[llvm] [IsolatePath] Add a pass to isolate paths with undefined behavior (PR #146791)

[Vitaly Buka via llvm-commits]

vitalybuka wrote:

> > How this is different from -fsanitize=null -fsanitize-trap=null, which is likely more precise?
> 
> This pass would run by default. The flags introduce calls to `@llvm.ubsantrap, which isn't what some people want. I'm not sure how it would be more precise as I assume they do roughly the same thing.

"Precise" in my comment means, that "miscompile"  can already happen before the pass, and I am not sure I understand why miscompile can't happen after such transformation.

Also the patch does not explain why trap() can be less desirable than the load from nullptr?
Either way should endup with termination. So why do we need something other than a trap?

https://github.com/llvm/llvm-project/pull/146791