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

[Nathan Gauër via cfe-commits]

Keenuts wrote:

> These should not have side effects.

I agree I'm stretching the "hasSideEffect" definition here.

> Whatever is removing the convergent needs to consider the uses (or more likely, just leave it alone)

I suspect the long-term change to change the default IR to assume convergent will take some time as it will impact many subprojects. Would you be OK with me patching the several DCE functions to not drop convergence intrinsics instead? It would solve this issue in practice, allowing us to move forward with addrspace cast legalization.


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