Suppress pass-failed warnings/errors

[SoniEx2]

Fixes #2403

simde obviously requests loop vectorization, but we shouldn't fail for missed vectorizations as we're more focused on testing for correctness.

[sbc100]

Can you give an example of the failure messages you are seeing?

Why would llvm be generating warning about loop vectorization failure unless we are explicitly asking to run that pass? (are we doing that?)

[SoniEx2]

see also simd-everywhere/simde#1151

[sbc100]

But if we aren't seeing these warning when we build/run our tests why suppress the warning here? If test/run-spec-wasm2c.py is generating warning why don't we see them in our CI?

[SoniEx2]

because our clang is too old (it's using clang 14)

(this is because we're stuck on ubuntu 22.04 until the next LTS comes out)

[sbc100]

because our clang is too old (it's using clang 14)

You mean the clang we use in the wabt CI?

(this is because we're stuck on ubuntu 22.04 until the next LTS comes out)

In that case I think we should combine this change some amount of CI test for recent versions of clang.

Do you know which version of clang is needed in order to reproduce this warning?

[SoniEx2]

the macos-14 runner (apple silicon, which we aren't using) reproduces the warning, but it also fails due to the other thing. (unimplemented simd read intrinsics or something?)

we could also wait a few months for CI to start failing.

we know it definitely reproduces on clang 17

[sbc100]

This sounds like maybe a bug in clang, no? Why would it tell the user about some internal pass failure, unless the user somehow opts into that pass specifically... are we somehow doing that in the generated code?

[SoniEx2]

are we somehow doing that in the generated code?

Yes. simde expands pragma clang loop vectorize(enable) which requests that pass specifically:

https://github.com/simd-everywhere/simde/blob/cf68aaf07105a71db9aa7dc076e9b75a701bf58c/simde/simde-common.h#L379

[sbc100]

are we somehow doing that in the generated code?

Yes. simde expands pragma clang loop vectorize(enable) which requests that pass specifically:

https://github.com/simd-everywhere/simde/blob/cf68aaf07105a71db9aa7dc076e9b75a701bf58c/simde/simde-common.h#L379

Thanks for context. I think that was what I was missing.

How about adding a comment here such as: # simde explicitly enables xxx via pragma yyy, which means clang can generate warnings when this pass fails.