Re: Vector Task Group minutes 2020/5/15

Andy Glew Si5

 Now I can add AsciiDoc  and  KramDoc artifacts to those HTML and PDF artifacts :-(

[Andrew Waterman]: We have tagged version 0.9 on github, including HTML/PDF artifacts:

From: Andrew Waterman <andrew@...>
Sent: Friday, May 15, 2020 3:23PM
To: Krste Asanovic <krste@...>
Cc: Tech-vector-ext <tech-vector-ext@...>
Subject: Re: [RISC-V] [tech-vector-ext] Vector Task Group minutes 2020/5/15


On 5/15/2020 3:23 PM, Andrew Waterman wrote:

On Fri, May 15, 2020 at 11:56 AM Krste Asanovic <krste@...> wrote:

Date: 2020/5/15
Task Group: Vector Extension
Chair: Krste Asanovic
Co-Chair: Roger Espasa
Number of Attendees: ~20
Current issues on github:

Issues discussed:

# MLEN=1 change

The new layout of mask registers with fixed MLEN=1 was discussed.  The
group was generally in favor of the change, though there is a proposal
in flight to rearrange bits to align with bytes.  This might save some
wiring but could increase bits read/written for the mask in a

#434 SLEN=VLEN as optional extension

Most of the time was spent discussing the possible software
fragmentation from having code optimized for SLEN=LEN versus
SLEN<VLEN, and how to avoid.  The group was keen to prevent possible
fragmentation, so is going to consider several options:

- providing cast instructions that are mandatory, so at least
  SLEN<VLEN code runs correctly on SLEN=VLEN machines.

- consider a different data layout that could allow casting up to ELEN
  (<=SLEN), however these appear to result in even greater variety of
  layouts or dynamic layouts

- invent a microarchitecture that can appear as SLEN=VLEN but
  internally restrict datapath communication within SLEN width of
  datapath, or prove this is impossible/expensive

# v0.9

The group agreed to declare the current version of the spec as 0.9,
representing a clear stable step for software and implementors.

We have tagged version 0.9 on github, including HTML/PDF artifacts:

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