Zve should be a strict subset of V, use new option to relax VLEN

Guy Lemieux


The way 18.1 and 18.2 currently read in the V spec is a bit confusing.

It defines Zve as "Vector extensions for Embedded Processors", and V as a "Vector Extension for Application Processor".

1) Processors vs Processor?

2) It appears the Zve extension relaxes VLEN rules which are not supported by V. This appears to be the only change that prevents Zve from being a strict subset of V.

3) I think Zve should be a strict subset of V.  The relaxation of VLEN should be an option that can be added to Zve or V. Some AP may wish to remain code-compatible with Zve, and this will make things more clear. This will clarify code generation and aid compatibility. Perhaps call this option Zvlen?

4) If there are other differences that I've missed in (3), they should be similarly separated.

Thank you,

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