[Libre-soc-dev] scalar instructions and SVP64

[Luke Kenneth Casson Leighton]

On Wednesday, March 10, 2021, Jacob Lifshay <programmerjake at gmail.com>
wrote:

> On Tue, Mar 9, 2021, 16:50 Luke Kenneth Casson Leighton <lkcl at lkcl.net>
> wrote:
>
> > On Wednesday, March 10, 2021, Jacob Lifshay <programmerjake at gmail.com>
> > wrote:
> >
> > > https://libre-soc.org/irclog/%23libre-soc.2021-03-10.log.
> > > html#t2021-03-10T00:11:21
> > >
> > > You see why we need VL to be ignored when there aren't any vector
> > > arguments?
> >
> >
> > late (1am), the short answer is no.
> >
>
> Well, then we need to change the spec


not happening.  clarification only.



>  since a "no" answer is effectively
> unworkable from a SW perspective, as (poorly) illustrated by that example
> code.


code was flawed (wrong).  missing absolutely critical setvli vl=1


> in compilers, and most the rest of SW, vector and scalar are two
> different classes of operations/types/values/etc. SV needs to be modified
> to account for that.


too late.  not happening.


>  scalar being just element 0 of a vector is deceptively
> alluring, but is really a trap.


i said "considered to be". it is a blurred line.


>
> We can discuss in further detail after you get some sleep.


solution is to add the missing instruction to algorithm.

setvli vl=1.

then r127 is accessible.

don't like it, tough, algorithm should have arranged for result to be in
r0-31.

l.



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