[llvm] [VectorCombine] Add initial nodes to the Worklist in VectorCombine (PR #149047)

[David Green via llvm-commits]

davemgreen wrote:

> Compile-time: https://llvm-compile-time-tracker.com/compare.php?from=60579ec3059b2b6cc9dad90eaac1ed363fc395a7&to=7322d4b393c94af7164439419100d9c25df1e420&stat=instructions:u
> 
> Adding the entire function to the worklist at once is quite expensive...
> 
> Possibly we could do something more targeted at removing dead instructions early?

Yeah it is probably not be very useful for a lot of node - many will not be vector instructions. I will look into erasing the instructions as we replace them if we can.

https://github.com/llvm/llvm-project/pull/149047