Re: broken JIT support on Fedora 40

> On Wed, Apr 10, 2024 at 12:43:23PM +1200, Thomas Munro wrote:
> On Tue, Apr 9, 2024 at 10:05 PM Dmitry Dolgov <9erthalion6@gmail.com> wrote:
> >         +       /* In assertion builds, run the LLVM verify pass. */
> >         +#ifdef USE_ASSERT_CHECKING
> >         +       LLVMPassBuilderOptionsSetVerifyEach(options, true);
> >         +#endif
>
> Thanks, that seems nicer.  I think the question is whether it will
> slow down build farm/CI/local meson test runs to a degree that exceeds
> its value.  Another option would be to have some other opt-in macro,
> like the existing #ifdef LLVM_PASS_DEBUG, for people who maintain
> JIT-related stuff to turn on.

Oh, I see. I'm afraid I don't have enough knowledge of the CI pipeline,
but at least locally for me installcheck became only few percent slower
with the verify pass.

> Supposing we go with USE_ASSERT_CHECKING, I have another question:
>
> -       const char *nm = "llvm.lifetime.end.p0i8";
> +       const char *nm = "llvm.lifetime.end.p0";
>
> Was that a mistake, or did the mangling rules change in some version?

I'm not sure, but inclined to think it's the same as with noundef -- a
mistake, which was revealed in some recent version of LLVM. From what I
understand the suffix i8 indicates an overloaded argument of that type,
which is probably not needed. At the same time I can't get this error
from the verify pass with LLVM-12 or LLVM-15 (I have those at hand by
accident). To make it even more confusing I've found a few similar
examples in other projects, where this was really triggered by an issue
in LLVM [1].

[1]: https://github.com/rust-lang/rust/issues/102738