[llvm] [WPD]: Enable speculative devirtualizatoin. (PR #159048)

[Hassnaa Hamdi via llvm-commits]

hassnaaHamdi wrote:

@teresajohnson I think it's better to handle the object visibility in this patch too ?
Direct devirtualization for hidden objects and speculative for non-hidden ones ?

https://github.com/llvm/llvm-project/pull/159048