[Libre-soc-isa] [Bug 1118] Review of fp/int moves/conversions ls006.fpintmv RFC

bugzilla-daemon at libre-soc.org bugzilla-daemon at libre-soc.org
Sat Jun 24 05:55:09 BST 2023


--- Comment #1 from Luke Kenneth Casson Leighton <lkcl at lkcl.net> ---
i cannot yet say why/where however the style of the words has to
match what is in the Power ISA spec.  "just" is not one of the
words.  it has to be an impersonal "declarative" style, more akin
to a programming language.  no pronouns *at all*

    "Let the thing equal this".

we cannot even have this: 

    "The reader should assume x y z"

because even the *implication of the existence* of another person
also indirectly implies that there was a writer with which to
have a relationship!  so not even 3rd person is permitted.

instead of

    "The reader should be familiar with the following documents:"

it has to be

    "The following are pre-requisite reading for this specification"

it is a very weird style, extremely rare outside of Specifications.

Move a 64-bit float from a FPR to a GPR, just copying bits of the IEEE 754
representation directly. This is equivalent to stfd followed by ld. As mffpr is
just copying bits, FPSCR is not affected in any way. mffpr is similar to
mfvsrd, except doesn't require VSX, which is useful for SFFS implementations.

* cut just
* cut "As mffpr is just copying bits" (which we already know from
  the first sentence), a *declaration* may be made: FPSCR is unchanged.
* the "similarity" sentence needs to be moved to "Observations"

can i suggest copying near-verbatim the text of mfvsrd?

Move a BFP32 from a FPR to a GPR, by using SINGLE to extract the standard BFP32
form from FRB and zero-extending the result to 64-bits and storing to RT. 


Moves a BFP32 from a FPR to a GPR.     (declaration of fact)

Let FRB be converted to BFP32 form,    (impersonal declaration)
zero-extended to 64-bit,               (programming style)
and the result stored in RT.           (action)

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