[PATCH] D109215: [RISCV] Fix arch sring parsing for multi-character extensions

[Alex Bradbury via Phabricator via llvm-commits]

asb added a comment.

In D109215#2981746 <https://reviews.llvm.org/D109215#2981746>, @jrtc27 wrote:

> RISC-V manual, §27.6:
>
>> Standard extensions can also be named using a single “Z” followed by an alphabetical name and an optional version number.
>
> Numbers are not in the alphabet, therefore they cannot be part of a valid name. If you start allowing numbers in the extension name then this introduces the need for all kinds of weird edge cases to remove ambiguity, but leads to huge amounts of confusion. Just don't do it.

+1. on this. Thanks for working on this patch @eopXD, but per the current spec, zvl128b isn't a legal extension name. I suppose ISA manual could be updated to allow extensions that include numbers as long as they end with an alphabetical character (other than p!) but as Jessica says, it gets messy...

I've created an issue on the V extension GitHub repo to discuss further https://github.com/riscv/riscv-v-spec/issues/729


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