set XER bits *still*
> need to stall.  microwatt only gets away with this because it is only
> a 2-stage pipeline.
> today i will see how it goes because am still recovering from the
> effects of three disrupted sleep nights in a row.
> l.
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Tobias Platen <libre-soc[at]platen-software[dot]de>

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