[PATCH] D113779: [Clang] Add mfp16, mfp16fml and mdotprod flags for ARM target features.

[David Spickett via Phabricator via cfe-commits]

DavidSpickett added a comment.

For (1) and (2) is there a need to be able to reset the architecture setting no matter the previous `march` and `<new extension options>` are?

Currently we're talking about *not* wanting having to use `-march=armv8-a+crc` but would you still want a way to reset the architecture no matter what the previous options are?

That said, applying the extra extensions to the last `-march` gives you a way to bump the base architecture which could be useful. `-march=armv8-a -add-extension=+crc -march=armv8.4-a` => armv8.4-a+crc.

For (3) I agree with your concern.

> There are a lot of supported ISA features, so there would be a lot of -m and -mno- options to document. It would become harder to separate out -m options related to architecture selection from -m options that do other things.

A rough count:

  $ clang --help | grep " \-m" | wc -l
  108

I also wouldn't want to get into a situation where we name an extension such that `-mextension` looks more like it's a general compiler option. E.g.

  -mnvj                   Enable generation of new-value jumps

"nvj" isn't far off what our extensions end up being called.


Repository:
  rG LLVM Github Monorepo

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https://reviews.llvm.org/D113779