[llvm] [X86][SimplifyCFG] Support hoisting load/store with conditional faulting (PR #96878)

[via llvm-commits]

DianQK wrote:

> > I think you need at least one backend test case to show this change? (llc also runs SimplifyCFG)
> 
> Hmm, how to let llc run simplifycfg? @DianQK I can't find simplifycfg in the log of `print-after-all`.

I think a `llc -O2` should be ok. I just believe we need a complete test case to demonstrate the final changes from this patch.

> If I add ` -start-before=simplifycfg` to the flags, it will crash. (not related this PR)
> 
> ```
> bash$ cat 1.c
> void f() {}
> 
> bash$ clang -O2 1.c -S -emit-llvm
> 
> bash$ llc --start-before=simplifycfg <1.ll
> 
> Assertion `!NodePtr->isKnownSentinel()' failed
> ```

I guess `--start-before` can only be used on MIR passes.

https://github.com/llvm/llvm-project/pull/96878