[clang] [llvm] [IR] Mark convergence intrins as has-side-effect (PR #134844)

[Matt Arsenault via cfe-commits]

arsenm wrote:

> > Turns out not really, I ran spec with this about 2 years ago and the only non-noise change was a mild improvement
> 
> Looking at the PR you linked, seems like there was still not a clear consensus on the default change no? 

Yes, there were people who are wrong and need to find the time to push this forward.

> (And I'd assume consumers like llvm-translator won't be too happy about this breaking change no?)

It's not a breaking change, it's a theoretical loss of optimization by default in unanalyzable call situations.

Even if we leave the wart of not fixing wrong by default, we still need a noconvergent attribute 


https://github.com/llvm/llvm-project/pull/134844