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Re: Mask Register Value Mapping

Nick Knight
 

The existing draft used the notation v0.mask[i] in dozens of places to denote subscripting of a mask vector (bit granularity). I opted to use the existing notation uniformly, rather than switch to David's proposed v0[i].m . Happy to debate.

The .mask suffix was not previously used in unsubscripted contexts, and I did not introduce it there.

My PR is here: https://github.com/riscv/riscv-v-spec/pull/572 . Let's move further discussion to Github.

Best,
Nick Knight


On Wed, Sep 23, 2020 at 3:11 PM Andrew Waterman <andrew@...> wrote:


On Wed, Sep 23, 2020 at 2:45 PM David Horner <ds2horner@...> wrote:


On Wed, Sep 23, 2020, 15:10 CDS, <cohen.steed@...> wrote:

Word of caution: there may be a utility/readability concern if the ".LSB" text is removed, only.

This would create a phrase











vs2[i] + vs1[i] + v0[i]











which can easily be misleading to the reader - while 'i' has the same value for all three terms, the first two indicate a SEW bit field, whereas the final term indicates a single bit.



Suggestions: include a reminder that v0[i] entries are a single bit under the opening comment in the code block ("Produce sum with carry."); Set a reminder at the bottom of the description section before starting the code text, or indicate a comment on the code line "#Vector-vector-bit".


Or my preference a similar annotation that explicitly identifies it as a mast bit:
vs2[i] + vs1[i] + v0[i].m
Or similar.

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