[Libre-soc-isa] [Bug 1056] questions and feedback (v2) on OPF RFC ls010

bugzilla-daemon at libre-soc.org bugzilla-daemon at libre-soc.org
Mon May 29 13:52:06 BST 2023


--- Comment #21 from Luke Kenneth Casson Leighton <lkcl at lkcl.net> ---
(In reply to Paul Mackerras from comment #8)

> Saying "Simple-V has been carefully designed" sounds self-congratulatory.

mmm... ah, i know why it seems that way.  the entire writing style
of the spec is "third person impersonal".  even hinting of the
*existence* of a person or persons who put thought into the wording
is anomalous.

a style guide document is very important here.

> I
> think you're just saying that all of the state needed to resume a sequence
> of iterations after an interruption at any point is available in the SVSTATE
> SPR. Is there more to it than that?

aside from REMAP, no there isn't! (it's taken literally years to think
that through).

> You say "and the four REMAP SPRs if in use at the time". How is an interrupt
> handler to know whether the REMAP SPRs are in use?
> Saying "Whilst this initially sounds unsafe ..." 

interesting. turning uncertainty into certainty. again another one for
the style guide.

> assumes a certain ignorance
> on the part of the reader which may not be justified.

again it breaks the "third person impersonal" paradigm/style. fascinating.

>  A Programming Note
> that says something along the lines of "Interrupt handlers and function
> prologs should generally avoid using SVP64 instructions until after Simple-V
> architected state has been saved to memory", with the possible addition of
> "just as they avoid using Floating-Point, Vector or VSX instructions until
> after the associated state has been saved to memory".

which is direct, clear, and most importantly *entirely third person*.

> Saying "which is very rare for Vector ISAs" is at risk of becoming dated,
> and doesn't help our understanding of Simple-V itself.

again it's an "observation" which in turn is an "opinion" which implies
"a person" which is not third-person-impersonal.  i am spotting the
general theme here at last (hooray).

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