[clang] [llvm] [ValueTracking] Add dominating condition support in computeKnownBits() (PR #73662)

[via cfe-commits]

XChy wrote:

> Here is another thing that I noticed after this patch: https://godbolt.org/z/1P7bnKGjh
> 
> So early instcombine is eliminating an `and` operation (in the foo example), resulting in simplifycfg not being able to collapse the control flow any longer.

I don't think it's a profitable transformation in simplifycfg with larger amount of instructions. In x86, backend generates much larger code for the example with collapsed cfg: https://godbolt.org/z/YP9GjjP8c.


https://github.com/llvm/llvm-project/pull/73662