Re: Mask Register Value Mapping

Nick Knight

Hi Cohen,

I think the "LSB references" are carryovers from pre-0.9 versions, when MLEN > 1 was possible.

I can put together a PR to fix this later tonight, unless someone else gets to it sooner.

Nick Knight

On Tue, Sep 22, 2020 at 12:25 PM CDS <cohen.steed@...> wrote:

From 0.9 stable spec, 5.3.1, table (no number), vector masking is referred to as having LSB. This suggests, yet does not require, that the mask field for each element is greater than bit-size 1.

From same spec, 4.6.1, each element mask bit is given an explicit location, as a single bit.

And yet, for individual operations, the LSB reference is still intact - such as in section 12.4 (Vector Integer Add-with-Carry / Subtract-with-Borrow Instructions).

This suggests some reformatting may be necessary regardless of the correct interpretation:
- If the single-bit-is-always-correct interpretation is to be asserted clearly, it would make sense to remove all of the ".LSB" references when discussing mask input/output fields.
- Otherwise, section 4.6.1 would need to be overhauled to be consistent with the idea of mask entries being multi-bit-per-element.


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