[Libre-soc-dev] daily kan-ban update 23nov2020

Luke Kenneth Casson Leighton lkcl at lkcl.net
Tue Nov 24 03:32:59 GMT 2020

On 11/24/20, Jacob Lifshay <programmerjake at gmail.com> wrote:
> today:
> working on a demo of how compressed instructions can be completely
> backward compatible with PowerPC64LE's current ABI. Ran out of time
> for today, will most likely work on it more tomorrow.


was it clear about the fact that the two encodings require "state" to
distinguish them? i.e. even though they are both LE compatible we
cannot possibly allow the two encodings to intermingle without an
instruction to swap the mode?

question.  if you have:

* a stream of standard LE v3.0B instructions
* aa stream of half-word swapped instructions

is it possible only from the stream to detwrmine which encoding is

this is a really important non-rhetorical  question that i would
appreciate if you could answer plainly yes or no.

we can then analyse what to do next.

> See "Demo of encoding that's backward-compatible with PowerISA v3.1 in
> both LE and BE mode" in
> https://libre-soc.org/openpower/sv/16_bit_compressed/

ah that looks really good athough it looks like it should be in
https://libre-soc.org/openpower/sv/major_opcode_allocation/  (for now)

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