[clang] [llvm] Reapply "InstCombine: Introduce SimplifyDemandedUseFPClass"" (PR #74056)

[Yingwei Zheng via cfe-commits]

dtcxzyw wrote:

> > @arsenm Can you rebase this patch first?
> 
> It was already fresh, I just re-merged again with no conflicts

I don't know why it fails:
```
error: patch failed: llvm/lib/Transforms/InstCombine/InstCombineInternal.h:551
error: llvm/lib/Transforms/InstCombine/InstCombineInternal.h: patch does not apply
error: patch failed: llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp:466
error: llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp: patch does not apply
```
baseline: 7e4ac8541dcc389ca8f0d11614e19ea7bae07af7

https://github.com/llvm/llvm-project/pull/74056