I just landed a change that might cause missed optimizations in the presence of intrinsics:
https://reviews.llvm.org/D123531
Long story short, you should annotate your (language & target) intrinsics properly. Consider DefaultIntrinsicAttrs as opposed to Intrinsic for anything that has “common” behavior.
Default intrinsic attributes include nosync and nocallback, both are needed for GlobalModRef to continue to operate as before.
Please reach out if you have questions or concerns.
~ Johannes